Wei Zhou | Harbin Insititute of Technology (original) (raw)
Papers by Wei Zhou
Chemosphere, 2021
Hydrogen peroxide (H2O2) electrosynthesis from 2-electron O2 reduction reaction (2eORR) is widely... more Hydrogen peroxide (H2O2) electrosynthesis from 2-electron O2 reduction reaction (2eORR) is widely regarded as a promising alternative to the current industry-dominant anthraquinone process. Design and fabrication of effective, low-cost carbon-based electrodes is one of the priorities. Many previous work well confirmed that hydrophilic carbon-based electrodes are preferable for 2eORR. Here, we proposed a strategy of hydrophilicity-hydrophobicity regulation. By using commercially available graphite felt (GF) as electrodes, we showed that both hydrophilic GF, hydrophobic GF, and Janus GF yielded significantly higher H2O2 production, which is 7.3 times, 7.6 times, and 7.7 times higher than the original GF, respectively. Results showed that currents and stirring rates affect the H2O2 yields. The enhancement of hydrophilic GF is due to the incorporation of oxygen-containing functional groups, while the hydrophobic and Janus GF comes from the locally confined O2 bubbles, which built a gas-liquid-solid interface inside GF and thus enhance the H2O2 formation kinetics. Finally, the effectiveness of the hydrophilicity-hydrophobicity regulation concept was tested in Electro-Fenton process by removing typical dyes and antibiotics. This work supply an effective but facile strategy to enhance the performance of carbon-based electrodes towards 2eORR by regulating the micro-environment of electrodes.
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Journal of the Electrochemical Society, 2020
The chemical-assisted electrochemical hydrogen evolution reaction (CAHER) emerges as a prospectiv... more The chemical-assisted electrochemical hydrogen evolution reaction (CAHER) emerges as a prospective energy-saving method to obtain high-purity hydrogen. Selecting suitable auxiliary reactive chemicals (ARC) for the CAHER system is vital. In this study, we propose that oxalic acid can be used as ARC of the CAHER system. Compared with water electrolysis, lower energy consumption is required for hydrogen production in the presence of oxalic acid. The anode potential needed by oxalic acid assisted water electrolysis (OAWE) is half of that of water electrolysis. For OAWE, more hydrogen is produced with the increase of oxalic acid concentration and temperature.
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Energy & Fuels, 2020
The potential energy of SO 2 is wasted in the process of converting Na 2 SO 3 to Na 2 SO 4 via ai... more The potential energy of SO 2 is wasted in the process of converting Na 2 SO 3 to Na 2 SO 4 via air oxidation during conventional treatment of SO 2-contaminated air. Considering that the oxidation of Na 2 SO 3 is thermodynamically and kinetically much easier than the oxygen evolution reaction (OER), this study proposes replacing the OER with Na 2 SO 3 oxidation to recover the potential energy of SO 2 and simultaneously reduce the energy consumption of water electrolysis. First, the influences of the reaction temperature and Na 2 SO 3 concentration on Na 2 SO 3-assisted water electrolysis (SAWE) were studied. Then, the difference between Na 2 SO 3 electrolysis and water electrolysis was compared under optimum conditions. Furthermore, the long-term stability of SAWE was assessed. The results of this study suggest that the onset potential of water electrolysis decreases from 0.73 V vs saturated calomel electrode (SCE) to 0.28 V vs SCE by replacing the OER with Na 2 SO 3 oxidation. The energy consumption of producing hydrogen by water electrolysis is reduced with the use of the potential energy of SO 2. For SAWE, the Na 2 SO 3 oxidation kinetics and hydrogen production rate are improved as the reaction temperature and Na 2 SO 3 concentration increase.
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Applied Catalysis B: Environmental, 2021
Electrochemical oxygen reduction has been regarded as a promising choice to enable H 2 O 2 on-sit... more Electrochemical oxygen reduction has been regarded as a promising choice to enable H 2 O 2 on-site production and utilization wherein the exploration of high-efficiency yet cost-effective catalysts is the key. Here, we demonstrate a low-cost activated coke (AC) electrocatalyst with size-tailored amorphous carbon clusters doped by oxygen groups, prepared through a facile CO 2 assisted mechanochemistry approach, to deliver among the highest performances reported in a typical alkaline system, including high activity (onset potential of 0.83 V), high H 2 O 2 selectivity (~90 %) and long-term stability. A series of control experiments, structural characterizations before and after electrochemical tests and density functional theory calculations provide a new insight into the coupling role of carbon cluster size and oxygen doping in H 2 O 2 electrochemical production process, that is, size-reduced amorphous carbon lattices with abundant edges contribute to the high activity, while the basal carbon atoms in ether-doped small-size carbon plane are the most active sites towards H 2 O 2 selectivity.
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Energy & Fuels, 2021
Understanding the evolution of carbon structure in coal-assisted water electrolysis for hydrogen ... more Understanding the evolution of carbon structure in coal-assisted water electrolysis for hydrogen production (CAWE) is essential for seeking strategies to improve the rate of CAWE and getting more insight into the potential significance of CAWE. In this study, 13C nuclear magnetic resonance (NMR) is used to understand the evolution of carbon structure in the CAWE. First, the electrolysis characteristics of three different-rank coals are revealed by using electrochemical methods. After then, before and after electrolysis, the evolution of carbon structure is analyzed. The results show that CAWE is a process of reducing carbon and increasing oxygen, and the accumulation of oxygen-containing groups is mainly owing to the increase of oxygen aliphatic carbons and oxygen aromatic carbons. After the CAWE, the aromatic cluster size decreases and increases for low-rank coals and high-rank coals, respectively.
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Separation and Purification Technology, 2021
H2O2 generation by 2-electron oxygen electroreduction reaction (2eORR) has attracted great attent... more H2O2 generation by 2-electron oxygen electroreduction reaction (2eORR) has attracted great attention as an alternative to the industry-dominant anthraquinone process. Electro-Fenton (EF) process, which relies on the H2O2 electrogeneration, is regarded as an important environmental application of H2O2 generation by 2eORR. However, its application is hindered by the relatively expensive electrode materials. Proposing cathode materials with low cost and facile synthetic procedures are the priority to advance the EF process. In this work, a composite cathode structure that uses graphitic granular bamboo-based biochar (GB) and stainless steel (SS) mesh (GBSS) is proposed, where SS mesh functions as current distributor and GB supports synergistic H2O2 electrogeneration and activation. The graphitic carbon makes GB conductive and the oxygen-containing groups serve as active sites for H2O2 production. 11.3 mg/L H2O2 was produced from 2.0 g GB at 50 mA after 50 min under neutral pH without external O2/air supply. The O-doped biochar further increased the H2O2 yield to 18.3 mg/L under same conditions. The GBSS electrode is also effective for H2O2 activation to generate ·OH, especially under neutral pH. Ultimately, a neutral Fe-free EF process enabled by GBSS cathode is effective for removal of various model organic pollutants (reactive blue 19, orange II, 4-nitrophenol) within 120 min, and for their partial mineralization (48.4% to 63.5%). Long-term stability of the GBSS electrode for H2O2 electrogeneration, H2O2 activation, and pollutants degradation were also examined and analyzed. This work offers a promising application for biomass waste for removals of organic pollutants in neutral Fe-free EF process.
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Chemical Engineering Journal, 2021
Hydrogen peroxide (H2O2) electrosynthesis via the oxygen reduction reaction (ORR) presents an att... more Hydrogen peroxide (H2O2) electrosynthesis via the oxygen reduction reaction (ORR) presents an attractive decentralized alternative to the industry-dominant anthraquinone process. Oxidized carbon materials have proven to be promising catalysts due to their low cost and facile synthesis procedures. However, the nature of the active sites is still controversial. The objective of this paper is to provide a critical review of the advances of this topic. The fundamentals of the ORR pathway and O-doping effects are described, followed by the experimental preparation methods for O-doped carbon, including chemical oxidation and electrochemical oxidation. To identify the contribution of each oxygen-containing functional group (OG) or combination of OGs towards 2-electron ORR, combined experimental and DFT calculation results were analyzed. This paper also reviews the new advancement in the co-doping of O and transition metals, which could realize high activity and high selectivity toward H2O2 generation. Future directions in this fascinating field are also highlighted.
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Energy, 2021
Fe3+-mediated coal-assisted water electrolysis (CAWE) for hydrogen production is an effective way... more Fe3+-mediated coal-assisted water electrolysis (CAWE) for hydrogen production is an effective way to utilize coal resources. Low-rank coal, which has a high abundance, is rich in mineral matter and oxygen-containing functional groups (OGs). To promote the development of Fe3+-mediated CAWE of low-rank coal, the roles of mineral matter and OGs in Fe3+-mediated CAWE are investigated in this study. Besides, to understand the reaction mechanism of coal electrolysis and provide guidance for the effective use of electrolyzed coal, the microstructural, surface structure, and microcrystalline changes of the coal are analyzed via Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. The results show that minerals and OGs have a positive and negative influence on the Fe3+-mediated CAWE, respectively. The hydrogen yields of demineralized coal and oxidized coal are 33.15% and 68.47% lower than that of raw coal owing to the influence of minerals and OGs, respectively. After electrolysis, the degree of aromatic ring condensation increases whereas coal rank decreases; the content of -OH on the coal surface increases and the composition of organic sulfur on the coal surface is altered; and the crystallite diameter of the coal changes.
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Chemical Engineering Journal Advances, 2021
The reusability of carbon-based adsorbents determines the techno-economics of the adsorption tech... more The reusability of carbon-based adsorbents determines the techno-economics of the adsorption technology. Various methods, which include conventional thermal and biological regeneration and the subsequently developed new methods are continuously being investigated and engineered. Among these, electrochemical regeneration is promising due to its energy efficiency, selectivity, cost-effectiveness, and environmental compatibility. Electrochemical regeneration covers various regeneration mechanisms and operational methods, but till now, they have not been properly classified or deeply reviewed. In this review, the basic mechanisms of electrochemical regeneration are summarized, followed by a review of various electrochemical regeneration methods with a detailed comparison in terms of regeneration efficiency. Electrochemical reactors are then given special attention because they are significant for the scaling-up of individual regeneration methods. Additionally, the cycling performances of carbon adsorbents are assessed based on an analysis of the physicochemical property changes of carbon adsorbents. Finally, future trends of electrochemical regeneration methods are discussed.
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Fuel, 2021
The effect of preheating primary air on the co-combustion characteristics of a 50-50% blend of pi... more The effect of preheating primary air on the co-combustion characteristics of a 50-50% blend of pinewood and corn straw in a fixed bed. The primary air temperatures were assessed from 20 to 130 • C. The co-combustion characteristics were included the co-combustion behaviors and emissions. In order to reveal the features of the combustion process in the porous bed, a two-dimensional unsteady state model was employed to investigate the combustion process in a fixed bed of blended biomass on the combustion process in a fixed bed reactor. Conservation equations of the bed were implemented to describe the combustion process. The gas phase turbulence was modeled using the k-ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. Results showed that by increasing primary air temperature the residual mass on bed decreased, while the average burning rates and ignition front propagation velocity increased At the primary air temperature of 85 • C the smallest unburned carbon was left in the ash, and the emissions of nitrogen-compounds were relatively small. In contrast, the primary air temperature of 85 • C was found to be well-operating condition, which can be suggested for industrial boiler during blend co-combustion. The simulation results were then compared with experimental data for different temperature, which shows that the combustion process in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data.
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Plasma Sources Science and Technology, 2020
Microwave-induced active coke discharge has been used in many researches in environment and energ... more Microwave-induced active coke discharge has been used in many researches in environment and energy due to its kinetics and thermal effect. However, the mechanisms of discharge for submillimeter particles are still not clear. The paper presents that the particle shape and gap distance between particles are the possible mechanisms of the microwave discharge. This paper also gives the scope of application of several mechanisms for different particulate materials. Submillimeter particles with about 40-110° tip angle and micron gap distance have the best effect on microwave electric field enhancement. The gap effect is only applicable to material with large refractive index, in detail, n > 3 or k > 2 for 300 μm particle. When gap distance is too narrow, the electron loss is large enough, leading to the failure of discharge.
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Journal of Applied Electrochemistry, 2020
Electro-Fenton (EF) and alkaline/persulfate systems are two important systems capable of producin... more Electro-Fenton (EF) and alkaline/persulfate systems are two important systems capable of producing ·OH and SO4-· for environmental remediation. However, the major drawbacks of these two processes are the necessity of operating in low pH (2.0~4.0) or high pH environments, where the acidification/alkalization steps and subsequent neutralization processes significantly increase the operation cost and limit their applicability. In this work, we propose a system that can simultaneously electrochemically develop acidic and alkaline environments in two divided compartments to solve this problem. pH values of 2.9~3.2 and 10.9~11.9 in two separated compartments were obtained, and the results show that the electrochemically developed acidic environment (pH of 3 and 4) enhances the EF process by facilitating H2O2 electrogeneration and Fe2+ regeneration. The alkaline environment (11 and 12) that was also developed electrochemically is effective for persulfate activation. Finally, the system was found to be effective for Rhodamine B removal using an acidic pH-enhanced EF process and an alkaline pH-supported persulfate process.
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Energy Conversion and Management, 2020
This study aimed to develop a novel sorbent for solar driven thermochemical heat storage. The cor... more This study aimed to develop a novel sorbent for solar driven thermochemical heat storage. The core-shell CaCl2@C composites with tunable CaCl2 loading were obtained by a facile one-pot pyrolysis strategy, with the low-cost and abundant coal tar being used as the carbon precursor. CaCl2 was confined to the mesopores and macropores of the carbon shell, which led to a better structural stability than that of the impregnated sorbent. Moreover, the light-to-heat conversion of carbon shell was followed by the thermal energy storage by calcium chloride. In addition, the surface temperature of Ca/CT200-700 under the simulated sunlight of 1000 W/m2 increased to 75 °C. After irradiation for 230 min, the volumetric energy storage density of Ca/CT200-700 was 254 kWh/m3, with the water loss of 0.81 g-H2O/g-sorbent. This core–shell sorbent will provide new insights into the field of solar thermal conversion and storage.
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Korean Journal of Chemical Engineering, 2019
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The Canadian Journal of Chemical Engineering, 2019
Development of an efficient and economic NO oxidation technology is the key step for the simultan... more Development of an efficient and economic NO oxidation technology is the key step for the simultaneous removal of NOx and SO2 in coal‐fired power plants. In this work, a novel advanced oxidation process of NO was proposed, which directly delivered highly oxidative hydroxyl radicals (·OH) generated from the thermal activation of H2O2 vapour into flue gas flow. The experiments were demonstrated in a lab‐scale device, measuring the oxidation of NO as the indicator of radical formation and delivery. The influence of various operational parameters on NO oxidation was evaluated. Increasing the H2O2 dosage, the temperature of the hot‐nitrogen, the flow rate of the hot‐nitrogen, and the total gas residence time greatly enhances the NO oxidation. The NO oxidation was inhibited obviously with the increasing of the H2O2 pH and the NO initial concentration. Increasing the H2O2 pH and the NO initial concentration obviously reduced the NO oxidation. The results indicated that the thermal activation of H2O2 is feasible to oxidize NO and that the H2O2 homogeneous thermal decomposition reaction is essential, therefore, the temperature and the flow rate of the hot‐nitrogen can significantly affect the conversion efficiency. Finally, a potential application was proposed, where NO oxidation by gas‐phase H2O2 can be coupled with the general SCR system to meet stringent regulatory requirements and with a low operating cost.
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Journal of Electroanalytical Chemistry, 2019
Hydrogen peroxide (H2O2) is considered to be an environmentally friendly chemical and the product... more Hydrogen peroxide (H2O2) is considered to be an environmentally friendly chemical and the production methods of H2O2 based on the oxygen reduction reaction (ORR) in the electrochemical system can achieve in-situ generation. The yield of H2O2 is highly dependent on cathode materials. However, the commercial graphite felts (GFs) have a low electrocatalytic activity, which greatly limits its wide-spread application. Here, three kinds of methods (H2O2 oxidation, Fenton reagent oxidation and electrochemical oxidation) were used to modify GFs as the cathode for electrochemical H2O2 production. Characterized by SEM, contact angle and XPS, the morphology and surface physicochemical properties after modification were considerably changed. After modification, the surface of GFs was etched, and some oxygen-containing functional groups (OGs) especially COOH appeared on the surface, leading to the improvement of the surface hydrophilic and the electrocatalytic activity for ORR. The H2O2 production of three GFs at 90 min were 18.67 mg/L, 32.13 mg/L and 37.47 mg/L, respectively, compared to only 3.24 mg/L by the original GFs. Additionally, the long-term stability of modified GFs were studied and the mechanism of the decreased stability was proposed. After 10 consecutive cycles, the H2O2 production of three modified GFs decreased by 42.29%, 61.24% and 58.19%, respectively. SEM, contact angle and XPS showed that the surface of the GFs was etched more, and the COOH content of all three materials significant decreased.
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Energy & Fuels, 2019
Combustion of biomass in a boiler releases alkali metals and chlorine which, together with silico... more Combustion of biomass in a boiler releases alkali metals and chlorine which, together with silicon and sulfur, are responsible for slagging, fouling, corrosion, and particulate emissions. This research investigated the effects of the primary (under-fire) air flow rate, ṁ air , and its preheating temperature on the ignition and burning rates of pinewood chips in a laboratory fixed bed furnace and on the release of alkali metals and alkali earth metals (potassium (K), sodium (Na), calcium (Ca), magnesium (Mg)) and chlorine. The air flow rate, ṁ air , through the bed was varied in the range of 0.085−0.237 kg/(m 2 s), resulting in an overall excess primary air coefficient λ varying from 0.56 to 1.1. Air was also preheated in the range of 20−135 °C. Results showed that increasing either ṁ air or the air preheat temperature increased the flame propagation rate (ignition rate) and the mass burning rate of the fuel. Moreover, the release of Cl was nearly complete (>99%) in all examined cases, whereas the release of alkalis was only partial. Calcium was the most predominant alkali in the pinewood; however, potassium was the predominant alkali in the released gases. The mass fraction of Na in the pinewood was much lower than that of K but it was released more comprehensively. Increasing the air flow rate enhanced the release of K and Na significantly, whereas it enhanced the release of Ca and Mg only slightly. Preheating the primary air preferentially increased the migration of K to the gas phase, whereas Na, Ca, and Mg were affected only mildly. The preheated air promoted the transfer of chlorine to HCl. Overall, moderately high primary air flow rates generate globally fuel lean conditions and mildly preheated air can enhance the mass burning rate of pinewood and its conversion to fully and partially oxidized gases. However, they result in enhanced gasification of the alkalis in the biomass. In the case of pinewood, this may be a minor concern, as the absolute values of such emissions are low relative to other biomass fuels.
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Journal of Energy Resources Technology, 2019
This research investigated the effects of the specific primary (under-fire) air flowrate on the c... more This research investigated the effects of the specific primary (under-fire) air flowrate on the combustion behavior of a 50–50 wt % blend of raw corn straw (CS) and raw pinewood wastes in a fixed-bed reactor. This parameter was varied in the range of 0.079–0.226 kg m−2 s−1, which changed the overall combustion stoichiometry from air-lean (excess air coefficient λ = 0.73) to air-rich (excess air coefficient λ = 1.25) and affected the combustion efficiency and stability as well as the emissions of hazardous pollutants. It was observed that by increasing m˙m˙air, the ignition delay time first increased and then decreased, the average bed temperatures increased, both the average flame propagation rates and the fuel burning rates increased, and the combustion efficiencies also increased. The emissions of CO as well as those of cumulative gas phase nitrogen compounds increased, the latter mostly because of increasing HCN, while those of NO were rather constant. The emissions of HCl decreased but those of other chlorine-containing species increased. The effect of m˙m˙air on the conversion of sulfur to SO2 was minor. By considering all of the aforesaid factors, a mildly overall air-rich (fuel-lean) (λ = 1.04) operating condition can be suggested for corn-straw/pinewood burning fixed-bed grate-fired reactors.
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Applied Thermal Engineering, 2017
In the present research, experiments were performed on corn straw in a one-dimensional bench fixe... more In the present research, experiments were performed on corn straw in a one-dimensional bench fixed-bed combustion test rig. The effects of different corn straw lengths and primary air (supplied through the grate) on the combustion characteristics of corn straw were investigated. The two parameters will directly relate to the burning rate, which affect combustion efficiency, burnout rate and gas emissions. The bed temperature distribution and gas components such as CO2, CO, O2, CH4, C2H6, NO, HCN, and SO2 were measured in the bed. The results indicate that shorter corn straw combustion resulted the higher CO concentration in later stage of combustion, while a higher temperature and less unburned carbon in bottom ash. As the main pyrolysis production, the concentration of CH4 emission was 2 orders of magnitude for C2H6. NO was the main product of NOx, and shared a similar trend to HCN in the combustion process of all parameters, while the yield was less than HCN. The C conversion to CO2 was much higher than to CO. The emission factors of SO2 and NO had the opposite trend with the length variation. With the flowrate increased, there is an increased tendency of C to CO2 and a reduced CO/CO2 ratio. This study improves the understanding of the operational characteristics of small-scale corn straw burning to help with the design and optimization of large-scale fixed-beds for power plants.
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Energy, 2018
In this paper, mathematical modelling is conducted on the combustion of corn straw in a one-dimen... more In this paper, mathematical modelling is conducted on the combustion of corn straw in a one-dimensional bench combustion test rig, and the effects of the primary air flow rate are assessed over a wide range. Due to complex solid combustion mechanisms and inadequate knowledge of the process, the development of such combustion system is limited. Numerical modelling of this combustion system has some advantages over experimental analysis, although the development of a complete model for this type of combustion system remains a challenge. Due to its characteristic properties, modelling of biomass combustion has to overcome many difficulties. One such problem is displaying the process of initiating the combustion in numerical modelling. This study finds that the volatile release and combustion of char increases, thus increasing the amount of primary air up to a critical point, where the starting time of ignition becomes shorter as the primary air flow rate increases. The peak concentration of NO decreases with the increase of primary air, whereas with the increase in the amount of air, there is a reduction in the release of SO2 as well as a reduction in CO emissions in the bed.
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Chemosphere, 2021
Hydrogen peroxide (H2O2) electrosynthesis from 2-electron O2 reduction reaction (2eORR) is widely... more Hydrogen peroxide (H2O2) electrosynthesis from 2-electron O2 reduction reaction (2eORR) is widely regarded as a promising alternative to the current industry-dominant anthraquinone process. Design and fabrication of effective, low-cost carbon-based electrodes is one of the priorities. Many previous work well confirmed that hydrophilic carbon-based electrodes are preferable for 2eORR. Here, we proposed a strategy of hydrophilicity-hydrophobicity regulation. By using commercially available graphite felt (GF) as electrodes, we showed that both hydrophilic GF, hydrophobic GF, and Janus GF yielded significantly higher H2O2 production, which is 7.3 times, 7.6 times, and 7.7 times higher than the original GF, respectively. Results showed that currents and stirring rates affect the H2O2 yields. The enhancement of hydrophilic GF is due to the incorporation of oxygen-containing functional groups, while the hydrophobic and Janus GF comes from the locally confined O2 bubbles, which built a gas-liquid-solid interface inside GF and thus enhance the H2O2 formation kinetics. Finally, the effectiveness of the hydrophilicity-hydrophobicity regulation concept was tested in Electro-Fenton process by removing typical dyes and antibiotics. This work supply an effective but facile strategy to enhance the performance of carbon-based electrodes towards 2eORR by regulating the micro-environment of electrodes.
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Journal of the Electrochemical Society, 2020
The chemical-assisted electrochemical hydrogen evolution reaction (CAHER) emerges as a prospectiv... more The chemical-assisted electrochemical hydrogen evolution reaction (CAHER) emerges as a prospective energy-saving method to obtain high-purity hydrogen. Selecting suitable auxiliary reactive chemicals (ARC) for the CAHER system is vital. In this study, we propose that oxalic acid can be used as ARC of the CAHER system. Compared with water electrolysis, lower energy consumption is required for hydrogen production in the presence of oxalic acid. The anode potential needed by oxalic acid assisted water electrolysis (OAWE) is half of that of water electrolysis. For OAWE, more hydrogen is produced with the increase of oxalic acid concentration and temperature.
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Energy & Fuels, 2020
The potential energy of SO 2 is wasted in the process of converting Na 2 SO 3 to Na 2 SO 4 via ai... more The potential energy of SO 2 is wasted in the process of converting Na 2 SO 3 to Na 2 SO 4 via air oxidation during conventional treatment of SO 2-contaminated air. Considering that the oxidation of Na 2 SO 3 is thermodynamically and kinetically much easier than the oxygen evolution reaction (OER), this study proposes replacing the OER with Na 2 SO 3 oxidation to recover the potential energy of SO 2 and simultaneously reduce the energy consumption of water electrolysis. First, the influences of the reaction temperature and Na 2 SO 3 concentration on Na 2 SO 3-assisted water electrolysis (SAWE) were studied. Then, the difference between Na 2 SO 3 electrolysis and water electrolysis was compared under optimum conditions. Furthermore, the long-term stability of SAWE was assessed. The results of this study suggest that the onset potential of water electrolysis decreases from 0.73 V vs saturated calomel electrode (SCE) to 0.28 V vs SCE by replacing the OER with Na 2 SO 3 oxidation. The energy consumption of producing hydrogen by water electrolysis is reduced with the use of the potential energy of SO 2. For SAWE, the Na 2 SO 3 oxidation kinetics and hydrogen production rate are improved as the reaction temperature and Na 2 SO 3 concentration increase.
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Applied Catalysis B: Environmental, 2021
Electrochemical oxygen reduction has been regarded as a promising choice to enable H 2 O 2 on-sit... more Electrochemical oxygen reduction has been regarded as a promising choice to enable H 2 O 2 on-site production and utilization wherein the exploration of high-efficiency yet cost-effective catalysts is the key. Here, we demonstrate a low-cost activated coke (AC) electrocatalyst with size-tailored amorphous carbon clusters doped by oxygen groups, prepared through a facile CO 2 assisted mechanochemistry approach, to deliver among the highest performances reported in a typical alkaline system, including high activity (onset potential of 0.83 V), high H 2 O 2 selectivity (~90 %) and long-term stability. A series of control experiments, structural characterizations before and after electrochemical tests and density functional theory calculations provide a new insight into the coupling role of carbon cluster size and oxygen doping in H 2 O 2 electrochemical production process, that is, size-reduced amorphous carbon lattices with abundant edges contribute to the high activity, while the basal carbon atoms in ether-doped small-size carbon plane are the most active sites towards H 2 O 2 selectivity.
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Energy & Fuels, 2021
Understanding the evolution of carbon structure in coal-assisted water electrolysis for hydrogen ... more Understanding the evolution of carbon structure in coal-assisted water electrolysis for hydrogen production (CAWE) is essential for seeking strategies to improve the rate of CAWE and getting more insight into the potential significance of CAWE. In this study, 13C nuclear magnetic resonance (NMR) is used to understand the evolution of carbon structure in the CAWE. First, the electrolysis characteristics of three different-rank coals are revealed by using electrochemical methods. After then, before and after electrolysis, the evolution of carbon structure is analyzed. The results show that CAWE is a process of reducing carbon and increasing oxygen, and the accumulation of oxygen-containing groups is mainly owing to the increase of oxygen aliphatic carbons and oxygen aromatic carbons. After the CAWE, the aromatic cluster size decreases and increases for low-rank coals and high-rank coals, respectively.
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Separation and Purification Technology, 2021
H2O2 generation by 2-electron oxygen electroreduction reaction (2eORR) has attracted great attent... more H2O2 generation by 2-electron oxygen electroreduction reaction (2eORR) has attracted great attention as an alternative to the industry-dominant anthraquinone process. Electro-Fenton (EF) process, which relies on the H2O2 electrogeneration, is regarded as an important environmental application of H2O2 generation by 2eORR. However, its application is hindered by the relatively expensive electrode materials. Proposing cathode materials with low cost and facile synthetic procedures are the priority to advance the EF process. In this work, a composite cathode structure that uses graphitic granular bamboo-based biochar (GB) and stainless steel (SS) mesh (GBSS) is proposed, where SS mesh functions as current distributor and GB supports synergistic H2O2 electrogeneration and activation. The graphitic carbon makes GB conductive and the oxygen-containing groups serve as active sites for H2O2 production. 11.3 mg/L H2O2 was produced from 2.0 g GB at 50 mA after 50 min under neutral pH without external O2/air supply. The O-doped biochar further increased the H2O2 yield to 18.3 mg/L under same conditions. The GBSS electrode is also effective for H2O2 activation to generate ·OH, especially under neutral pH. Ultimately, a neutral Fe-free EF process enabled by GBSS cathode is effective for removal of various model organic pollutants (reactive blue 19, orange II, 4-nitrophenol) within 120 min, and for their partial mineralization (48.4% to 63.5%). Long-term stability of the GBSS electrode for H2O2 electrogeneration, H2O2 activation, and pollutants degradation were also examined and analyzed. This work offers a promising application for biomass waste for removals of organic pollutants in neutral Fe-free EF process.
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Chemical Engineering Journal, 2021
Hydrogen peroxide (H2O2) electrosynthesis via the oxygen reduction reaction (ORR) presents an att... more Hydrogen peroxide (H2O2) electrosynthesis via the oxygen reduction reaction (ORR) presents an attractive decentralized alternative to the industry-dominant anthraquinone process. Oxidized carbon materials have proven to be promising catalysts due to their low cost and facile synthesis procedures. However, the nature of the active sites is still controversial. The objective of this paper is to provide a critical review of the advances of this topic. The fundamentals of the ORR pathway and O-doping effects are described, followed by the experimental preparation methods for O-doped carbon, including chemical oxidation and electrochemical oxidation. To identify the contribution of each oxygen-containing functional group (OG) or combination of OGs towards 2-electron ORR, combined experimental and DFT calculation results were analyzed. This paper also reviews the new advancement in the co-doping of O and transition metals, which could realize high activity and high selectivity toward H2O2 generation. Future directions in this fascinating field are also highlighted.
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Energy, 2021
Fe3+-mediated coal-assisted water electrolysis (CAWE) for hydrogen production is an effective way... more Fe3+-mediated coal-assisted water electrolysis (CAWE) for hydrogen production is an effective way to utilize coal resources. Low-rank coal, which has a high abundance, is rich in mineral matter and oxygen-containing functional groups (OGs). To promote the development of Fe3+-mediated CAWE of low-rank coal, the roles of mineral matter and OGs in Fe3+-mediated CAWE are investigated in this study. Besides, to understand the reaction mechanism of coal electrolysis and provide guidance for the effective use of electrolyzed coal, the microstructural, surface structure, and microcrystalline changes of the coal are analyzed via Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. The results show that minerals and OGs have a positive and negative influence on the Fe3+-mediated CAWE, respectively. The hydrogen yields of demineralized coal and oxidized coal are 33.15% and 68.47% lower than that of raw coal owing to the influence of minerals and OGs, respectively. After electrolysis, the degree of aromatic ring condensation increases whereas coal rank decreases; the content of -OH on the coal surface increases and the composition of organic sulfur on the coal surface is altered; and the crystallite diameter of the coal changes.
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Chemical Engineering Journal Advances, 2021
The reusability of carbon-based adsorbents determines the techno-economics of the adsorption tech... more The reusability of carbon-based adsorbents determines the techno-economics of the adsorption technology. Various methods, which include conventional thermal and biological regeneration and the subsequently developed new methods are continuously being investigated and engineered. Among these, electrochemical regeneration is promising due to its energy efficiency, selectivity, cost-effectiveness, and environmental compatibility. Electrochemical regeneration covers various regeneration mechanisms and operational methods, but till now, they have not been properly classified or deeply reviewed. In this review, the basic mechanisms of electrochemical regeneration are summarized, followed by a review of various electrochemical regeneration methods with a detailed comparison in terms of regeneration efficiency. Electrochemical reactors are then given special attention because they are significant for the scaling-up of individual regeneration methods. Additionally, the cycling performances of carbon adsorbents are assessed based on an analysis of the physicochemical property changes of carbon adsorbents. Finally, future trends of electrochemical regeneration methods are discussed.
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Fuel, 2021
The effect of preheating primary air on the co-combustion characteristics of a 50-50% blend of pi... more The effect of preheating primary air on the co-combustion characteristics of a 50-50% blend of pinewood and corn straw in a fixed bed. The primary air temperatures were assessed from 20 to 130 • C. The co-combustion characteristics were included the co-combustion behaviors and emissions. In order to reveal the features of the combustion process in the porous bed, a two-dimensional unsteady state model was employed to investigate the combustion process in a fixed bed of blended biomass on the combustion process in a fixed bed reactor. Conservation equations of the bed were implemented to describe the combustion process. The gas phase turbulence was modeled using the k-ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. Results showed that by increasing primary air temperature the residual mass on bed decreased, while the average burning rates and ignition front propagation velocity increased At the primary air temperature of 85 • C the smallest unburned carbon was left in the ash, and the emissions of nitrogen-compounds were relatively small. In contrast, the primary air temperature of 85 • C was found to be well-operating condition, which can be suggested for industrial boiler during blend co-combustion. The simulation results were then compared with experimental data for different temperature, which shows that the combustion process in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data.
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Plasma Sources Science and Technology, 2020
Microwave-induced active coke discharge has been used in many researches in environment and energ... more Microwave-induced active coke discharge has been used in many researches in environment and energy due to its kinetics and thermal effect. However, the mechanisms of discharge for submillimeter particles are still not clear. The paper presents that the particle shape and gap distance between particles are the possible mechanisms of the microwave discharge. This paper also gives the scope of application of several mechanisms for different particulate materials. Submillimeter particles with about 40-110° tip angle and micron gap distance have the best effect on microwave electric field enhancement. The gap effect is only applicable to material with large refractive index, in detail, n > 3 or k > 2 for 300 μm particle. When gap distance is too narrow, the electron loss is large enough, leading to the failure of discharge.
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Journal of Applied Electrochemistry, 2020
Electro-Fenton (EF) and alkaline/persulfate systems are two important systems capable of producin... more Electro-Fenton (EF) and alkaline/persulfate systems are two important systems capable of producing ·OH and SO4-· for environmental remediation. However, the major drawbacks of these two processes are the necessity of operating in low pH (2.0~4.0) or high pH environments, where the acidification/alkalization steps and subsequent neutralization processes significantly increase the operation cost and limit their applicability. In this work, we propose a system that can simultaneously electrochemically develop acidic and alkaline environments in two divided compartments to solve this problem. pH values of 2.9~3.2 and 10.9~11.9 in two separated compartments were obtained, and the results show that the electrochemically developed acidic environment (pH of 3 and 4) enhances the EF process by facilitating H2O2 electrogeneration and Fe2+ regeneration. The alkaline environment (11 and 12) that was also developed electrochemically is effective for persulfate activation. Finally, the system was found to be effective for Rhodamine B removal using an acidic pH-enhanced EF process and an alkaline pH-supported persulfate process.
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Energy Conversion and Management, 2020
This study aimed to develop a novel sorbent for solar driven thermochemical heat storage. The cor... more This study aimed to develop a novel sorbent for solar driven thermochemical heat storage. The core-shell CaCl2@C composites with tunable CaCl2 loading were obtained by a facile one-pot pyrolysis strategy, with the low-cost and abundant coal tar being used as the carbon precursor. CaCl2 was confined to the mesopores and macropores of the carbon shell, which led to a better structural stability than that of the impregnated sorbent. Moreover, the light-to-heat conversion of carbon shell was followed by the thermal energy storage by calcium chloride. In addition, the surface temperature of Ca/CT200-700 under the simulated sunlight of 1000 W/m2 increased to 75 °C. After irradiation for 230 min, the volumetric energy storage density of Ca/CT200-700 was 254 kWh/m3, with the water loss of 0.81 g-H2O/g-sorbent. This core–shell sorbent will provide new insights into the field of solar thermal conversion and storage.
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Korean Journal of Chemical Engineering, 2019
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The Canadian Journal of Chemical Engineering, 2019
Development of an efficient and economic NO oxidation technology is the key step for the simultan... more Development of an efficient and economic NO oxidation technology is the key step for the simultaneous removal of NOx and SO2 in coal‐fired power plants. In this work, a novel advanced oxidation process of NO was proposed, which directly delivered highly oxidative hydroxyl radicals (·OH) generated from the thermal activation of H2O2 vapour into flue gas flow. The experiments were demonstrated in a lab‐scale device, measuring the oxidation of NO as the indicator of radical formation and delivery. The influence of various operational parameters on NO oxidation was evaluated. Increasing the H2O2 dosage, the temperature of the hot‐nitrogen, the flow rate of the hot‐nitrogen, and the total gas residence time greatly enhances the NO oxidation. The NO oxidation was inhibited obviously with the increasing of the H2O2 pH and the NO initial concentration. Increasing the H2O2 pH and the NO initial concentration obviously reduced the NO oxidation. The results indicated that the thermal activation of H2O2 is feasible to oxidize NO and that the H2O2 homogeneous thermal decomposition reaction is essential, therefore, the temperature and the flow rate of the hot‐nitrogen can significantly affect the conversion efficiency. Finally, a potential application was proposed, where NO oxidation by gas‐phase H2O2 can be coupled with the general SCR system to meet stringent regulatory requirements and with a low operating cost.
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Journal of Electroanalytical Chemistry, 2019
Hydrogen peroxide (H2O2) is considered to be an environmentally friendly chemical and the product... more Hydrogen peroxide (H2O2) is considered to be an environmentally friendly chemical and the production methods of H2O2 based on the oxygen reduction reaction (ORR) in the electrochemical system can achieve in-situ generation. The yield of H2O2 is highly dependent on cathode materials. However, the commercial graphite felts (GFs) have a low electrocatalytic activity, which greatly limits its wide-spread application. Here, three kinds of methods (H2O2 oxidation, Fenton reagent oxidation and electrochemical oxidation) were used to modify GFs as the cathode for electrochemical H2O2 production. Characterized by SEM, contact angle and XPS, the morphology and surface physicochemical properties after modification were considerably changed. After modification, the surface of GFs was etched, and some oxygen-containing functional groups (OGs) especially COOH appeared on the surface, leading to the improvement of the surface hydrophilic and the electrocatalytic activity for ORR. The H2O2 production of three GFs at 90 min were 18.67 mg/L, 32.13 mg/L and 37.47 mg/L, respectively, compared to only 3.24 mg/L by the original GFs. Additionally, the long-term stability of modified GFs were studied and the mechanism of the decreased stability was proposed. After 10 consecutive cycles, the H2O2 production of three modified GFs decreased by 42.29%, 61.24% and 58.19%, respectively. SEM, contact angle and XPS showed that the surface of the GFs was etched more, and the COOH content of all three materials significant decreased.
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Energy & Fuels, 2019
Combustion of biomass in a boiler releases alkali metals and chlorine which, together with silico... more Combustion of biomass in a boiler releases alkali metals and chlorine which, together with silicon and sulfur, are responsible for slagging, fouling, corrosion, and particulate emissions. This research investigated the effects of the primary (under-fire) air flow rate, ṁ air , and its preheating temperature on the ignition and burning rates of pinewood chips in a laboratory fixed bed furnace and on the release of alkali metals and alkali earth metals (potassium (K), sodium (Na), calcium (Ca), magnesium (Mg)) and chlorine. The air flow rate, ṁ air , through the bed was varied in the range of 0.085−0.237 kg/(m 2 s), resulting in an overall excess primary air coefficient λ varying from 0.56 to 1.1. Air was also preheated in the range of 20−135 °C. Results showed that increasing either ṁ air or the air preheat temperature increased the flame propagation rate (ignition rate) and the mass burning rate of the fuel. Moreover, the release of Cl was nearly complete (>99%) in all examined cases, whereas the release of alkalis was only partial. Calcium was the most predominant alkali in the pinewood; however, potassium was the predominant alkali in the released gases. The mass fraction of Na in the pinewood was much lower than that of K but it was released more comprehensively. Increasing the air flow rate enhanced the release of K and Na significantly, whereas it enhanced the release of Ca and Mg only slightly. Preheating the primary air preferentially increased the migration of K to the gas phase, whereas Na, Ca, and Mg were affected only mildly. The preheated air promoted the transfer of chlorine to HCl. Overall, moderately high primary air flow rates generate globally fuel lean conditions and mildly preheated air can enhance the mass burning rate of pinewood and its conversion to fully and partially oxidized gases. However, they result in enhanced gasification of the alkalis in the biomass. In the case of pinewood, this may be a minor concern, as the absolute values of such emissions are low relative to other biomass fuels.
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Journal of Energy Resources Technology, 2019
This research investigated the effects of the specific primary (under-fire) air flowrate on the c... more This research investigated the effects of the specific primary (under-fire) air flowrate on the combustion behavior of a 50–50 wt % blend of raw corn straw (CS) and raw pinewood wastes in a fixed-bed reactor. This parameter was varied in the range of 0.079–0.226 kg m−2 s−1, which changed the overall combustion stoichiometry from air-lean (excess air coefficient λ = 0.73) to air-rich (excess air coefficient λ = 1.25) and affected the combustion efficiency and stability as well as the emissions of hazardous pollutants. It was observed that by increasing m˙m˙air, the ignition delay time first increased and then decreased, the average bed temperatures increased, both the average flame propagation rates and the fuel burning rates increased, and the combustion efficiencies also increased. The emissions of CO as well as those of cumulative gas phase nitrogen compounds increased, the latter mostly because of increasing HCN, while those of NO were rather constant. The emissions of HCl decreased but those of other chlorine-containing species increased. The effect of m˙m˙air on the conversion of sulfur to SO2 was minor. By considering all of the aforesaid factors, a mildly overall air-rich (fuel-lean) (λ = 1.04) operating condition can be suggested for corn-straw/pinewood burning fixed-bed grate-fired reactors.
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Applied Thermal Engineering, 2017
In the present research, experiments were performed on corn straw in a one-dimensional bench fixe... more In the present research, experiments were performed on corn straw in a one-dimensional bench fixed-bed combustion test rig. The effects of different corn straw lengths and primary air (supplied through the grate) on the combustion characteristics of corn straw were investigated. The two parameters will directly relate to the burning rate, which affect combustion efficiency, burnout rate and gas emissions. The bed temperature distribution and gas components such as CO2, CO, O2, CH4, C2H6, NO, HCN, and SO2 were measured in the bed. The results indicate that shorter corn straw combustion resulted the higher CO concentration in later stage of combustion, while a higher temperature and less unburned carbon in bottom ash. As the main pyrolysis production, the concentration of CH4 emission was 2 orders of magnitude for C2H6. NO was the main product of NOx, and shared a similar trend to HCN in the combustion process of all parameters, while the yield was less than HCN. The C conversion to CO2 was much higher than to CO. The emission factors of SO2 and NO had the opposite trend with the length variation. With the flowrate increased, there is an increased tendency of C to CO2 and a reduced CO/CO2 ratio. This study improves the understanding of the operational characteristics of small-scale corn straw burning to help with the design and optimization of large-scale fixed-beds for power plants.
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Energy, 2018
In this paper, mathematical modelling is conducted on the combustion of corn straw in a one-dimen... more In this paper, mathematical modelling is conducted on the combustion of corn straw in a one-dimensional bench combustion test rig, and the effects of the primary air flow rate are assessed over a wide range. Due to complex solid combustion mechanisms and inadequate knowledge of the process, the development of such combustion system is limited. Numerical modelling of this combustion system has some advantages over experimental analysis, although the development of a complete model for this type of combustion system remains a challenge. Due to its characteristic properties, modelling of biomass combustion has to overcome many difficulties. One such problem is displaying the process of initiating the combustion in numerical modelling. This study finds that the volatile release and combustion of char increases, thus increasing the amount of primary air up to a critical point, where the starting time of ignition becomes shorter as the primary air flow rate increases. The peak concentration of NO decreases with the increase of primary air, whereas with the increase in the amount of air, there is a reduction in the release of SO2 as well as a reduction in CO emissions in the bed.
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