In situ synthesis of ordered mesoporous Co-doped TiO2 and their enhanced photocatalytic activities and selectivities in reduction of CO2 (original) (raw)
A review on advances in photocatalysts towards CO2 conversion
RSC Advances, 2014
The present situation reveals the dependence on fossil fuels, which is seriously accountable for two major impediments: (i) global warming due to increasing atmospheric carbon dioxide (CO2) and (ii) the alarming consumption of energy assets. The reduction of green CO2 in terms of producing solar fuels would be an expedient accomplishment to resolve both problems, simultaneously. The review classifies different categories of photocatalysts applied in foregoing photocatalytic CO2 conversion processes with detailed information concerning operating conditions, preparation techniques and physical properties of catalysts, radiation sources, and selectivity. The categories are concentrated on metal oxides, sulfides, phosphides, and p-type and nonmetal oxide semiconductors. In addition, their modification by doping co-metals, noble metals, transition metals and non-metals for visible light response is emphasized. Besides, for harnessing solar fuel, the recent prospect and advancement of novel sensitized catalysts by dye elements, phthalocyanines and quantum dots (QDs) are also highlighted in this review. This technology needs more efficient solar active catalysts to increase production rates as well as selectivity. The recent scenario indicates that massive prospects and opportunities still exist in this area for further investigation on catalyst selection. This journal is © the Partner Organisations 2014. http://pubs.rsc.org/en/Content/ArticleLanding/2014/RA/c4ra01769b
Recent Progress in the Photocatalytic Reduction of Carbon Dioxide
ACS Omega, 2017
Elimination or reduction of CO 2 in the atmosphere is a serious problem faced by humankind, and it has become imperative for chemists to find ways of transforming undesirable CO 2 to useful chemicals. One of the best means is the use of solar energy for the photochemical reduction of CO 2. In spite of considerable efforts, discovery of stable photocatalysts which work in the absence of scavengers has remained a challenge although encouraging results have been obtained in the photocatalytic reduction of CO 2 in both gas and liquid phases. Semiconductor-based catalysts, multicomponent semiconductors, metal−organic frameworks (MOFs), and dyes as well as composites involving novel composite materials containing C 3 N 4 and MoS 2 have been employed for the photoreduction process. Semiconductor heterostructures, especially those containing bimetallic alloys as well as chemical modification of oxides and other materials with aliovalent anion substitution (N 3− and F − in place of O 2−), remain worthwhile efforts. In this article, we provide a brief perspective of the present status of photocatalytic reduction of CO 2 in both liquid and gas phases.
The reduction of carbon dioxide to useful chemicals has received a great deal of attention as an alternative to the depletion of fossil resources without altering the atmospheric CO 2 balance. As the chemical reduction of CO 2 is energetically uphill due to its remarkable thermodynamic stability, this process requires a significant transfer of energy. Achievements in the fields of photocatalysis during the last decade sparked increased interest in the possibility of using sunlight to reduce CO 2 . In this review we discuss some general features associated with the photocatalytic reduction of CO 2 for the production of solar fuels, with considerations to be taken into account of the photocatalyst design, of the limitations arising from the lack of visible light response of titania, of the use of co-catalysts to overcome this shortcoming, together with several strategies that have been applied to enhance the photocatalytic efficiency of CO 2 reduction. The aim is not to provide an exhaustive review of the area, but to present general aspects to be considered, and then to outline which are currently the most efficient photocatalytic systems.
Advances in Photocatalytic CO2 Reduction with Water: A Review
Materials
In recent years, the increasing level of CO 2 in the atmosphere has not only contributed to global warming but has also triggered considerable interest in photocatalytic reduction of CO 2. The reduction of CO 2 with H 2 O using sunlight is an innovative way to solve the current growing environmental challenges. This paper reviews the basic principles of photocatalysis and photocatalytic CO 2 reduction, discusses the measures of the photocatalytic efficiency and summarizes current advances in the exploration of this technology using different types of semiconductor photocatalysts, such as TiO 2 and modified TiO 2 , layered-perovskite Ag/ALa 4 Ti 4 O 15 (A = Ca, Ba, Sr), ferroelectric LiNbO 3 , and plasmonic photocatalysts. Visible light harvesting, novel plasmonic photocatalysts offer potential solutions for some of the main drawbacks in this reduction process. Effective plasmonic photocatalysts that have shown reduction activities towards CO 2 with H 2 O are highlighted here. Although this technology is still at an embryonic stage, further studies with standard theoretical and comprehensive format are suggested to develop photocatalysts with high production rates and selectivity. Based on the collected results, the immense prospects and opportunities that exist in this technique are also reviewed here.
Photocatalytic Reduction of CO2 into Fuels: A Short Review
Journal of Advanced Catalysis Science and Technology, 2014
The photocatalytic reduction of CO2 with water vapour and catalysts under UV irradiation to yield hydrocarbons is a potential way of decreasing greenhouse gas and it represents an attractive alternative energy source to fossil fuels. However, this process still has to overcome several hurdles, because it involves the activation of two stable molecules, H2O and CO2, and simultaneous conversion through a multi-step electron transfer reaction. The problem of CO2 emission and the possibility of exploiting CO2 as a raw material reaction is first reported in this short review. Subsequently, the fundamentals of photocatalysis are described. Finally, TiO2-based photocatalysts are reviewed, taking into consideration the optimization methods that can be adopted to improve performances. The information gained from this analysis will help to contribute towards a better understanding of the main parameters that affect the activity of photocatalysts and will ultimately lead to the optimized synthesis of more efficient photocatalytic material for the photocatalytic reduction of CO2 to fuels.
Journal of CO2 Utilization, 2019
An alternative source for carbon-doped TiO 2 photocatalysts, synthesized with glucose as precursor, calcined and tested for the reduction of CO 2 have been investigated. These samples are characterized using XRD, FTIR, DRUV-Vis, XPS and HR-TEM. Glucose with 6 wt.% loading (6C-TiO 2) corresponds to the optimum amount of carbon doped into TiO 2 achieving a methanol yield of 19.5 mmol g cat −1 h −1 , a more than 2-fold increase from that of bare TiO 2 at 9.5 mmol g cat −1 h −1. Moreover, the quantum yield of carbon-doped TiO 2 increases by ca. 50% compared to bare TiO 2. From XPS results, various surface species with CeOH, C]C and C]O functional groups confer the association of ligand-metal-charge-transfer (LMCT) complex between TiO 2 and carbon. The low band gap and UV-vis light absorption capacity of carbon-doped TiO 2 facilitates the transfer of photo-generated electrons. 6C-TiO 2 demonstrates high photostability with constant yield even after five cycles of testing. The mechanism of the carbon-doped TiO 2 in reduction of CO 2 to methanol is postulated to be consistent with the LMCT complex phenomena. Therefore, 6C-TiO 2 photocatalyst provides heterojunction for localization of electrons, hinders the charge recombination rate and narrows the band gap for enhanced photocatalytic activity under UV-VIS light irradiation.
Recent Advances on Photocatalytic Material for Artificial Photosynthesis
Proceedings of 2nd International Electronic Conference on Materials, 2016
Artificial photosynthesis is copying in practically less complex structure to achieve the consequences of natural photosynthesis. The process includes coupling solar powered driven water splitting and CO2 reduction. It takes place in a way that dispenses with the requirement for an external, sacrificial electron donor is one of the colossal difficulties for the utilization of renewable energy and a sustainable development. For all intents and purposes, ʹʹCO2 reductionʹʹ is more emerging than ʹʹwater splittingʹʹ since it not just adds to worldwide carbon cycling for carbon unbiased natural powers, mimicking what genuine leaves do (characteristic carbon reduction), additionally mitigating worldwide atmosphere changes. However, as CO2 is a generally dormant and stable exacerbate, its diminishment is entirely testing. The photo catalytic dwindling of CO2 has been generally expected for quite a while and additionally water splitting. For heterogeneous photo catalyst, numerous endeavors still concentrate on TiO2-based materials while different photo catalysts, for example, LiNbO3, ZnGa2O4, ALa4Ti4O15 (A=Ca, Sr, and Ba) etc. have additionally been accounted for as of late. Nevertheless, the advance accomplished in this field had not been as sensational as that in water splitting for a few decades in view of the low efficiencies, limited photo catalyst and/or requiring the utilization of sacrificial reducing agents. The study finds out current gaps inside of the advancement of recent photo-catalytic materials for artificial photosynthesis.
Journal of Colloid and Interface Science, 2023
Tricobalt tetroxide (Co3O4) has been developed as a promising photocatalyst material for various applications. Several reports have been published on the self-modification of Co3O4 to achieve optimal photocatalytic performance. The pristine Co3O4 alone is inadequate for photocatalysis due to the rapid recombination process of photogenerated (PG) charge carriers. The modification of Co3O4 can be extended through the introduction of doping elements, incorporation of supporting materials, surface functionalization, metal loading, and combination with other photocatalysts. The addition of doping elements and support materials may enhance the photocatalysis process, although these modifications have a slight effect on decreasing the recombination process of PG charge carriers. On the other hand, combining Co3O4 with other semiconductors results in a different PG charge carrier mechanism, leading to a decrease in the recombination process and an increase in photocatalytic activity. Therefore, this work discusses recent modifications of Co3O4 and their effects on its photocatalytic performance. Additionally, the modification effects, such as enhanced surface area, generation of oxygen vacancies, tuning the band gap, and formation of heterojunctions, are reviewed to demonstrate the feasibility of separating PG charge carriers. Finally, the formation and mechanism of these modification effects are also reviewed based on theoretical and experimental approaches to validate their formation and the transfer process of charge carriers. Keywords: Co3O4, photocatalyst, charge carrier, modification, heterojunction, energy conversion
Applied Catalysis B-environmental, 2022
The development of sustainable processes for CO 2 reduction to fuels and chemicals is one of the most important challenges to provide clean energy solutions. The use of sunlight as renewable energy source is an interesting alternative to power the electron transfer required for artificial photosynthesis. Even if redox sites are mainly responsible for this process, other reactive acidic/basic centers also contribute to the overall reaction pathway. However, a full understanding of the CO 2 photoreduction mechanism is still a scientific challenge. In fact, the lack of agreement on standardized comparison criteria leads to a wide distribution of reported productions, even using the same catalyst, which hinders a reliable interpretation. An additional difficulty is ascertaining the origin of carbon-containing products and effect of surface carbon residues, as well as the reaction intermediates and products under real dynamic conditions. To determine the elusive reaction mechanism, we report an interconnected strategy combining in-situ spectroscopies, theoretical studies and catalytic experiments. These studies show that CO 2 photoreduction productions are influenced by the presence of carbon deposits (i.e. organic molecules, carbonates and bicarbonates) over the TiO 2 surface. Most importantly, the acid/base character of the surface and the reaction medium play a key role in the selectivity and deactivation pathways. This TiO 2 deactivation is mainly initiated by the formation of carbonates and peroxo-species, while activity can be partially recovered by a mild acid washing treatment. We anticipate that these findings and methodology enlighten the main shadows still covering the CO 2 reduction mechanism, and, most importantly, provide essential clues for the design of emergent materials and reactions for photo(electro)catalytic energy conversion.
2013
Solar conversion of CO 2 to hydrocarbon fuels seems promising to reduce global warming for improved sustainability. Solar energy, as direct solar irradiations, is excessively available and it is imperious to utilize it for solar fuel production. This review paper is organized to discuss recent innovations and potential applications of phototechnology to recycle CO 2 via visible light responsive (VLR) TiO 2 -based photocatalyst. In this perspective various enhancement methods such as doping with metals and non-metals and sensitization to expand TiO 2 band gap toward visible region are critically discussed. This review paper also presents applications of VLR photocatalysts, advances in photoreactors, and future prospects of VLR based technology for conversion of CO 2 to hydrocarbon fuels. The findings of this study revealed both metals and non-metals could improve TiO 2 photoactivity, but non-metals and especially co-metals were more efficient. The combination of co-metals with sensitizers exhibited much higher CO, CH 4 and CH 3 OH yield rates. Among photocatalytic reactors, optical fibers and monolith photoreactors are more efficient because of their efficient light harvesting potential. Although the progress in CO 2 reduction to fuels is encouraging, further considerations are required for commercialization purposes.