Controlled addition of Cu/Zn in hierarchical CuO/ZnO p-n heterojunction photocatalyst for high photoreduction of CO2 to MeOH (original) (raw)
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CuO/ZnO/g-C3N4 heterostructures as efficient visible light-driven photocatalysts
Journal of environmental chemical engineering, 2019
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2018
As rising atmospheric CO2 levels change Earth’s climate change, CO2 reduction has become an increasingly active area in energy research over the past several years. The present work is developing artificial photosynthesis technologies that use visible light to convert CO2 and water into methanol. In this study, TiO2 loaded copper oxide (CuO-TiO2) was synthesized, characterized and studied for photoelectrochemical (PEC) reduction of CO2 into methanol under visible light (λ > 470 nm) irradiation. In this perspective, the catalyst was synthesized via Sol-gel method. Catalyst characterization was done by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectra, and Mott-Schottky (MS). Linear sweep voltammetry (LSV) was employed to evaluate the photocatalytic activity of the prepared photocatalyst under visible light (λ >420 nm) irradiation for CO2 reduction reactions. XRD results indicated that the particle size of the as-prepared photocatalyst wa...
Effect of copper on the performance of ZnO and ZnO1−xNx oxides as CO2 photoreduction catalysts
Catalysis Today, 2013
The photocatalytic conversion of carbon dioxide using water as electron donor to produce fuels, frequently known as artificial photosynthesis (AP), has a great interest due to its potential to reduce anthropogenic CO 2 emissions. In this paper, ZnO-based materials have been investigated as photocatalysts for the AP process. Different synthesis approaches have been studied in order to improve the physicochemical properties of ZnO-based materials. The effect of a variety of chemical and morphological modifications has been explored as a way to enhance the photocatalytic properties of this semiconductor: a) N-doping to produce changes in the band structure, b) use of a porogen agent to improve the textural properties, leading to a mesoporous ZnO, and c) Cu deposition and doping to induce a decrease of the electrons-holes recombination rate and also to act as co-catalyst. The best results have been obtained with the Cu addition over the mesoporous ZnO, resulting in an enhancement of the CO 2 conversion and leading to the formation of CO, H 2 , CH 4 and CH 3 OH as main products.
Hierarchical CuO/ZnO “corn-like” architecture for photocatalytic hydrogen generation
International Journal of Hydrogen Energy, 2011
Novel high efficient photocatalyst is the key for photocatalytic hydrogen generation from water splitting. In this study, a novel hierarchical CuO/ZnO "corn-like" architecture was designed and synthesized via a combination of hydrothermal and photodeposition method. The as-prepared nanostructured materials was shown to effectively generate hydrogen in the mixture of methanol and water (v/v ¼ 1:10). This is because the hierarchical CuO/ZnO "corn-like" architecture: 1) greatly enhances the light utilization rate due to its special architecture, 2) enlarges the specific surface area, providing more reaction sites and promoting mass transfer, 3) promotes the photogenerated electrons transfer from ZnO to CuO, achieving the anti-recombination effect of electrons and holes, and 4) avoids the photocorrosion of ZnO to improve the stability of ZnO as a catalyst during water splitting. Moreover, the novel hierarchical CuO/ZnO "corn-like" architecture is easily recovered for reuse.
Applied Catalysis B: Environmental, 2010
a b s t r a c t Efficient ZnO based visible-light photocatalysts, Cu(II) modified Cd x Zn 1−x O were developed by adopting a hybrid approach, consisting of band-engineering by formation of a solid solution and surface modification of co-catalysts. The Cd x Zn 1−x O solid solution exhibited the visible-light activity for decomposing gaseous acetaldehyde, while bare ZnO showed negligible activity under visible-light. Further, the visible-light activity of Cd x Zn 1−x O photocatalysts was greatly improved by the surface modification of Cu 2+ ions. Photogenerated electrons in Cd x Zn 1−x O are injected into the modified Cu 2+ ions under visible-light irradiation, and electrons in Cu 2+ /Cu + redox couples cause the efficient reduction of absorbed oxygen molecules. The strategy in the present study is a promising approach for applying ZnO-based photocatalysts for indoor applications.
Journal of Nanoscience and Nanotechnology, 2013
The p-n junction photocatalyst, p-CuO/n-ZnO, was prepared via ball milling of ZnO and CuO nanoparticles in water. The structural, optical, and surface properties of the p-n junction photocatalyst p-CuO/n-ZnO were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectroscopy, and Zeta potential analyzer. The PCA of the photocatalyst was evaluated via photocatalytic oxidation of Methylene Blue (MB) in the presence of UV light. This study demonstrates a novel p-n junction oxide photocatalyst p-CuO (wt. 10%)/n-ZnO having superior photocatalytic activity (PCA) for the degradation of model dye under the illumination of UV-Vis light. The MB solution was degraded by 100% within 15 min by the use of CuO (wt. 10%)/ZnO photocatalyst. Effectivley 365% increase in degradation rate constant was notice for CuO (10 Wt.%)/ZnO nanocomposite as compared to that of pure ZnO nanoparticles. The enhanced PCA is anticipated from the presence of many micro p-n junctions formed between ZnO-CuO nanoparticles upon ball milling, which helps in efficient electron/hole pair charge separation upon excitation. The study highlights the fact that PCA of p-n junction CuO/ZnO photocatalyst can be effectively tuned by manipulating the interface of the heterostructure and by adjusting the parameters affecting the PCA. The result obtained from PCA is further verified by the zeta potential study.
Journal of alloys and compounds , 2017
In the present study, we report morphology dependent photocatalytic activity of CuO/ZnO nanorods by simple chemical synthesis for the first time. The nanorod morphology was clearly evidenced by field emission scanning electron microscope (FESEM) and hig resolution transmission electron microscope (HRTEM) analysis and confirmed the particle size of 20 nm. The composition and oxidation states of the CuO/ZnO nanorods were confirmed by XPS analysis. The potential efficacy of CuO/ZnO nanorods was evaluated towards the photocatalytic degradation of congo red (CR) and rhodamine B (RhB) dye solution. Very interestingly, the CuO/ZnO nanorods showed significantly superior photocatalytic activity compared to CuO, ZnO, a mixture of nano CuO and nano ZnO. The complete degradation of dye solution was successfully achieved within a short span of time. The effects of the different operational parameters viz amount of photocatalyst loading, initial concentration and pH were evaluated and the optimum condition for the superior activity was discovered. The prevention of the electron-hole pair recombination was strongly evidenced by photoluminescence (PL) analysis. Importantly, active involvement of hydroxyl radical in the photocatalytic degradation mechanism was strongly supported by the trapping experiments using different scavengers and fluorescence analysis. The CuO/ZnO nanorods photocatalyst also showed excellent degradation activity against the mixed dye solutions (CR and RhB). The stability and reusability results were clearly indicated that the sustainability of the CuO/ZnO nanorods in the photocatalytic reaction.
Morphology-dependent photocatalytic activities of hierarchical microstructures of ZnO
Materials Letters, 2011
CuO nanoparticles have been extensively used as a photocatalyst because of their superior activity, selectivity and stability properties. The catalytic efficiency of these oxide nanoparticles can be improved by varying the size and shape of nanoparticles. Here, we report the synthesis of different shaped CuO nanoparticles and their impregnation on TiO 2. Optical analysis revealed that a considerable red shift (420 nm to 550 nm) in absorption spectra of CuO-TiO 2 nanocomposites was observed compared to bare CuO nanoparticles. DLS measurements showed that the average hydrodynamic size of CuO nanostars was increased from 160 nm to 584 nm after deposition on TiO 2. These nanocomposites were examined for photocatalytic degradation of methyl orange under sunlight radiation. It was observed that CuO-TiO 2 nanostars exhibited superior photocatalytic efficiency compared to CuO-nanoneedles, nanocrumbles and bare CuO nanoparticles. The CuO nanoparticles act as co-catalyst on the surface of TiO 2 and alter the physicochemical properties of TiO 2. The higher activity arises due to the fact that the doping of CuO reduces the recombination of charge carries (e − −h + and creates the intra-gap states which result in higher absorption of light radiations. Therefore, CuO nanoparticles impregnated on TiO 2 found to be an effective and ideal catalyst for the photodegradation of methyl orange dye.
Nanomaterials, 2020
The construction of heterostructured photocatalyst with an appropriate energy band structure will help realize highly efficient photo-excited charge separation. In this study, ternary CuO/CeO2/ZnO nano-particle (NP) composites were synthesized by a facile two-step sol-gel method, which exhibit significantly enhanced photocatalytic degradation performance for various organic pollutants under UV and visible light excitation. The photo-responses to both UV and visible light, as well as the visible light absorption and utilization rates of ZnO are found to be synergistically intensified by CeO2 and CuO co-coupling. The first-order kinetic constants (K) of 3%CuO/CeO2/ZnO for methylene blue (MB) degradation are ~3.9, ~4.1 and ~4.8 times higher than ZnO under UV light, visible light and simulated sunlight illumination, respectively. The roles of CuO and CeO2 in optical properties and photo-degradation under UV and visible light were explored. Besides, the photogenic holes (h+) of ZnO, CeO2...
p-Type Cu 2 O/n-type ZnO core/shell photocatalysts has been demonstrated to be an efficient photocatalyst as a result of their interfacial structure tendency to reduce the recombination rate of photogenerated electron− hole pairs. Monodispersed Cu 2 O nanocubes were synthesized and functioned as the core, on which ZnO nanoparticles were coated as the shells having varying morphologies. The evenly distributed ZnO decoration as well as assembled nanospheres of ZnO were carried out by changing the molar concentration ratio of Zn/Cu. The results indicate that the photocatalytic performance is initially increased, owing to formation of small ZnO nanoparticles and production of efficient p−n junction heterostructures. However, with increasing Zn concentration, the decorated ZnO nanoparticles tend to form large spherical assemblies resulting in decreased photocatalytic activity due to the interparticle recombination between the agglomerated ZnO nanoparticles. Therefore, photocatalytic activity of Cu 2 O/ZnO heterostructures can be optimized by controlling the assembly and morphology of the ZnO shell.