Photocatalytic CO 2 reduction vs. H 2 production: The effects of surface carbon-containing impurities on the performance of TiO 2 -based photocatalysts (original) (raw)
Related papers
Photocatalytic reduction of CO2 with H2O on TiO2 and Cu/TiO2 catalysts
Research on Chemical Intermediates, 1994
Abstraet-Photoinduced reduction of CO 2 by H20 to produce CH 4 and CHaOH has been investigated on wellcharacterized standard TiO 2 catalysts and on a Cu 2 § loaded TiO 2 catalyst. The efficiency of this photoreaction depends strongly on the kind of catalyst and the ratio of H20 to CO 2. Anatase TiO2, which has a large band gap and numerous surface OH groups, shows high efficiency for photocatalytic CH 4 formation. Photogenerated Ti 3* ions, H and CH 3 radicals are observed as reactive intermediates, by ESR at 77 K. Cu-loading of the small, powdered TiO 2 catalyst (Cu/TiO2) brings about additional formation ofCH3OH. XPS studies suggest that Cu § plays a significant role in CH3OH formation.
Photocatalysis for Hydrogen Production and CO2 Reduction: The Case of Copper-Catalysts
ChemCatChem
Problems derived from climate change dictate the reestablishment of our prospective in energy production. In this direction, converting solar energy through photocatalysis into suitable fuels such as hydrogen and carbon-based fuels by water splitting and CO 2 reduction, respectively, has been established as a promising approach. Currently, the main concern in this field is the development of cost-effective and efficient photocatalysts. Among the different systems studied, Cu-based photocatalysts are considered attractive candidates for both applications due to their relative low-cost, the natural abundance of the constituents and their promising reactivity. In this review, the current progress in the field of Cu-based photoactive materials for both H 2 production and CO 2 reduction will be discussed. Finally, an outlook on the challenges and future research directions is given.
On the current status of the mechanistic aspects of photocatalytic reduction of carbon dioxide
2017
Photocatalytic reduction of carbon dioxide, one of the pathways involved in the carbon dioxide conversion process, has been receiving significant attention from the scientific community in the last four decades. Nevertheless, the mechanism of carbon dioxide reduction is still unclear and the information available is not sufficient for developing it into large scale applications, possibly because of the invariable hurdles associated with the reduction process. The reductive photocatalytic conversion of CO2 involves all the redox reactions occurring at the interface of the semiconductor such as water splitting, hydrogen evolution, oxygen evolution, photo-oxidation reactions and reactions of radical intermediates. The overall product yield is highly dependent on the extent of these competing reactions. Herein, we discuss our perceptions and current status of the interface reactions and their involvement in the fundamental mechanistic aspects of the photocatalytic conversion of CO2.
Photocatalytic CO 2 reduction by H 2 O and/or H 2 reductant to selective fuels over Cu-promoted In 2 O 3 /TiO 2 photocatalyst has been investigated. The samples, prepared via a simple and direct sol-gel method, were characterized by XRD, SEM, TEM, XPS, N 2 adsorption-desorption, UV–vis diffuse reflectance, Raman and PL spectroscopy. Cu and In loaded into TiO 2 , oxidized as Cu 2+ and In 3+ , promoted efficient separation of photo-generated electron/hole pairs (e − /h +). The results indicate that the reduction rate of CO 2 by H 2 O to CH 4 approached to 181 mol g −1 h −1 using 0.5% Cu-3% In 2 O 3 /TiO 2 catalyst, a 1.53 fold higher than the production rate over the 3% In 2 O 3 /TiO 2 and 5 times the amount produced over the pure TiO 2. In addition, Cu was found to promote efficient production of CH 3 OH and yield rate reached to 68 mol g −1 h −1 over 1% Cu-3% In 2 O 3 /TiO 2 catalyst. This improvement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. More importantly, H 2 reductant was less favorable for CH 4 production, yet a significant amount of CH 4 and CH 3 OH were obtained using a mixture of H 2 O/H 2 reductant. Therefore , Cu-loaded In 2 O 3 /TiO 2 catalyst has shown to be capable for methanol production, whereas product selectivity was greatly depending on the amount of Cu-loading and the type of reductant. A photocatalytic reaction mechanism was proposed to understand the experimental results over the Cu-loaded In 2 O 3 /TiO 2 catalyst.
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.
Reduction of CO2 photocatalyzed by Cu-TiO2-based catalysts: a review
Revista de Energía Química y Física
The continuous combustion of non-renewable fossil fuels and the depletion of the natural resources from which they come and, consequently, the continuous increase of carbon dioxide (CO2) emissions into the atmosphere are intensifying the search for the conversion of carbon dioxide to fuels and value-added chemicals, with the main objective of reducing emissions and creating renewable and sustainable energy sources. In this sense, there is a lot of interest in the photocatalytic reduction of CO2 with H2O, mainly using solar energy, which is a renewable source with a continuous and easily available light supply. Recent progress in this area has focused on the development of promising photocatalysts, primarily based on TiO2. In this context, this article analyzes: (i) the role of CO2 in the treatment of problems related to energy and global warming, (ii) the fundamental knowledge of the photocatalytic reduction of CO2, (iii) the role of the catalysts of copper-doped TiO2 in the photoca...
The use of CO2 for the production of fuels and chemicals has attracted much attention under the current background of the depletion of fossil resources and the increase of emissions of CO2. However, the activation of CO2, a very stable molecule, is one of the biggest challenges in chemistry. In the long term, the photocatalytic conversion of CO2 using solar energy, that is, the artificial photosynthesis, is the most attractive route for the transformation of CO2 to fuels and chemicals. Since the pioneering work by Inoue et al.,[1] many studies have been devoted to the semiconductor-based photocatalytic reduction of CO2 with H2O and the pace has increased enormously in recent years.[2] Several kinds of semiconductors such as TiO2,[2] Ga2O3,[3] ZnGe2O4,[4] ZnGa2O4,[5] and BaLa4Ti4O15 [6] have been reported for the photocatalytic conversion of CO2, although the activity is still very low.
On the mechanism of photocatalytic CO 2 reduction with water in the gas phase
Catalysis Today
The mechanism of photocatalytic reduction of CO 2 with H 2 O over Pt-TiO 2 films produced by the sol-gel deposition over glass beads was investigated. The accumulation of significant amount of carbonaceous intermediate on the surface followed by deactivation indicated the rate limiting reaction is the water splitting reaction, similar to the natural photosynthetic systems. When gas phase hydrogen was allowed in the system, the carbonaceous intermediates were converted to methane at rates higher than the artificial photosynthesis conditions. In the presence of hydrogen, formation of methane reaction proceeded in the dark albeit at lower rates. The progress of the reaction is very similar to the natural photosynthetic reactions however the rates are seven orders of magnitude slower than the reactions in the natural photosynthetic processes. Furthermore, the role of spilled over hydrogen in the reaction was also demonstrated.
Insight into the Roles of Metal Loading on CO2 Photocatalytic Reduction Behaviors of TiO2
Nanomaterials, 2022
The photocatalytic reduction of carbon dioxide (CO2) into value-added chemicals is considered to be a green and sustainable technology, and has recently gained considerable research interest. In this work, titanium dioxide (TiO2) supported Pt, Pd, Ni, and Cu catalysts were synthesized by photodeposition. The formation of various metal species on an anatase TiO2 surface, after ultraviolet (UV) light irradiation, was investigated insightfully by the X-ray absorption near edge structure (XANES) technique. CO2 reduction under UV-light irradiation at an ambient pressure was demonstrated. To gain an insight into the charge recombination rate during reduction, the catalysts were carefully investigated by the intensity modulated photocurrent spectroscopy (IMPS) and photoluminescence spectroscopy (PL). The catalytic behaviors of the catalysts were investigated by density functional theory using the self-consistent Hubbard U-correction (DFT+U) approach. In addition, Mott–Schottky measurement ...