Effect of Copper Species in a Photocatalytic Synthesis of Methanol from Carbon Dioxide over Copper-doped Titania Catalysts (original) (raw)
Related papers
Catalysis Communications, 2005
Photocatalytic reduction of CO 2 by copper-doped titania catalysts has been investigated. The photocatalysts with various copper species (Cu 0 , Cu I , Cu II) were prepared by an improved-impregnation method, where copper nitrate is doped into TiO 2 Degussa-P25. It is likely that copper present on the catalyst surface and the grain size of copper-titania catalysts is uniform, with crystallite size approximately 23 nm. The dispersion capacity of CuO in the vacant sites of TiO 2 is about 4.16 Cu 2+ nm À2 (%2.2 wt% of Cu), as indicated by XRD analysis. The activation energy (E a) for Degussa-P25 and 3%CuO/TiO 2 is ca. +26 and +12 kJ/mol, respectively. These E a values suggest that the desorption event is a rate limiting step, and the lower E a of 3%CuO/TiO 2 may suggest a catalytic role of copper species that enhance the methanol production.
In this study, Cu/TiO 2 and Cu/g-C 3 N 4 catalysts were tested for CO 2 reduction to methanol. The catalysts were prepared by the wet impregnation method and, characterized by XRD and FESEM. The product identification and yield were determined using a GC with FID. The CO 2 photoreduction process was performed in each of the following reaction mediums: H 2 O, NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , NaHCO 3 and KHCO 3. The efficiency was studied by comparing the methanol yield for each. A slurry type photoreactor with a UV lamp of 365 nm wavelength was used. CO 2 photoreduction to methanol using NaOH as the reaction medium registered the highest yield of 431.65 μmole/g-cat • hr. This is due to the higher solubility of CO 2 in the alkali as compared to that of the other reaction mediums, the ability of NaOH to serve as a hole scavenger owing to the formation of OH • ions and the higher selectivity of NaOH solution for CO 2 photoreduction to methanol. It was obvious the choice of reaction medium affected the photoreduction of CO 2 to methanol. The trend of results indicated the use of NaOH as a reaction medium improved the efficiency of the photoreduction process. The findings from this research could promote research in the field of photocatalysis by improving the yield which will encourage the support for methanol economy.
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.
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...
Photo reduction of CO 2 to methanol via TiO 2 photocatalyst
Greenhouse gas such as CO 2 is the primary cause of global warming. Alternative energy source should be provided without producing more CO 2 , such as solar energy. One of the best routes to remedy CO 2 is to transform it to hydrocarbons using photo reduction. In our study, CO 2 was photocatalytically reduced to produce methanol using a Hg lamp with wavelength 365 nm in a steady-state optical-fiber photo reactor. The optical-fiber photo reactor, comprised of near 120 Cu/TiO 2-coated fibers, was designed and assembled to transmit and spread light uniformly inside reactor. TiO 2 film was coated on optical fiber using dip-coating method. Titania and Cu-loaded solutions were prepared by a thermal hydrolysis method. The thickness of Cu/TiO 2 film was 53 nm and consisted of very fine spherical particle with diameter of near 14 nm. The XRD spectra indicated the anatase phase of all TiO 2 and Cu/TiO 2 films. The wavelength of absorption edge was on 367 nm, equivalent to near 3.3 eV. Most active Cu species on TiO 2 surface were Cu 2 O clusters, and played an important role for the formation of methanol. The methanol yield increased with UV irradiative intensity. Photo activity increased with increasing Cu loadings. Maximum methanol rate was 0.45 µmole/g-cat • hr using 1.2 wt%-Cu/TiO 2 catalyst under 16 W/cm 2 irradiation, 1.3 bar pressure of CO 2 , and 5000 seconds mean residence time. Higher than 1.2 wt% Cu loading gave less rate of methanol yield because of the masking effect of Cu 2 O clusters on the surface of TiO 2 .
Water, Air, & Soil Pollution, 2018
Photocatalytic reduction of CO 2 in seawater into chemical fuel, methanol (CH 3 OH), was achieved over Cu/C-co-doped TiO 2 nanoparticles under UV and natural sunlight. Photocatalysts with different Cu loadings (0, 0.5, 1, 3, 5, and 7 wt%) were synthesized by the sol-gel method and were characterized by XRD, SEM, UV-Vis, FTIR, and XPS. Co-doping with C and Cu into TiO 2 remarkably promoted the photocatalytic production of CH 3 OH. This improvement was attributed to lowering of bandgap energy, specific catalytic effect of Cu for CH 3 OH formation, and the minimization of photo-generated carrier recombination. Co-doped TiO 2 with 3.0 wt% Cu was found to be the most active catalyst, giving a maximum methanol yield rate of 577 μmol g-cat −1 h −1 under illumination of UV light, which is 5.3-fold higher than the production rate over C-TiO 2 and 7.4 times the amount produced using Degussa P25 TiO 2. Under natural sunlight, the maximum rate of the photocatalytic production of CH 3 OH using 3.0 wt% Cu/C-TiO 2 was found to be 188 μmol g-cat −1 h −1 , which is 2.24 times higher than that of C-TiO 2 , whereas, no CH 3 OH was observed for P25. Keywords CO 2 photoreduction. Cu/C-co-doped TiO 2. Methanol. Copper. Seawater
2016
Photoreduction of CO2 to useful chemicals have shown promising results from the research on CO2 conversion and utilization. The objective of this study is to synthesize copper and carbon nitride based titanium dioxide nanocomposites for selective photoreduction of carbon dioxide to methanol under visible light irradiations. The nanocomposites were synthesized by a chemical precipitation method and characterized using XRD, FT-IR, FESEM, TEM, DRS, BET and XPS. The XRD results confirmed the presence of TiO2, g-C3N4 and Cu in the nanocomposite by their characteristic peaks. The doping of Cu metal reduced the intensity of the PL emission and the rate of recombination. The most effective catalysts was g−C3N4/(3% Cu/TiO2) which gave a maximum methanol yield of 948.14μmol/g.cat after 2 h. Cu doped TiO2 enhanced its photoactivity by fostering carrier separation. The position of Cu in the composite affected the distribution of electrons and hence the photo-activity. Parameters investigated we...
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...
Journal of Catalysis, 2012
The photo-induced vapor-phase reaction of methanol was investigated on Pt metals deposited on pure and N-doped TiO 2. Infrared spectroscopic measurements revealed that illumination of the CH 3 OH-TiO 2 and CH 3 OH-M/TiO 2 systems led to the conversion of adsorbed methoxy species into adsorbed formate. In the case of metal-promoted TiO 2 catalysts CO bonded to the metals was also detected. Pure titania exhibited very little photoactivity, its efficiency, however, increased with the narrowing of its bandgap by N-doping, a feature attributed to the prevention of electron-hole recombination. Deposition of Pt metals on pure and N-doped TiO 2 dramatically enhanced the extent of photoreaction of methanol even in visible light: hydrogen and methyl formate with selectivities of 83-90% were the major products. The most active metal was Pt followed by Pd, Ir, Rh, and Ru. The effect of metal was explained by a better separation of charge carriers induced by illumination and by enhanced electronic interaction between metal nanoparticles and TiO 2 .
International Journal of Hydrogen Energy, 2018
To utilize the full spectrum of solar light, we prepared a series of self-organized CueTiO 2 photocatalysts via the sonothermal-hydrothermal route with high reactivity under both UV and visible region. The obtained catalysts were characterized by XRD, UVeVis, BET surface area, SEM, TEM, XPS, and TPR. The Cu species were doped in the lattice of TiO 2 and also present on the surface of TiO 2 as revealed by TEM, XPS, and TPR. Catalytic potential of prepared catalysts was checked for photocatalytic reduction of CO 2. The effects of the different base including K 2 CO 3 , Na 2 CO 3 , NaOH, KOH, the concentration of base, catalyst amount, copper doping amount, light source, reaction medium and reaction time were monitored to get optimum reaction conditions. The Cu 2 eTiO 2 catalyst performed the best; 6.6 mmol g À1 of methane, 472.5 mmol g À1 methanol, and 743.8 mmol g À1 of acetone were obtained in KOH/H 2 O medium in 24 h under UVA. While in acetonitrile (ACN)/Triethanolamine (TEOA)/H 2 O mixture, the Cu 2 eTiO 2 catalyst was able to selectively catalyze methanol formation (99.99%) 8469.6 mmol g À1 in 24 h under visible light. The formation of H is also an intermediate step in the photocatalytic reduction of CO 2. Therefore, the Cu 2 eTiO 2 catalyst was also tested for H 2 production with or without CO 2 at different reaction media such as H 2 O, KOH/H 2 O, ACN/H 2 O, ACN/TEOA/H 2 O under UVA light. The highest H 2 production, i.e., 152.0 mmol g À1 was observed with ACN/TEOA/H 2 O in the presence of CO 2 in 8 h. The prepared series of CueTiO 2 catalysts are highly active for CO 2 reduction and H 2 production.