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Design of spatially separated Au and CoO dual cocatalysts on hollow TiO2 for enhanced photocatalytic activity towards the reduction of CO2 to CH4
摘要： Photocatalytic reduction of CO2 to solar fuels has been considered as a promising route to solve the energy crisis and environmental issues. Herein, the spatially separated CoO and Au dual cocatalysts are used as the hole and electron collectors, which are loaded on the internal and external surface of TiO2 hollow sphere (THS), respectively (denoted as Aux@THS@CoO). It is found that the Au nanoparticle and Co species are homogenous deposited on the surface of THS without doping. DRS results show that the photoabsorption performances of THS are enhanced obviously in the visible light region. XPS analysis reveals that an internal electric field is constructed, which could promote the separation of photoinduced charge carriers. Subsequently, Au2.0@THS@CoO displays the highest photocurrent density compared with the counterparts. Furthermore, the results of CO2 adsorption, ESR spectra and in-situ FTIR spectra show the high adsorption capacity of CO2 on the sample and the chemisorption of CO2 on the oxygen defects of THS conversed into the active intermediate CO2-. As a result, Au2.0@THS@CoO presents a remarkably enhanced photocatalytic activity for the reduction of CO2 with H2O in CH4. The optimal activity of the catalyst is 13.3 μmol h-1 g-1, which is 60 times higher than that of THS. In addition, in-situ FTIR spectra also suggest that H2O participates in the reaction as electron donator and hole scavenger during the photocatalysis process. Finally, a possible photocatalytic process has also been proposed.
关键词： Photocatalysis,Synergistic effect,Spatial separation,Dual cocatalysts,CO2 reduction
更新于2025-09-04 15:30:14
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Enhanced photocatalytic carbon dioxide reforming of methane to fuels over nickel and montmorillonite supported TiO2 nanocomposite using monolith photoreactor
摘要： Conversion of carbon dioxide (CO2) and methane (CH4) to fuels using photo-technology is a cleaner pathway compared to thermal reforming, since its uses only light irradiations, while producing valuable chemicals. In this study, structured nickel (Ni) and montmorillonite (MMT) supported TiO2 composite, synthesized by a sol-gel method, was tested for photocatalytic reduction of CO2 using fixed-bed and monolith photoreactors. The performance of structured nanocatalyst was evaluated using CO2-H2 system via photocatalytic reverse water gas shift (RWGS) reaction and CO2-CH4 system via photocatalytic dry reforming of methane (DRM). Using photocatalytic RWGS, CO was detected as the main products, while the performance of Ni-MMT/TiO2 composite was expressively higher than using MMT/TiO2 and TiO2 catalysts. This was obviously due to larger surface area by MMT dispersion and hindered charges recombination rate by Ni. Similarly, using DRM, H2 and CO were the main products, while their selectivity was greatly dependent on the initial CH4/CO2 molar feed ratios. At a lower CH4/CO2 ratio, more CO was produced, while a higher feed ratio promoted H2 production. This shows, composite catalyst was more favorable for CO2 adsorption, while CH4 was competitively adsorbed during photo-catalysis process. Comparatively, Ni-MMT/TiO2 catalyst reveals higher photo-activity and selectivity in a monolith photoreactor than using fixed-bed reactor under the same operating conditions. This enhanced photoactivity was due to higher photonic flux with enlarged active surface area due to monolithic support and efficient sorption process. The stability of Ni/TiO2 dispersed MMT for CO and H2 production via DRM process sustained in cyclic runs using monolithic support. Hence, using Ni/MMT modified TiO2 catalyst and monolith photoreactor, CO2 and CH4 can efficiently be converted to renewable fuels under light irradiations and would be a great benefit to the environment.
关键词： Photo-technology,Ni/TiO2,Dry reforming of CH4,Monolith photoreactor,Montmorillonite,CO2 reduction
更新于2025-09-04 15:30:14
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Generic Assay of Sulfur-Containing Compounds Based on Kinetics Inhibition of Gold Nanoparticle Photochemical Growth
摘要： This work describes a new, equipment-free, generic method for the determination of sulfur-containing compounds that is based on their ability to slow down the photoreduction kinetics of gold ions to gold nanoparticles. The method involves tracking the time required for a red coloration to appear in the tested sample, indicative of the formation of gold nanoparticles, and compare the measured time relative to a control sample in the absence of the target analyte. The method is applicable with minimal and simple steps requiring only two solutions (i.e., a bu?er and a gold solution), a source of light (UV or visible), and a timer. The method responds to a large variety of sulfur-containing compounds including thiols, thioesters, disul?des, thiophosphates, metal?sulfur bonds, and inorganic sulfur and was therefore such as applied to the determination of a variety of compounds dithiocarbamate and organophosphorous pesticides, biothiols, pharmaceutically active compounds, and sul?des in di?erent samples such as natural waters and wastewater, biological ?uids, and prescription drugs. The analytical ?gures of merit of the method include satisfactory sensitivity (quantitation limits at the low μM levels), good recoveries (from 93 to 109%), and satisfactory reproducibility (from 4.8 to 9.8%). The method is easily adoptable to both laboratory settings and nonlaboratory conditions for quantitative and semiquantitative analysis, respectively, is user-friendly even for the minimally trained user, and can be performed with limited resources at low cost.
关键词： equipment-free method,sulfur-containing compounds,time-based assay,gold nanoparticles,photochemical reduction
更新于2025-09-04 15:30:14
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Multi-electron reduction of Wells–Dawson polyoxometalate films onto metallic, semiconducting and dielectric substrates
摘要： The investigation of conditions allowing multi-electron reduction and reoxidation of polyoxometalate (POM) films onto solid substrates is considered an issue of critical importance for their successful incorporation in electronic devices, different types of sensors and catalytic systems. In the present paper, the rich multi-electron redox chemistry of films of Wells–Dawson ammonium salts, namely (NH4)6P2Mo18O62 and (NH4)6P2W18O62, on top of metallic (Al), semiconducting (ITO) and dielectric (SiO2) substrates under ambient conditions is investigated. The respective Keggin heteropolyacids, H3PMo12O40 and H3PW12O40, are also investigated for comparison. On Al substrates, the Wells–Dawson ammonium salts are found to be significantly more reduced (4–6e?) compared to the respective Keggin heteropolyacids (≤2e?), in accordance with their deeper lying lowest unoccupied molecular orbital (LUMO) level. Subsequent thermal treatment in air results in reoxidation of the initially highly reduced POM films. Similar behavior is found on ITO substrates, but in initially less reduced (2–4e?) Wells–Dawson POM films. On the other hand, on SiO2 substrates, the thermal reduction of (NH4)6P2Mo18O62 film is observed and attributed to the thermal oxidation of ammonium counterions by [P2Mo18O62]6? anions. Overall, the multi-electron reduction of Wells–Dawson ammonium salts onto metallic and semiconducting substrates (Al, ITO) is determined by the relative position of the LUMO level of POMs in relation to the Fermi level of the substrate (i.e. substrate work function) and affected in a synergistic way by the presence of ammonium counterions. In contrast, on dielectric substrates (SiO2) the reduction of Wells–Dawson POMs ((NH4)6P2Mo18O62) is attributed only to the oxidation of ammonium counterions.
关键词： Polyoxometalates,Semiconducting substrates,Ammonium counterions,Wells–Dawson ammonium salts,Redox chemistry,Keggin heteropolyacids,Metallic substrates,Dielectric substrates,Thermal treatment,Multi-electron reduction
更新于2025-09-04 15:30:14
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Three-Dimensional Superlattices Based on Unusual Chalcogenide Supertetrahedral In–Sn–S Nanoclusters
摘要： Reported here are two novel metal chalcogenide superlattices built from unusual supertetrahedral TO2-InSnS clusters. With regard to only one previously reported case of a TO2-InS-based 2D-layered structure, such a combination of In?Sn?S components is leading to the first observation of 3D superlattices based on TO2-InSnS clusters. Besides, these title semiconducting materials also display good performance on the electrocatalytic oxygen reduction reaction.
关键词： 3D superlattices,metal chalcogenide,electrocatalytic oxygen reduction reaction,supertetrahedral clusters
更新于2025-09-04 15:30:14
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Enhanced photocatalytic simultaneous removals of Cr(VI) and bisphenol A over Co(II)-modified TiO2
摘要： To enhance the electron-hole separation and boost the practical performance of commercial titania (Degussa P25) under natural solar light, in this work, P25 was modified with Co(II) species (CoP25) through post-treatment with decomposition of Co-EDTA precursors in a wet chemical anchoring process. With appropriate Co(II) loading amount as molecular cocatalyst, the resulted CoP25-4 showed significantly improved photocatalytic performance for Cr(VI) reduction and bisphenol A (BPA) oxidation under UV-light irradiation. The co-existence of Cr(VI) and BPA promoted mutually the degradation of both pollutants. Under simulated solar light (AM 1.5G) illumination, the Cr(VI) reduction rate over CoP25-4 was 8.5 times enhanced compared with that over P25, while the simultaneous degradation rate of BPA over CoP25-4 was 8 times higher than that over P25. Further investigations indicated that the covalent atomic Co(II) anchoring on P25 significantly promoted the photogenerated electron-hole separation and facilitated Cr(VI) reduction via the formation of Co(I) intermediate and simultaneously boosted BPA oxidation. Our results demonstrated a facile strategy to modify P25 with remarkably improved performance for the practical application in environmental pollution management under natural light excitation.
关键词： bisphenol A,electron-hole separation,Cr(VI) reduction,photocatalytic,Co(II)-modified TiO2
更新于2025-09-04 15:30:14
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Enabling the electrocatalytic fixation of N <sub/>2</sub> to NH <sub/>3</sub> by C-doped TiO <sub/>2</sub> nanoparticles under ambient conditions
摘要： The conventional Haber–Bosch process for industrial NH3 production from N2 and H2 is highly energy-intensive with a large amount of CO2 emissions and finding a more suitable method for NH3 synthesis under mild conditions is a very attractive topic. The electrocatalytic N2 reduction reaction (NRR) offers us an environmentally benign and sustainable route. In this communication, we report that C-doped TiO2 nanoparticles act as an efficient electrocatalyst for the NRR with excellent selectivity. In 0.1 M Na2SO4, it achieves an NH3 yield of 16.22 mg h?1 mgcat.?1 and a faradaic efficiency of 1.84% at ?0.7 V vs. the reversible hydrogen electrode. Furthermore, this catalyst also shows good stability during electrolysis and recycling tests.
关键词： ambient conditions,C-doped TiO2 nanoparticles,NH3 synthesis,electrocatalytic N2 reduction reaction
更新于2025-09-04 15:30:14