查看更多>>摘要：? 2022 Elsevier B.V.Hydrogen generation from electrical water splitting has become a greatly increasing requirement for energy systems, however, highly effective and durable electrocatalysts towards universal-pH hydrogen evolution reaction (HER) remain a big challenge. Herein, we design and synthesize ruthenium di-phosphide (RuP2) confined in carbon layers (RuP2-C) with a unique yolk-shell structure (RuP2-C@RuP2-C) from MOF. As expected, it not only exceeds the HER activity of Pt catalysts, with very tiny overpotentials at 10 mA cm?2 (9 and 17 mV in 1.0 M KOH and 0.5 M H2SO4, individually), but also has high stability. Besides, it also exhibits a low overpotential (40 mV) close to Pt catalysts and high stability in 1.0 M PBS, indicating that RuP2-C@RuP2-C (RPC@RPC) owns outstanding HER performance at all pH values. Density functional theory (DFT) calculation results further unravel that the P-site on the surface of RPC@RPC possesses low hydrogen adsorption energy, beneficial for boosting the HER activity.
查看更多>>摘要：? 2021 Elsevier B.V.Aiming at improving the activity of supported catalysts toward oxidative desulfurization (ODS) reaction, an increasing support utilization rate strategy is developed by introducing additional phosphotungstic acid (HPW) on V anchored zeolite SiBeta. Both the Keggin HPW on the surface of SiBeta and the tetrahedral V species into the framework of SiBeta possess high intrinsic catalytic activity for the oxidation of sulfides. Grafting V species into the framework of SiBeta can create Lewis acid sites and HPW serves as a typical source of Br?nsted acidity, while the synergistic effect between Lewis and Br?nsted acids contributes to the formation of numerous peroxometallate complexes with strong oxidizing capacity. The obtained catalyst exhibits outstanding catalytic performance toward ODS reaction and can adsorb ODS products, thus removing them from oil phase. In addition, series of efficient catalysts were prepared by adjusting the types of heteropolyacids and transition metal (V, Ti, Nb and Zr) to control their acidity. It is indicated that the ODS activity is favored by the enhancing the strength and density of Lewis acid sites and the density of Br?nsted acid sites. Such concepts of engineering both increasing support utilization and synergistic effect of dual-active sites herald a new paradigm for the construction of supported catalysts.
查看更多>>摘要：? 2021 Elsevier B.V.In this study, we demonstrated high-rate H2 generation by coupling with the sulfite oxidation reaction (SOR) as an alternative to the oxygen evolution reaction for solar H2 production. The emerging and cost-effective molybdenum phosphide electrocatalyst was appropriately optimized and used as a bifunctional catalyst in an alkaline electrolyte for both SOR and HER. Powered by state-of-the-art perovskite–Si tandem photovoltaics, a remarkable photocurrent density of over 17 mA cm?2 was achieved in the HER coupled with the SOR. In addition to the significantly enhanced photocurrent, the SOR can further reduce the overall cost of solar H2 production owing to the elimination of the expensive membranes required for H2 and O2 gas separation. Considering the high global demand for desulfurization via the SOR, the strategy proposed here will enable practical H2 production from renewable sources while effectively converting the toxic SO2 gas into a value-added product for the chemical industry.
查看更多>>摘要：? 2021 Elsevier B.V.Solar-driven conversion of nitrogen (N2) into ammonia (NH3) is a promising alternative to the Haber-Bosch process, while still suffers from low conversion efficiency due to inactive N[tbnd]N bond. Herein, a novel pathway of photocatalytic air redox reaction (ARR) to ammonia via NO is proposed and tested over an effective catalyst of oxygen-vacancy-rich bimetallic Cu-Co organic framework ultrathin nanosheets (OVR-CuCo-MOFs NS) under visible light. The catalyst with unique oxygen defective sites shows an excellent NH3 synthesis rate from air (287.76 ± 7.02 μmol g-1·h-1), which is 5.4-fold higher than that from pure N2. Moreover, experiments and theoretical calculations indicate that the transformation of air mainly follows a redox pathway, in which N2 and O2 can be trapped at the oxygen vacancies to generate nitric oxide (*NO) and further be reduced to ammonia by visible light. The ARR process shows a lower barrier of free energies in the onset activation step (*N2 → *N-NO, ?0.08 eV) and rate-limiting step (*NO → *NHO, 1.23 eV) compared with those of traditional nitrogen reduction (*N2 → *N-NH, 1.48 eV and H2N-NH2 → *NH2, 1.29 eV, respectively). This work provides a new and sustainable pathway for photo-driven ammonia synthesis.
查看更多>>摘要：? 2021 Elsevier B.V.Photocatalytic water-splitting to generate hydrogen (H2) and hydrogen peroxide (H2O2) is a green and renewable method to convert solar energy into chemical energy. The water impurity in organic solvents is usually hard to be removed. Here, we firstly used an organic semiconductor (DAnTMS) synthesized from 9,10-dibromoanthracene and trimethylsilylacetylene to convert the water impurity in organic solvent into H2 and H2O2 by photocatalysis. Under visible light, for 300.0 μL water in 20.0 mL methyl cyanide (MeCN) system, the DAnTMS catalyst can produce H2 and H2O2 with rate of 245.9 μmol g?1 h?1 and 3923.4 μmol g?1 h?1, respectively. Furthermore, a practical photocatalytic experiment was performed in 20.0 mL commercially available MeCN (99.8%, H2O ≤ 0.01%) with 10.0 mg DAnTMS as catalyst, in which, the total 15.4 μmol H2 and 176.7 μmol H2O2 were generated after 12 h reaction, suggesting the water impurity in MeCN was completely removed. In present catalytic system, on DAnTMS, O2 and H2O are reduced into H2O2 and H2, respectively, while, H2O is oxidized into H2O2 through a 2e- pathway.
查看更多>>摘要：? 2022 Elsevier B.V.In-decorated PdAu catalysts were synthesized and investigated for the aqueous reduction of nitrate. We first synthesized PdAu nanoparticles (NPs) with varying Pd:Au ratios onto which we deposited In. These In-on-PdAu NPs showed higher activity than In-on-Pd NPs for NO3- (kcat=4.0–7.2 vs 2.7 L/gtotal_(Pd+In)/min) due to electronic and ensemble effects. Au-rich NPs had lower activity (kcat=1.3–1.5 L/gtotal_(Pd+In)/min) due to unfavorable hydrogen and nitrate/nitrite binding energies. In-on-PdAu NPs showed higher N2 selectivity than In-on-Pd NPs (90 +% vs 60% at 40% conversion), and had higher activity for NO2-. Density functional theory calculations suggest that Au weakens metal-N bonding which enables nitrite reduction over Pd. Nitrate reduction is promoted by greater mobility of H-adatoms to regenerate InOx and faster spillover of nitrite onto PdAu. When challenged with species found in drinking water, the trimetallic NPs were more active than bimetallic NPs (1.0–1.6 vs 0.6 L/gtotal_(Pd+In)/min). These results expand the prospects of practical catalytic denitrification.
查看更多>>摘要：? 2021 Elsevier B.V.Fe singly anchored onto graphite carbon nitride (Fe-SA/PHCNS) as [tbnd]Fe-N6 was synthesized to realize efficient peroxymonosulfate (PMS) activation and superior organic pollutant oxidation. The [tbnd]Fe-N6 was the core catalytic site of activation via forming high-valent iron–oxo species ([tbnd]FeN6 =O) as the transient reactive intermediate as evidenced by X-ray adsorption fine spectroscopy (XAFS), in-situ Raman spectrum and theoretical calculation. The cycle of [tbnd]Fe-N6 and [tbnd]FeN6 =O interconversion was sustainably observed with organic pollutant as the electron-donor and PMS as the electron-acceptor. As results, the equivalent steady state concentration of [tbnd]FeN6 =O was as high as 2.39 × 10?8 M and this system exhibited 97.2% average PMS utilization rate. Fe-SA/PHCNS can be immobilized onto carbon felt for the simultaneous filtration and oxidation with stable and efficient performance. This study elucidated the mechanism and superiority of [tbnd]FeN6 =O mediated oxidation pathway and can advance the research and application of this new approach in advanced oxidation processes.
查看更多>>摘要：? 2022 Elsevier B.V.A green and solvent-free aerobic protocol for ethybenzene (EB) oxidation mediated by efficient and stable solid catalysts remains a big challenge. In the present study, we report a finding of phase-dependent reactivity of MnO2 materials with α, β, and δ phases, with the order of EB oxidation performance following δ-MnO2 > α-MnO2 > β-MnO2. A clear negative correlation exists between the reactivity and average oxidation state (AOS) value of Mn, while positive correlations can be found between the reactivity and (Mn2++Mn3+)/Mn4+ ratio and OII/OI ratio. DFT studies also validate that molecular oxygen can be adsorbed and activated much more easily over the δ-MnO2, contributing to the generation of active oxygen species. This work provides insights into the MnO2-based materials with different crystal phases for catalytic synthesis of high value-added chemicals.
查看更多>>摘要：? 2022 Elsevier B.V.The effect of UV irradiation on titanium dioxide catalyzed glucose conversion in value added molecules was studied at high temperatures, 120–150 °C, in anaerobic conditions. The reaction was implemented in a batch reactor designed to combine high temperature/pressure and irradiation. Inhibition of the titanium dioxide catalytic performances to produce gluconic acid was observed upon UV irradiation which allows the selective formation of levulinic acid in high yield, ~ 60% at 150 °C, together with the co-production of ethylene and hydrogen in the gas phase. The formation of levulinic acid could be explained by the creation of Br?nsted acidity in the reaction medium upon irradiation. The reasons of this phenomenon are discussed considering that UV could modify the electronic properties of titanium dioxide by electron-holes pairs formation and the possible H+ promotion.
查看更多>>摘要：? 2022 Elsevier B.V.Catalytic ketonization of carboxylic acids is promising for the synthesis of renewable products. Despite its potential, fatty acid ketonization and its kinetics in the liquid phase are less investigated. This work encompasses kinetic evaluation of two TiO2 catalysts (anatase and rutile) for C-C coupling of C12-C18 fatty acids in inert dodecane solvent. The rutile catalyst, with higher Lewis acid density, showed higher intrinsic activity and more favorable activation energy barriers. Unfortunately, this material suffers from stronger product inhibition by ketone, water and carbon dioxide compared to anatase. Langmuir-Hinshelwood kinetic models were developed and validated against the experimental data, supporting that C-C coupling of adsorbed species is rate determining in the ketonization mechanism. The Lewis acid site density and distance between active Ti species at the surface were invoked to explain the activity patterns. The impacts of substrate chain length, solvent and liquid phase purging on the ketonization kinetics were investigated, showcasing potential for future improvements.
NSTL
Elsevier