MnO2–CoOX catalysts with different Mn/Co ratios were prepared using polyvinyl pyrrolidone (PVP) as an assistant to control the morphology and exposed crystal faces of composite oxides. The physicochemical properties of the catalysts were systematically characterized and the catalytic activity of NH3-SCR and resistance to SO2/H2O were investigated. It was found that the NO conversion over Mn–Co-0.2-PVP was apparently higher compared with that over Mn–Co-X-PVP (X = 0.9, 0.8, 0.6, and 0.4). This can be interpreted in terms of exposed crystal surface (110) and enhanced adsorption of NH3/NO, and better redox performance resulting from higher Co3+/Co2+ ratio. Furthermore, different PVP and HAc additives have different H2O and SO2 resistance. Mn–Co-0.2-PVP showed good resistance to H2O and SO2 poisoning owing to having more low-temperature (∼200 °C) NO adsorption sites, which are beneficial to promote the de-NOX reaction and less affected by SO2.
Jiuwang Gu,Qitong Huang,Yufei Yuan,Kai-Hang Ye,Zilong Wang,Wenjie Mai
Unfavorable interfacial electron back-injection, sluggish surface kinetics, and poor bulk conductivity leading to remarkable recombination are the key issues which significantly hinder the solar-to-hydrogen efficiency of PEC photoanodes. In this study, Ti foil is employed as the substrate for fabricating BiVO4 photoanodes. Surface passivation of TiO2 is sophisticatedly designed to block interface recombination in solar water splitting for the first time, so that a significant two-fold increase in photocurrent and a large decrease in dark current are observed. In addition, to address the other two issues, CoOx oxygen evolution catalysts (OECs) and Mo/N doping are applied to increase the photocurrent density and applied bias photon-to-current efficiency to 5.04 mA cm−2 at 1.23 VRHE and 1.41% at 0.75 VRHE, respectively, under AM 1.5 G illumination, which suggests the great potential of integrating strategies to target specific issues in BiVO4 photoanodes.
Catalytic hydrogenation of ethyl levulinate (EL) to 1,4-pentanediol (1, 4-PDO) could provide a potential approach to obtain valuable chemicals from renewable biomass. In this study, a CuZr/CoOx catalyst was developed based on a structural topotactic transformation process of layered double hydroxides. The prepared CuZr/CoOx catalysts possess a double functionality of metal-acid sites and showed superior catalytic activity in the production of 1, 4-PDO from cascade conversion of EL. A complete EL conversion (100 %) and 93.1 % 1, 4-PDO yield were obtained under optimized conditions over catalyst CuZr/CoOx-400. The co-existence of Cu 0 and Cu + on the surface of catalyst CuZr/CoOx was confirmed by XRD and XAES characterizations. In addition, the XPS results suggested a strong interaction between Co and Cu, which would effectively stabilize the Cu + species in the catalyst. The Cu 0 was believed to activate hydrogen, while the Cu + could promote the adsorption of carbonyl group of the substrate thus facilitating the hydrogenolysis. The introducing of Zr in the catalyst greatly improved the dispersion of Cu species and increased the abundance of the acid sites as revealed by the TEM and NH 3 -TPD analysis. Catalyst CuZr/CoOx-400 also exhibited highly catalytic activity after five reaction cycles. Together with the low cost of the non-precious metals, the CuZr/CoOx catalysts demonstrate a potential for the scaled-up application in the biomass refinery process.
Anqiu Liu,Xixi Liu,Yaping She,Xiaoqiang Hu,Miao Hu,Zehui Zhang,Xiaochen Wang,Bing Liu
Selective hydrodeoxygenation transformations constitute the most pivotal industrial processes in chemistry and catalysis. Herein, we have rationally designed a heterogeneous Co/CoOx catalytic system with metallic Co and oxygen vacancies in CoOx for selective hydrodeoxygenation of structurally diverse ketones and nitro compounds under mild conditions (80–100 °C and 10 bar H2), which shows a superior performance compared to state-of-the-art noble-metal catalysts. Experimental results and DFT calculation revealed that oxygen vacancies not only promote the adsorption and activation of substrates and the intermediates via electronic interactions, but also enable the hydrodeoxygenation reactions in a low-energy pathway via the direct hydrogenolysis process, instead of the dehydration–hydrogenation process. Given its generality and efficiency, it is believed that this method can serve as a practical, economically viable approach for selective hydrodeoxygenation reactions, which should impact both the chemical industry and scientific research.
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