Co–Mo–S based catalysts have promising applications in both the hydrogen evolution reaction (HER) and hydrodesulfurization (HDS). Herein, Co–Mo–S catalyst and Co–Mo–S catalyst with and without NaBH4 modification have been successfully synthesized by a simple hydrothermal synthesis method. Co–Mo–S catalysts with NaBH4 modification show better catalytic activity towards both HDS and the HER. The phase purity, morphology, crystal structures and electron valence distribution of the catalysts with and without NaBH4 modification were studied by experimental characterizations and theoretical calculations. The catalysts without NaBH4 modification are mostly 2H-MoS2, while the catalysts without NaBH4 modification have 1T-MoS2, and 1T-MoS2 is exposed to more active sites, which will be conducive to the results of HDS performance of the catalyst. DFT calculations investigated the required activation energies of 1T-MoS2 and 2H-MoS2 for HDS and HER, respectively. The activation energy required for both HDS and H2 generation of 1T-MoS2 is significantly lower than that for the 2H-MoS2 structure.
Guojun Hao,Hongying Liu,Zhibing Chang,Kechen Song,Xin Yang,Han Ma,Wenjing Wang
In this work, lignin depolymerization was examined over CoMo sulfide catalysts supported on different carriers in supercritical ethanol system. The temperature, time, MoS 2 and carrier effects on the lignin depolymerization were investigated. 95.76% liquefaction yield with negligible char was achieved over Co–Mo–S/ZrO 2 at 340 °C for 150 min. The liquid product was mainly composed of C 4 –C 8 alcohols, C 4 –C 10 esters and C 7 –C 10 aromatic compounds . The synergistic effect of active sites and acid-base sites on support played an important role in lignin depolymerization. Furthermore, the Co–Mo–S/ZrO 2 catalyst is reusable with 8% loss in liquefaction yield after 5 cyclic runs. We believe that acid/base carriers or additives that can promote the medium to generate abundant free radicals or ions to replace external hydrogen pressure are one of the prospects for the design of depolymerization lignin catalysts.
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