Preparation Of Cobalt Based Composites And Study Of Catalytic Properties Towards HER And HDS

With the reduction of fossil energy and the aggravation of environmental pollution,it is urgent to produce clean fuel and develop low-cost,sustainable and efficient new energy to replace fossil fuel.The hydrogen evolution reaction(HER)of electrolytic water plays an important role in hydrogen production.Meanwhile,hydrodesulfurization(HDS)technology is the most effective and widely used technology for sulfur removal from petroleum and petroleum products.In recent years,transition metal catalysts,especially cobalt-based catalysts,have attracted much attention because of their good catalytic performance,abundant reserves and low price.In this paper,we mainly investigated the effect of the morphology and composition effects of the catalyst on the HER and HDS activity after Mo and Fe doping with ZIF-67 as a cobalt source,respectively.the relationship between the catalytic reaction of HER and HDS was also explored.The specific studies are as follows:1.Using the ZIF-67 as a cobalt source,Mo atoms were introduced into the synthesis process to obtain the MoS2-Co3S4 hollow polyhedral structure by solvothermal method.The hollow polyhedron structures have a large specific surface area,which can expose more active sites and improve the catalytic performance.Compared with the pure MoS2,Co3S4 and MoS2-Co3S4-coprecipitation nanoparticles,the MoS2-Co3S4 hollow polyhedral structure exhibited superior HER and HDS catalytic activity due to morphology effects and synergistic effects between Co3S4 and MoS2.In addition,DFT calculations investigated the activation energy required for the HER and HDS by MoS2 and Co-Mo-S structures,respectively.The results show that the activation energy required for the C-S bond fracture and the formation of H2 on the Co-Mo-S structure is significantly lower than that of MoS2.Theoretically proved that MoS2-Co3S4 hollow polyhedral have excellent catalytic properties and the catalytic activities of HER and HDS are consistent for sulfide.2.Introducing different carbon materials and Fe in the ZIF-67 synthesis process,the metal hydroxyl compounds were obtained by solvothermal method,and then the FeCoP/C nanosheets were obtained by phosphating of sodium hypophosphite.Different carbon materials can induce the formation of catalysts with different morphologies during the synthesis process,while enhancing the conductivity of the catalysts.It is proved that the catalytic activity of the carbon material can be greatly improved when the carbon material is Cabot.Compared with pure FeP/C and CoP/C catalytic materials,FeCoP/C has more excellent HER catalytic performance due to the composition effect.But the HDS evaluation results are different,and the CoP/C materials have the best catalytic performance.The required activation energies of CoP,FeP and FeCoP for HER and HDS were calculated by DFT,respectively.The activation energy required for H2 generation on the FeCoP structure is significantly lower than that of the CoP and FeP structures.But the activation energy required for C-S bond breaking on FeCoP is higher than that of CoP and lower than that of FeP.Therefore,it is theoretically proved that FeCoP/C has better HER catalytic performance and CoP/C has better HDS catalytic performance,and for phosphides,the HER and HDS catalytic performance are inconsistent.