Synthesis Of Non-platinum Catalysts Based On Mo₂C And CoS₂ For Hydrogen Evolution Reaction

With the development of the economy,people's demand for energy is increasing.Traditional fossil energy is not only non-renewable,but also brings a series of environmental pollution problems.Hydrogen energy is favored by researchers as a clean energy source.However,electrolytic water is one of the technologies to realize large-scale production of hydrogen.The hydrogen evolution reaction(HER)occurring on the cathode requires high-efficiency catalyst to reduce energy consumption.Currently,the highest activity of HER catalyst is platinum-based noble metal,but its expensive price limits industrial production.Therefore,the preparation of non-noble metal catalysts for HER with low cost and high efficiency become the focus of current research.In this paper,for the deficiency of Mo2C and CoS2 in catalytic HER,N-Mo2C@CNT was prepared by solvothermal-calcination method,CoS2/CNT and CoS2/P were prepared by one-step hydrothermal method.As well as electrochemical tests,the results show that they all have high catalytic activity and good stability.The main research contents are as follows:1.A series of N-Mo2C@CNT catalysts supported on different carbon nanotubes were synthesized by solvothermal-calcination method.N-Mo2C was prepared firstly and the feed amount of raw materials was optimized to obtain the controllable preparation rule of the catalyst for optimal hydrogen evolution performance.On this basis,N-Mo2C@CNT composites with different contents carbon nanotube were studied in detail through a series of characterization and electrochemical tests.The results revealed that the N-Mo2C@CNT composite with optimum content of CNTs exhibits an excellent catalytic activity with less overpotential of 183 mV at 10 mA cm-2 and smaller Tafel slope of 74 mV dec-1 in acidic media.Furthermore,it has a good cycling stability after 1,000 cycles.This is not only that the carbon nanotubes increase the conductivity of the material,but the synergy between N,Mo,and C also contributes to the improvement of the HER performance of the catalyst.2.The CoS2/CNT composites were synthesized by a facil one-step hydrothermal method.The effect of CNT amount on the hydrogen evolution of CoS2 was studied in 0.5 mol L-1 H2SO4 solution.The results show that the CoS2/CNT composite prepared by 8 wt%CNT offers an outstanding HER activity with smallest overpotential of 155 mV at 10 mA cm-2 and lowest Tafel slope of 59 mV dec-1 when comparing with pure CoS2(254 mV,90 mV dec-1).Also,the optimized CoS2/CNT composite provided a good stability after 1,000 cycles.This is attributed to the good conductivity of CNTs encapsulated in micro-nanospheres CoS2,which CoS2 exposes to more marginal active sites.3.A series of CoS2/P materials with different phosphorus contents were prepared by using polyethylene glycol-assisted hydrothermal reaction.The effect of phosphorus content on CoS2 was studied.SEM found that the morphology of the material changed from microsphere to nanosheet after doping with phosphorus source.Electrochemical tests showed that HER had the best performance when the ratio of sulfur to phosphorus was 8:5,and its overpotential at the current density of 10 mA cm-2 and Tafel slope were 109 mV and 48 mV dec-1,respectively.After 1,000 cycles,the catalytic activity was not significantly attenuated.This is because phosphorus doping can optimize the surface properties of CoS2 and promote charge transfer,which provides a way to enhance the HER activity of CoS2.