Studies On Modification Of Molybdenum-based Catalysts And Their Electrocatalytic Performance For Hydrogen Evolution

Molybdenum-based catalysts,such as molybdenum phosphide and molybdenum disulfide,have biomimetic active sites similar to hydrogenase with efficient catalytic activity from electrochemical water splitting to hydrogen.Also,they have the advantages of low price and abundant reserves.They are promising substitutes for platinum or other precious metal-based catalysts,which have attracted widespread attention.However,the intrinsic poor electrical conductivity,inert edge base surface and fewer exposed active sites of molybdenum-based catalysts severely limited the improvement of electrocatalytic hydrogen production activity.In this work,we developed two strategies including vacancy engineering and metal loading to increase the numbers of exposed active sites in order to enhance the electrocatalytic performance of molybdenum-based catalysts.Vacancy engineering increases the active sites through the absence of surface atoms,while metal loading directly introduces additional active sites,thereby improving the catalytic activity of the electrochemical water splitting.The main research contents are as follows:1.Molybdenum phosphide（Mo P）precursors were synthesized via a combination of hydrothermal and thermal annealing route.Mo P-Pv with abundant phosphorus vacancies was synthesized for the first time by the hydrogen reduction of the precursor Mo P under the negative pressure（P<250 Pa）in a mixture of hydrogen and argon（10%H₂-Ar）atmosphere.Combining a series of material characterizations and electrocatalytic performance tests,we illustrated that the phosphorus vacancy itself and corresponding induced uncoordinated Mo can serve as the active sites for the electrochemical hydrogen evolution.In addition,phosphorus vacancies can accelerate the charges transportation thus enhance the electronic conductivity,improving the catalytic activity.The result of long-term electrocatalytic hydrogen evolution experiment shows that Mo P-Pv electrocatalyst has good stability in both alkaline and acidic media.2.A series of non-noble metal（Ni/Co Ni/Fe Ni）supported molybdenum disulfide（Mo S₂）electrocatalysts for hydrogen production were synthesized via a one pot hydrothermal route.The loaded metal atoms can significantly reduce the overpotential of Mo S₂ in the electrocatalytic hydrogen evolution reaction in alkaline medium.The loaded metal itself can serve as active sites and enlarge the surface roughness of Mo S₂electrocatalyst thus further enhancing the active sites exposure.In addition,the conductivity of metal supported Mo S₂ electrocatalysts are significantly improved,thereby enhancing the catalytic activity of Mo S₂.At the same time,metal supported Mo S₂ also has good catalytic stability.Overall,both two strategies can effectively increase the number of active sites and enhance the conductivity of the electrocatalysts,thereby significantly improving the catalytic performance of hydrogen production from electrolytic water splitting.