Study On The Performance Of Photo-electrolytic Hydrogen Evolution Based On Nickel-cobalt Phosphide Catalyst

With the shortage of fossil fuels and environmental pollution becoming more and more serious,it is urgent to develop the green renewable energy.Hydrogen energy has attracted more and more attention as a potential substitute for fossil fuels in the future because of its high energy density and zero greenhouse gas emissions.Hydrogen evolution through electrocatalytic and photocatalytic water splitting are currently the two relatively green and environmentally friendly methods for hydrogen production.In the above-mentioned two methods,noble metals or noble metal oxides are required.However,due to its scarcity and high price,noble metal is difficult to realize the large-scale application.Therefore,there is an urgent need to develop an efficient and stable non-noble metal catalyst to achieve high-efficiency and low-consumption hydrogen production.Transition metals（Ni,Co,etc.）and their chalcogenides,nitrides and phosphides had been widely researched to the noble precious metal-based catalysts.Among these substitute materials,transition metal phosphides（TMPs）are particularly attractive due to its high conductivity and good corrosion resistance.And bimetallic phosphides showed a better electrocatalytic performance than single metal phosphides due to the synergistic effect.According to the volcanic theory of hydrogen evolution reaction,this paper selected Ni and Co transition metal elements,NiCoP was used as a catalyst to study its application in electrocatalytic hydrogen evolution and photocatalytic hydrogen production.The main research content included the following two aspects:（1）We used carbon cloth（CC）as the base of the self-supporting electrode.Nickel and cobalt,rich non-noble metals,were introduced to the carbon cloth through hydrothermal reaction.The composite phosphides of nickel and cobalt were obtained by low-temperature phosphating.The prepared materials possess a sea urchin-like microstructure which is composed of microspheres in center and nanospines on its surface.Based on this unique sea urchin-like structure,NiCoP/CC self-supporting electrode exhibits a good hydrogen evolution performance in acidic solutions.The required overpotentials were only 178 m V and 395 m V vs RHE at 10 and 100 m A cm^-2,respectively.We used this NiCoP/CC self-supporting electrode as the cathode and the pure CC as the anode.Under the condition of a constant current density of 2 m A cm^-2,the degradation efficiency of methylene blue（MB）at 90minutes was 88%and hydrogen was produced constantly on the NiCoP/CC self-supporting electrode,which provided an idea for the combination of hydrogen evolution reaction（HER）and organic matter degradation.（2）NiCoP was used as a non-noble metal promoter to modify g-C₃N₄ nanosheets for photocatalytic water splitting to produce hydrogen.The g-C₃N₄ nanosheets were prepared by thermal decomposition,and NiCoP nanoparticles were immobilized on the surface of the g-C₃N₄ nanosheets through hydrothermal reaction and low-temperature phosphating,so that the light absorption capacity of g-C₃N₄ was significantly improved.Result shown that the light absorption capacity of the NiCoP/g-C₃N₄ composite photocatalyst is significantly improved,and the hydrogen evolution rate of NiCoP/g-C₃N₄ composite photocatalyst reached203.7μmol h^-1 g^-1,which is 18.56 times and 1.86 times that of pure g-C₃N₄ and g-C₃N₄-3%Pt,respectively.At the same time,it exhibited an excellent stability.Through the research of photoluminescence,transient photocurrent and impedance tests,the addition of NiCoP nanoparticles was proved to be able to effectively promote the separation and migration of photogenerated electrons and holes,inhibit electron-hole recombination,and hence improve the photocatalytic hydrogen production performance of g-C₃N₄.