Preparation Of Iron-group Metal Phosphide/three-dimensional Graphene As Composite Catalysts For Electrocatalytic Hydrogen Evolution Reaction

With the increasingly serious energy crisis and environmental problems,the exploration of sustainable and environment-friendly new energy has become an urgent task for social de-velopment.Hydrogen is regareded as one of the most promising alternatives to fossil fuels in clean energy.Among hydrogen generation methods,water electrolysis is considered to be a promising method.However,water electrolysis for cathodic reaction requires highly efficient electrocatalysts to reduce its overpotential and accelerate its reaction kinetics.At present,Pt is regarded as the best electrocatalytic catalyst for hydrogen evolution,but its high cost and lim-ited reserves limit its wide application in the water electrolysis for hydrogen production.Therefore,the development of non-noble metal catalysts with high catalytic performance is the key to promote the large-scale application of water electrolysis for hydrogen production.Among non-noble metal catalysts,iron metal phosphides have been proved to be a promising catalyst for hydrogen evolution due to their rich content,multiple active sites and catalytic properties similar to hydrogenase.However,single-component iron metal phosphides are easy to agglomeration and poor conductivity,which limit their catalytic activities.In order to overcome this problem,iron metal phosphide catalysts are usually supported to the carrier to form composite catalysts,which can not only prevent the agglomeration of catalysts,improve the stability of catalysts,but also make the catalysts easy to recover.Based on the above theo-ries,this paper developed new methods to construct iron metal phosphide/3D graphene com-posite catalysts,and studied the relationship between their morphology,structure and catalytic performance,so as to prepare electrocatalysts with excellent catalytic performance in hydro-gen evolution.The main contents are as follows:1.Three-dimensional graphene was synthesized by hydrothermal method using nickel foam as template.Co–Ni–P and other alloys were deposited on the three-dimensional gra-phene carrier by electroless plating to synthesize new electrocatalysts for hydrogen evolution（Co–Ni–P/rGO/NF）.The surface properties and structure of Co–Ni–P/rGO/NF composite catalysts were studied by scanning electron microscopy（SEM）,X-ray photoelectron spec-troscopy（XPS）and other advanced characterization techniques.The results showed that the dispersion of Co–Ni–P alloy was uniform and its composition was stable.The relationship between electrocatalytic hydrogen evolution performance and structure composition was ana-lyzed by means of electrochemical test and characterization results.The Co–Ni–P/rGO/NF catalyst delivers excellent HER performance including an overpotential of 65 mV to generate a cathodic current density of 10 mA cm^-2,a Tafel slope close to that of commercial Pt/C cata-lysts,and long lifetime indicated by a more constant cathodic current density during continu-ous operation for 10 h.2.A large specific surface area and porosity graphene vertical array was established by freeze-drying with one-way ice template.Electroless plating was used to deposit Fe–Co–Ni–P,Fe–Co–P,Fe–Ni–P and other alloys onto the graphene vertical array to synthesize new elec-trocatalyst for hydrogen evolution（Fe–Co–Ni–P/VrGO）.The morphology and composition of Fe–Co–Ni–P/VrGO composite catalyst were studied by SEM,XRD and other advanced char-acterization techniques.The results showed that the particles of Fe–Co–Ni–P alloy were closely distributed and uniform in size.Characterized by electrochemical test,combining with the results of electric performance and structure,the results show that at the current density of10 mA cm^-2,the overpotential was 62 mV for alkaline,127 mV for neutral and 83 mV for acid,and in the process of stability test（0-14pH）,catalytic activity basically remain unchanged,showing good stability.In this paper,the methods of structure regulation and performance optimization of mul-tielement iron series metal phosphides are studied,and a series of electrocatalysts with high catalytic activity are synthesized.