The Preparation Of Transition Metal Phosphides And The Performance Of Electrocatalytic Hydrogen Production

Hydrogen is a clean and renewable energy carrier which serves as one of the most promising alternative candidates for replacing the traditional fossil fuels in the future.The efficient production has become an attractive research topic in recent years.HER is the cathode reaction of water electrolysis.Methane reforming,coal gasification and water electrolysis are current methods used for hydrogen production in industry.Among them,methane reforming and coal gasification strongly rely on the use of fossil fuels,which is not environmentally friendly and sustainable.Alternatively,water electrolysis offers a sustainable way to split hydrogen from water and thereby receives considerable attention.With a number of advantages such as using water as starting material,no emission of greenhouse gases and other polluted gases,high hydrogen production efficiency and high-purity product,electrolysis of water is considered to be a clean and efficient method to produce H₂.Noble metals（e.g.Pt,Ru,Ir and Pd）and their oxides have been investigated as electrocatalyst for water splitting.However,the high cost and scarcity of these noble metals restricts their large scale application.Consequently,there is an urgent need to develop nonprecious electrocatalysts with high activity and long-term stability.For example,transition metal sulfides,phosphides,carbides,etc.Recently,in the study of non-precious metal HER catalysts,TMPs have become one of the most catalytically active,stable and cost-effective electrocatalysts because of their unique electronic structures and metalloid properties.In the following,we prepared three different types of TMPs and applied them to electrocatalytic hydrogen production,demonstrating superior electrocatalytic activity and stability.Firstly,a 3D flower-like CoNi LDH precursor was synthesized by hydrothermal method.Subsequently,the CoNi LDH precursor was transformed into CoP₃/Ni₂P in Ar atmosphere at 650°C in the presence of NaH₂PO₂.Ni₂P in CoP₃/Ni₂P grows on CoP₃ and forms a large number of heterostructure interfaces.The CoP₃/Ni₂P was subsequently tested for HER activity.the CoP₃/Ni₂P heterostructure exhibits a higher HER intrinsic catalytic activity with low onset overpotential,small Tafel slope,and robust durability.Theoretical calculations reveal that the heterostructure interface can efficiently regulate the electronic environment around the surface active sites of CoP₃/Ni₂P,thus optimizing the hydrogen adsorption strength and improving the HER electrocatalytic activity.We synthesized MoP/Fe₂P/RGO composites in a facile two-step method.The MoP/Fe₂P nanoparticles are uniformly dispersed on RGO and have a particle size of less than 200 nm.The HER catalytic test showed that MoP/Fe₂P/RGO had superior catalytic performance.The high catalytic HER activity of MoP/Fe₂P/RGO originates from the following advantages:1)the synergistic effect of MoP and Fe₂P promotes the whole process of HER;2)MoP/Fe₂P/RGO has a high electrochemical active surface area;3)The introduction of RGO not only prevents the aggregation and coalescence of particles during high temperature phosphating,but also improves the conductivity of the catalyst.Co-based nanowire precursors were prepared by hydrothermal method,and then Co-based nanowire precursors were converted to CoP and CoP₂ by different phosphating methods,and their HER catalytic properties were tested.The HER test showed that the catalytic activity of CoP₂ was significantly higher than that of CoP,and CoP₂ had a very good electrochemical stability.