The Research On The Synthesis And Catalytic Properties Of Nanoarrays Electrode For Overall Water Splitting

Due to the increased global warming and serious shortages of fossil fuel,the development of clean and sustainable new energy has become particularly important.Hydrogen,as a kind of efficient energy,has attracted widespread attention due to its unique advantages including high energy density,environmental friendliness and renewability.Water electrolysis,which composes of hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）has been regard as one of the most efficient,simple and environment-friendly technologies for hydrogen production.At present,most of the HER and OER catalytic electrode materials still rely on the precious metals,such as Pt and Ir.However,the high cost of precious material seriously hinders the development of water electrolysis industrial.Therefore,the fabrication of transition metal based catalytic electrode materials with high activity and low-cost will be the most important thing in the future.In the paper,a series of transition metal phosphide catalysts with nanosheet array structure had been successfully prepared on nickel foam（NF）with high conductivity by two steps,including hydrothermal and low-temperature phosphatization.Moreover,their activities towards water electrolysis were also studied.The specific research is as follows:（1）Firstly,the Ni₂P nanosheet array was fabricated on the high-conductive nickel foam substrate（Ni₂P/NF）by hydrothermal and low-temperature phosphatization process.It shows the favorable catalytic performance for water electrolysis in alkaline electrolyte（1M KOH solution）.Only 105 mV and 452mV overpotentials are required to afford the current density of10 mA/cm² and 100 mA/cm² during the HER and OER,respectively.（2）On the base of experiment（1）,the manganese nitrate is used instead of nickel nitrate during the hydrothermal process.So a series of different Mn doping content Ni₂P nanosheet array on NF（Mn@X-Ni₂P/NF,X represents the usage of manganese nitrate）has been developed as the catalytic electrode towards water electrolysis.The electrochemical test results show that Mn@5-Ni₂P/NF possesses the best performance towards the water electrolysis.In1M KOH solution,96 mV overpotential is needed to afford the 10 mA/cm² current density during the HER;and 399 mV overpotential is needed to afford the 100mA/cm² current density during the OER.（3）Based on the characteristic of Mn element,a Ni₂P nanosheet array with cation vacancy(V_Mn-Ni₂P/NF)as catalytic electrode has been fabricated on NF by removal of Mn element in Mn@5-Ni₂P/NF through the nitric acid etching.In the 1M KOH,81 mV overpotential is needed to afford the 10 mA/cm² current density during the HER;and 349 mV overpotential is needed to afford the 100mA/cm² current density during the OER.This catalytic performance is obviously better than Ni₂P/NF and Mn@5-Ni₂P/NF,indicating that the engineering cation defect is an effective way to improve the catalytic activity.At last,an electrolyzer with two-electrode was fabricated to test the water electrolysis performance of Ni₂P/NF,Mn@5-Ni₂P/NF,V_Mn@15-Ni₂P/NF.V_Mn-Ni₂P/NF only requires a cell voltage of1.59 V to reach the current density of 10mA/cm²,which is much lower than Ni₂P/NF（1.684V）,Mn@5-Ni₂P/NF（1.635 V）.