Study On The Controllable Synthesis And Electrocatalytic Performance Of Transition Metal Phosphides

As an ideal sustainable hydrogen production method,electrolyzed water has received widespread attention,but its large-scale commercial application is limited by the high cost of platinum-based hydrogen evolution reaction(HER)catalysts.Transition metal phosphides(TMPs)have been extensively studied because of their abundant reserves,low cost,and potential to become substitutes.However,there is still a gap between the HER activity of TMPs and Pt.For improving the catalytic activity and stability,heteroatom doping and construction of micro-nano array structures are more effective strategies.In addition,the application of TMPs to proton exchange membrane water electrolysis(PEMWE)for investigating the factors affecting performance has important practical value for optimizing operating conditions and improving the performance of PEMWE.This thesis focuses on the preparation,composition and morphology characterization,HER electrochemical performance testing and mechanism exploration of doped TMPs nanoarrays and analysis of factors affecting PEMWE performance.The specific contents are as follows:(1)The Cr-doped CoP nanorod array(Cr-CoP-NR/CC)was synthesized by a simple hydrothermal-low-temperature gas phase phosphating method.It exhibited high HER electrocatalytic performance,requiring only 38 and 209 mV overpotentials to drive current densities of 10 and 500 mA·cm-2,which surpassed the performance of commercial Pt/C at high current densities.After working for 20 h at a current density of 500 mA·cm-2,the HER performance is almost not lost,showing good electrochemical stability.The high performance of HER is derived from the doping of Cr,which can optimize the hydrogen binding energy of CoP and prevent its oxidation,improve the intrinsic activity and stability;moreover,the nanorod array structure helps to fully expose the active sites and escape H2,so as to adapt to the working conditions under high current density.As non-precious metal-based TMPs,Cr-CoP-NR/CC has shown the potential to replace the platinum-based HER catalyst with limited reserves and high cost in PEMWE.(2)Using Cr-CoP as the cathode catalyst and commercial IrO2 as the anode catalyst to construct membrane electrode assembly,which was applied to PEMWE device,and the influence of operating parameters on the performance of PEMWE was explored.By optimizing the Cr-CoP load,electrolyte pH,electrolyte flow and test temperature,the performance of PEMWE has been improved.Tested at 55℃,the current density corresponding to 2.5 V reached 1.414 A·cm-2.Using high-load catalyst,low-pH electrolyte,high-flow liquid delivery,and high-temperature test conditions can improve the performance of PEMWE within a certain range,but the impact of extreme conditions on the stability of the test system should also be considered,and the working conditions parameters should be selected reasonably.