Controlled Synthesis And Hydrogen Evolution Properties Of Transition Metal Phosphating Catalyst For Water Electrolysis In Proton Exchange Membrane

Proton exchange membrane electrolysis of water（PEMWE）is an efficient and environmentally friendly green hydrogen production technology,which is expected to be commercialized in the near future and become an important part of the future sustainable energy structure.However,the commercial application of PEMWE is still limited by the extensive use of yin-yang-based noble metal catalysts.Among them,the discovery of low-cost and resource-abundant transition metal phosphide（TMPs）hydrogen evolution catalysts has enabled the replacement of cathode platinum-based hydrogen evolution catalysts.Aiming at the shortcoming of the activity and stability of TMPs hydrogen evolution catalysts in PEMWE applications,in this paper,metal oxide nanocrystal self-template method was used to synthesize TMPs nanocatalysts with clear morphology and composition.Corresponding to the relationship between the catalytic performance of TMPs for hydrogen evolution reaction,and through synthesis optimization,TMPs hydrogen evolution catalysts with high PEMWE device performance were obtained.The results of the paper are detailed as follows:（1）Iron phosphide nanoparticles（NPs）are promising noble metal-free electrocatalysts for the hydrogen evolution reaction（HER）,but they usually show inferior activity due to the limited surface area and oxidative passivation.We reported a facile synthetic method to prepare Fe P hollow NPs（HNPs）with various precursors.It was proven that the structural parameters（i.e.,size,phosphating temperature,phase,and surfactant）of oxide precursors were correlated to the electrochemically active surface area（ECSA）,phase purity,surface oxidation,and hollow morphology of Fe P HER catalysts,thus affecting the HER activity.Among the three Fe P HNPs,the 9 nm Fe P HNPs prepared using the Fe₃O₄precursor exhibited the highest overall activity with the lowest overpotential of 76 m V to drive a cathodic current density of 10 m A·cm^-2due to the highest ECSA,while 25 nm Fe P prepared using the Fe₂O₃precursor showed the highest turnover frequency because of the high phase purity and low surface oxidation degree.（2）Based on the work on single metal phosphides in the first part,the study of double metal phosphides in HER was carried out by doping with second metal cations.We found that some metals in bimetallic phosphides help to promote the HER catalytic activity in the hydrogen evolution reaction,in which Co_0.33Fe_0.67P/C only needs an overpotential of 68 m V at a lower loading(0.5 mg·cm^-2)to achieve Cathode current density of 10 m A/cm².The catalyst obtained a stability of up to 10 h,which is due to the higher phase purity after phosphating,and the stability of the electronic structure can be increased by a moderate amount of cobalt doping.The catalyst was further applied to a proton exchange membrane electrolyzer and achieved a hydrogen production efficiency comparable to that of the platinum-carbon catalyst.