Iron Phosphide Nanosheets As Efficient Electrocatalyst For Hydrogen Evolution Reaction

Metal phosphides have been considered as promising electrocatalysts for hydrogen evolution reaction(HER)due to their facile synthesis and low-cost.Ultrathin nanosheets of non-layer materials have attracted intensive interests due to their highly abundant exposed active sites.Herein,we demonstrate the synthesis of porous FeP nanosheets(FeP-I NS)with?0.7 nm thickness and with abundant Fe2P2O7 dopants using ultrathin y-Fe2O3 NS as precursors.The obtained catalyst displays good HER catalytic activity with an low overpotential(?)of 95/160 mV at the current densities of 10/100 mA cm-2 and small Tafel slope of 41 mV dec-1 as well as good stability during a period of 24 h in acid media.Additional experimental data reveal that the unique structural features of FeP-I NS(i.e.,ultralow thickness,moderate porosity,structural distortion and amorphous domains)are key factors for achieving good HER activity.The computational studies demonstrate that the Fe2P2O7 dopants contribute to the HER performance of FeP by reducing the Gibbs free energy of intermediate H*adsorption(?GH*)and tailoring the electronic properties of the catalyst.To further improve the catalytic activity of the materials,a series of FexRui1-x-P nano-composites were prepared via a two-step procedure.Their morphologies,structures and compositions were characterized using scan electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and ect,while their HER catalytic activities in acidic media were evaluated using linear sweep voltammetry(LSV).Results suggest that FexRui1-x-P nano-composites display better HER catalytic activities than the similarly prepared Fe-P and Ru-P nanomaterials.Among them,Feo.3Ru0.7-P exhibits the best HER catalytic activity in terms of a low overpotential(?10)of 31 mV at 10 mA·cm-2and small Tafel slope of 37.98 mV dec-1,which are even comparable to those of commercial Pt/C.After 2000 cyclic voltammetry sweeps,the ?10 of Feo.3Ruo.7-P only slightly increased by 8 mV,indicating the good stability of the catalyst.Further studies were performed to investigate the possible mechanism behind the excellent catalytic performance of Feo.3Ruo.7-P.