Design,Preparation And Electrochemical Performance Of NiCoP-Based Materials

As a sustainable green energy carrier,hydrogen is an ideal alternative to traditional energy.Hydrogen evolution reaction（HER）is an efficient and feasible method in various hydrogen production methods.NiCoP are widely used as electrocatalysts due to the unique electronic structure.However,the insufficient active sites and low conductivity of NiCoP are the main reasons for the sluggish kinetics in electrochemical reactions.Tuning the spatial configuration and electronic structure of NiCoP is an effective strategy to increase the number of active sites and enhance conductivity.The construction of multi-dimensional morphologies can tune the spatial configuration of catalysts to expose more active sites.The doping of heteroatoms can modulate the electronic structure of catalysts to enhance conductivity.Morphology regulation and atomic doping be used as design the spatial configuration and electronic structure of NiCoP for high-efficiency NiCoP-based catalysts.Based on the structure-activity relationship of catalysts,the high-active HER electrocatalysts have been controllable prepared.The specific research contents are as follows:（1）Multidimensional controllable preparation of NiCoP to construct different spatial configurations for efficient HER electrocatalytic performance.The 1D nanowires（NW-NiCoP）and 2D nanosheets（NS-NiCoP）were constructed in theoretical calculations.The corresponding density of states and adsorption energy of NW-NiCoP and NS-NiCoP were calculated based on first principle.Theoretical calculations showed that the electron density of states near the Fermi level of NW-NiCoP(10.05 eV^-1)was higher than NS-NiCoP(6.29 eV^-1),indicating the conductivity of NW-NiCoP was better than NS-NiCoP.NS-NiCoP（-0.85 eV）exhibited higher adsorption energy than NW-NiCoP（-0.02 eV）,the higher adsorption energy was more favorable for the Volmer reaction.NiCoP with 1D nanowires,2D nanosheets and 3D hybrid nanosheet-wires structure was synthesized by hydrothermal and phosphating process.The catalytic performances of NiCoP with different dimensions were analyzed.The results showed that the overpotential of 3D hybrid nanosheet-wire was 45 mV at 10 mA/cm².The double-layer capacitance and charge transfer impedance of the 3D hybrid nanosheet-wire was 41.2 mF/cm² and 3.17Ω,respectively.The efficient performance of hybrid nanosheet-wire was attributed to the enhanced charge transfer rate and more exposed active sites.（2）Heteroatoms Fe was introduced to NiCoP（Fe-NiCoP）to modulate electron structure for efficiency HER electrocatalytic performance.The theoretical models of Fe-NiCoP and NiCoP were constructed in theoretical calculation.The corresponding charge density,charge distribution difference and Gibbs free energy of Fe-NiCoP and NiCoP were calculated based on density functional theory.Theoretical calculations showed that the electronic density of states of Fe-NiCoP near the Fermi level(11.75 eV^-1)was shifted upward compared with NiCoP(10.63 eV^-1),indicating the conductivity of Fe-NiCoP was better than NiCoP.The redistribution of surface charge induced the formation of active sites.The Gibbs free energy（0.14 eV）of Fe-NiCoP was closer to 0 eV,predicting that Fe-NiCoP with excellent HER performance.Fe-NiCoP and NiCoP were prepared via hydrothermal and phosphating methods.Compared with the un-doped NiCoP,effect of Fe doping on catalytic performance of HER was analyzed.The results showed that the overpotential of Fe-NiCoP was 84 mV at 10 mA/cm²,which was lower than that of NiCoP（129 mV）.The double-layer capacitance and charge transfer resistances of Fe-NiCoP were 23.2 mF/cm² and 2.86Ω,respectively.The results confirmed that Fe doping provided more active sites and enhanced the charge transfer rate.