碳掺杂MoS_(2)@Mo电极增强电解水析氢反应

Enhancement of the hydrogen evolution reaction in water electrolysis using a carbon-doped MoS_(2)@Mo electrode

高性能电极材料开发是大电流密度电解水制氢的关键.实验采用微波等离子体化学气相沉积(MPCVD)实现Mo基体直接生长活性MoS_(2)纳米片阵列,设计CH4/H2等离子体实现碳掺杂原位调控活性层MoS_(2)晶相结构,制备了呈异质结构的1T/2H-MoS_(2)@Mo电极.电化学性能测试显示,1T/2H-MoS_(2)@Mo电极在1000 mA cm^(-2)大电流密度下表现出281 mV低过电位和超100 h的持续稳定性.Butler-Volmer(B-V)拟合证实,1T/2H-MoS_(2)@Mo具有媲美Pt的动力学性能.密度泛函理论(DFT)计算表明,C掺杂诱导形成的1T/2H-MoS_(2)晶体畴壁具有非对称性结构,造成MoS_(2)表面电荷的不均匀分布,进而激活表面惰性S位点,降低氢吸附自由能(ΔGH*);同时,Mo基体与活性层1T/2H-MoS_(2)间的能带重叠效应,赋予1T/2H-MoS_(2)@Mo优异的载体/活性层界面结构稳定性.MPCVD自生长晶相结构调控策略为大电流密度非贵金属析氢电极制备提供了技术支持.

As a clean and sustainable energy carrier,hydrogen plays a pivotal role in meeting critical national needs and can be used to address the challenges of achieving carbon neutrality.Electrocatalytic water splitting has emerged as an optimal strategy in this endeavor.Due to its remarkable cost efficiency and distinctive physical and chemical properties,molybdenum disulfide(MoS_(2))is a promising candidate for replacing platinum-based precious metals in facilitating large-scale hydrogen production.However,MoS_(2)has various drawbacks such as poor conductivity,inadequate active sites,and limited mass transfer efficiency at the microscale reaction interface;these drawbacks pose significant barriers to the widespread adoption of MoS_(2)-based catalysts in water electrolysis for hydrogen evolution.Numerous experimental and theoretical works have confirmed that the electrocatalytic activity of MoS_(2)is highly related to its phase components and electronic structure.Therefore,the intrinsic properties of MoS_(2)can be significantly enhanced by regulating the surface geometry,atomic coordination structure,electronic band effects,and interactions at the contact interface.The manipulation of the crystal phase is considered a classical approach to fine-tune the electron landscape of the reactive sites and thus the electrochemical activity of MoS_(2).Research has shown that constructing a composite heterojunction with nonuniform boundaries between the 1T phase and the 2H phase can facilitate fast charge carrier transfer and create abundant electrochemically active sites on catalysts.Moreover,the challenges related to the long-term stability of MoS_(2)-based electrodes need to be addressed.In this regard,Mark A.Lukowski and colleagues demonstrated that the coupling interactions between the support and the active component can effectively enhance the mechanical stability even under high current densities.Therefore,novel methods for preparing robust monomeric catalyst electrodes to scale up the HER warrant further examination.Along this line,we directly developed homologous self-supported Mo-based MoS_(2)electrodes(MoS_(2)@Mo)on Mo foil via microwave plasma chemical vapor deposition(MPCVD).CH4/H2 was used to control the crystalline phase structure of the MoS_(2)active layer in situ.This resulted in the synthesis of a 1T/2H-MoS_(2)@Mo electrode with a heterostructure.Characterization results from techniques such as transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and Raman spectroscopy revealed that the 1T/2H-MoS_(2)@Mo electrode contained two coexisting crystal phases of 1T and 2H.Electrochemical evaluation revealed that the 1T/2H-MoS_(2)@Mo electrode exhibited a low overpotential of 281 mV and sustained stability over 100 h at a large current density of 1000 mA cm^(-2).Butler-Volmer(B-V)fitting results further confirmed that 1T/2H-MoS_(2)@Mo had a comparable kinetic behavior to that of the Pt foil under kinetic control,resulting in an optimized mass transfer process and excellent intrinsic HER performance at a large current density of 1000 mA cm^(-2).Based on the density functional theory(DFT)calculations,the asymmetric structure at the 1T/2H-MoS_(2)domain wall induced by C doping led to an uneven distribution of surface charges on MoS_(2),thereby activating surface inert S sites and reducing the hydrogen adsorption free energy(ΔGH*).Moreover,the energy band overlap effect between the Mo support and the active 1T/2H-MoS_(2)component provided excellent substrate/active layer interface stability to 1T/2H-MoS_(2)@Mo.Our study confirms the structural advantages of homogeneous support electrodes and presents a viable strategy for designing nonnoble metal electrodes for industrial-scale HER.