Boosting The Water Electrolysis Performance Of Transition Metal Sulfides Through Surface-interface Engineering

Hydrogen production by electrolysis of water is expected to be one of the important technologies for sustainable clean energy production but the sluggish kinetics of the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)hampers commercialization.Developing non-precious transition metal catalysts with high activity and low cost is a big challenge for industrial alkaline water splitting.It is a feasible strategy to enhance its electrocatalytic activity through construction of heterostructures and doping engineering.Furthermore,first-principles calculations reveal the intrinsic mechanism of why surface-interface engineering can improve the performance of HER and OER.1.3D Ni Co₂O₄ nanocones are coated with four different sizes carbon nanospheres and prepared on flexible graphite felt(GF)by a two-step hydrothermal technique.Strong interactions occur between carbon nanospheres and urchin-like Ni Co₂O₄,leading to the superior performance towards HER and OER.As the size of the nanospheres increases,the catalytic performance of the electrode first increases and then decreases.The optimized carbon-coated Ni Co₂O₄ electrode exhibits excellent catalytic reactivity.This study improves the catalytic performance by constructing a carbon-Ni Co₂O₄ surface interface.2.Co-doped Ni₃S₂ nanocones(Co12@Ni₃S₂/NF)are prepared by vulcanizing a cobalt oxide nanofilm on the porous nickel foam(NF)by atomic layer deposition(ALD).The Co12@Ni₃S₂/NF electrode provides excellent bifunctional catalytic reactivity.First-principles calculations show that proper Co dopant concentration in Ni₃S₂ can cause large surface lattice distortion which results in the high effective ionic charge of Co atoms and finally leads to great enhance of water splitting.3.Zr is injected into Mo S₂@Ni₃S₂(MSNF)heterogeneous nanorods by controllable plasma ion implantation to enhance the electrocatalytic activity.MSNF implanted with a Zr fluence of 5×10¹⁶ ions-cm^-2(Zr500-MSNF)shows remarkable bifunctional electrocatalytic characteristics.The experimental results and first-principles calculations reveal that after introduction of Zr into MSNF,the S sites in the basal plane have more empty states and play a significant role in enhancing the electrocatalytic reaction.4.On the basis of theory calculations,Ag-doped Mo S₂ has a higher hydrogen adsorption activity,and the"resurrection"of S sites on the basal plane of Mo S₂ caused by Ag plasma doping facilitates water splitting.Ag and other dopants are plasma-implanted into Mo S₂ to tailor the surface and interface in order to enhance the HER activity.The HER activty increases initially and then decreases with increasing dopant concentrations.Moreover,implantation of Ag is observed to produce better results than Ti,Zr,Cr,N,and C.The experimental results and first-principles calculations confirm each other.5.We designed the surface modification of Mo S₂@Ni₃S₂ hetero nanorods with Ti metal plasma and N non-metallic plasma based on plasma implantation.The relationship between the HER reactivity and the doping dose was also explored in an alkaline environment.With the increase of plasma doping dose,the HER performance showed a trend of first enhancement and then decay.In particular,the N1.0@Ti500-MSNF electrode exhibits the best electrocatalytic HER activity.The first-principles calculations and experimental results jointly reveal that it has a stronger ability to control the surface and interface activity than the single plasma modification.In summary,this work activates the HER and OER activities of transition metal catalysts by constructing a heterostructured surface and doping,respectively,systematically explores the direct link between nanotopography,chemical composition,dopant dose and electrocatalytic activity within the process of catalysts surface and interface modification.In addition,the intrinsic mechanism of the activation of the reaction sites by dopant atoms is revealed based on the first-principles calculations.This study provides a flexible and controllable strategy for optimizing the surface and interface of transition metal catalysts for commercial water splitting for hydrogen production.