Catalysts for the hydrogen evolution reaction in alkaline medium:Configuring a cooperative mechanism at the Ag-Ag_(2)S-MoS_(2) interface

Designing electrocatalysts for HER in alkaline conditions to overcome the sluggish kinetics associated with the additional water dissociation step is a recognized challenge in promoting the hydrogen economy.To this end,delicately tuning the atomic-scale structure and surface composition of nanoparticles is a common strategy and,specifically,making use of hybrid structures,can produce synergistic effects that lead to highly active catalysts.Here,we present a core-shell catalyst of Ag@MoS_(2)that shows promising results towards the hydrogen evolution reaction(HER)in both 0.5 M H_(2)SO_(4)and 0.5 M KOH.In this hybrid structure,the MoS_(2)shell is strained and defective,and charge transfer occurs between the conductive core and the shell,contributing to the electrocatalytic activity.The shelling process results in a large fraction of Ag_(2)S in the cores,and adjusting the relative fractions of Ag,Ag_(2)S,and MoS_(2)leads to improved catalytic activity and fast charge-transfer kinetics.We suggest that the enhancement of alkaline HER is associated with a cooperative effect of the interfaces,where the Ag(Ⅰ)sites in Ag_(2)S drive the water dissociation step,and the formed hydrogen subsequently recombines on the defective MoS_(2)shell.This study demonstrates the benefits of hybrid structures as functional nanomaterials and provides a scheme to activate MoS_(2)for HER in alkaline conditions.