Engineering Interface on a 3D Co x Ni 1- x (OH) 2 @MoS 2 Hollow Heterostructure for Robust Electrocatalytic Hydrogen Evolution.

Clarifying the responsibilities and constructing the synergy of different active phases are of great significance but still an urgent challenge for the heterostructure catalyst to improve the hydrogen evolution reaction (HER) process. Here, three-dimensional (3D) Co x Ni (1- x ) (OH) 2 hollow structure integrating MoS 2 nanosheet catalysts [Co x Ni (1- x ) (OH) 2 @MoS 2 ] were ingeniously designed and prepared. This unique structure has realized the construction of a dual active phase for the optimized stepwise-synergetic hydrogen evolution process over a universal pH range through interface assembly engineering. Meanwhile, the 3D hollow heterostructure with a high surface-to-volume ratio can effectively avoid the agglomeration of MoS 2 and enhance the Co x Ni (1- x ) (OH) 2 -MoS 2 heterointerfaces. Thus, superior HER activity and stability were obtained over the universal pH range. Density functional theory calculation reveals that Co x Ni (1- x ) (OH) 2 and MoS 2 phases provide efficient active sites for rate-determining water dissociation and H* adsorption/H 2 generation on Co x Ni (1- x ) (OH) 2 -MoS 2 heterointerfaces, respectively, resulting in an optimized energy barrier for HER. This work proposes a constructive strategy to design highly efficient electrocatalysts based on the heterointerface with a defined responsible active phase of electrocatalysts.