Synergizing Hydrogen Spillover and Deprotonation by the Internal Polarization Field in a MoS 2 /NiPS 3 Vertical Heterostructure for Boosted Water Electrolysis.

Hydrogen spillover (HSo) has emerged to upgrade the hydrogen evolution reaction (HER) activity of Pt-support electrocatalysts, but it is not applicable to the deprotonated oxygen evolution reaction (OER). Non-precious catalysts that can perform well in both HSo and deprotonation (DeP) are extremely desirable for a sustainable hydrogen economy. Herein, an affordable MoS 2 /NiPS 3 vertical heterostructure catalyst is presented to synergize HSo and DeP for efficient water electrolysis. The internal polarization field (IPF) is clarified as the driving force of HSo in HER electrocatalysis. The HSo from the MoS 2 edge to NiPS 3 can activate the NiPS 3 basal plane to boost the HER activity of the MoS 2 /NiPS 3 heterostructure (112 mV vs reversible hydrogen electrode (RHE) at 10 mA cm -2 ), while for OER, the IPF in the heterostructure can facilitate the hydroxyl diffusion and render MoS 2 -to-NiPS 3 /P-to-S dual-pathways for DeP. As a result, the stacking of OER-inactive MoS 2 on the NiPS 3 surface still brings intriguing OER enhancements. With them serving as electrode couples, the overall water splitting is attested stably with a cell voltage of 1.64 V at 10 mA cm -2 . This research puts forward the IPF as the criterion in the rational design of HSo/DeP-unified non-precious catalysts for efficient water electrolysis.