Sulfur doping and heterostructure on NiSe@Co(OH)2 with facilitated surface reconstruction and interfacial electron regulation to boost oxygen evolution reaction

Abstract

Cobalt hydroxide (Co(OH)₂) with nanosheets structure are considered as promising OER electrocatalysts due to the divalent cobalt ions occupied octahedral (MO₆) structure and the exposition of more active sites, but pure Co(OH)₂ suffers from poor OER performance because of the sluggish OER kinetics and poor mass-transport ability. Herein, three-dimensional NiSe@S-Co(OH)₂ nanoarrays are synthesized by electrodepositing S doped Co(OH)₂ nanosheets on NiSe nanowires/Ni foam. The optimal NiSe@S-Co(OH)₂ achieves lower overpotential (285 mV at 50 mA cm⁻²) with smaller Tafel slope (101.8 mV dec^-1) in basic solution. In-situ UV–vis experiments unveil that S doping can facilitate the formation of CoOOH (active sites) reconstructed from Co(OH)₂. The experiments and theoretical simulations prove that the intense electronic interaction exists at the interface of NiSe@S-CoOOH, where the electrons transfer from NiSe to S-CoOOH. The interfacial synergy induced by coupling NiSe and sulfur doping can change the rate-controlling step and reduce the energy barrier from 3.17 eV (S-CoOOH) and 2.59 eV (NiSe@CoOOH) to 1.93 eV (NiSe@S-CoOOH). The two-electrode electrolyer made up of NiSe@S-Co(OH)₂//Pt-C couple reveal the low potential of 1.78 V at 300 mA cm⁻² for all alkaline water splitting. This work puts forward a simple tactic for synthesizing three-dimensional structure, and combines interfacial electron regulation and active sites engineering to enhance OER activities of Co(OH)₂.