A quaternary heterojunction nanoflower for significantly enhanced electrochemical water splitting

Abstract

Designing highly-efficient, cost-effective, and stable electrocatalysts for water splitting is essential to producing green hydrogen. In this work, a nanoflower quaternary heterostructured Ni(NO₃)₂(OH)₄/Ni(OH)₂/Ni₃S₂/NiFe-LDH electrocatalyst is successfully synthesized by two-step hydrothermal reactions. The sulfur in the electrocatalyst induces higher valence state metal atoms as active sites to accelerate the formation of O₂. As expected, benefiting from the unique structural features and solid electronic interactions, Ni(NO₃)₂(OH)₄/Ni(OH)₂/Ni₃S₂/NiFe-LDH exhibits remarkable oxygen evolution reaction performance with a low overpotential of 223 mV at a current density of 100 mA cm⁻², a slight Tafel slope of 65.4 mV dec⁻¹, and outstanding stability in alkaline media. Attractively, using Ni(NO₃)₂(OH)₄/Ni(OH)₂/Ni₃S₂/NiFe-LDH as both a cathode and an anode, the alkaline electrolyzer delivers a current density of 10 mA cm⁻² only at a cell voltage of 1.67 V, accompanied by superior durability. This work provides a facile method for the rational design of high-performance quaternary electrocatalysts.