A quaternary heterojunction nanoflower for significantly enhanced electrochemical water splitting.

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(NO 3 ) 2 (OH) 4 /Ni(OH) 2 /Ni 3 S 2 /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 O 2 . As expected, benefiting from the unique structural features and solid electronic interactions, Ni(NO 3 ) 2 (OH) 4 /Ni(OH) 2 /Ni 3 S 2 /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(NO 3 ) 2 (OH) 4 /Ni(OH) 2 /Ni 3 S 2 /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.