Oxygen Vacancies and Interface Engineering on Amorphous/Crystalline CrOx -Ni3 N Heterostructures toward High-Durability and Kinetically Accelerated Water Splitting

Abstract

Manipulating catalytic active sites and reaction kinetics in alkaline media is crucial for rationally designing mighty water-splitting electrocatalysts with high efficiency. Herein, the coupling between oxygen vacancies and interface engineering is highlighted to fabricate a novel amorphous/crystalline CrO_x -Ni₃ N heterostructure grown on Ni foam for accelerating the alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Density functional theory (DFT) calculations reveal that the electron transfer from amorphous CrO_x to Ni₃ N at the interfaces, and the optimized Gibbs free energies of H₂ O dissociation (ΔG_H-OH ) and H adsorption (ΔG_H ) in the amorphous/crystalline CrO_x -Ni₃ N heterostructure are conducive to the superior and stable HER activity. Experimental data confirm that numerous oxygen vacancies and amorphous/crystalline interfaces in the CrO_x -Ni₃ N catalysts are favorable for abundant accessible active sites and enhanced intrinsic activity, resulting in excellent catalytic performances for HER and OER. Additionally, the in situ reconstruction of CrO_x -Ni₃ N into highly active Ni₃ N/Ni(OH)₂ is responsible for the optimized OER performance in a long-term stability test. Eventually, an alkaline electrolyzer using CrO_x -Ni₃ N as both cathode and anode has a low cell voltage of 1.53 V at 10 mA cm^-2 , together with extraordinary durability for 500 h, revealing its potential in industrial applications.

Keywords: alkaline water splitting; amorphous/crystalline CrO x-Ni 3N; density functional theory; interface engineering; oxygen vacancy; structure reconstruction.