Ternary Ni:Fe- activated inert Cu-based electrocatalyst as efficient bifunctional electrocatalysts for water splitting

Abstract

Cost-effective copper-based materials with their abundant reserves, good electrical conductivity, and a wide range of redox properties that are promising for the electrochemical energy field, but they exhibit inertness and slow reaction kinetics for electrocatalysis. Therefore, improving the catalytic activity of Cu is prospective but still challenging. Herein, we developed a Ni and Fe-doped CuO/Cu₂O heterojunction catalyst with oxygen vacancies, which presented distinguished bifunctional catalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. Remarkably, the adsorption/desorption energy of H₂O on surface of the catalyst had been definitely demonstrated via theoretical calculation and experiments, indicating that Fe, Ni bimetallic activated the inertness of the Cu-based materials. Fe doped corroded the Cu substrate and induced more oxygen vacancies, thereby increasing the electrochemically active area and ultimately enhancing the catalytic performance of the overall catalyst. Consequently, the cell voltage of Ni:Fe-CuO/Cu₂O catalysts for a current density of 10/20 mA·cm⁻² in an alkaline electrolyzer was just 1.51/1.69 V, and it exhibited an excellent stability. In addition, the cell voltage of the electrolyzer at of 10 mA·cm⁻² was just 1.30 V in simulated industrial hydrogen production via water electrolysis, and the current density can be as high as 1.8 A·cm⁻² at a voltage of 2.5 V. This study highlights the significant impact of electronic structure modulation and oxygen vacancies on copper-based catalysts, greatly enhancing the electrocatalytic activity of inert copper.