Dynamic Mo leaching and vacancy engineering synergize HER and OER kinetics in NiFe-based catalysts for overall water electrolysis

Abstract

Developing efficient and stable non-precious metal bifunctional catalysts for overall water splitting (OWS) is a promising strategy for industrial hydrogen production. A major challenge is how to balance the distinct active site requirements for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we report a NiFe layered double hydroxide incorporated with molybdenum (Mo) (NFM_0.5–H) for the purpose. During the electrochemical process, Mo leaching generates oxygen vacancies, which facilitate the formation of OER active sites and modulate the interfacial microenvironment to enhance HER kinetics. The integration of atomic incorporation and defect engineering significantly accelerates the overall reaction kinetics. NFM_0.5–H delivers outstanding performance for overall water splitting (OWS), achieving low HER and OER overpotentials of 40 and 230 mV, respectively, at 10 mA cm⁻² in alkaline media. It drives a low cell voltage of 1.51 V (10 mA cm⁻²) for OWS and maintains long-term stability at 500 mA cm⁻² for over 300 hours. Tests in an alkaline anion exchange membrane water electrolyzer (AEMWE) further confirm the industrial application potential of NFM_0.5–H. This work offers new insights into the rational design of advanced OWS catalysts with both high activity and durability.