Interface engineering of Ni/CoMoO₄ heterostructure for high-efficiency water electrolysis in alkaline media

The development of high-performance bifunctional electrocatalysts is crucial for advancing sustainable hydrogen production through water splitting. In this work, we reported a Nickel-modified cobalt molybdate (Ni/CoMoO₄) catalyst synthesized by hydrothermal and followed by electrodeposition on nickel foam (NF). The incorporation of Ni significantly improved the electrical conductivity, enhanced the surface wettability, and further strengthened the structural stability, which dramatically enhanced the electrocatalytic reaction kinetics. Consequently, the Ni/CoMoO₄ catalyst exhibited outstanding bifunctional activity for both HER and OER in alkaline media, delivering exceptionally low overpotentials of 47 mV (HER) and 222 mV (OER) at 10 mA cm^-2. Moreover, the catalyst demonstrated exceptional operational stability, maintaining performance for over 100 h (HER) and 200 h (OER) without significant degradation. in-situ Raman spectroscopy revealed that the catalyst maintained structural stability during HER, while undergoing reconstruction into Co-modified NiOOH during OER due to Mo leaching. Mo leaching increased the accessibility of exposed nickel sites, while the concurrent formation of γ-NiOOH expanded the population of active sites, collectively enhancing the current density. Additionally, overall water-splitting test in 1.0 M KOH revealed a low cell voltage of 1.53 V at 10 mA cm^-2, demonstrating over 450 h of excellent stability at 100 mA cm^-2. These findings advanced the development of efficient and stable bifunctional catalysts.