Metal-semiconductor interfacial engineering for enhanced electrocatalytic water reduction activity in alkaline media

The development of efficient electrocatalysts for the hydrogen evolution reaction in alkaline media is crucial for advancing energy technologies. Therefore, the design of electrocatalysts based on electronic properties like work function and band potentials has gained enormous attention. Herein, the Cu@Co3O4 and Cu@MnNi2O4 metal–semiconductor junctions engineered Ohmic and Schottky interfaces based on the work function and band potential adjustments were reported. Moreover, the p-n junction and copper-loaded p-n junctions were also explored. The copper loading causes a decrease in work function in the metal–semiconductor junctions and p-n junction (semiconductor-semiconductor). Moreover, the band potentials were also altered by loading copper NPs. The improved interfacial electron transfer, and modulated electronic structures facilitate enhanced electrocatalytic water reduction activity in alkaline media. The Cu@MnNi2O4 catalyst demonstrated superior HER performance, with an overpotential of just 110 mV at 10 mA·cm−2, attributed to the presence of a Mott-Schottky junction that induces a built-in electric field, enhancing charge separation and minimizing current loss. Moreover, the presence of Mn3+ in MnNi2O4 enhances the low-valence Ni2+ state to accelerate the Volmer step. This work emphasizes the synergistic role of copper loading in improving the electrocatalytic water reduction performance of spinel oxides and proposes a versatile interfacial engineering strategy for designing efficient, non-noble metal-based catalysts.