Electrocatalytic Hydrogen Evolution in Alkaline Medium Using the ZnCo2O4–WO3 Heterostructure: Experimental and DFT Insights

Abstract

Hydrogen is a clean and environmentally friendly energy carrier, and it is a promising alternative to fossil fuels for sustainable energy applications. The hydrogen evolution reaction (HER) through water splitting offers a direct and cost-effective method to address the increasing global energy demand. Although the hydrogen evolution reaction (HER) is generally regarded as faster than the oxygen evolution reaction (OER), its performance in alkaline electrolytes is hindered by slow kinetics, which poses a significant challenge to its overall efficiency. Developing electrocatalysts that match the efficiency of Pt while utilizing inexpensive, earth-abundant materials is crucial for commercially viable water electrolysis. In this work, we have synthesized a ZnCo₂O₄–WO₃ (ZCO-WO₃) heterostructure via an electrostatic self-assembly method and explored its effectiveness toward the electrocatalytic HER in the alkaline electrolyte. This electrocatalyst exhibits excellent HER performance with a low overpotential and Tafel slope of 165 mV (at 10 mA cm^–2) and 91.64 mV dec^–1, respectively, and demonstrates long-term stability for a duration of 20 h at 50 mA cm^–2. Further, density functional theory (DFT) calculations were carried out to gain insights into the structure–activity relationship of ZCO-WO₃. The DFT study confirmed that it can reduce hydrogen adsorption energy, achieve a small Gibbs free energy difference, and enhance charge carrier density on the catalyst surface, suggesting the synergy between the components and improved electrocatalytic performance of the ZCO-WO₃ heterostructure.