Vacancy-fused multiple layers of copper sulfoselenide superstructures: a propitious HER electrocatalyst in acidic medium

Abstract

An advanced vacancy-rich bi-chalcogenide, Cu₂S–Se@Cu, was perceived to be a highly efficient and sustainable catalyst towards HER in acid due to its synergistic effects. Interestingly, the selenization of Cu₂S@Cu foams created oxygen vacancies with enriched layered Cu₂S–Se superstructures by wet-chemical and hydrothermal approaches. The best catalyst Cu₂S–Se@Cu-Wet exhibited a small overpotential of 315 mV at 100 mA cm⁻² and a low Tafel slope of 97 mV dec⁻¹. Benefiting from the intrinsic activity, Cu₂S–Se-Wet delivered a high mass activity of 2675 mA mg⁻¹ cm⁻² and a turnover frequency of 0.371 s⁻¹. Moreover, the Faradaic efficiency measured by gas chromatography (GC) for Cu₂S–Se@Cu-Wet showed 97.16% efficiency. Density functional theory (DFT) studies for HERs depicted that Cu₂S–Se at the surface of the Cu(001) plane revealed a favourable free energy ΔG_H* of −0.36 eV. From the density of states (DoS), it is affirmed that Cu₂S–Se over the Cu surface has reduced the band gap close to zero, which stressed the enhanced HER catalytic activity with O-vacancies. The HER enhancement of such vacancy with the electrocatalytic system creates a new response toward stability and reproducibility in the near future.