Boosting the HER performance of binary MnO₂–CdSe heterostructure via interface engineering with g-C₃N₄

The water-splitting process is significant in meeting the global energy demands, but HER's enormous potential has limited its large-scale utilization. So, cost-effective and active electrocatalysts have been extensively researched to maximize hydrogen evolution performance. We present here the unique and attractive strategy of hetero-interface engineering, as a combination of bimetallic compound (MnO₂–CdSe) with carbon material (g-C₃N₄), which provides different phases analyzed via powder XRD. We explored the crumpled structure of MnO₂–CdSe/g-C₃N₄ that gives rise to the surface area and conductivity through generated plane defects/abundant open spaces. Moreover, XPS confirmed the good synergistic interaction and displayed vacancies in the MnO₂–CdSe/g-C₃N₄ structure, which significantly promoted the charge transfer potential and attracted the H⁺ ions for hydrogen formation. Benefitted from modifying the electronic environment of the bimetallic centre via interface engineering, the MnO₂–CdSe/g-C₃N₄ electrocatalyst achieved outstanding HER activity: the overpotential and Tafel slope are as low as 99 mV and 53 mV dec⁻¹, respectively, evaluated at 10 mA cm⁻² current density. Moreover, DFT calculation found the dramatically reduced energy barriers for coupling H∗ on MnO₂–CdSe, suggesting that the synergistic interaction between MnO₂ and CdSe corresponds to the Volmer-Heyrovsky pathway. By taking the DFT analysis of bimetallic MnO₂–CdSe, we can assume that the MnO₂–CdSe/g-C₃N₄ heterostructure with multiple active sites could reduce the adsorption energy of H∗, even less than the adsorption energy on MnO₂–CdSe. Moreover, EIS investigated the small impedance effects at an electrode-electrolyte surface that ensured its good conductive property for the HER mechanism. The proposed strategy showed superior catalyst stability throughout 80 h with no decay, emphasizing the interface engineering with a growing family of carbon materials for future applications.