Interface prompted highly efficient hydrogen evolution of MoS₂/CoS₂ heterostructures in a wide pH range

Interfacial electronic characteristics are crucial for the hydrogen evolution reaction (HER), especially in nanoscale heterogeneous catalysts. In this work, we found that the synergistic activation of CoS₂ and MoS₂ (2H-MoS₂ and 1T-MoS₂) greatly enhances the HER activity in a wide pH range compared to those of each component. The Gibbs free energies for hydrogen adsorption at interfacial Co sites are as low as -0.08 (-0.25) eV and -0.20 (0.01) eV for 2H-MoS₂/CoS₂ and 1T-MoS₂/CoS₂ heterostructures in acidic (alkaline) media, respectively, which are even superior to that of Pt(111) (-0.09 eV). Moreover, the theoretical exchange current density of MoS₂/CoS₂ can reach ∼1.98 × 10^-18 A site^-1 (∼8.43 A mg^-1). Experimentally, MoS₂/CoS₂ exhibits a greatly reduced overpotential of 54 (46) mV and a Tafel slope of 42 (50) mV dec^-1 under acidic (alkaline) conditions. The improved performance mainly originates from the synergistically activated interfacial Co atoms with better electron localization and local bonding. The interfacial effect enhances the electron conductivity and improves the H adsorption characteristics, making MoS₂/CoS₂ highly valuable as efficient HER electrocatalysts.