Interfacial Water Activation by Single-Atom Co–N3 Sites Coupled with Encapsulated Co Nanocrystals for Accelerating Electrocatalytic Hydrogen Evolution

Using high-efficiency and low-cost catalyst to replace noble metal platinum for electrocatalytic hydrogen evolution reaction (HER) provides a broad prospect for the development of renewable energy technology, which is an important task yet to be solved. Herein, we proposed an efficient doping–adsorption–pyrolysis strategy for constructing a robust coupling catalyst composed of single-atom Co–N3 sites anchored on an N-doped carbon (N–C) layer and encapsulated Co nanocrystals (NCs) to activate the interfacial water for accelerating HER. Beneficial to the strong synergistic effect of Co–N3 sites and Co NCs, the optimized CoNC‑SA/N*–C catalyst showed excellent HER activity and stability in both acidic and alkaline electrolytes. In situ attenuated total reflectance–surface-enhanced infrared absorption spectroscopy revealed that the rigid interfacial water layer of Co–N3 sites inhibited the transport of H2O*/OH*, while Co NCs promoted the transport of H2O*/OH* and increased the amount of available H2O* on Co–N3 sites by disordering the rigid interfacial water network. Theoretical calculation showed that the coupling interface structure destroyed the rigid interfacial network, and Co NCs modified the electronic structure of Co–N3 sites, which is beneficial to H2O dissociation and H adsorption, thus accelerating the HER process. This work opens up new avenues for the construction of coupling catalysts from the atomic scale to activate the interfacial water for boosting HER electrocatalysis.