Interfacial Engineering of Cobalt Nitrides and Mesoporous Nitrogen-Doped Carbon: Toward Efficient Overall Water-Splitting Activity with Enhanced Charge-Transfer Efficiency

Nonoxides have been widely employed as highly efficient catalysts for water splitting. However, these nonoxides suffer from obvious surface transformation and poor structural stability, which must be urgently remedied. Herein, the interfacial engineering of Co₄N via mesoporous nitrogen-doped carbon (NC) was first carried out, in which NC can significantly suppress the oxidization of Co₄N in alkaline media, ensuring the efficient interfacial charge transport between Co₄N and NC. As a result, extremely low overpotentials @10 mA cm^-2 of 62 mV (hydrogen evolution reaction, HER) and 257 mV (oxygen evolution reaction, OER) and small Tafel slopes of 37 mV (HER) and 58 mV dec^-1 (OER) were achieved in alkaline media. Theoretical calculations suggest that their synergetic coupling effects can significantly facilitate the charge-transfer process and further greatly reduce the energy barrier for water splitting. This work underscores the importance of the surface engineering of nonoxides and efficient approaches for the design of stable catalysts for electrocatalysis.