Abstract: The practicality of electrochemical water-splitting technology relies on the development of novel and efficient bifunctional electrocatalysts capable of facilitating both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Black phosphorus (BP) holds tremendous promise for HER and OER electrocatalysis owing to its fully exposed atoms and high carrier mobility. However, the electrocatalytic performance of BP is still much lower than the expected theoretical limit, presenting an exciting challenge for further advancements. Herein, we embed electrochemically exfoliated few-layer BP nanosheets in higher Fermi level (E_F) of cobalt, nitrogen co-doped carbons to form a new heterojunction (CoNC-BP), as efficient bifunctional electrocatalysts toward HER and OER for the advancement overall water splitting applications. A directed interfacial electron transfer is realized from CoNC to BP, facilitated by the lowering Fermi level (E_F). This interfacial electron transfer plays a crucial role in optimizing the adsorption and desorption of active intermediates, while also introducing an abundance of hypervalent Co sites. These factors collectively contribute to the remarkable electrocatalytic activities of HER and OER performance, leading to the efficient performance of the developed CoNC-BP heterojunction in water-splitting applications. This work demonstrates a promising breakthrough that can inspire the design of high-efficiency catalysts.

Key words: Directional charge transfer, Black phosphorus, Co, N co-doped carbon, Heterointerface, Electrocatalytic water splitting