Electronic‐State Modulation of Metallic Co‐Assisted Co7Fe3 Alloy Heterostructure for Highly Efficient and Stable Overall Water Splitting

Manipulating electronic structure of alloy‐based electrocatalysts can eagerly regulate its catalytic efficiency and corrosion resistance for water splitting and fundamentally understand the catalytic mechanisms for oxygen/hydrogen evolution reactions (OER/HER). Herein, the metallic Co‐assisted Co7Fe3 alloy heterojunction (Co7Fe3/Co) embeds in a 3D honeycomb‐like graphitic carbon is purposely constructed as a bifunctional catalyst for overall water splitting. As‐marked Co7Fe3/Co‐600 displays the excellent catalytic activities in alkaline media with low overpotentials of 200 mV for OER and 68 mV for HER at 10 mA cm−2. Theoretical calculations reveal the electronic redistribution after coupling Co with Co7Fe3, which likely forms the electron‐rich state over interfaces and the electron‐delocalized state at Co7Fe3 alloy. This process changes the d‐band center position of Co7Fe3/Co and optimizes the affinity of catalyst surface to intermediates, thus promoting the intrinsic OER/HER activities. For overall water splitting, the electrolyzer only requires a cell voltage of 1.50 V to achieve 10 mA cm−2 and dramatically retains 99.1% of original activity after 100 h of continuous operation. This work proposes an insight into modulation of electronic state in alloy/metal heterojunctions and explores a new path to construct more competitive electrocatalysts for overall water splitting. Co7Fe3/Co heterojunction embeds in 3D honeycomb‐like graphitic carbon is constructed as a bifunctional catalyst. What is distinctive in the structure is that metallic Co is devoted entirely to assist the formation of electron‐rich state over interface and delocalize the surface electronic state at Co7Fe3. This process changes d‐band center position of Co7Fe3/Co and optimizes affinity of catalyst surface to intermediates.