Coupling Adsorbed Evolution and Lattice Oxygen Mechanism in Fe‐Co(OH) 2 /Fe 2 O 3 Heterostructure for Enhanced Electrochemical Water Oxidation

Abstract Oxygen evolution reaction (OER) remains a bottleneck for electrocatalytic water‐splitting to generate hydrogen. However, the traditional adsorbed evolution mechanism (AEM) possesses sluggish reaction kinetics due to the scaling relationship, while lattice oxygen mechanism (LOM) triggers an unstable structure due to the escaping of lattice oxygen. Herein, a proof‐of‐concept Fe‐Co(OH) 2 /Fe 2 O 3 heterostructure is put forward, where Fe‐Co(OH) 2 following AEM can complete rapidly deprotonation process while Fe 2 O 3 following LOM can trigger O─O coupling step. Combining the theoretical and experimental investigation confirmed that the redistributed space‐charge of Fe‐Co(OH) 2 /Fe 2 O 3 junction can optimize synergistically adsorbed and lattice oxygen, the coupling mechanism of AEM and LOM can facilitate synchronously the OER activity and stability. As a result, the Fe‐Co(OH) 2 /Fe 2 O 3 heterostructure shows excellent OER performance with low overpotential of only 219 and 249 mV to reach a current density of 10 and 100 mA cm −2 . Specifically, the Fe‐Co(OH) 2 /Fe 2 O 3 electrocatalyst maintains excellent long‐term stability for 100 h at a large current density of 100 mA cm −2 . This work paves an avenue to break through the limit of the conventional OER mechanism.