Engineering Confined Reconstruction in Au‐Co ₂ P Yolk‐Shell Heterostructure Enables Crystalline CoOOH for High‐Current and Photo‐Enhanced Oxygen Evolution

ABSTRACT The reconstruction of transition‐metal phosphides during the oxygen evolution reaction (OER) typically produces amorphous oxyhydroxides accompanied by severe phosphorus loss, which may lead to undesired catalytic behavior at high current densities. Here we introduce a confined reconstruction strategy enabled by Au‐Co 2 P yolk‐shell heterostructure, which fundamentally reshapes the evolution pathway of Co 2 P under OER conditions. The channel‐rich shell and internal cavity suppress rapid phosphorus loss and promote the formation of crystalline CoOOH, rather than the amorphous phases formed in the Au/Co 2 P core/shell and pristine Co 2 P. Therefore, the Au‐Co 2 P yolk‐shell catalyst exhibits markedly enhanced OER activity and durability, which could be further enhanced under light illumination, requiring an overpotential of 371 mV at 200 mA cm −2 with a Tafel slope of 46.4 mV dec −1 . This work provides new insights into the structural design of OER catalysts capable of operating at high current densities and responding to photoactivation.