Phosphorus and Cobalt Codoped Transition-Metal Oxides with Accelerated Surface Reconstruction for Efficient Alkaline Oxygen Evolution Reactions

Developing highly efficient nonprecious metal catalysts for oxygen evolution reactions (OERs) is crucial for the development of water electrolysis; however, these catalysts face challenges such as high overpotential and insufficient durability at high current densities. In this study, we successfully prepared ordered needlelike structured Co-Fe hydroxide with F-ion immersion (Fe/Co(OH)F) on the surface of nickel foam and explored the synergistic strengthening effects of Mo cation doping and P anion doping. The ordered needlelike structure of Fe/Co(OH)F was destroyed during the phosphating calcination process, while Mo doping transformed it into a rough surface platelike structure. By combining Mo doping with phosphating treatment, the obtained Fe/F-MoCo-PO_x catalyst presented a crystalline-amorphous heterostructure and platelike morphology with enhanced OER performance. At a high current density of 200 mA cm^-2, the Fe/F-MoCo-PO_x catalyst exhibited an overpotential of 300 mV without i-R compensation and maintained a potential decay rate of only 0.16 mV h^-1 after a 560 h durability test. Electrochemical testing combined with phase structure and composition analysis revealed that P doping induced the formation of an amorphous surface layer of hypophosphite Fe(PO₃)₃, which was found to undergo anion exchange with *OH during electrochemical testing. This surface reconstruction thus formed a rich -OH catalytic layer on the surface of Fe/F-MoCo-PO_x, which then exhibited a remarkably lowered overpotential and boosted OER kinetics, surpassing most state-of-the-art OER electrocatalysts. This finding underscores the synergistic effect of Mo and P doping in forming a crystalline-amorphous heterostructure, which boosts alkaline OER performance, aiding in cost reduction and improvement of the hydrogen production efficiency through water electrolysis at high current densities.