Phosphorus and Cobalt Codoped Transition-Metal Oxides with Accelerated Surface Reconstruction for Efficient Alkaline...

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 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 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, 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.