P vacancies at the crystalline-amorphous interface of NiFe(OH)x/NiPx/NF enhance the catalytic activity of the oxygen evolution reaction

Efficient electrocatalysts are crucial for overcoming the sluggish kinetics of the oxygen-evolution reaction (OER) and facilitating the advancement of energy storage technologies such as metal-air batteries and hydrogen production through water electrolysis. This study proposes a synergistic approach combining amorphization and interfacial engineering to improve OER performance by fabricating heterojunctions between crystalline NiFe(OH) x and amorphous NiP x . The formation of a strongly coupled crystalline-amorphous heterojunction enables optimization of the electronic structure at the catalytic site and accelerates charge transfer at the interface, thereby improving the reaction kinetics. Notably, we investigate the dynamic adsorption behavior of PO 4 3− during the OER process by introducing Na 3 PO 4 into the electrolyte, revealing that P vacancies serve as active sites in promoting OER activity. Lastly, electrochemical measurements demonstrate that NiFe(OH) x /NiP x /NF exhibits a low overpotential of 220 mV at 10 mA cm −2 and Tafel slope of 35 mV·dec −1 , surpassing the performance of laboratory-prepared noble metal catalysts and most reported NiFe-based electrocatalysts.