Oxygen evolution reaction activity of Ni3(PO4)2 and bimetallic Ni3M3(PO4)4 (M = Mn, Fe, Co): Insights from DFT and experimental validation

The high demand for clean and renewable energy is driving the need for efficient and economical catalysts for the oxygen evolution reaction (OER), which is the most important step in water electrolysis for hydrogen production. However, the main problem in OER is the high overpotential required, so finding a catalyst to reduce the overpotential remains a major challenge. In this work, we investigated the oxygen evolution reaction (OER) activity of nickel phosphate [Ni3(PO4)2] and bimetallic nickel phosphates [Ni3M3(PO4)4; M = Mn, Fe, Co] using a combination of DFT calculations and experimental validation. Our findings show that the (100) surface is the most stable among the surfaces studied for both Ni3(PO4)2 and the bimetallic Ni3M3(PO4)4 compounds. Among the catalysts, the best OER performance was observed on Ni3Fe3(PO4)4(100), with a minimum overpotential of 0.31 V, followed by Ni3Co3(PO4)4(100) (0.37 V), Ni3Mn3(PO4)4(100) (0.38 V), and Ni3(PO4)2(100) (0.58 V). The OER overpotential trend of these catalysts correlates with the adsorption strengths of *O or *OH intermediates. We also synthesized Ni3(PO4)2 and Ni3M3(PO4)4 using self-templating techniques through solvothermal methods. Electrochemical measurements successfully reproduced the OER activity trend predicted by our theoretical calculations.