Tuning\nPalladium Nickel Phosphide toward Efficient\nOxygen Evolution Performance

Abstract

Highly\nefficient and durable catalysts are increasingly sought\nin water electrolysis, particularly\nfor resolving the sluggish oxygen evolution reaction (OER) kinetics.\nHerein, ternary phosphides in the palladium–nickel–phosphorus\nsystem developed via a simple reduction approach as hollow and dense\nnanostructures (PdNiP-H and PdNiP-D, respectively) are shown to overcome\nthe kinetic drawbacks of Pd and deliver superior alkaline OER activity.\nThe PdNiP-H showed OER activity at a significantly lower overpotential\n(300 mV) and Tafel slope (48 mV dec^–1) in addition\nto having a longer stability than the corresponding dense particles\n(PdNiP-D) (330 mV and 49 mV dec^–1) and the commercial\nbenchmark, RuO₂ (360 mV and 67 mV dec^–1), in half-cell conditions. While combining experiments and density\nfunctional theory (DFT) calculations, these enhancements are shown\nto arise from surface properties and the modified electronic environment\nof the ternary phosphide as well as by the enhanced charge transfer\nsites due to the hollow architecture. DFT calculations identify the\ndensity of states (DOS) and support Pd lattice alteration, the shift\nin the d band center, and the subsequent modification in electronic\nproperties of Pd that is favorable for OER. The phosphodization methodology\nadopted here highlights an efficient strategy for generating a range\nof morphologies of ternary phosphides as sustainable and stable energy\nconversion/storage materials.