Insight into the Superior Electrocatalytic Performance of a Ternary Nickel Iron Poly-Phosphide Nanosheet Array: An X-ray Absorption Study.

Although ternary components and doping with foreign atoms have been widely studied to enhance the electrocatalytic performance of transition metal phosphides, the underlying mechanism is not clear. Here, we fabricated ternary Ni-Fe-P nanosheets on carbon fiber paper as efficient electrodes and studied the local atomic and electronic structure alteration through X-ray absorption spectroscopy. The optimized ternary Ni-Fe-P nanosheet electrode exhibited superior hydrogen evolution activity and stability in 0.5 M H2SO4 with a low overpotential of 56 mV at 10 mA cm-2. X-ray absorption spectroscopy studies revealed that with the Fe ion incorporation into the system, the Ni-P bonds elongated and few electrons transferred from Ni to P which resulted in a reduced oxidation state of Ni and reduced the interaction between the hydrogen atom and the catalyst surface. Our work not only demonstrates the future potential of high-performance electrocatalysts based on ternary Ni-Fe-P but also offers a promising method to explore the unique synergistic effect in ternary compounds.