N-Doping Effects On Electrocatalytic Water Splitting of Non-Noble High-Entropy Alloy Nanoparticles Prepared by Inert Gas Condensation

The unique catalytic activities of high-entropy alloys (HEAs) emerge from the complex interaction among different elements in a single-phase solid solution. As a "green" nanofabrication technique, inert gas condensation (IGC) combined with laser source opens up a highly efficient avenue to develop HEA nanoparticles (NPs) for catalysis and energy storage. In this work, the novel N-doped non-noble HEA NPs are designed and successfully prepared by IGC. The N-doping effects of HEA NPs on oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are systematically investigated. The results show that N-doping is conducive to improving the OER, but unfavorable for HER activity. The FeCoNiCrN NPs achieve an overpotential of 269.7 mV for OER at a current density of 10 mA cm in 1.0 M KOH solution, which is among the best reported values for non-noble HEA catalysts. The effects of the differences in electronegativity, ionization energy and electron affinity energy among mixed elements in N-doped HEAs are discussed as inducing electron transfer efficiency. Combined with X-ray photoelectron spectroscopy and the extended X-ray absorption fine structure analysis, an element-design strategy in N-doped HEAs electrocatalysts is proposed to improve the intrinsic activity and ameliorate water splitting performance.