High-entropy alloys for enhanced electrocatalytic methane oxidation via nanoparticle-impact technique

The direct electrochemical oxidation of methane to high-value products under mild conditions holds significant economic importance, but challenges, such as insufficient active sites, poor product selectivity, and sluggish reaction kinetics, often persist. Herein, NiCuCoMnAg high-entropy alloys (HEAs) were prepared via a freeze-thaw method as highly active and selective catalysts for the methane electrooxidation reaction (CH₄OR). The NiCuCoMnAg HEAs achieved a Faradaic efficiency (FE) of 95.3% for ethanol (CH₃CH₂OH) production at 1.4 V vs. reversible hydrogen electrode (RHE), outperforming NiCuCoAg medium-entropy alloys (MEAs) and NiCuAg low-entropy alloys (LEAs). Furthermore, in the nano-impact electrochemical system at 1.4 V vs. RHE, the NiCuCoMnAg HEAs exhibited a significantly higher current of 0.821 mA compared to NiCuCoAg MEAs and NiCuAg LEAs. This superior catalytic performance likely stems from the unsaturated metal sites, complex coordination environment, and high configurational entropy of the NiCuCoMnAg HEAs, which facilitate *CH₃ dehydrogenation and the adsorption of *CH₂OH and *CH₃ intermediates, thereby promoting C–C coupling and ultimately enhancing CH₃CH₂OH production. Additionally, this work not only provides insights into the controllable synthesis of alloy materials with varying configurational entropy but also pioneers the application of HEAs in the electrocatalytic oxidation of methane to ethanol.