Optimizing bulk high-entropy alloys: In-situ carbide microdomains empower efficient electrocatalysis for overall...

Developing cost-effective, simply fabricated, and highly active integrated bulk electrodes is a key target for overall water-splitting electrocatalysts. High-entropy alloys (HEAs) have emerged as promising candidates in electrocatalysis due to their tunable electronic structures and broad design space, yet enhancing the electrocatalytic performance of bulk HEAs remains challenging. Herein, we obtained carbon-containing bulk FeCrNiMoC_x (x = 0.1, 0.2, 0.3, 0.4) HEAs via a facile arc melting method. These HEAs feature in-situ precipitated M₂₃C₆/M₆C carbides, and we for the first time systematically investigated the effect of carbon content on their electrocatalytic performance for overall water splitting. The results show that introducing carbon generates abundant network-like carbides in the alloy structure, and the combination of metal carbides and HEAs improves electrocatalytic activity. Specifically, FeCrNiMoC_0.3 exhibits excellent oxygen evolution reaction (OER, 229 mV @ 10 mA cm^-2, 31.4 mV dec^-1) and hydrogen evolution reaction (HER, 183 mV @ 10 mA cm^-2, 79.2 mV dec^-1) activity. Notably, the catalyst maintains stable overall water-splitting performance for at least 1000 h at 300 mA cm^-2. These improvements stem from in-situ formed carbides in the alloy matrix and surface reconstruction. This work offers a valuable reference for designing high-performance bulk HEA electrocatalysts.