Electrocatalytic Performance of Trace Vanadium-Doped Fe(CoCrNiMn)V High-Entropy Alloys toward Efficient Freshwater and Seawater Splitting

Against the background of carbon peaking and carbon neutrality goals, green hydrogen has become a clean and efficient energy carrier and a core driving force for energy transition. Water electrolysis accounts for 90% of green hydrogen production and serves as the key route for green hydrogen preparation. However, performance bottlenecks of conventional catalysts severely restrict the large-scale application of green hydrogen. High-entropy alloys, with their unique cocktail effect and lattice distortion, offer an approach to overcome this challenge and have emerged as a critical breakthrough in the green hydrogen field. This work systematically investigated the effect of vanadium content on the electrocatalytic performance of Fe40−x(CoCrNiMn)60Vx high-entropy alloys, focusing on the optimization of hydrogen evolution reaction (HER) activity, and aimed to develop non-noble metal bifunctional electrocatalysts suitable for both freshwater and seawater working conditions. The results showed that the Fe39(CoCrNiMn)60V1 alloy exhibited excellent HER performance within the same system in 1 M KOH electrolyte at a current density of −10 mA cm−2, with an HER overpotential of only 98.3 mV, which was superior to that of most non-noble metal catalysts. This alloy also delivered favorable oxygen evolution reaction (OER) activity with an OER overpotential of 291.7 mV, and no obvious performance decay occurred after a 30 h stability test. In alkaline seawater electrolyte, the alloy maintained stable HER activity, with the HER overpotential slightly increasing to 106.2 mV at an equivalent current density, and the OER overpotential reached 350 mV. In overall water splitting tests, the Fe39(CoCrNiMn)60V1 alloy retained outstanding performance after 100 h of testing in both alkaline freshwater and alkaline seawater electrolytes, which fully demonstrated its great potential to replace noble metal catalysts and realize efficient hydrogen production from seawater. This work not only provided insights into the design of high-entropy alloy electrocatalysts but also was of great significance for enhancing HER performance, promoting large-scale green hydrogen production, and achieving efficient utilization of seawater resources.