Laser-induced high-entropy alloys as long-duration bifunctional electrocatalysts for seawater splitting

Abstract

Electrocatalytic seawater splitting has garnered significant attention as a promising approach for eco-friendly, large-scale green hydrogen production. Development of high-efficiency and cost-effective electrocatalysts remains a frontier in this field. Herein, we report a rapid in situ synthesis of FeNiCoCrRu high-entropy alloy nanoparticles (HEA NPs) by direct CO₂ laser induction of metal precursors on carbon paper under ambient conditions. Due to the induced ultrahigh temperature and ultrafast heating/quenching rates, FeNiCoCrRu HEA NPs with sizes ranging from 5 to 40 nm possess uniform phase homogeneity. FeNiCoCrRu HEA NPs exhibit exceptional bifunctional electrocatalytic activities, delivering overpotentials of 0.148 V at 600 mA cm⁻² for the hydrogen evolution reaction and 0.353 V at 300 mA cm⁻² for the oxygen evolution reaction in alkaline seawater. When assembled FeNiCoCrRu HEA NPs to an electrolyzer, it shows a negligible voltage increase at 250 mA cm⁻² even after over 3000-hour operation. This superior performance can be attributed to the high-entropy design, large electrochemical specific area, and excellent chemical and structural stability. An operando Raman spectroscopy study discloses that the Ni and Ru sites serve as active sites for hydrogen evolution, while the Ni site acts as an active site for oxygen evolution. This work demonstrates a laser-induced eco-friendly nanomaterial synthesis. The systematic studies offer an in-depth understanding of HEA design and its correlation with high-efficiency seawater splitting.