In situ capturing site-to-site reactive species in CO2-laser-patterned high-entropy alloy nanoflowers for robust alkaline seawater electrolysis

Abstract

Designing and synthesizing highly competent and stable electrocatalysts for the hydrogen evolution reaction (HER) in both alkaline and natural seawater media remain major obstacles. Herein, we present an ultrafast synthetic approach for producing AuRuIrPdPt high-entropy alloys (HEAs) through continuous-wave CO₂-laser irradiation for 90 s. HEAs synthesized using different CO₂-laser powers (30%, 60%, and 90% of the total 25 W laser power) demonstrated distinctive regularly ordered structures with numerous active sites for the HER. The optimized HEA-60 revealed outstanding HER activity with low overpotentials of 37, 34, and 45 mV at 10 mA cm⁻² in alkaline, simulated seawater, and natural seawater, respectively, outperforming a commercial Pt/C catalyst. In situ/operando electrochemical Raman analysis revealed the involvement of metals (M = Pt, Pd, and Ru) in the HER process, with M–H and M–O observed as intermediates rather than M–OH. Moreover, an overall water-splitting assembly using the IrO₂(+)‖HEAs-60(−) configuration achieved an exceptionally low cell voltage of 1.62 V to reach 10 mA cm⁻² in a natural seawater electrolyte, demonstrating excellent stability. This study emphasizes the use of an ultrafast CO₂-laser-irradiation method for synthesizing extremely stable and active HEAs for hydrogen production via seawater electrolysis.