Grain boundary segregation engineering in high-entropy multiphase alloys for overall water splitting at ultra-high current density

In industrial water splitting, alkaline electrolyzers demonstrate promising development prospects due to lower costs and enhanced safety. However, for anion-exchange membrane (AEM) systems, require high current densities (> 2 A cm⁻²) to optimize energy utilization efficiency. High-entropy alloys (HEAs) have recognized as viable electrocatalysts for water splitting owing to their exceptional activity and cost-effectiveness. However, their complex composition design and practical application at ultra-high industrial current density remains a significant challenge. Herein, we develop a theoretical and experimental approach combined efficient component screening and heterostructure regulation to improve the oxygen evolution reaction (OER) activity and stability at ultra-high current density in high-entropy multiphase alloys, leveraging machine learning (ML) techniques and grain boundary segregation engineering (GBSE). The Fe₂₀Co₂₀Ni₂₀Mo₂₀Cu₁₅Al₅ electrocatalyst, synthesized via a melt-extraction method and exhibiting intrinsic self-supporting properties, demonstrated outstanding OER performance with an overpotential (ŋ) of 370@1 A cm⁻² and 497 mV@3 A cm⁻², while maintained stability for approximately 800 and 95 h. A notable achievement is that the voltage of electrolyzer is approximately 1.90 V at current density of 0.5 A cm⁻² with stable operation for 100 h when using the Fe₂₀Co₂₀Ni₂₀Mo₂₀Cu₁₅Al₅ as both anode and cathode for overall water splitting in an AEM electrolyzer. The mixing enthalpy and prepared method facilitates Cu grain boundary segregation, enhancing both the activity of Ni sites and the overall conductivity. These findings offer a practicable HEAs design strategy for catalysis that realizes the manipulation of active sites on atomic scale and underscore the potential of HEAs for industrial-scale applications in water splitting.