Rational design of multi-metal oxysulfide electrocatalysts for efficient scalable anion exchange membrane water electrolyzer

The rational design of efficient, non-precious electrocatalysts for anion exchange membrane water electrolysis (AEMWE) remains critical for sustainable hydrogen production. This work aims to develop cost-effective, noble metal-free transition metal nano electrocatalysts for the simultaneous generation of green hydrogen through water splitting. Herein, we synthesize multi-metal transitional oxysulfide Fe_0.2Cu_0.2Co_0.2Zn_0.2Ni_0.2 (FCCZN) electrocatalysts via solution combustion synthesis and chemical bath deposition, resulting in nanoball-nanosheet architectures. Cu-FCCZN achieves a hydrogen evolution reaction (HER) overpotential of 70 mV at 10 mA cm⁻² with a Tafel slope of 87.92 mV dec⁻¹, while Fe-FCCZN requires 273 mV for the oxygen evolution reaction (OER) at 10 mA cm⁻². The optimized Cu-FCCZN and Fe-FCCZN exhibit excellent operational stability for over 100 h at a current density of 200 mA cm⁻². Structural analysis reveals interfacial oxygen/sulfur-rich active sites that enhance conductivity and stabilize intermediates. Moreover, a scalable 16 cm² overall AEM water electrolyzer constructed using a Cu-FCCZN||Fe-FCCZN electrocatalyst operates stably for 250 h at 200 mA cm⁻² with a cell voltage of 4.41 V in 1 M KOH, outperforming reported noble-metal-free devices. This work provides a cost-effective strategy for designing high-performance electrocatalysts, advancing industrial-scale green hydrogen production.