Efficient stainless steel-based bifunctional water electrolysis electrode: Activating the OPM mechanism in OER and enhancing HER performance

Low-cost, resource-rich and efficient bifunctional catalysts play a crucial role in advancing hydrogen production and its applications. In this study, based on inexpensive and readily available stainless steel materials, we designed and synthesized an efficient and cost-effective stainless steel-based bifunctional water electrolysis electrode (Ru-PSS) through a coupling interface and doping strategy. Specifically, at a current density of 500 mA∙cm^-2, the electrode exhibited a hydrogen evolution reaction (HER) overpotential of just 248 mV and an oxygen evolution reaction (OER) overpotential of only 353 mV. Notably, a symmetrical anion exchange membrane (AEM) electrolyser assembled with Ru-PSS electrodes can achieve an industrial high current density of 500 mA∙cm^-2 at a low voltage of only 1.82 V. In situ electrochemical Fourier transform infrared spectroscopy (FTIR) experiments further indicate that the electrode involves the adsorption evolution mechanism (AEM) and oxide pathway mechanism (OPM), both of which jointly promote oxygen evolution reaction. Comprehensive material characterization and density-functional theory (DFT) indicate that in situ phosphorylation synthesizes heterostructures (FeP₄/Ni₂P) on the stainless steel surface, providing abundant active sites for catalytic reactions. Subsequently, trace Ru doping (Ru-FeP₄/Ni₂P) not only significantly improves the HER performance by optimizing the free energy of hydrogen adsorption (ΔG_H*), but also activates a more catalytically active OPM reaction mechanism by modulating the electronic structure. This study provides innovative design ideas and theoretical guidance for the development of highly efficient and stable new steel-based catalysts for water electrolysis.