Interfacial evolution: A hydrothermal activation strategy to boost OER activity for stainless steel

Water electrolysis is one of the most competitive approaches to generate hydrogen. The economical stainless steel, which consists of transition metals such as Ni and Fe, has impressive catalytic tunability and tremendous application potential in hydrogen production. In this work, a hydrothermal activation strategy is proposed for breaking the inert oxide layer of stainless steel and producing an active catalytic layer dominated by NiFe2O4 spinel nanoparticles on the surface. The molybdate further complexes with the metal ions, disrupting the initial regular crystals of NiFe2O4 and exposing more defects. At the same time, Mo atoms can further optimize the electronic structure, which is conducive to the kinetic process of the reaction. Consequently, the modified stainless steel requires only 270 mV to achieve a current density of 10 mA·cm−2, much lower than 387 mV of bare 304 stainless steel (SS304). Moreover, the robust catalytic layer, evolved from the stainless steel's own elements, grows firmly on the surface and shows excellent stability in the test of 120 h. This work provides a novel strategy for developing low-cost stainless steel electrodes with superior performance and stability for oxygen evolution.