Self-activated anodic nanoporous stainless steel electrocatalysts with high durability for the hydrogen evolution reaction

Stainless steel-based electrocatalysts have attracted tremendous attention as alternatives to precious noble metal-based catalysts for renewable energy research, as they are readily available and inexpensive. Herein, self-activated anodic nanoporous stainless steel is demonstrated as a highly efficient and durable electrode with improved catalytic performance for the hydrogen evolution reaction. Etched and anodized stainless steel (EASS) is prepared by anodization using etched stainless steel 304 foil with a rough surface, followed by thermal annealing. Due to its extremely high surface area, evolved oxygen vacancies, and excellent durability for 100 h at 100 mA cm⁻², EASS that has been annealed in an Ar/H₂ atmosphere (EASS-Ar/H₂) exhibits an overpotential of 370 mV, lower than that of pristine etched stainless steel electrode (466 mV) in 1 M KOH aqueous solution. In contrast, EASS annealed in air (EASS-air) displays no catalytic activity. Interestingly, the overpotential of EASS-Ar/H₂ is further reduced to 244 mV after 10,000 cycles of linear sweep voltammetry by self-activation due to the generation of Ni-rich hydroxide with increasing oxygen vacancies.