Activation protocols for stainless steel in alkaline water electrolysis: trends and limitations

Stainless steel offers low cost and broad industrial availability, yet its intrinsic activity toward the oxygen evolution reaction is insufficient unless suitable surface-activation treatments are applied. Despite extensive research, the literature relies on heterogeneous and inconsistently reported activation protocols, which complicates cross-comparison and limits the identification of reliable structure–property relationships. This review systematically examines representative chemical, thermochemical, and electrochemical surface-modification strategies applied to stainless steel electrodes, compiling detailed treatment protocols and comparing performance metrics obtained under equivalent electrolyte conditions, temperatures, and benchmark current densities. The analysis reveals a consistent trend: low overpotentials are achieved predominantly only when activation treatments generate Ni-rich oxyhydroxide layers, whereas surfaces dominated by Fe- or Cr-oxides exhibit poorer performance. Electrochemical activation routes provide the most favorable balance of activity and processing time. Overall, the findings highlight stainless steel as a viable low-cost oxygen evolution reaction (OER) for the anode. They further indicate that, when appropriately activated, it may become a promising option for alkaline electrolyzers. At the same time, the review underscores the urgent need for standardized reporting and testing protocols to improve reproducibility, enable meaningful comparison, and guide the scale-up of activation strategies toward industrial implementation.