Ultrafast treatment of stainless steel for efficient and stable water electrolysis

Abstract

Stainless steel is widely utilized in industrial applications of alkaline water electrolysis due to its high anti-corrosion property, but it usually suffers from low catalytic activity. The complete activation of stainless steel to improve its efficiency while maintaining its excellent corrosion resistance is thus important for lowering the energy consumption of H2 production. Here, we developed an ultrafast one-step activation for stainless steel based on high-temperature heat treatment and quenching in an aqueous solution. After the activation, the resulting Ni-doped stainless-steel mat (Ni-SSM) exhibited significantly improved activity for both the hydrogen evolution reaction and the oxygen evolution reaction in comparison to pristine SSM. When assembled for overall water electrolysis, Ni-SSM delivered a current density of 100 mA/cm2 at a cell voltage of 1.72 V in 1 M KOH at 25 °C, outperforming most of the stainless-steel-based electrodes reported thus far. Under a quasi-industrial environment of 6 M KOH at 60 °C, Ni-SSM displayed extraordinary performance, producing a current density of 500 mA/cm2 at a low cell voltage of 1.615 V. Further durability testing showed that Ni-SSM maintains high performance at a current density of 500 mA/cm2 under this quasi-industrial environment for at least 150 h. Similar activation processes were applied to different substrates to verify the versatility of this strategy, and enhanced performance for alkaline water electrolysis was observed among all the selected substrates. Finally, 5 × 5 cm2 pieces of Ni-SSM were prepared and assembled in an anion exchange membrane (AEM) electrolyzer, in which they delivered a current of 12.5 A at a cell voltage of 1.93 V in 1 M KOH at 65 °C. Therefore, the effectiveness of this activation strategy for improving activity and its feasibility and versatility together suggest its great potential for industrial application.