Concentrated KOH-activated 3D-printed martensitic steel for high-performance alkaline water electrolysis

Alkaline water electrolysis (AWE) is a promising green hydrogen production technology, yet it is hindered by high-cost noble metal catalysts and poor low-cost alternatives. This study shows that 3D-printed martensitic steel, particularly a Ni11.0-Co13.5-Cr3.2-Mo1.2-C0.2-Fe70.9 alloy, becomes a highly efficient AWE electrocatalyst after cyclic voltammetry activation in KOH. Before activation the HER performance improved with higher Co but remained suboptimal, while after activation the alloy exhibited a remarkable enhancement: low overpotential at high current density and a drastically reduced Tafel slope. This improvement stems from surface reconstruction forming a nanoporous structure and a hydroxylated layer, increasing the electrochemically active surface area. This work provides a low-cost, high-performance alternative to noble metal catalysts, advancing green hydrogen scalability for energy and environmental challenges.