Precatalytic surface roughness of Fe-modified Ni electrodes translates into intrinsic sites for oxygen evolution reactivity

Abstract

Optimizing electrode surfaces in alkaline water electrolysis is critical for performance and long-term stability. Industrial nickel-based electrodes are typically conditioned via acid leaching to increase surface roughness and Fe deposition to enhance electrocatalytic properties for the oxygen evolution reaction (OER). Here, we establish a mechanistic link between real nickel foam electrodes and morphology-controlled Ni(111) model surfaces. We show that increased electrocatalytic activity from induced surface roughness in the precatalytic state is not primarily due to higher electrochemically active surface area, but to the preferential formation of the intrinsically OER active phases. Undercoordinated step sites on Ni(111) favor active NiOOH whereas inactive NiO forms on planar facets. Furthermore, Fe preferentially deposits at step-edge sites, creating a site-specific synergy that stabilizes Fe-promoted NiOOH phases. These findings demonstrate a dual role of surface roughness, revealing how nanoscale surface topology in the preconditioned state directly governs catalytic OER performance.