Surface modification for the enhanced electrocatalytic HCHO oxidation performance of Ni-thin-film-based catalysts

Highlights: • Electrodeposited Ni films were modified by potential cycling in KOH. • KOH modification increases the amount of structurally disordered Ni(OH)₂/NiOOH. • The amount of structurally disordered Ni(OH)₂/NiOOH influences the catalytic properties. • The KOH-modified Ni films provide better catalytic activity towards HCHO oxidation. The main challenge with electrocatalysis is finding low-cost electrocatalysts that can work efficiently to oxidize the HCHO. Here, we propose a mechanism for the voltammetric formation of a highly active, structurally disordered β-Ni(OH)₂/β-NiOOH redox pair on the surface of electrodeposited Ni thin films to achieve an extraordinary catalytic performance with respect to HCHO oxidation in alkaline media. We report electrochemical, XRD and FT-IR measurements on as-deposited and voltammetrically treated (i.e., KOH-modified) Ni thin films, and calculations based on the electrical charge to investigate the changes in the surface composition, crystal structure and related HCHO oxidation activity. We found that the KOH-modification process plays a crucial role in the formation of surface highly active, disordered β-Ni(OH)₂/β-NiOOH. The KOH-modified Ni film with the largest amount of the structurally disordered β-Ni(OH)₂/β-NiOOH resulted in improved catalytic performance, i.e., an onset overpotential reduced by 400 mV and a catalytic rate increased by 69 mV dec⁻¹. The presented technique has a wide range of applications and provides advances with a novel design idea and a new synthesis strategy for the preparation of highly active, structurally disordered Ni(OH)₂/NiOOH redox systems on the surface of Ni thin films and other Ni-based nanostructured electrocatalysts for HCHO oxidation.