Controllable voltammetric formation of a structurally disordered NiOOH/Ni(OH)2 redox pair on Ni-nanowire electrodes for enhanced electrocatalytic formaldehyde oxidation

In present work, we report on the enhanced electrocatalytic activity of formaldehyde oxidation in alkaline media for modified Ni nanowires (NWs)-based electrodes. Electrochemically deposited Ni NWs composed of metallic Ni and surface NiO were modified in KOH via cyclic voltammetry using different scan rates (10, 200 and 400 mV s−1) in order to transform an inactive NiO to the surface-catalytic-active structurally disordered β-NiOOH/β-Ni(OH)2. Various characterisations (XRD and FT-IR) and calculations based on the electric charge were performed to understand the surface transformations which were found to be scan-rate dependant. The cyclic voltammetry results and kinetic parameters (Tafel plot) of formaldehyde oxidation revealed the superior electrocatalytic activity of the Ni-NW-electrode modified at 200 mV s−1. The enhanced electrocatalytic performance, i.e., decreased onset overpotential by 400 mV when compared to Ni-based electrocatalysts, of this electrode was attributed to the thickness of structurally disordered the Ni–NiOOH/Ni(OH)2 and composite layered structure that enables the electron injection to reduce the NiOOH work function and thus promote the catalysis of formaldehyde oxidation. The proposed technique provides advances with a novel synthesis strategy for the preparation of highly active, structurally disordered β-Ni(OH)2/β-NiOOH redox systems on the surface of Ni-based nanostructured electrocatalysts for HCHO oxidation.