Controllable voltammetric formation of a structurally disordered NiOOH/Ni(OH)2 redox pair on Ni-nanowire electrodes for enhanced electrocatalytic formaldehyde oxidation
Špela Trafela, Janez Zavašnik, Sašo Šturm, Kristina Žužek Rožman
Abstract
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.