Boosted performance of NiOx/Pt nanocatalyst for the electro-oxidation of formic acid: A substrate's functionalization with multi-walled carbon nanotubes

A NiOx/Pt nanostructured catalyst was developed on a glassy carbon substrate that was functionalized with mutli-walled carbon nanotubes (CNTs) for the electro-oxidation of formic acid (EOFA); the essential oxidation reaction in the direct formic acid fuel cells (DFAFCs). The sequential deposition technique was adapted for the electrodeposition of platinum (n-Pt) and nickel oxide (n-NiOx) nanoparticles onto a CNTs-functionalized glassy carbon (GC) substrate. The presence of CNTs in the catalyst restricted the deposition of n-Pt and n-NiOx mostly onto their walls. Interestingly, this NiOx/Pt/CNTs/GC catalyst displayed a significant enhancement in the catalytic activity toward EOFA. This occurred by driving the reaction mechanism exclusively via the desirable direct dehydrogenation pathway with a large (-116 mV) shift (relative to that of the Pt/GC catalyst) in the onset potential with a complete suppression for the undesirable poisoning dehydration route. It also offered a much (up to 5-fold) better tolerance against the CO poisoning that normally deteriorates the performance of the DFAFCs. The electrochemical impedance spectroscopy and the Tafel representations agreed on the effective role of n-NiOx in improving the electronic properties of Pt at the surface. On parallel, an oxidative stripping voltammetry of CO from the NiOx/Pt/CNTs/GC catalyst confirmed the potential geometrical influence of CNTs in the divergence of n-Pt that mitigated the CO poisoning. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.

Automated summary

The study introduced a NiOx/Pt/CNTs/GC catalyst that significantly enhanced the electro-oxidation activity of formic acid and exhibited better tolerance against CO poisoning. By driving the reaction mechanism exclusively via the desirable direct dehydrogenation pathway, the catalyst suppressed the undesirable poisoning dehydration route and showed improved performance in direct formic acid fuel cells.