Synergistic Effect of Nickel Oxyhydroxide and Tungsten Carbide in Electrocatalytic Alcohol Oxidation

Abstract

Design and synthesis of efficient small organic molecule-based electrooxidation catalysts in replacing conventional oxygen evolution reaction (OER) catalysts has been considered as an alternative path to enable large-scale renewable energy storage. In contrast to OER, alcohol oxidation reactions can be implemented at lower applied potentials along with generating higher value-added byproducts than oxygen. Here, the ultrafine Ni/WC hybrid nanoparticles (NPs) were successfully synthesized via an in situ trapping and space-confinement pyrolysis strategy. The as-synthesized Ni/WC hybrid NPs exhibit high electrooxidation performances in oxidizing methanol, ethanol, iso-propanol, ethylene glycol, and propylene glycol in alkaline solution. Particularly, for the methanol oxidation reaction, Ni/WC NPs demonstrate high reaction activity (specific activity: 325 mA cm–2 at 0.6 V vs Ag/AgCl/3.5 M KCl; mass activity: 1363 mA mg–1) and excellent stability (catalytic current drops ∼6.8% after 4 h). In the first 6 h of the electrolysis process, methanol was effectively converted into formate with ca. 93.8% Faraday efficiency. Based on in situ IR spectra and control catalyst experiments, tungsten carbide (WC) and nickel oxyhydroxide (NiOOH, derived from Ni) species are capable of activating different functional groups of methanol. More interestingly, their hybrid structure (Ni/WC) demonstrates improved catalytic performance in converting methanol into a formate product for the synergistic effect.