Fabrication of CuO_x-Pd Nanocatalyst Supported on a Glassy Carbon Electrode for Enhanced Formic Acid Electro-Oxidation

摘要

Formic acid (FA) electro-oxidation (FAO) was investigated at a binary catalyst composed of palladium nanoparticles (PdNPs) and copper oxide nanowires (CuO_xNWs) and assembled onto a glassy carbon (GC) electrode. The deposition sequence of PdNPs and CuO_xNWs was properly adjusted in such a way that could improve the electrocatalytic activity and stability of the electrode toward FAO. Several techniques including cyclic voltammetry, chronoamperometry, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were all combined to report the catalyst's activity and to evaluate its morphology, composition, and structure. The highest catalytic activity and stability were obtained at the CuO_x/Pd/GC electrode (with PdNPs directly deposited onto the GC electrode followed by CuO_xNWs with a surface coverage, Γ, of ca. 49%). Such enhancement was inferred from the increase in the peak current of direct FAO (by ca. 1.5 fold) which associated a favorable negative shift in its onset potential (by ca. 30 mV). The enhanced electrocatalytic activity and stability (decreasing the loss of active material by ca. 1.5-fold) of the CuO_x/Pd/GC electrode was believed originating both from facilitating the direct oxidation (decreasing the time needed to oxidize a complete monolayer of FA, increasing turnover frequency, by ca. 2.5-fold) and minimizing the poisoning impact (by ca. 71.5%) at the electrode surface during FAO.