Competitive oxidation of formaldehyde and formate on amorphous copper-palladium-zirconium alloy electrodes in alkaline media

Abstract

Raney-type Cu−Pd alloy electrodes were prepared from amorphous Cu−Pd−Zr ternary alloys by treatment with aq. HF, and competitive anodic oxidation reactions of HCHO and HCOO− were studied on these electrodes in alkaline media. The initial HCHO oxidation product was HCOO− even on Pd or Pd-rich alloy electrodes which should be more active to the HCOO− oxidation than to HCHO. The product HCOO− was oxidized only after a large decrease of the HCHO concentration in the electrolyte. The oxidation rate of HCOO− was considerably lowered by the existence of even a small amount of HCHO, as well as by the introduction of CO. These results suggest that the HCHO electro-oxidation is accompanied by production of a surface contaminant such as adsorbed CO. The optimum nominal Pd atomic fraction in the Cu−Pd alloy electrodes suitable for the steady simultaneous oxidation of HCHO and HCOO− in mixed solution was shown to be 0.25 and 0.4 in 1.0 M NaOH (M=moldm−3) and 0.5 M K2CO3, respectively.