Electrochemically Deposited Pd–Pt and Pd–Au Codeposits on Graphite Electrodes for Electrocatalytic H2O2 Reduction

Improved electrocatalytic activity and selectivity for the reduction of H2O2 were obtained by electrodepositing Pd–Pt and Pd–Au on spectrographic graphite from solutions containing salts of the two metals at varying ratio. The electrocatalytic activity of the resulting binary codeposits for H2O2 reduction was evaluated by means of the redox-competition mode of scanning electrochemical microscopy (SECM) and voltammetric methods. In a potential range from 0 to −600 mV (vs. Ag/AgCl/3 M KCl) at pH 7.0 in 0.1 M phosphate citrate buffer, the electrocatalytic activity of both Pd–Pt and Pd–Au codeposits was substantially improved as compared with the identically deposited single metals suggesting an electrocatalytic synergy of the codeposits. Pd–Pt and Pd–Au codeposits were characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Codepositing with Au caused a change of hedgehog-like shaped Pd nanoparticles into cauliflower-like nanoparticles with the particle size decreasing with increasing Au concentration. Codepositing Pd with Pt caused the formation of oblong structures with the size initially increasing with increasing Pt content. However, the particle size decreases with further increase in Pt concentration. The improved electrocatalytic capability for H2O2 reduction of the Pd–Pt electrodeposits on graphite was further demonstrated by immobilizing glucose oxidase as a basis for the development of an interference-free amperometric glucose biosensor.