nPd0 · (Hx–2nMoO3) composites as catalysts of methanol and formic acid electrooxidation

Resumo

nPd⁰ · (H_x–2nMoO₃)/GC electrodes (0 < n < 1) were obtained by currentless redox reaction between hydrogen-containing molybdenum bronzes and palladium(II) chloride. The composites were characterized by electrochemical methods and by SEM, TEM, XRD, XPS, and AES–ICP. The morphology, structure, and composition of the electrodes depend on the degree of reduction of the starting molybdenum bronze. The use of red molybdenum bronze H_xMoO₃ (x ≈ 1.55) led to the formation of a composite characterized by longer palladium/molybdenum oxide compound boundaries than in the case of green molybdenum bronze (x ≈ 1.9). On the nPd⁰ · (H_x–2nMoO₃)red/GC electrodes, the catalytic effect with respect to methanol electrooxidation (MEO) was significant, while formic acid electrooxidation (FAEO) was accelerated insignificantly. Possible reasons for the difference in the effect of Pd modification with molybdenum bronzes on MEO and FAEO were discussed.