Catalytic oxidation of methanol on molybdate-modified platinum electrode in sulfuric acid solution

The catalysis of methanol oxidation on molybdate-modified platinum was studied by using linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry in the solutions with H2SO4 concentrations from 0.5 to 4.5 M. It was found that methanol oxidation was catalyzed on the modified platinum by lowering methanol oxidation potential and promoting methanol oxidation cur-rent. There was the strongest catalysis in 3.7 M H2SO4 solution. In this solution, methanol oxidation took place on the modified platinum at the potential 0.2 V more negatively than on the non-modified platinum and the steady oxidation current of methanol on the modified platinum at 0.7 V versus SCE was 10 times that on the non-modified platinum. Molybdates were reduced to adsorbed hydrogen molybdenum(IV) bronzes on platinum in H2SO4 solution at a very negative potential. The amount of reduced molybdates decreased with decreasing H2SO4 concentrations. The reduced molybdates were oxidized to different forms of hydrogen molybdenum bronzes (HxMoO3, 0 < x < 2) depending on the H2SO4 concentration. Platinum was modified by these hydrogen molybdenum bronzes, but under-modified in the solution with lower H2SO4 concentration and over-modified in the solution with higher H2SO4 concentration. The catalysis of methanol oxidation was weakened when the platinum was under- or over-modified. (C) 2002 Elsevier Science B.V. All rights reserved.