Abstract: Platinum catalyst(Pt) and its composite catalyst with hydrogen molybdenum bronze(Pt-H_xMoO₃) were prepared on a glass carbon electrode with cyclic voltammetry, in 0.5 mol/L H₂SO₄ solution containing 5 mmol/L H₂PtCl₆ and 5 mmol/L H₂PtCl₆+5 mmol/L Na₂MoO₄, respectively. Their catalytic activity toward the oxygen reduction reaction(ORR) in 0.5 mol/L H₂SO₄ solution saturated with oxygen was studied with rotating disk electrode. The result shows that the catalytic activity of platinum toward ORR can be improved by H_xMoO₃. The catalytic mechanism was understood, based on the analysis on the relationship between the peak current of ORR and scan rate on the quiescent electrodes and the relationship between the current of ORR and rotating speed on the rotating electrodes. The transfer coefficient of charge transfer step for ORR on Pt is improved by H_xMoO₃, thus the kinetics of ORR is enhanced significantly. The transfer coefficient on Pt-H_xMoO₃ for ORR is 1.2 times that on Pt, and the kinetic current on Pt-H_xMoO₃ at 0.3 V(vs. SCE) is 5 times that on Pt.

Key words: Oxygen reduction reaction, Catalysis, Platinum, Hydrogen molybdenum bronze