Pollution of surface water and groundwater with ClO 4 – is serious problem. Catalytic reduction of ClO 4 – with H 2 is an ideal method because harmless Cl– is the only product. In this study, we evaluated catalytic performances of seven metals (Ru, Rh, Pd, Re, Ir, Pt, and Ni) supported on Al 2 O 3 for reduction of ClO 4 – with H 2 at 353 K. Among them, only Ru/Al 2 O 3 exhibited a decent activity for the reaction. To improve the catalytic performance, we investigated support effect and found that CeO 2 was the best support owing to the high dispersion of Ru. Ru/CeO 2 did not lose any activity even in neutral and weakly basic solutions, which is a great advantage for practical applications. Kinetic analysis and reactivity tests of possible intermediates over Ru/CeO 2 in the presence and absence of H 2 revealed that the reduction of ClO 4 – proceeded successively through ClO 3 – and then ClO 2 –, and ClO 2 – disproportionated to Cl–. [Display omitted] • Supported Ru catalysts showed activity for ClO 4 – reduction at 353 K. • Ru/CeO 2 was active in wide pH ranges including pH 7. • Ru/CeO 2 showed stable activity evaluated in a continuous flow reactor. • Reduction of ClO 4 – was proceeded successively to Cl–, but not through ClO–. • Intermediate ClO 2 – disproportionated to Cl– and ClO 3 –. [ABSTRACT FROM AUTHOR]