Photocatalytic reduction of nitrate in water in the co-presence of Pt/SrTiO3:Rh and SnPd/Al2O3 under visible light irradiation (lambda > 420 nm) was investigated. This reaction system efficiently and selectively promoted the photocatalytic reduction of nitrate to nitrogen, whereas Pt/SrTiO3:Rh or SnPd/Al2O3 alone showed little activity under the reaction conditions. The selectivity to N-2 was 94% under the optimum reaction conditions, where the amounts of Pt/SrTiO3:Rh and SnPd/Al2O3 loaded in the reaction system were 500 mg and 150 mg, respectively. This reaction system showed a superior nitrate decomposition rate and superior selectivity to nitrogen compared with SrTiO3:Rh directly modified with SnPd bimetal. From analysis of the reaction mechanism, hydrogen formed by photoreduction of water over Pt/SrTiO3:Rh acted as the reductant for a non-photocatalytic nitrate conversion reaction over SnPd/Al2O3. Moreover, the products, including formaldehyde and formic acid, formed by photo-oxidation of methanol over Pt/SrTiO3:Rh acted as reductants for nitrate over SnPd/Al2O3. (C) 2013 Elsevier B.V. All rights reserved.