The extension of photocatalytic nitrate reduction in water by a 1%Pd-1%Cu (%wt) catalyst supported on TiO2 was evaluated under different reaction conditions. A series of electron sacrificial donors such as formic acid, oxalic acid, ethanol, methanol, and humic acid were used for inhibiting the mechanism of electron/hole recombination on the semiconductor by hole scavenging. In addition, the roles of H-2 as reducing agent and CO2 as buffer are also discussed. The photocatalytic process is found to be more selective towards nitrogen than the dark catalytic process. Hole scavengers, or reducing H-2 increase significantly the photocatalytic reduction of nitrate. Complete (100%) conversion was obtained when both H-2 and CO2 were used as reducing and buffer agent, respectively. Among the hole scavengers tested, 0.08 M formic acid solution represents the best compromise between nitrate conversion (84%) and nitrogen selectivity (83%). (C) 2014 Elsevier B.V. All rights reserved.