Photocatalytic nitrate reduction over Pd–Cu/TiO2

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 H2 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 H2 increase significantly the photocatalytic reduction of nitrate. Complete (100%) conversion was obtained when both H2 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%).