Improving photocatalytic reduction of 4-nitrophenol over ZrO₂-TiO₂ by synergistic interaction between methanol and sulfite ions

The effect of two sacrificial agents (methanol and sodium sulfite) on the photocatalytic reduction of 4-nitrophenol employing a ZrO₂-TiO₂ photocatalyst is reported. The experimental results showed a decrease in the generation of OH radicals and diminution in the charge transfer resistance that favor the electron transfer toward 4-nitrophenolate ions. Based on the results, it is possible to establish that methanol acts as a hole scavenger while sulfite ions act as radical scavengers, improving the reduction from 4-nitrophenol to 4-aminophenol. The synergistic effect has been corroborated by photoluminescence and photoelectrochemical measurements.