On the photocatalytic degradation of phenol and dichloroacetate by BiVO4: The need of a sacrificial electron acceptor

The photodegradation of phenol and dichloroacetic acid (DCAA) by \ce{BiVO4} was studied in the absence as well as presence of selected electron scavengers. The experiments were performed under the visible (vis) irradiation of aqueous solutions over a wide pH range (1--13). Phenol was photocatalytically degraded by \ce{BiVO4} into \emph{p}-benzoquinone below pH3 and into an open-ring structure at pH13. Methylene blue (MB) accelerated the reaction below the isoelectric point of \ce{BiVO4} and did not undergo significant degradation. In presence of \ce{H2O2}, phenol was rapidly degraded up to pH9. The degradation rates are two orders of magnitude higher than in absence of electron scavenger. The degradation of dichloroacetic acid was only possible in presence of \ce{H2O2}. High initial concentrations of \ce{H2O2} inhibit the reaction and its consumption is very fast. Sequential additions of this sacrificial electron acceptor (SEA) enables the total degradation of a 1mM DCAA solution.