Selective photocatalytic benzene hydroxylation to phenol using surface-modified Cu2O supported on graphene

Abstract

The photocatalytic activity for benzene hydroxylation to phenol by hydrogen peroxide has been evaluated using a series of photocatalysts based on defective graphene. The series includes defective graphene containing or not Au and Cu₂O nanoparticles. The latter exhibits the highest activity, but a very low phenol yield as a consequence of the occurrence of a large degree of mineralization. A considerable increase in phenol selectivity was achieved by modifying the surface of the Cu₂O nanoparticles supported on defective graphene with long-chain alkanethiols. Under the optimal conditions using an octanethiol-modified Cu₂O-graphene photocatalyst, a selectivity to phenol of about 64% at 30% benzene conversion was achieved. This remarkable selectivity was proposed to derive from the larger hydrophobicity of the alkanethiol-modified Cu₂O-graphene photocatalyst that favors the preferential benzene adsorption versus adsorption of phenol and hydroxybenzenes.