Enhanced Photocatalytic Activity for Selective Oxidation of Toluene over Cubic–Hexagonal CdS Phase Junctions

Phase junction construction has been regarded as a valid and facile way to enhance semiconductors’ photocatalytic activity through improving the separation and migration efficiency of charge carriers. Herein, a CdS phase junction with tight crystal face contact was prepared by a one-step hydrothermal method. The particle size and the ratio of the cubic to hexagonal phase could be easily regulated by adjusting the preparation temperature. For this cubic–hexagonal CdS phase junction, the separation and migration of charge carriers are improved, and there is the transfer of electrons to the surface to promote O2 activation for the generation of superoxide radicals (•O2–). The CdS-150 sample prepared at 150 °C provides a proper ratio of cubic and hexagonal CdS, thus exhibiting outstanding photocatalytic performance for the conversion of toluene to benzaldehyde. After 2 h of reaction, the conversion of toluene reaches 34.4%, which is 3 and 4 times that of pure cubic- and hexagonal-phase CdS, respectively. When pure oxygen and full-spectrum light were used, the conversion of toluene is up to 83.8% and the selectivity to benzaldehyde remains at 94.8% after 6 h of reaction.