Solvent-Free Synthesis of Cu/In Dual-Single-Atom-Doped TiO2 for Photocatalytic Reduction of Cr (VI) with High Efficiency

Recently, photocatalysts with single-atom doping have been highly focused on modulating charge separation and maximizing the reaction active sites that result in efficiency maximization. In this work, Cu and In dual-single-atom-doped mesoporous nano TiO2 (Cu/In-TiO2) with high crystallinity was prepared through a facile solvent-free self-assembly method by grinding and heating raw materials. The performances of the prepared catalysts were evaluated via photocatalytic reduction of Cr (VI). The results show that both single-atom doping and dual-single-atom doping can improve the photocatalytic activity of TiO2 significantly, but Cu/In dual-single-atom doping is better than that of single-atom (Cu or In) doping alone, and Cu single-atom doping is better than that of In single-atom doping. The Cu/In-TiO2 exhibited outstanding photocatalytic activity for the reduction of Cr (VI). Its photocatalytic reduction efficiency is 6.87 times higher than that of pure TiO2. More interestingly, its photocatalytic activity is better than that of benchmark reagents of P25 and previously reported similar photocatalysts. The much-improved performance can be mainly ascribed to the Cu and In dual-single-atom doping on TiO2, which promote the separation and transfer of the charge carriers and decrease the recombination rate of the charge carriers. This work provides an efficient catalyst for the photocatalytic reduction of Cr (VI) and a simple-effective strategy for the synthesis of highly efficient mesoporous metal oxide nanophotocatalysts and facilitates their applications.