Pd and carbon quantum dots co-decorated TiO2 nanosheets for enhanced photocatalytic H2 production and reaction mechanism

TiO2-based composites are promising photocatalysts for efficient generation of the clean energy, H2, from water splitting. Herein, series of Pd nanoparticles and carbon quantum dots (CQDs) co-decorated TiO2 nanosheets (NSs), Pd-CQDs/TiO2, were designed by overall considering taking advantages of the three components: highly active TiO2 NSs, highly conductive CQDs and electron sink of Pd. Series of photocatalytic experiments were performed and the photocatalytic reaction mechanism was explored. The Pd-0.5CQDs/TiO2 exhibited an excellent photocatalytic hydrogen evolution rate (HER), which is 901.5, 41.8 and 1.7 times higher than those of the bare TiO2, 0.5CQDs/TiO2 and Pd/TiO2, respectively. The synergistic effect of the CQDs and Pd was found responsible for the enhanced photocatalytic activity of the Pd-0.5CQDs/TiO2. Besides, the CQDs was found facilitating complete conversion of Pd2+ to metallic Pd on the surface of TiO2 NSs, which may offer a new thought for design of other composite materials.