Increase and enrichment of active electrons by carbon dots induced to improve TiO2 photocatalytic hydrogen production activity

Recombination of photogenerated carriers severely reduces the efficiency of photocatalytic reactions. Herein, Bio-CDs/TiO2 were produced using the hydrothermal method to tightly load biomass-based carbon dots (Bio-CDs) onto the surface of TiO2 via Ti-O-C bonds. Finite-difference time-domain (FDTD) simulations showed that the Bio-CDs act as electron storage pools in the Bio-CDs/TiO2, enhancing optical absorption and promoting the transfer and storage of photogenerated electrons from TiO2 to the Bio-CDs, and thus effectively inhibiting the recombination of electron-hole pairs. Photocatalytic hydrogen production by the Bio-CDs/TiO2 was significantly improved compared with that by pristine TiO2 (603.92 μmol h−1 g−1 vs 94.18 μmol h−1 g−1) and, importantly, the Bio-CDs/TiO2 performed well over several cycles. Surprisingly, Bio-CDs/TiO2 also exhibits nice catalytic performance for hydrogen production under the combined action of photoelectricity, and its Tafel slope was significantly lower than that of pristine TiO2, which confirmed that the same research potential of Bio-CDs/TiO2 in the field of photoelectrocatalysis. This work introduces new ways to study the synergistic effects of multiple mechanisms (enhanced optical absorption, increased separation of photogenerated carriers and promotion of transfer and storage of photogenerated electrons) in the enhancement of photocatalytic and photoelectrocatalytic activity of semiconductors by carbon dots.