Synergistic Effect of Dual Particle-Size AuNPs on TiO2 for Efficient Photocatalytic Hydrogen Evolution

Design of efficient catalysts for photocatalytic water-splitting hydrogen evolution is of fundamental importance for the production of sustainable clean energy. In this study, a dual particle-size AuNPs/TiO2 composite containing both small (16.9 +/- 5.5 nm) and large (45.0 +/- 9.8 nm) AuNPs was synthesized by annealing two different sized AuNPs onto TiO2 nanosheets. Dual particle-size AuNPs/TiO2 composites of 2.1 wt% catalyze photocatalytic H-2 evolution 281 times faster than pure TiO2. Control experiments indicate the observed rate increase for the 2.1 wt% dual particle-size AuNPs/TiO2 composites is larger than 2.1 wt% small AuNPs/TiO2 composites, or 2.1 wt% large AuNPs/TiO2 composites in isolation. The observed photocatalytic enhancement can be attributed to the synergistic effect of dual particle-size AuNPs on TiO2. Specifically, small-sized AuNPs can act as an electron sink to generate more electron-hole pairs, while the surface plasmon resonance (SPR) effect of large-sized AuNPs concurrently injects hot electrons into the TiO2 conduction band to enhance charge transfer. In addition, a gold-dicyanodiamine composite (GDC)-directed synthesis of 2.1 wt% dual particle-size AuNPs/TiO2 composites was also completed. Notably, a photocatalytic efficiency enhancement was observed that was comparable to the previously prepared 2.1 wt% dual particle-size AuNPs/TiO2 composites. Taken together, the synergistic effects of dual particle-size AuNPs on TiO2 can be potentially used as a foundation to develop semiconductor photocatalyst heterojunction with enhanced photocatalytic activity.