Polydopamine-Inspired Design and Synthesis of Visible-Light-Driven Ag NPs@C@elongated TiO₂ NTs Core–Shell Nanocomposites for Sustainable Hydrogen Generation

The primary challenge of photocatalytic hydrogen generation is to exploit a catalyst with good durability and low cost. Here, we designed a facile and efficient process of loading silver nanoparticles (Ag NPs) in situ on the core–shell nanocomposite of the elongated titanium dioxide nanotubes with a carbon layer (C@TiO2 NTs) by polydopamine (PDA) without addition of any binder. The combination of C@TiO2 NTs with Ag NPs has excellent performance toward photocatalytic hydrogen production and degradation of rhodamine B (RhB) under visible light irradiation. The characterizations (SEM, TAM, XRD, XPS, etc.) showed that the carbon layer on nanotubes could conformably cover the whole of TiO2 NTs to form the core–shell structure, which not only prevented Ag NPs from aggregating but also acted as the electronic transport channel. Meanwhile, Ag NPs were uniformly distributed on the surface of C@TiO2 NTs. In conclusion, under the synergistic effect of Ag nanoparticles and the outer-carbon layer, the utilization efficiency of visible light has been enhanced, and the recombination of electrons/holes has been suppressed for Ag@C@TiO2 NTs nanocomposites. Therefore, the degradation efficiency of RhB and hydrogen generation rate are 2.5 times and 4.8 times higher than those of the pure TiO2 NTs, respectively. This work may provide fruitful experience for developing a novel strategy into the design and fabrication of stable and highly active visible-light catalysts with noble metal modification toward sustainable hydrogen production in the energy filed.