Carbon quantum dots induced one-dimensional ordered growth of single crystal TiO2 nanowires while boosting photoelectrochemistry properties

TiO2 nanowire arrays (TNWAs) thin film of flexible substrates has great application potential in photoelectrochemical (PEC) hydrogen evolution. Moreover, the photoquantum efficiency of TNWAs can be effectively enhanced by reducing the nanoscale as much as possible or combining with other co-catalysts. This work presents a simple and effective strategy for the synthesis of ultrafine TiO2 nanowire arrays by a one-step hydrothermal method using CQDs as an inducer for single crystal growth. Meanwhile, CQDs recombine on the surface of TNWAs to form CQDs/TNWAs heterojunction during the synthesis process. The synthesized TNWAs have well ordered separability, whose average diameter is regulated at 11.21 nm with an average aspect ratio of 1097. PEC analysis showed that the performance of TNWAs was significantly improved compared with initial TiO2 with unregulated morphology. The charge separation efficiency increased by 120%, applied bias photon-to-current efficiency (ABPE) reached 0.37%(0.68 v vs RHE), and incident photon-to-current conversion efficiency (IPCE) reached 50.31% (380 nm). The influence of TiO2 nano-morphology optimization and formation of CQDs/TiO2 heterojunction on the PEC performance were discussed in detail.