Ultra-high-aspect-ratio vertically aligned 2D MoS2-1D TiO2 nanobelt heterostructured forests for enhanced photoelectrochemical performance

Vertically aligned one-dimensional (1D) materials offer numerous advantages for photoelectrochemical (PEC) energy conversion due to highly accessible surface area, direct charge transport pathway along the aligned direction, and suppressed electron-hole recombination. Hierarchical 1D-2D materials generate heterogeneous interfaces that can modify intrinsic chemical and physical material properties. Here, we report an ultra-high-aspect-ratio perfectly aligned 2D MoS2-1D TiO2 nanobelts (NBs) heterostructured nanoforest electrode and demonstrate enhanced PEC performance. The vertically aligned nanoforest electrode with an ultra-high aspect ratio of approximately 3000 was achieved using high-voltage electrophoretic deposition (EPD). The thickness of the vertical nanoforest correlated well with the length of the NBs and there was no evidence of vertical stacking. In addition, both semi-conductive 2H phase and metallic 1T phase MoS2 were discovered to form on TiO2 (011) and (001) surfaces, respectively. The nanoforest drastically enhanced light penetration into the interstice of the electrode and increased the probability of photon-semiconductor interaction due to reduced band gap as well as local surface plasmonic resonance (LSPR) evidenced by numerical studies. A remarkable 98% enhancement of the PEC photocurrent was achieved for the MoS2-TiO2 NB forest electrode compared with its un-aligned counterpart. (C) 2019 Published by Elsevier Ltd.