1D WO3 Nanorods/2D WO3-x Nanoflakes Homojunction Structure for Enhanced Charge Separation and Transfer towards Efficient Photoelectrochemical Performance.

Designing and fabricating photoelectrodes with low carrier recombination, high carrier transfer, and high light-capture capability is of great significance for achieving effective photoelectrochemical (PEC) water splitting. Herein, for the first time, 2D nonstoichiometric WO3-x nanoflakes (NFs) were vertically grown by hydrothermal synthesis on 1D WO3 nanorods (NRs) obtained by a hydrothermal method and high-temperature annealing (HTA). In this 1D HTA-WO3 /2D WO3-x photoanode, the 2D WO3-x NFs with active areas could maximize light harvesting, and the unique 1D/2D homojunction structure could improve the carrier-separation efficiency. At the same time, the 1D WO3 NRs with high aspect ratio were more beneficial to charge transfer after HTA. As expected, the 1D HTA-WO3 /2D WO3-x photoanode yielded an enhanced photocurrent density of 0.98 mA cm-2 at 1.23 V versus reversible hydrogen electrode, which is approximately 3.16 times that of pristine WO3 . The improvement could be attributed to the synergistic effect of HTA and the homojunction structure in the 1D HTA-WO3 /2D WO3-x photoanode, which could effectively improve carrier separation and transfer. Furthermore, this work may provide a promising strategy for the design and fabrication of semiconductor-based photoelectrodes.