1D WO 3 Nanorods/2D WO 3− x Nanoflakes Homojunction Structure for Enhanced Charge Separation and Transfer towards Efficient Photoelectrochemical Performance

Abstract 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 WO 3− x nanoflakes (NFs) were vertically grown by hydrothermal synthesis on 1D WO 3 nanorods (NRs) obtained by a hydrothermal method and high‐temperature annealing (HTA). In this 1D HTA‐WO 3 /2D WO 3− x photoanode, the 2D WO 3− 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 WO 3 NRs with high aspect ratio were more beneficial to charge transfer after HTA. As expected, the 1D HTA‐WO 3 /2D WO 3− 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 WO 3 . The improvement could be attributed to the synergistic effect of HTA and the homojunction structure in the 1D HTA‐WO 3 /2D WO 3− 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.