Crystal Facet Engineering of TiO_(2) Nanostructures for Enhancing Photoelectrochemical Water Splitting with BiVO_(4) Nanodots

Although bismuth vanadate(BiVO4)has been promising as photoanode material for photoelectrochemical water splitting,its charge recombination issue by short charge diffusion length has led to various studies about heterostructure photoanodes.As a hole blocking layer of BiVO4,titanium dioxide(TiO_(2)) has been considered unsuitable because of its relatively positive valence band edge and low electrical conductivity.Herein,a crystal facet engineering of TiO_(2) nanostructures is proposed to control band structures for the hole blocking layer of BiVO4 nanodots.We design two types of TiO_(2) nanostructures,which are nanorods(NRs)and nanoflowers(NFs)with different(001)and(110)crystal facets,respectively,and fabricate BiVO4/TiO_(2) heterostructure photoanodes.The BiVO4/TiO_(2) NFs showed 4.8 times higher photocurrent density than the BiVO4/TiO_(2) NRs.Transient decay time analysis and time-resolved photoluminescence reveal the enhancement is attributed to the reduced charge recombination,which is originated from the formation of type II band alignment between BiVO4 nanodots and TiO_(2) NFs.This work provides not only new insights into the interplay between crystal facets and band structures but also important steps for the design of highly efficient photoelectrodes.