Highly efficient photoelectrochemical ZnO and TiO_2 nanorod/Sb_2S_3 heterostructured photoanodes through one step thermolysis of Sb-MPA complex

摘要

Semiconductor heterostructures such as TiO2/Sb2S3 and ZnO/Sb2S3 are promising for photoelectrochemical applications. In this work, we demonstrate the photoelectrochemical performance with enhanced current densities of Sb2S3 sensitized nanorods of TiO2 (TNR) and ZnO (ZNR) photoanodes. ZNR and TNR are synthesized by the hydrothermal method and annealed in the air (AA) and hydrogen (HA) ambient. Stoichiometric Sb2S3 are coated on ZNR and TNR by a facile one-step method using thermolysis of Sb-MPA precursor in air ambient. Structural, optical and microstructural studies are carried out to confirm the formation of phase pure Sb2S3 on ZnO and TiO2 oxide nanorods in the TiO2/Sb2S3 and ZnO/Sb2S3 heterojunction photoanodes. Photoelectrochemical studies show enhanced performance from the Sb2S3 sensitized photoanodes in comparison to the bare TNR or ZNR photoanodes. TNR-AA/Sb2S3(MPA) and TNR-HA/Sb2S3(MPA) heterostructures exhibit current densities of 1.79 mA/cm2 and 1.58 mA/cm2, respectively, which is six times higher than the uncoated photoanodes (0.38 mA/cm2 for TNR-AA and 0.20 mA/cm2 for TNR-HA). In the case of ZNR, we see a 10 to 15 fold increase in current density (-3.3 to 4 mA/cm2) upon sensitizing with Sb2S3 on photoanodes. Further hydrogen annealed ZNR sensitized with Sb2S3 (ZNR-HA/Sb2S3(MPA)) shows a slightly higher current density (3.9 mA/ cm2) than the air annealed ZNR-AA/Sb2S3(MPA) (3.32 mA/cm2). Hydrogen annealing is beneficial for ZNR, whereas air-annealing is favored for TNR. Also, stability studies and photocurrent measurements are discussed for these photoanodes.