Bismuth sulphide decorated ZnO nanorods heterostructure assembly via controlled SILAR cationic concentration for enhanced photoelectrochemical cells

Abstract

The current study investigates Bi _2 S _3 thin films coated on ZnO NRAs with varying cationic concentrations through ionic layer adsorption and reaction (SILAR) technique. XRD patterns reveal that Bi _2 S _3 is successfully synthesised and exhibits orthorhombic structure on the wurtzite ZnO NRAs. The band gap energy (E _g ) of Bi _2 S _3 /ZnO NRAs shows a notable red shift with increasing cationic concentration. The photocurrent density increases significantly with increasing concentration from 1 mM to 3 mM before decreases at higher concentration due to agglomeration of Bi _2 S _3 NPs and formation of recombination centres. The hybrid photoanode Bi _2 S _3 /ZnO NRAs at 3 mM exhibits the highest photocurrent value (1.92 mA cm ^−2 ), which is about six times greater than that of plain ZnO NRAs (0.337 mA cm ^−2 ). The high photoconversion efficiency value of 1.65% versus 0.5 V Ag A ^−1 g ^−1 C ^−1 l ^−1 is obtained by Bi _2 S _3 /ZnO NRAs (3 mM) in comparison with pristine ZnO NRs, mainly due to the stepwise band alignment edge and significant enhancement of morphological and optical properties. The study reveals that controlling the cationic concentration can potentially improve the photoconversion efficiency.

Keywords

• heterostructure
• photoelectrochemical cells
• ZnO NRAs
• SILAR method
• Bi2S3
• photoconversion efficiency