Enhancement of photoconversion efficiency and light harvesting ability of TiO2 nanotube-arrays with Cu2ZnSnS4

Abstract

We report an underpotential deposition (UPD) route of Cu2ZnSnS4/TiO2 nanotube arrays (TiO2-NTAs) in which the Kesterite (Cu2ZnSnS4) was employed as a sensitizer to enhance the photoconversion efficiency of the TiO2-NTAs. Cu2ZnSnS4 was simultaneously coated on TiO2-NTAs by depositing its constituent metals from the precursor ions via electrochemical atomic layer deposition (EC-ALD) and subsequent annealing. The detailed synthesis process, the surface morphology, crystalline structure, photoelectrochemical properties and hydrogen production rate of the as-prepared Cu2ZnSnS4/TiO2-NTAs were discussed. Thickened TiO2 nanotubes were observed, suggesting that the Cu2ZnSnS4 coating was about 5 ± 0.5 nm. The results showed that the light harvesting of TiO2-NTAs has an obvious improvement after sensitizing them with Cu2ZnSnS4. In comparison with pure TiO2-NTAs, a two-fold increment in photoconversion efficiency was achieved using the composite of Cu2ZnSnS4/TiO2-NTAs. The novel photoanode of CZTS/TiO2 NTAs achieved a maximum hydrogen generation rate of 49 ml h−1 cm−2.