Zn0.5Cd0.5S nanoparticles modified TiO2 nanotube arrays with efficient charge separation and enhanced light harvesting for boosting visible-light-driven photoelectrochemical performance

Abstract

Vertically aligned TiO2 nanotube arrays (TiO2 NTAs) modified with uniformly dispersed Zn0.5Cd0.5S (ZCS) nanoparticles as novel heterojunction photoanodes have been prepared for the first time through a typical two-step anodization followed by successive ionic layer adsorption and reaction (SILAR) process. The photoelectrochemical (PEC) performance of ZCS nanoparticles modified TiO2 NTAs (TiO2 NTAs/ZCS) photoanodes strongly depends on the loading amount of ZCS. By optimizing the amount of ZCS in TiO2 NTAs/ZCS photoanodes, the highest photocurrent density of 10.95 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under visible-light illumination is obtained. The optimum photoconversion efficiency is up to 4.54% at 0.49 V vs. RHE, while it is only 0.04% at 0.67 V vs. RHE for bare TiO2 NTAs photoanode. The maximum incident photon-to-current efficiency (IPCE) value in TiO2 NTAs/ZCS photoanodes is 65.0% at 390 nm, which is 2.3-fold as high as that of bare TiO2 NTAs photoanode (28.1% at 340 nm). The formed heterostructure structure between TiO2 NTAs and ZCS possesses a typical type-II band alignment, which is beneficial to drastically promote the improvement of PEC performance due to the efficient charge separation and increased light harvesting.