Enhancement of photoelectrochemical activity of nanocrystalline CdS photoanode by surface modification with TiO2 for hydrogen production and electricity generation

Nanocrystalline CdS films on the FTO glass substrates using doctor-blade method were used as photoanodes in two different photoelectrochemical (PEC) cells for hydrogen production and electricity generation. The influence of surface modification by overcoating with a thin amorphous TiO2 on the PEC performance of CdS films has also been investigated. It was found that TiO2 content have a dominant effect on the performance of PEC cells. The optimized PEC cells with CdS/TiO2 (1.8 wt.% TiO2, content) electrode showed a 4-fold increase in hydrogen production and a five times enhancement of the cell efficiency (a maximum power conversion efficiency of 2.7%) compared to that of the unmodified one. Furthermore, surface modification has similar effect on these two PEC cells. The electrochemical investigation suggests that the TiO2 layer on CdS reduces the interfacial charge recombination and induces a downward shift of the flat band potential in both PEC cells. This work reveals that the interfacial charge recombination is essentially critical for both hydrogen production and electricity generation. (C) 2011 Elsevier Ltd. All rights reserved.