Abstract
The performance of the PEC cells with nanocrystalline CdS films for hydrogen production and electricity generation can be significantly improved with thin TiO 2 overcoating. ► CdS PEC cells for hydrogen production in comparison with electricity generation. ► The performance of the PEC cells can be significantly improved with TiO 2 coating. ► Surface modification has similar influence on PEC cells 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 TiO 2 on the PEC performance of CdS films has also been investigated. It was found that TiO 2 content have a dominant effect on the performance of PEC cells. The optimized PEC cells with CdS/TiO 2 (1.8 wt.% TiO 2 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 TiO 2 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.
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