Enhanced Photocurrent Responses and Antiphotocorrosion Performance of CdS Hybrid Derived from Triple Heterojunction

Abstract

The enhanced photocurrent responses and dramatic antiphotocorrosion performance of CdS hybrid were obtained by formation of triple heterojunction (TH), i.e., n-CdS/n-TiO 2 /p-BDD:n-TiO 2 cube tubes were vertically grown on p-type boron-doped diamond (BDD) film. Then n-CdS nanoparticles (NPs) were randomly assembled onto the surface of TiO 2 and BDD, forming a film of CdS NPs. This triple heterojunction CdS hybrid reveals 36.5% improvement of initial photocurrent and 78% reduction of photocorrosion rate in contrast with that of the coupled CdS/TiO 2 hybrid, which has only single heterojunctions (SH). The mechanisms of TH on charge separation and transport during the photocatalytic reaction have been emphasized. Except for the CdS/TiO 2 (n−n) heterojunction, another two p−n heterojunctions, i.e., p-BDD/n-CdS and p-BDD/n-TiO 2 exist in the TH. The conduction band (CB) position of TiO 2 is lower than the corresponding band positions of CdS and BDD, so TiO 2 can act as an acceptor for the photogenerated electrons. Also, the valence band (VB) position of BDD is higher than those of CdS and TiO 2 , so BDD can act as a sink for the photogenerated holes. Under simulated solarlight, the photogenerated electrons on the conduction band (CB) of CdS flow to the CB of TiO 2 , whereas the photogenerated holes on valence band (VB) CdS and TiO 2 inject to the VB of BDD. It promotes charge separation and leaves not enough holes on CdS to cause photoanodic corrosion, leading to the enhancement of photocurrent responses and the remarkable inhibited photocorrosion.

Sono-intercalation of CdS nanoparticles into the layers of titanate facilitates the sunlight degradation of Congo red

“…This is an inherent disadvantage of CdS photocatalyst and it considers as a defect for its cyclic operation and in environmental applications [37,38]. In order to improve the photoactivities and photostabilities of CdS semiconductor, some efforts have been devoted to producing CdS-based nanocomposites [39,40]. In fact, composites with CdS acted as acceptors for the photogenerated electrons and promoting charge separation and leaving holes on the CdS to cause photocorrosion.…”

Photovoltaic Properties of Bi2S3 and CdS Quantum Dot Sensitized TiO2 Solar Cells

“…The relative increment of 50% in the photoconversion efficiency in TCBZ is explained by the extended photo-absorption spectral range of the Bi 2 S 3 QDs, and by the relative energy positions of the valence and conduction bands (VB and CB, respectively) of both sensitizers. The energy diagrams for all samples under study were determined from Mott-Schottky plots [53] and are displayed in Fig. 4; the energy gap (E g ) was obtained from the absorption spectra.…”

High-performance heterostructured CdS/Ba1−xSrxTiO3 system with unique synergism for photocatalytic H2 evolution

“…When CdS is used as a catalyst, it is generally recognized that the CdS photocorrosion is a big issue because CdS is oxidized by the photogenerated holes [31].…”

“…Additionally, since the valence band (VB) of Ba 1−x Sr x TiO 3 is more negative than that of CdS, photogenerated holes in the VB of CdS can flow into that of Ba 0.4 Sr 0.6 TiO 3 (see Scheme S1 in SI). Such a design can suppress the photocorrosion of CdS [31,32]. As a result, the present photocatalyst system can simultaneously suppress photocorrosion of CdS and accelerate the separation of photogenerated holes and electrons.…”