All-solid-state Z-scheme in CdS–Au–TiO2 three-component nanojunction system

Abstract

Natural photosynthesis, which achieves efficient solar energy conversion through the combined actions of many types of molecules ingeniously arranged in a nanospace, highlights the importance of a technique for site-selective coupling of different materials to realize artificial high-efficiency devices. In view of increasingly serious energy and environmental problems, semiconductor-based artificial photosynthetic systems consisting of isolated photochemical system 1 (PS1), PS2 and the electron-transfer system have recently been developed. However, the direct coupling of the components is crucial for retarding back reactions to increase the reaction efficiency. Here, we report a simple technique for forming an anisotropic CdS-Au-TiO2 nanojunction, in which PS1(CdS), PS2(TiO2) and the electron-transfer system (Au) are spatially fixed. This three-component system exhibits a high photocatalytic activity, far exceeding those of the single- and two-component systems, as a result of vectorial electron transfer driven by the two-step excitation of TiO2 and CdS.

Z‐Scheme Photocatalytic Systems for Promoting Photocatalytic Performance: Recent Progress and Future Challenges

“…Additionally, it is often difficult to maintain long‐term stability and active state for the redox mediators, resulting in a decrease in reaction rates. To avoid these disadvantages, Z‐scheme systems without redox mediators have attracted much attention because they eliminate these limitations 7, 26…”

“…Noble‐metal particles (such as Au, Ag) and reduced graphene oxide (RGO) were explored as electron mediators for the Z‐scheme system, and a high efficiency of the charge‐carrier separation and transport can be achieved at the interface of the two semiconductors 26, 47, 48…”

“…The CdS/Au/TiO 2 system, which was fabricated using a simple photochemical technique, is the first example of an all‐solid‐state Z‐scheme system 26. Under UV irradiation, the photoexcited electrons in the CB of TiO 2 transferred to Au and then to the VB of CdS, subsequently recombined with the holes photogenerated in CdS.…”

“…Many works studied different connection modes of Z‐scheme photocatalytic systems 13, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, …”

Enhanced photocatalytic H2 evolution over CdS/Au/g-C3N4 composite photocatalyst under visible-light irradiation

“…[16][17][18] In 2006, Tada et al reported a first all-solid-state Z-scheme TiO 2 -Au-CdS system, which exhibits much higher photocatalytic activity than the two-component TiO 2 -CdS and Au-TiO 2 systems. 19 Nevertheless, the overall solar conversion efficiency of this system is limited because TiO 2 only absorbs UV light. In consideration of this issue, combining two visible-light-response photocatalysts in Z-scheme photocatalytic systems might be a promising strategy for the conversion of solar energy into H 2 fuel.…”