Insight into the Transfer Mechanism of Photogenerated Carriers for WO₃/TiO₂ Heterojunction Photocatalysts: Is It the Transfer of Band–Band or Z-Scheme? Why?

Abstract

The transfer mechanism of photoexcited charge carriers is always a hot topic in the photocatalysis research field. Coupling a photocatalyst with other photocatalysts is one of the most widely used strategies to realize effective transfer of the photogenerated carriers. In the study, a series of WO3/TiO2 composites with different weight ratios were prepared. The WO3/TiO2 composites were characterized in detail. The result showed that regardless of whether the primary part of WO3/TiO2 composites is TiO2 or WO3, the photocatalytic activities of WO3/TiO2 are much higher than those of pure TiO2 or WO3. The reason may be the generation of a relative p–n heterojunction between WO3 and TiO2. Under the effect of the built-in electric field, the transfer directions of the photogenerated charge carriers in the heterojunctions are opposite to the migration directions of the photogenerated charge carriers in the conduction band (CB) and valence band (VB) of WO3 and TiO2. Thus, the transfer of the photogenerated charge carriers adopts a Z-scheme system in the WO3/TiO2 heterojunctions. The accumulated photogenerated electrons in the CB of TiO2 with more negative potential can reduce O2 to a superoxide radical (•O2 –), and the photogenerated holes in the VB of WO3 with more positive potential may oxidate H2O (or OH–) into a hydroxyl radical (•OH). The photocatalytic activities of the WO3/TiO2 heterojunctions are significantly promoted. The transfer mechanisms and natural law for the WO3/TiO2 heterojunction photocatalysts were proved by physical and chemical methods. This work not only reveals the transfer mechanisms of photogenerated carriers and internal natural behavior of heterojunction photocatalysts, but also guides the design and constructing of composite photocatalysts, and thus has theoretical and practical significance.

Photocatalytic properties of a new Z-scheme system BaTiO3/In2S3 with a core–shell structure

“…In IS, two peaks at 161.3 eV, 162.6 eV were deconvoluted, corresponding to S 2+ 2p 3/2 and S 2p 1/2 , 40,41 respectively. With respect to BTIS, besides the two peaks at 161.3 eV and 162.6 eV which are respectively attributed to S 2+ 2p 3/2 and S 2p 1/2 in the location far from the heterojunction of BT@IS, there are still two additional peaks at 160.0 eV and 162.4 eV were tted, also ascribed to S 2p 3/2 and S 2p 1/2 in the heterojunction of BT@IS, 38,39 respectively.…”

“…It is reported that built-in electric elds in the heterojunctions WO 3 /TiO 2 and CdSe/CdTe could would result in the shi of binding energy. 39,40 Therefore, the shi to higher binding energy for In 3+ 3d 5/2 and In 3+ 3d 3/2 could be ascribed to the heterojunction BT@IS. Fig.…”

Direct observation of charge transfer between molecular heterojunctions based on inorganic semiconductor clusters

“…[5][6][7] On the other hand, exploration of explicit charge carrier migration pathways/ directions can deepen our understanding of the complicated physical phenomena and catalytic reactions involving charge transfer processes. 1,8 The construction of semiconductor heterojunctions with staggered band gap alignment is an effective strategy to promote the separation of photogenerated charge carriers and study charge migration dynamics. [9][10][11][12] However, it remains challenging to achieve the desired charge separation efficiency and deeply understand the charge migration direction based on the information available for conventional semiconductor heterojunctions commonly synthesized by multistep procedures and comprising size-variable interfacial phases with a relatively unclear interface location, complicated interface structures, and randomly positioned dopants (Scheme 1a, b and e).…”

Synthesis and Characterization of a Novel Rambutan‐like ZnO@SrTiO3/TiO2 Microsphere

“…[6][7][8][9] However, the photocatalytic activity of these composite catalysts is still low and far from practical applications due to the limited light response range and fast recombination of the photogenerated carriers. [10][11][12] Developing novel composite systems or novel composite structures are effective strategies to improve the photocatalytic performance of the photocatalytic materials. [13,14] The unique structure of multicomponent composite provides a basis for the structural design of high performance composite photocatalyst.…”