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Often the choice of semiconductor material for light‐chemical energy conversion in solar cell technology is TiO2 polymorphs. However, quantum‐mechanical phenomena of electron self‐trapping (polaron) in these polar semiconductors present a challenge to optimize their performance for absorption of solar radiation. The electron trapped in the defect site of the lattice may suppress the recombination of charge carriers and improve the efficiency of light‐chemical energy conversion. Therefore, it is crucial to study polarons in transition metal oxides and semiconductors using first‐principles methods to elucidate the nature of charge carriers and trapping sites for ameliorating the performance of energy conversion. In this work, a comprehensive review is presented using selected literature of polaron studies in TiO2 from first‐principles methods. Overview of the Landau–Pekar model to the recent development of ab initio theory of polaron is presented. The popular DFT+U approach and hybrid functional method are discussed to show the general way of studying polaron using ab initio methods. Introduction of electron‐phonon interaction and the ab initio theory of polaron are briefly presented Therefore, this review presents the development of first‐principles methods from Landau theory to the state‐of‐the‐art to study polarons using TiO2 as the toy model. Finally, conclusions and future perspectives are outlined. [ABSTRACT FROM AUTHOR]

Developing interfacial connections is one of the breakthrough strategies to improve the photocatalytic activity. Herein, ZnBi 2 O 4 nanoparticles-ZnO nanorods heterojunction was successfully synthesized and used, as a dual-function photocatalyst, for photocatalytic degradation of Bisphenol A and hydrogen production with improved photocatalytic activity under simulated sunlight irradiation. The highest H 2 production (3.44 mmol g−1 h−1) was obtained for ZnO-20 wt% ZnBi 2 O 4 sample, which is around 12.7 times higher than pure ZnO. According to the HRTEM result, the intimate interfacial connections are formed between ZnO and ZnBi 2 O 4 which could act as trapping centers for charge carriers and results in the boosted photocatalytic activity. Further, a high aspect ratio of 1D ZnO nanorods and small size of 0D ZnBi 2 O 4 nanoparticles (~10 nm) increases the number of interfacial contacts and thus the charge carriers' recombination was suppressed more efficiently. Based on the trapping experiments, ESR and Mott-Schottky analysis, ZnBi 2 O 4 –ZnO hybrid photocatalyst followed the S -scheme charge transfer mechanism. • Novel 0D/1D ZnBi 2 O 4 /ZnO p-n heterojunction was successfully prepared. • The prepared hybrid system revealed improved H 2 production and BPA decomposition. • The highest hydrogen evolution (3.44 mmol.g−1.h−1) was achieved on ZnO–20%ZnBi 2 O 4. • S -scheme mechanism was suggested for boosted photocatalytic activity. • The defects formed at the interfacial contacts decreased the recombination rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel visible driven WO 3 -CeO 2 heterojunction was successfully synthesized. • The prepared photocatalyst was applied for degradation of Sulfamerazine from an aqueous solution. • Incorporation of CeO 2 on WO 3 significantly enhanced the photodegradation percentage. • S-scheme mechanism was suggested for the boosted photocatalytic activity. • Photodegradation pathways of Sulfamerazine antibiotic were investigated. In this work, hierarchical WO 3 -CeO 2 hollow sphere heterojunctions were fabricated via a two-step hydrothermal method and applied for degradation of sulfamerazine antibiotic under visible light irradiation. The incorporation of CeO 2 into the WO 3 microspheres was confirmed by XRD, BET, HRTEM, and XPS analysis. The results revealed that the photocatalytic activity of WO 3 -CeO 2 heterojunction was greatly enhanced compared to pure CeO 2 and WO 3 samples, and the highest degradation percentage of sulfamerazine was achieved on the WO 3 -CeO 2 heterojunction with 30 mol. % CeO 2 content. This could be ascribed to the efficient separation of charge carriers which was facilitated by oxygen vacancies formed at the interfaces of two coupled semiconductors. EIS analysis verified that the charge transfer resistance of WO 3 -30CeO 2 heterojunction was decreased, which is due to the heterojunction effect. Moreover, based on the Mott-Schottky calculations, radical trapping experiments and ESR analysis, hydroxide radicals were identified as the main active species, and an S-scheme charge transfer mechanism was suggested to explain the enhanced photocatalytic activity. The possible degradation pathway of sulfamerazine was suggested through the detection of degradation intermediates by mass spectroscopy. [ABSTRACT FROM AUTHOR]