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Environmental protection and the necessity of green energy have become fundamental concerns for humankind. However, rapid recombination of photoexcitons in semiconductors often gets in the path of photocatalytic reactions and annoyingly suppresses the photocatalytic activity. In this study, a polypyrrole (PPY)-supported step-scheme (S-scheme) ZnFe 2 O 4 @WO 3- X (PZFW15) ternary composite was fabricated by a multistep process: hydrothermal and calcination processes, followed by polymerization. During the formation of the heterojunction, the oxygen vacancy (OV) on WO 3- X promotes effective separation and increases the redox power of the photogenerated excitons via the built-in internal electric field of S-scheme pathways between ZnF and WO 3- X . The successful construction of the S-scheme heterojunction was substantiated through X-ray photoelectron spectroscopy, experimental calculations, radical trapping experiment, and liquid electron spin resonance (ESR) characterization, whereas the existence of OVs was well confirmed by EPR and Raman analyses. Meanwhile, the PPY served as a supporter, and the polaron and bipolaron species of PPY acted as electron and hole acceptors, respectively, which further enhances the charge-carrier transmission and separation in the ternary PZFW15 photocatalyst. The designed ternary nanohybrid (PZFW15) displays outstanding gemifloxacin detoxification (95%, 60 min) and hydrogen generation (657 μmol h -1 ), i.e., 1.5 and 2.2 times higher than the normal S-scheme ZFW15 heterostructure and pure ZnFe 2 O 4 (ZnF), respectively, with an apparent conversion efficiency of 4.92%. The ESR and trapping experiments indicate that the generated • OH and • O 2 - radicals from the PZFW15 photocatalyst are responsible for gemifloxacin degradation. This unique PPY-supported S-scheme heterojunction is also beneficial for the enhanced electron-transfer rate and provides abundant active sites for photocatalytic reactions., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Lethargic kinetics is the foremost bottleneck of the photocatalytic water oxidation reaction. Hence, in this respect, the CeO 2 coral reef made up of nanosheets is studied focusing on the oxygen vacancy that affects the water oxidation reaction. First, CeO 2 was prepared in an oyster shell/crucible with the presence/absence of urea by a simple calcination technique to tune the oxygen vacancy. More oxygen vacancy was detected in CeO 2 prepared from urea and oyster shell, which is evidenced from Raman and PL analyses. Further, the oyster shell-treated sample was found to be of nanosheet type with numerous pores as observed via TEM analysis. The theoretical approach was adopted to expose the role of oxygen vacancies and the fate of scavenging agents in the water oxidation mechanism. It was observed that an oxygen vacancy plays a vital role in minimizing the activation energy hump and opposes the reverse reaction. The apparent conversion efficiency of 7.1% is calculated for the oxygen evolution reaction. Oxygen vacancy, quantum confinement effect, and charge separation efficiency are mainly responsible for the better photocatalyzed water oxidation reaction and hydroxyl radical production. This investigation will help in providing valuable information toward designing cost-effective oxygen vacancy-oriented nanosheet systems and the importance of vacancy in the water-splitting reaction., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

To surmount incompatibility provoked efficiency suppression of an anisotype heterojunction and to pursue an improved intrinsic photocatalytic activity by manipulating oriented transfer of photoinduced charge carriers, an In 2 S 3 /BiVO 4 (1:1) n-n isotype heterojunction was fabricated successfully through a simple two-step calcination method, followed by a wet-chemical deposition method. The formation of an n-n isotype heterojunction was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy. The photocatalytic efficiency of the In 2 S 3 /BiVO 4 catalyst was examined over degradation of oxytetracycline hydrochloride (O-TCH) and oxygen (O 2 ) evolution reaction. Consequently, an n-n In 2 S 3 /BiVO 4 isotype heterojunction exhibits a superior O-TCH degradation efficiency (94.6%, 120 min) and O 2 evolution (695.76 μmol, 120 min) of multiple folds as compared to the pure BiVO 4 and In 2 S 3 solely. This is attributed to the proper band alignment and intimate interfacial interaction promoted charge carrier separation over the n-n isotype heterojunction. The intimate interfacial contact was confirmed by transmission electron microscopy (TEM), high-resolution TEM, and field emission scanning electron microscopy analysis. The proper band alignment was confirmed by Mott-Schottky analysis. The photoelectrochemical linear sweep voltammetric study shows a superior photocurrent density (269 μA/cm 2 ) for In 2 S 3 /BiVO 4 as compared to those for pristine BiVO 4 and In 2 S 3 , which is in good agreement with the photocatalytic results. Furthermore, the superior charge antirecombination efficiency of the n-n isotype heterojunction was established by photoluminescence, electrochemical impedance spectroscopy, Bode analysis, transient photocurrent, and carrier density analysis. The improved photostability of the heterojunction was confirmed by chronoamperometry analysis. An orderly corelationship among physicochemical, electrochemical, and photocatalytic properties was established, and a possible mechanistic pathway was presented to better understand the outcome of the n-n isotype heterojunction. This study presents an effective way to develop new n-n isotype heterojunction-based efficient photocatalysts and could enrich wide applications in other areas., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)