Self‐templated Constructing of Heterophase Junction into Hierarchical Porous Structure of Semiconductors for Promoting Photogenerated Charge Separation

Electron confinement promoted the electric double layer effect of BiOI/β-Bi2O3 in photocatalytic water splitting

In the realm of photocatalysis, understanding the interface issues (solid/solid and solid/liquid) inherent in heterojunction at the atomic level is the ultimate for engineering an efficient photocatalyst. Herein, an electrophoretic deposition technique is adopted to synthesize BiOI/β-Bi2O3 heterojunction, exhibiting superior photocatalytic activity and stability in H2 evolution (91.5 μmol g-1 h-1) and H2O2 production (11.3 mg L-1 h-1). Combined with the experimental and computational results, a lower free energy of hydrogen evolution reaction (252.4 meV) has been observed contrast to BiOI and β-Bi2O3 samples. A carrier transfer process of like S-scheme heterojunction is proposed based on density of states (DOS) and carrier distribution calculations. The theoretical calculations illustrate the transition dipole moment, migration and accumulation of carrier in BiOI/β-Bi2O3 heterojunction. Subsequent ab initio molecular dynamics (AIMD) results of solid/liquid interface systems (BiOI/β-Bi2O3/H2O and β-Bi2O3/H2O) unravel the interface H2O (solvent) behaviors. The local aggregation of photo-generated electrons in BiOI/β-Bi2O3/H2O leads to a large potential drop, high proton migration rate and the steady electric double layer (EDL) structure compared to the β-Bi2O3/H2O, which facilitates the occurrence of photocatalytic reactions in solution. In addition to offering new insights into the hydrogen evolution and proton transfer in the EDL model and the association between the heterojunction effect and EDL structure, this work also introduces a novel design strategy for Bi-based heterojunctions.

Bimetallic CoCu-ZIF material for efficient visible light photocatalytic fuel denitrification

Effective design of photocatalysts is an effective method to improve the separation of photogenerated carriers, which improves the photocatalytic performance of photocatalysts. In this work, CoCu-ZIF materials with bimetallic structure were synthesized at room temperature for efficient photocatalytic fuel denitrification. The properties and structures of CoCu-ZIF photocatalysts can be effectively controlled by adjusting the molar ratio of cobalt to copper. The as-prepared CoCu-ZIF photocatalysts were characterized by XRD, FT-IR, SEM, TEM, UV-vis, Raman, BET and other techniques. The photoactivity of CoCu-ZIF for the denitrogenation of NCCs has been evaluated using visible light (λ ≥ 420 nm). The results indicate that Co₈Cu₂-ZIF photocatalysts exhibit excellent photocatalytic properties, in which the denitrification rate almost reached 80% after 4 hours under visible light irradiation, which is higher than the degradation ability of ZIF-67 (38%). Transient photoelectrochemical experiments and EIS Nyquist plots indicate that Co₈Cu₂-ZIF with unique structure efficiently improves the separation and transfer of photogenerated electron-hole pairs. Moreover, a possible reaction mechanism was proposed by LC-MS analysis.

In-situ fabrication of 3D hierarchical flower-like β-Bi2O3@CoO Z-scheme heterojunction for visible-driven simultaneous degradation of multi-pollutants

Development of an efficient heterojunction catalyst with a superior visible-light driven activity is regarded as a promising strategy to decontaminate organic wastewater. Herein, a novel direct Z-scheme β-Bi₂O₃@CoO heterojunction was well designed and successfully fabricated by in situ incorporating the two energy band-matched semiconductors. The obtained β-Bi₂O₃@CoO hybrid presented a unique 3D hierarchical structure with a mass of open channels and mesoporous, which afforded not only rapid mass transfer of targets but also good light-harvesting in view of the multiple reflections. Compared to the pristine β-Bi₂O₃ and CoO, the β-Bi₂O₃@CoO hybrid exhibited remarkably improved photocatalytic activity towards the simultaneous degradation of chlorotetracycline (CTC), tetracycline hydrochloride (TCH), oxytetracycline (OTC) and nitrobenzene (NB) under visible-light irradiation. The possible intermediates and degradation pathways were also tracked by mass spectra (MS) analysis. Moreover, a direct Z-scheme charge transfer mechanism in the intimate contact interface between β-Bi₂O₃ and CoO was verified for the improved catalytic activity, endowing the effective separation/transportation of the photo-excited charge carriers and maintenance of the strong redox ability in β-Bi₂O₃@CoO heterojunction. The present work affords a simple approach to design and construct 3D hierarchical direct Z-scheme photocatalysts with promising applications in water environment remediation.