Hydrothermal synthesized novel nanoporous g-C3N4/MnTiO3 heterojunction with direct Z-scheme mechanism

Recent progress in g-C3N4, TiO2 and ZnO based photocatalysts for dye degradation: Strategies to improve photocatalytic activity

Water contamination by dyes is a matter of concern for human health and the environment. Various methods (membrane separation, coagulation and adsorption) have been explored to remove/degrade dyes. However, now the exploitation of semiconductor assisted materials using renewable solar energy has emerged as a potential candidate to resolve the issue. Although, single component photocatalysts (ZnO, TiO₂, ZrO₂) were experimented, due to their low efficiency and stability due to the high recombination rate electron-hole pair and inefficient visible light absorption, composites of semiconductor materials are being used. Semiconductor heterojunction systems are developed by coupling two or more semiconductor components. The synergistic effect of their properties, such as adsorption and improved charge carrier migration, is observed to increase overall stability. This review covers recent progress in advanced nanocomposite materials based on g-C₃N₄, TiO₂ and ZnO used as photocatalysts with details of enhancing the photocatalytic properties by heterojunctions, crystallinity and doping. The conclusion at the end displays a summary, research gaps and future outlook. A holistic analysis of recent progress to demonstrate the efficient heterojunctions for photodegradation with optimal conditions, this review will be helpful for the development of efficient heterostructured systems for photodegradation. This review covers references from the year 2017-2020.

Novel BP/BiOBr S-scheme nano-heterojunction for enhanced visible-light photocatalytic tetracycline removal and oxygen evolution activity

Designing heterojunction photocatalysts with strong interfacial interaction and matched band structure is an effective way to reduce the recombination of photogenerated carriers. Herein, the exfoliated black phosphorus (BP) nanosheets were coupled with BiOBr nanosheets having higher Fermi level, and thereby it constructed a novel layered BP/BiOBr nano-heterojunction with chemically bonding, larger contact interface and unique band structures. BiOBr nanosheets were self-assembled on the surface of BP nanosheets by a facile liquid-phase ultrasound combined with solvothermal method. The photocatalytic performance for tetracycline (TC) degradation, oxygen evolution and H₂O₂ production rate of Sol-10BP/BiOBr was 7.8, 7.0 and 2.6 times than that of pure BiOBr, respectively. The in-situ generated H₂O₂ and OH became the main active species of mineralization and decomposition of TC. The novel S-scheme two-dimensional BP/BiOBr nano-heterojunction for boosting spatial charge separation retained the useful holes-electrons with higher redox ability, which was very beneficial for producing more OH, H₂O₂ and O₂, and the photocatalytic activity was greatly improved.

Significantly Enhanced Aqueous Cr(VI) Removal Performance of Bi/ZnO Nanocomposites via Synergistic Effect of Adsorption and SPR-Promoted Visible Light Photoreduction

Bismuth nanoparticles (BiNPs) and Zinc Oxide photocatalysts (BiNPs/ZnO) with different Bi loadings were successfully prepared via a facile chemical method. Their morphology and structure were thoroughly characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis (Ultraviolet-Visible) diffuse reflectance spectroscopy (DRS), photoluminescence spectra (PL), and electrochemical impedance spectroscopy (EIS). The results showed that a modification of hexagonal wurtzite-phase ZnO nanoparticles with Bi is achievable with an intimate interfacial interaction within its composites. The performance of the photocatalytic Cr(VI) removal under visible light irradiation indicated that BiNPs/ZnO exhibited a superior removal performance to bare ZnO, Bi, and the counterpart sample prepared using a physical mixing method. The excellent performance of the BiNPs/ZnO photocatalysts could be ascribed to the synergistic effect between the considerable physical Cr (VI) adsorption and enhanced absorption intensity in the visible light region, due to the surface plasmon resonance (SPR) as well as the effective transfer and separation of the photogenerated charge carriers at the interface.