Novel MoSSe/Bi2WO6 S-scheme heterojunction photocatalysts for significantly improved photoelectrochemical and photocatalytic performance

Heterogeneous photocatalytic ozonation of sulfamethoxazole by Z-scheme Bi2WO6/TiO2 heterojunction: Performance, mechanism and degradation pathway

The development of novel photocatalysts for efficient utilization of solar energy is highly essential for the most critical humanitarian challenges, i.e., energy and water crises as well as environmental pollution. Bismuth tungstate (Bi2WO6), an outstanding Aurivillius phase perovskite, has attracted intensive attention as a visible-light-responsive photocatalyst because of its non-toxicity, low cost, and outstanding physicochemical characteristics, i.e., nonlinear dielectric susceptibility, ferroelectric piezoelectricity, pyroelectricity, catalytic behavior, modifiable morphology, strong oxidation power, and good photochemical stability. However, the photocatalytic activity of bare Bi2WO6 is restricted because of the inherent drawbacks such as poor light-harvesting efficiency, weak reduction potential, relatively low specific surface area, the fast recombination rate of photoinduced charge carriers, and thus poor quantum yields of photocatalytic reactions. Moreover, the impossibility of simultaneous strong redox ability (demanding wide bandgap) and high light-harvesting efficiency (requiring narrow bandgap) is considered as a big challenge for the practical application of Bi2WO6. Undeniably, the construction of Z-scheme photocatalytic systems is recommended strategy to overcome the above-mentioned disadvantages because of the efficient spatial separation of photogenerated charge carriers and the boosting the redox performance. This review summarizes the principles and recent developments on Z-scheme photocatalytic systems with special emphasis on the Bi2WO6-based photocatalysts, including the types, photocatalytic mechanisms and practical applications. Moreover, major differences between type-II heterojunction and Z-scheme photocatalyst have also been discussed. Additionally, the significant role of unique structures (e.g., core-shell and 2D/2D) for the improvement of photocatalytic activity of Z-scheme photocatalyst has been presented. Indeed, Bi2WO6-based Z-scheme photocatalysts have exhibited superior photocatalytic activity for various applications. For example, they show high photocatalytic activity towards water/wastewater treatment (removal of organic and inorganic pollutants, as well as microorganisms), air purification (decomposition of volatile organic compounds and inorganic matters), “green” energy conversion (e.g., generation of H2 and CH4 fuels under solar irradiation), and organic synthesis. It is thought that this remarkable activity of Bi2WO6-based Z-scheme photocatalysts might be attributed to the efficient solar light harvesting, separation and further transfer of charge carriers and strong redox ability. To the best of our knowledge, the present paper is the first attempt to summarize the Bi2WO6-based Z-scheme photocatalytic reactions, providing important insights and up-to-date information for the scientific community to fully explore the potential of Bi2WO6-based photocatalysts for renewable environmental remediation, energy conversion, and chemical synthesis. 

Bi2WO6‐based Z-scheme photocatalysts: Principles, mechanisms and photocatalytic applications

Graphite carbon nitride has many excellent properties as a two-dimensional semiconductor material so that it has a wide application prospect in the field of photocatalysis. However, the traditional problems such as high recombination rate of photogenerated carriers limit its application. In this work, we introduce nitrogen deficiency into g-C3N4 to solve this problem a simple and safe in-situ reduction method. g-C3N4/CaCO3 was obtained by a simple and safe one-step calcination method with industrial-grade micron particles CaCO3. Cyano group modification was in-situ reduced during the thermal polymerization process, which would change the internal electronic structure of g-C3N4. The successful combination of g-C3N4 and CaCO3 and the introduction of cyanide have been proved by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometer. The formation of the cyano group, an electron-absorbing group, promotes the effective separation of photogenic electron hole pairs and inhibits the recombination of photogenic carriers. These advantages result in the generation of more •O2- and 1O2 in the catalytic system, which increases the photocatalytic efficiency of nicotine degradation by ten times. Furthermore, the degradation process of nicotine has been studied in this work to provide a basis for the degradation of nicotine organic pollutants in the air. 

In-situ-reduced synthesis of cyano group modified g-C3N4/CaCO3 composite with highly enhanced photocatalytic activity for nicotine elimination.

Simultaneous electrochemical detection of gallic acid and uric acid with p-tert-butylcalix[4]arene-based coordination polymer/mesoporous carbon composite

Z-scheme Cu2(OH)3F nanosheets-decorated 3D Bi2WO6 heterojunction with an intimate hetero-surface contact through a hydrogen bond for enhanced photoinduced charge separation and transfer

One-step synthesis of novel Ni-doped Cu2(OH)3F Fenton-like catalyst driven by visible light: Single activity and synergistic effect enhanced by bimetallic cooperation

The structural modulation of graphitic carbon nitride (g-C3N4) is regarded as an effective strategy to boost its photocatalytic behavior. Herein, we have synthesized 4,6-dimethyl-2-hydroxypyrimidine-doped and cyano defects co-modified graphitic carbon nitride (HDMP–CD-g-C3N4) using a facile in situ co-condensation method. HDMP–CD-g-C3N4 was employed for the degradation of tetracycline hydrochloride, exhibiting enhanced photocatalytic activity and catalyst stability. The characterization results demonstrate that the doping of HDMP decreases the band gap, thus promoting the light absorption of g-C3N4. Meanwhile, as an electron acceptor, HDMP broadens the π-conjugated off-domain system and accelerates the transfer of photogenerated electrons. In addition, the introduction of cyano defects further improves the separation efficiency of photogenerated electrons and holes. Analysis of time-resolved fluorescence spectra solidly supports these conclusions. Therefore, the photocatalytic degradation rate of HDMP–CD-g-C3N4 was 3.8 times that of the original g-C3N4, 2 times that of HDMP-doped g-C3N4 (HDMP-g-C3N4) and 2.5 times that of cyano defects-modified g-C3N4 (CD-g-C3N4). This work provides a way for collaboratively modulating the structure of g-C3N4 with molecular doping and defects, which is expected to bring novel prospects for the application of g-C3N4 in the treatment of waste water.

Construction of molecularly doped and cyano defects co-modified graphitic carbon nitride for the efficient photocatalytic degradation of tetracycline hydrochloride

Xueying Zhang

Papers

Z-scheme Cu2(OH)3F nanosheets-decorated 3D Bi2WO6 heterojunction with an intimate hetero-surface contact through a hydrogen bond for enhanced photoinduced charge separation and transfer

One-step synthesis of novel Ni-doped Cu2(OH)3F Fenton-like catalyst driven by visible light: Single activity and synergistic effect enhanced by bimetallic cooperation

Construction of molecularly doped and cyano defects co-modified graphitic carbon nitride for the efficient photocatalytic degradation of tetracycline hydrochloride