Direct Z-scheme photocatalysts: Principles, synthesis, and applications

The high carrier recombination rate and serious photocorrosion of Ag3PO4 greatly restrict its photocatalytic application. Here, we fabricated an Ag3PO4/Ti3C2 Schottky catalyst and found that Ti3C2 can greatly enhanced the catalytic activity and stability of Ag3PO4. This arises from: (i) the abundant surface hydrophilic functional groups of Ti3C2 construct strong interfacial contact with Ag3PO4, which facilitate the separation of carriers; (ii) the strong redox reactivity of surface Ti sites promote multiple electron reduction reactions to induce more OH production; and (iii) a Schottky junction formed at Ag3PO4-Ti3C2 interface timely transfer electrons to Ti3C2 surface by built-in electric field, inhibiting the photocossion of Ag3PO4 caused by photogeneration electrons. Consequently, Ag3PO4/Ti3C2 exhibited excellent photocatalytic activity and stability for the degradation of organic pollutants. Especially, the apparent rate constant of 2,4-Dinitrophenol degradation with Ag3PO4/Ti3C2 was 2.5 times that of Ag3PO4/RGO and 10 times that of Ag3PO4. The photocatalytic performance of Ag3PO4/Ti3C2 toward tetracycline hydrochloride still maintained 68.4% after 8 cycles, while Ag3PO4/RGO and Ag3PO4 only maintained 36.2% and 7.8%, respectively. Furthermore, the efficient photoreduction of Cr6+ using AgI/Ti3C2 further illustrated an enormous potential in coupling Ti3C2 with other photosensitivity semiconductor to improve their catalytic activity and stability.

Ag3PO4/Ti3C2 MXene interface materials as a Schottky catalyst with enhanced photocatalytic activities and anti-photocorrosion performance

Solar energy is a renewable resource that can supply our energy needs in the long term. A semiconductor photocatalysis that is capable of utilizing solar energy has appealed to considerable interests for recent decades, owing to the ability to aim at environmental problems and produce renewal energy. Much effort has been put into the synthesis of a highly efficient semiconductor photocatalyst to promote its real application potential. Hence, we reviewed the most advanced methods and strategies in terms of (i) broadening the light absorption wavelengths, (ii) design of active reaction sites, and (iii) control of the electron-hole (e--h+) recombination, while these three processes could be influenced by remodeling the crystal lattice, surface, and interface. Additionally, we individually examined their current applications in energy conversion (i.e., hydrogen evolution, CO2 reduction, nitrogen fixation, and oriented synthesis) and environmental remediation (i.e., air purification and wastewater treatment). Overall, in this review, we particularly focused on advanced photocatalytic activity with simultaneous wastewater decontamination and energy conversion and further enriched the mechanism by proposing the electron flow and substance conversion. Finally, this review offers the prospects of semiconductor photocatalysts in the following three vital (distinct) aspects: (i) the large-scale preparation of highly efficient photocatalysts, (ii) the development of sustainable photocatalysis systems, and (iii) the optimization of the photocatalytic process for practical application.

A Critical Review on Energy Conversion and Environmental Remediation of Photocatalysts with Remodeling Crystal Lattice, Surface, and Interface

Optimizing the heterojunction structure of semiconductor photocatalysts is significant for taking full advantage of their abilities for organic molecules degradation. Here, we demonstrate a feasible strategy of polymerizing the quantum-thick graphitic carbon nitride (g-C3N4) on to the surface of anatase titanium dioxide (TiO2) nanosheets with exposed {001} facets to form the TiO2@g-C3N4 (TCN) core-shell quantum heterojunction for improving photocatalytic tetracycline degradation activity. 100 mg of TCN photocatalyst shows the highest tetracycline degradation rate of 2.2 mg/min, which is 36% higher than that of the TiO2/g-C3N4 random mixture (TCN(mix)), 2 times higher than that of TiO2, and 2.3 times higher than that of bulk g-C3N4. Results also indicate that h+ and ·O2− are the main oxidant species for the efficient photocatalytic reaction. The decisive factors in improving the photocatalytic activity of TCN is the unique structural advantages of quantum-thick g-C3N4 shell, compact and uniform contact interface, richly available reaction sites, more surface adsorbed hydroxyl (OH) groups. Efficient electron transfer between TiO2 and g-C3N4 is also demonstrated by the significant enhancement of photocurrent response of TCN electrodes and decrement of fluorescence emission spectra. This work demonstrates new sights for synthesizing high-efficient and environment-stable photocatalysts by engineering the surface heterojunction.

Compact and uniform TiO2@g-C3N4 core-shell quantum heterojunction for photocatalytic degradation of tetracycline antibiotics

Efficient heavy metal removal from industrial melting effluent using fixed-bed process based on porous hydrogel adsorbents

A highly efficient polyampholyte hydrogel sorbent based fixed-bed process for heavy metal removal in actual industrial effluent.

The serious photocorrosion of silver phosphate (Ag 3 PO 4 ) has limited its practical applications. In this work, we propose a strategy to suppress its photocorrosion by the construction of a Z-Scheme photocatalytic system, which composed of reduced graphene oxide-enwrapped Ag 3 PO 4 (Ag 3 PO 4 @RGO) and La,Cr-codoped SrTiO 3 (La,Cr:SrTiO 3 ). Dramatically, this system shows superior anti-photocorrosion and photocatalytic performances in degradation of both RhB and 2,4-DNP. Especially for RhB, it can be completely degraded after only 5 min under intense sunlight irradiation. The improved photoactivity and anti-photocorrosion of Ag 3 PO 4 @RGO@La,Cr:SrTiO 3 can be attributed to the following: (i) The sufficient interfacial contact between Ag 3 PO 4 and RGO is favorable to transfer the carriers and lengthen the lifetime of it; (ii) the package of Ag 3 PO 4 with RGO could work as a sheltering layer to protect Ag 3 PO 4 from photocorrosion. (iii) The aggregation of photogenerated holes in the VB of Ag 3 PO 4 makes it a rich-hole region due to Z-Scheme electrons transport mechanism, which can protect Ag 3 PO 4 from the photo-reduction. This strategy provides a new thought of protecting photosensitive semiconductor from photocorrosion and could regard as an efficient application method for environmental cleaning under natural sunlight irradiation. Furthermore, it even could be extended to outdoor or indoor air cleaning in the future.

Silver phosphate-based Z-Scheme photocatalytic system with superior sunlight photocatalytic activities and anti-photocorrosion performance

A ethylenediaminetetra-acetic acid (EDTA) cross-linked chitosan and N,N-methylenebis(acrylamide) (MBA) cross-linked polyacrylamide based double network hydrogel was successfully synthesized via a two-step method and then employed for heavy metal ion adsorption. Various adsorption conditions, such as pH, ionic strength, adsorbent dosage, and contact time were investigated. CTS/PAM gel have a theoretical maximum Cd(II), Cu(II), and Pb(II) sorption capacities of 86.00, 99.44, and 138.41 mg/g, respectively, at experimental conditions. The adsorption process of CTS/PAM gel on the heavy metal ion was identified to be endothermic and follows an ion-exchange reaction. The application of this gel adsorbent was demonstrated using practical industrial effluent. We found that it could effectively treat practical wastewater with all kinds of heavy metals. At an adsorbent dosage of 8 g/L, the total metal ions concentration declined from 448.5 to 5.0 mg/L. Simultaneously, the CTS/PAM gel exhibited remarkable mechanical ...

Jianhong Ma

Papers

A highly efficient polyampholyte hydrogel sorbent based fixed-bed process for heavy metal removal in actual industrial effluent.

Silver phosphate-based Z-Scheme photocatalytic system with superior sunlight photocatalytic activities and anti-photocorrosion performance

Efficient Removal of Heavy Metal Ions with An EDTA Functionalized Chitosan/Polyacrylamide Double Network Hydrogel

Fast and efficient removal of As(III) from water by CuFe2O4 with peroxymonosulfate: Effects of oxidation and adsorption.

Fast adsorption of heavy metal ions by waste cotton fabrics based double network hydrogel and influencing factors insight