Developing sustainable, high-performance perovskites in photocatalysis: design strategies and applications

Solar energy is attractive because it is free, renewable, abundant and sustainable. Photocatalysis is one of the feasible routes to utilize solar energy for the degradation of pollutants and the production of fuel. Perovskites and their derivatives have received substantial attention in both photocatalytic wastewater treatment and energy production because of their highly tailorable structural and physicochemical properties. This review illustrates the basic principles of photocatalytic reactions and the application of these principles to the design of robust and sustainable perovskite photocatalysts. It details the structures of the perovskites and the physics and chemistry behind photocatalytic reactions and describes the advantages and limitations of popular strategies for the design of photoactive perovskites. This is followed by examples of how these strategies are applied to enhance the photocatalytic efficiency of oxide, halide and oxyhalide perovskites, with a focus on materials with potential for practical application, that is, not containing scarce or toxic elements. It is expected that this overview of the development of photocatalysts and deeper understanding of photocatalytic principles will accelerate the exploitation of efficient perovskite photocatalysts and bring about effective solutions to the energy and environmental crisis.

Pollutant degradation with mediator Z-scheme heterojunction photocatalyst in water: A review

The Z-scheme heterojunction is a photocatalyst with narrow band gap and sufficiently high oxidization and reduction powers for degradation of pollutants in waters. This review firstly summarizes the fundamentals of photocatalysis, and explains the need to develop Z-scheme heterojunctions to harvest energy from sunlight effectively. Secondly, contemporary reports of degradation wastewater pollutants, including organic dyes, antibiotics, and other chemicals are reviewed and discussed. A challenge in the selection of an appropriate Z-scheme for removing a specific pollutant is the lack of available energy levels that are offered by the catalyst and the lack of redox energy levels that are required to break down essential chemical bonds of the pollutants. With reference to the redox energy levels offered by the active photocatalytic species, the redox energy levels of specific pollutants studied in literature are estimated. Challenges and prospects concerning the use of the Z-scheme to degrade recalcitrant pollutants under irradiation by sunlight are outlined at the end of this review.

Construction of a novel step-scheme CdS/Pt/Bi2MoO6 photocatalyst for efficient photocatalytic fuel denitrification

Construction of step-scheme (S-scheme) heterojunction (HJ) structures is an excellent strategy to achieve efficient photogenerated carrier separation and retain strong redox ability. Recently, the development of efficient S-scheme HJ photocatalysts for the degradation of environmental organic pollutants has attracted considerable attention. In this work, a novel S-scheme CdS/Pt/Bi₂MoO₆ (CPB) photocatalyst was prepared for the first time by sonochemical and solvothermal methods. By anchoring Pt nanoparticles (NPs) at the interface between CdS nanorods (NRs) and Bi₂MoO₆ nanosheets (NSs), the migration of photogenerated electron–hole pairs along the stepped path was achieved. The ternary CPB samples were characterized by various analytical techniques, and their photocatalytic performance was investigated by conducting simulated fuel denitrification under visible-light irradiation. It was found that the CPB-4 composites exhibited the highest pyridine degradation activity, which reached 94% after 4 h of visible-light irradiation. The superior photocatalytic performance of the CPB-4 composite could be attributed to the synergistic effect of the Pt NPs and Bi₂MoO₆ NRs on the photocatalytic degradation as well as to the introduction of Pt and Bi₂MoO₆, which led to an excellent response and large specific surface area of the CPB-4 composite. Lastly, the bridging role of the Pt NPs introduced into the S-scheme system was also notable, as it effectively improved the separation and transfer of the CdS/Bi₂MoO₆ interfaces for the photogenerated electron–hole pairs while retaining strong redox ability.

The S-scheme heterojunction in which Pt nanoparticles were anchored between CdS and Bi₂MoO₆ as ‘bridges’ enhanced the utilization of visible light and efficient separation of photogenerated electron–hole pairs.

Z-scheme BiVO4/Ag/Ag2S composites with enhanced photocatalytic efficiency under visible light

The Z-scheme BiVO4/Ag/Ag2S photocatalyst was fabricated via a two-step route. The as-prepared samples were characterized by XRD, FE-SEM, HRTEM, XPS and UV-vis diffuse reflectance spectroscopy. The results of PL and photocurrent response tests demonstrate that the ternary BiVO4/Ag/Ag2S composites had a high separation and migration efficiency of photoexcited carriers. As a result, the ternary photocatalyst exhibits enhanced photocatalytic activity for decomposing Rhodamine B (RhB) under LED light (420 nm) irradiation. The results of trapping experiments demonstrate both h+ and ˙OH play crucial roles in decomposing RhB molecules. Additionally, the energy band structures and density of states (DOS) of BiVO4 and Ag2S were investigated via the density functional theory (DFT) method. Finally, a Z-scheme electron migration mechanism of BiVO4 → Ag → Ag2S was proposed based on the experimental and calculated results.

Silver-based semiconductor Z-scheme photocatalytic systems for environmental purification

Silver-based semiconductor photocatalysts are promising materials for solving environmental and energy issues due to their strong optical absorption, excellent quantum efficiency and photoelectrochemical properties. However, the uncontrollable photocorrosion and high use cost of single silver-based semiconductor photocatalysts limit its practical application. The construction of Z-scheme photocatalytic systems that mimic natural photosynthesis can not only enhance the photocatalytic activity of silver-based semiconductor photocatalysts, but also improve their stability and reduce the use costs. This critical review concisely highlights the basic principles of Z-scheme photocatalytic systems, and discusses the construction of silver-based semiconductor Z-scheme photocatalytic systems and the roles of metallic Ag in there and summarizes the synthesis methods of silver-based semiconductor Z-scheme photocatalytic systems. Then, a series of the solar-driven applications are elaborated, including organic pollutants degradation, hydrogen production, and carbon dioxide reduction. Meanwhile, the mechanism and difficult level of these photocatalytic reactions are also described. Besides, metal organic frameworks (MOFs) as a novel type of photocatalysts have attracted growing attention. The novel combination of silver-based semiconductors with typical photoactive MOFs is highlighted based on the Z-scheme photocatalytic systems. Eventually, the future challenges and prospects in the development of silver-based semiconductor Z-scheme photocatalytic systems are presented.

Selective oxidation of alcohols by using CoFe2O4/Ag2MoO4 as a visible-light-driven heterogeneous photocatalyst

Using a CoFe₂O₄/Ag₂MoO₄ heterostructure as a novel, stable, inexpensive, and reusable photocatalyst with high-performance for the oxidation of alcohols.

Modulation of Bi2 MoO6 -Based Materials for Photocatalytic Water Splitting and Environmental Application: a Critical Review

Highly active photocatalysts driving chemical reactions are of paramount importance toward renewable energy substitutes and environmental protection. As a fascinating Aurivillius phase material, Bi₂ MoO₆ has been the hotspot in photocatalytic applications due to its visible light absorption, nontoxicity, low cost, and high chemical durability. However, pure Bi₂ MoO₆ suffers from low efficiency in separating photogenerated carriers, small surface area, and poor quantum yield, resulting in low photocatalytic activity. Various strategies, such as morphology control, doping/defect-introduction, metal deposition, semiconductor combination, and surface modification with conjugative π structures, have been systematically explored to improve the photocatalytic activity of Bi₂ MoO₆ . To accelerate further developments of Bi₂ MoO₆ in the field of photocatalysis, this comprehensive Review endeavors to summarize recent research progress for the construction of highly efficient Bi₂ MoO₆ -based photocatalysts. Furthermore, benefiting from the enhanced photocatalytic activity of Bi₂ MoO₆ -based materials, various photocatalytic applications including water splitting, pollutant removal, and disinfection of bacteria, were introduced and critically reviewed. Finally, the current challenges and prospects of Bi₂ MoO₆ are pointed out. This comprehensive Review is expected to consolidate the existing fundamental theories of photocatalysis and pave a novel avenue to rationally design highly efficient Bi₂ MoO₆ -based photocatalysts for environmental pollution control and green energy development.

Enhanced visible-light photocatalytic activity and photostability of Ag3PO4/Bi2WO6 heterostructures toward organic pollutant degradation and plasmonic Z-scheme mechanism

Novel Ag3PO4/Bi2WO6 heterostructured materials with enhanced visible-light catalytic performance were successfully synthesized by assembly combined with a hydrothermal treatment. The microstructures, morphologies, and optical properties of the prepared samples were characterized by multiple techniques. The irregular Ag3PO4 nanospheres dispersed on the surface of Bi2WO6 nanoflakes, and their catalytic performances were evaluated via the degradation of organic pollutants including rhodamine B (RB), methylene blue (MB), crystal violet (CV), methyl orange (MO), and phenol (Phen) under visible-light irradiation. The resulting Ag3PO4/Bi2WO6 heterostructured materials displayed higher photocatalytic activity than that of either pure Bi2WO6 or Ag3PO4. The enhanced photocatalytic activity was due to the good formation of heterostructures, which could not only broaden the spectral response range to visible light but also effectively promoted the charge separation. Meanwhile, the reasonable photoreactive plasmonic Z-scheme mechanism was carefully investigated on the basic of the reactive species scavenging tests, photoelectrochemical experiments, and photoluminescence (PL) spectrum. In addition, the excellent photostability of Ag3PO4/Bi2WO6 was obtained, which Ag formed at the early photocatalytic reaction acted as the charge transmission-bridge to restrain the further photoreduction of Ag3PO4.

Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

Efficient charge transfer at the interfaces of an In₂S₃/Ag₂CrO₄ composite, due to the formation of a Z-scheme system between In₂S₃ and Ag₂CrO₄, effectively facilitates photogenerated electron–hole pair separation.

Effective removal of colourless pollutants and organic dyes by Ag@AgCl nanoparticle-modified CaSn(OH)6 composite under visible light irradiation

The Ag@AgCl nanoparticles could broaden visible-light absorption of pure CSH and depress the recombination of photoinduced electron–hole pairs.

New insights into Ag-doped BiVO4 microspheres as visible light photocatalysts

This study describes the synthesis of Ag–bismuth vanadate (Ag–BiVO₄) microspheres, a highly efficient visible light photocatalyst for the degradation of methylene blue, via a one-step hydrothermal method.

Fabrication of g-C3N4/Au/CdZnS Z-scheme photocatalyst to enhance photocatalysis performance

Sandwich-structured C₃N₄/Au/CdZnS photocatalyst.