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

S-Scheme heterojunction of Cs2SnBr6/C3N4 with interfacial electron exchange toward efficient photocatalytic NO abatement

Photocatalytic technology is of great significance in environmental purification due to its eco-friendly and cost-effective operations. However, low charge-transfer efficiency restricts the photocatalytic activity of the catalyst. Herein, we report Cs2SnBr6/C3N4 composite catalysts that exhibit a robust interfacial electron exchange thereby enhancing photocatalytic nitric oxide (NO) oxidation. A comprehensive study has demonstrated the S-scheme electron transfer mechanism. Benefiting from the interfacial internal electric field, the C-Br bond serves as a direct electron transfer channel, resulting in enhanced charge separation. Furthermore, the S-scheme heterojunction effectively traps high redox potential electrons and holes, leading to the production of abundant reactive oxygen radicals that enhance photocatalytic NO abatement. The NO removal rate of the Cs2SnBr6/C3N4 heterogeneous system can reach 86.8 %, which is approximately 3-fold and 18-fold that of pristine C3N4 and Cs2SnBr6, respectively. The comprehensive understanding of the electron transfer between heterojunction atomic interfaces will provide a novel perspective on efficient environmental photocatalysis.

Encapsulation engineering of porous crystalline frameworks for delayed luminescence and circularly polarized luminescence

Delayed luminescence (DF), including phosphorescence and thermally activated delayed fluorescence (TADF), and circularly polarized luminescence (CPL) exhibit common and broad application prospects in optoelectronic displays, biological imaging, and encryption. Thus, the combination of delayed luminescence and circularly polarized luminescence is attracting increasing attention. The encapsulation of guest emitters in various host matrices to form host-guest systems has been demonstrated to be an appealing strategy to further enhance and/or modulate their delayed luminescence and circularly polarized luminescence. Compared with conventional liquid crystals, polymers, and supramolecular matrices, porous crystalline frameworks (PCFs) including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), zeolites and hydrogen-bonded organic frameworks (HOFs) can not only overcome shortcomings such as flexibility and disorder but also achieve the ordered encapsulation of guests and long-term stability of chiral structures, providing new promising host platforms for the development of DF and CPL. In this review, we provide a comprehensive and critical summary of the recent progress in host-guest photochemistry via the encapsulation engineering of guest emitters in PCFs, particularly focusing on delayed luminescence and circularly polarized luminescence. Initially, the general principle of phosphorescence, TADF and CPL, the combination of DF and CPL, and energy transfer processes between host and guests are introduced. Subsequently, we comprehensively discuss the critical factors affecting the encapsulation engineering of guest emitters in PCFs, such as pore structures, the confinement effect, charge and energy transfer between the host and guest, conformational dynamics, and aggregation model of guest emitters. Thereafter, we summarize the effective methods for the preparation of host-guest systems, especially single-crystal-to-single-crystal (SC-SC) transformation and epitaxial growth, which are distinct from conventional methods based on amorphous materials. Then, the recent advancements in host-guest systems based on PCFs for delayed luminescence and circularly polarized luminescence are highlighted. Finally, we present our personal insights into the challenges and future opportunities in this promising field.

High-Entropy Photothermal Materials

High-entropy (HE) materials, celebrated for their extraordinary chemical and physical properties, have garnered increasing attention for their broad applications across diverse disciplines. The expansive compositional range of these materials allows for nuanced tuning of their properties and innovative structural designs. Recent advances have been centered on their versatile photothermal conversion capabilities, effective across the full solar spectrum (300-2500 nm). The HE effect, coupled with hysteresis diffusion, imparts these materials with desirable thermal and chemical stability. These attributes position HE materials as a revolutionary alternative to traditional photothermal materials, signifying a transformative shift in photothermal technology. This review delivers a comprehensive summary of the current state of knowledge regarding HE photothermal materials, emphasizing the intricate relationship between their compositions, structures, light-absorbing mechanisms, and optical properties. Furthermore, the review outlines the notable advances in HE photothermal materials, emphasizing their contributions to areas, such as solar water evaporation, personal thermal management, solar thermoelectric generation, catalysis, and biomedical applications. The review culminates in presenting a roadmap that outlines prospective directions for future research in this burgeoning field, and also outlines fruitful ways to develop advanced HE photothermal materials and to expand their promising applications.

Construction of Cs2AgBiCl6/COF Heterojunction for Boosted Photocatalytic Thioester Oxidation

Lead-free halide perovskites as a new kind of potential candidate for photocatalytic organic synthesis have attracted much attention recently. The rational heterojunction construction is regarded as an efficient strategy to delicately regulate their catalytic performances. Herein, a semi-conductive covalent organic framework (COF) nanosheet, C4N, is employed as the functional component to construct Cs2AgBiCl6/C4N (CABC/C4N) heterojunction. It is found that the C4N nanosheets with rich surface functional groups can serve as heterogeneous nucleation sites to manipulate the growth of CABC nanocrystals and afford close contact between each other, therefore facilitate the transfer and spatial separation of photogenerated charge carriers, as verified by in situ X-ray photoelectronic spectroscopy and Kelvin probe force microscopy. Moreover, the oxygen affinity of C4N endows the heterojunctions with outstanding aerobic reactivity, thus improving the photocatalytic performance largely. The optimal CABC/C4N heterojunction delivers a thioanisole conversion efficiency of 100% after 6 h, which is 2.2 and 7.7-fold of that of CABC and C4N. This work provides a new ideal for the design and application of lead-free perovskite heterojunction photocatalysts for organic reactions.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

Silver doped barium titanate nanoparticles for enhanced visible light photocatalytic degradation of dyes

Due to the rapid growth of global population, new, fast and reliable methods must be developed to purify contaminated water. Various photocatalysts have been developed to remove organic dyes from water. Herein, Ag doped BaTiO3 has been synthesized using a facile solvothermal method and its excellent photocatalytic activities were demonstrated in degradation of both anionic and cationic dyes under visible light illumination. Ag doped BaTiO3 nanoparticles showed greater efficacy in the degradation of methylene blue (MB) and eosin yellow (EY) than undoped BaTiO3 nanoparticles, which makes them a better candidate for photocatalysis. 1.0 AgBT sample showed the highest photocatalytic activity for MB (99.1 % in 100 min) and EY (99.3 % in 60 min) dye degradation compared with those of other samples. Further, the trapping experiments revealed that hydroxyl radicals and holes are the active species in the photocatalytic process of MB and EY dye degradation and recycle test showed excellent stability of the synthesized material.

Improving the stability of perovskite nanocrystals via SiO2 coating and their applications

Lead halide perovskite nanocrystals (LHP NCs) with outstanding optical properties have been regarded as promising alternatives to traditional phosphors for lighting and next-generation display technology. However, the practical applications of LHP NCs are seriously hindered by their poor stability upon exposure to moisture, oxygen, light, and heat. Hence, various strategies have been proposed to solve this issue. In this review, we have focused our attention on improving the stability of LHP NCs via SiO2 coating because it has the advantages of simple operation, less toxicity, and easy repetition. SiO2 coating is classified into four types: (a) in situ hydrolytic coating, (b) mesoporous silica loading, (c) mediated anchoring, and (d) double coating. The potential applications of SiO2-coated LHP NCs in the field of optoelectronics, biology, and catalysis are presented to elucidate the reliability and availability of SiO2 coating. Finally, the future development and challenges in the preparation of SiO2-coated LHP NCs are analyzed in order to promote the commercialization process of LHP NC-related commodities.

A comprehensive review on the application of semiconducting materials in the degradation of effluents and water splitting

In this comprehensive review article, we delve into the critical intersection of environmental science and materials science. The introduction sets the stage by emphasizing the global water shortage crisis and the dire consequences of untreated effluents on ecosystems and human health. As we progress into the second section, we embark on an intricate exploration of piezoelectric and photocatalytic principles, illuminating their significance in wastewater treatment and sustainable energy production. The heart of our review is dedicated to a detailed analysis of the detrimental impacts of effluents on human health, underscoring the urgency of effective treatment methods. We dissected three key materials in the realm of piezo-photocatalysis: ZnO-based materials, BaTiO3-based materials, and bismuth-doped materials. Each material is scrutinized for its unique properties and applications in the removal of pollutants from wastewater, offering a comprehensive understanding of their potential to address this critical issue. Furthermore, our exploration extends to the realm of hydrogen production, where we discuss various types of hydrogen and the role of piezo-photocatalysis in generating clean and sustainable hydrogen. By illuminating the synergistic potential of these advanced materials and technologies, we pave the way for innovative solutions to the pressing challenges of water pollution and renewable energy production. This review article not only serves as a valuable resource for researchers and scholars in the fields of material science and environmental engineering but also underscores the pivotal role of interdisciplinary approaches in addressing complex global issues.

Regulating the Active Sites of Cs2 AgBiCl6 by Doping for Efficient Coupling of Photocatalytic CO2 Reduction and Benzyl Alcohol Oxidation

Halide perovskites exhibit outstanding optoelectronic properties, which make them an ideal choice for photocatalytic CO2 reduction and benzyl alcohol (BA) oxidation. Nevertheless, the simultaneous realization of the above redox coupling reactions on halide perovskites remains a great challenge, as it requires distinct catalytic sites for different target reactions. Herein, the catalytic sites of Cs2 AgBiCl6 (CABC) are regulated by doping Fe for efficient coupling of photocatalytic CO2 reduction and BA oxidation. The Fe-doped CABC (Fe: CABC) exhibits an enhanced visible-light response and effective charge separation. Experimental results and theoretical calculations reveal a synergistic interplay between Bi and Fe sites, where the Bi and Fe sites have lower activation energies toward CO2 reduction and BA oxidation. Further investigations demonstrate that electrons and holes prefer to accumulate at the Bi site and Fe site under light irradiation, respectively, which creates favorable conditions for facilitating CO2 reduction and BA oxidation. The resultant Fe: CABC achieves a high photocatalytic performance toward CO (18.5 µmol g-1  h-1 ) and BD (1.1 mmol g-1  h-1 ) generation, which surpasses most of the state-of-the-art halide photocatalysts. This work demonstrates a facile strategy for regulating the catalytic site for redox coupling reactions, which will pave a new way for designing halide perovskites for photocatalysis.

Rational Atom Substitution to Obtain Efficient, Lead-Free Photocatalytic Perovskites Assisted by Machine Learning and DFT Calculations

Inorganic lead-free halide perovskites, devoid of toxic or rare elements, have garnered considerable attention as photocatalysts for pollution control, CO2 reduction and hydrogen production. In the extensive perovskite design space, factors like substitution or doping level profoundly impact their performance. To address this complexity, a synergistic combination of machine learning models and theoretical calculations were used to efficiently screen substitution elements that enhanced the photoactivity of substituted Cs2 AgBiBr6 perovskites. Machine learning models determined the importance of d10 orbitals, highlighting how substituent electron configuration affects electronic structure of Cs2 AgBiBr6 . Conspicuously, d10 -configured Zn2+ boosted the photoactivity of Cs2 AgBiBr6 . Experimental verification validated these model results, revealing a 13-fold increase in photocatalytic toluene conversion compared to the unsubstituted counterpart. This enhancement resulted from the small charge carrier effective mass, as well as the creation of shallow trap states, shifting the conduction band minimum, introducing electron-deficient Br, and altering the distance between the B-site cations d band centre and the halide anions p band centre, a parameter tuneable through d10 configuration substituents. This study exemplifies the application of computational modelling in photocatalyst design and elucidating structure-property relationships. It underscores the potential of synergistic integration of calculations, modelling, and experimental analysis across various applications.

Exploration of the origin of the excellent charge-carrier dynamics in Ruddlesden-Popper oxysulfide perovskite Y2Ti2O5S2

Although the efficient separation of electron-hole (e-h) pairs is one of the most sought-after electronic characteristics of materials, due to thermally induced atomic motion and other factors, they do not remain separated during the carrier transport process, potentially leading to rapid carrier recombination. Here, we utilized real-time time-dependent density functional theory in combination with nonadiabatic molecular dynamics (NAMD) to explore the separated dynamic transport path within Ruddlesden-Popper oxysulfide perovskite Y2Ti2O5S2 caused by the dielectric layer and phonon frequency difference. The underlying origin of the efficient overall water splitting in Y2Ti2O5S2 is systematically explored. We report the existence of the bi-directional e-h separate-path transport, in which, the electrons transport in the Ti2O5 layer and the holes diffuse in the rock-salt layer. This is in contrast to the conventional e-h separated distribution with a crowded transport channel, as observed in SrTiO3 and hybrid perovskites. Such a unique feature finally results in a long carrier lifetime of 321 ns, larger than that in the SrTiO3 perovskite (160 ns) with only one carrier transport channel. This work provides insights into the carrier transport in lead-free perovskites and yields a novel design strategy for next-generation functionalized optoelectronic devices.

Selective Metal-Free CO2 Photoreduction in Water Using Porous Nanostructures with Internal Molecular Free Volume

The conversion of CO2 to a sole carbonaceous product using photocatalysis is a sustainable solution for alleviating the increasing levels of CO2 emissions and reducing our dependence on nonrenewable resources such as fossil fuels. However, developing a photoactive, metal-free catalyst that is highly selective and efficient in the CO2 reduction reaction (CO2RR) without the need for sacrificial agents, cocatalysts, and photosensitizers is challenging. Furthermore, due to the poor solubility of CO2 in water and the kinetically and thermodynamically favored hydrogen evolution reaction (HER), designing a highly selective photocatalyst is challenging. Here, we propose a molecular engineering approach to design a photoactive polymer with high CO2 permeability and low water diffusivity, promoting the mass transfer of CO2 while suppressing HER. We have incorporated a contorted triptycene scaffold with "internal molecular free volume (IMFV)" to enhance gas permeability to the active site by creating molecular channels through the inefficient packing of polymer chains. Additionally, we introduced a pyrene moiety to promote visible-light harvesting capability and charge separation. By leveraging these qualities, the polymer exhibited a high CO generation rate of 77.8 μmol g-1 h-1, with a high selectivity of ∼98% and good recyclability. The importance of IMFV was highlighted by replacing the contorted triptycene unit with a planar scaffold, which led to a selectivity reversal favoring HER over CO2RR in water. In situ electron paramagnetic resonance (EPR), time-resolved photoluminescence spectroscopy (TRPL), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques, further supported by theoretical calculations, were employed to enlighten the mechanistic insight for metal-free CO2 reduction to exclusively CO in water.

Rechargeable Multifunctional Anti-Bacterial AEMs for Electrodialysis: Improving Anti-Biological Performance via Synergistic Antibacterial Mechanism

Constructing a functional layer on the surface of commercial membrane (as a substrate) to inhibit the formation of biofilms is an efficient strategy to prepare an antibacterial anion exchange membrane (AEM). Herein, a rechargeable multifunctional anti-biological system is reported by utilizing the mussel-inspired L-dopa connection function on commercial AEMs. Cobalt nanoparticles (Co NPs) and N-chloramine compounds are deposited on the AEM surface by a two-step modification procedure. The anti-biofouling abilities of the membranes are qualitatively and quantitatively analyzed by adopting common Gram-negative (E. coli) and Gram-positive (S. aureus & Bacillus) bacteria as model biofouling organisms. The optimized membrane exhibits a high stability concerning the NaCl solution separation performance within 240 min. Meantime, the mechanism of the anti-adhesion is un-veiled at an atomic level and molecular dynamics (MD) simulation are conducted to measure the interaction, adsorption energy and average loading by using lipopolysaccharide (LPS) of E. coli. In view of the superior performance of antibacterial surfaces, it is believed that this work could provide a valuable guideline for the design of membrane materials with resistance to biological contamination.

All Printed Photoanode/Photovoltaic Mini-Module for Water Splitting

Printing a large-area bismuth vanadate photoanode offers a promising approach for cost-effective photoelectrochemical (PEC) water splitting. However, the light absorption trade-off with charge transfer, as well as stability issues always lead to poor PEC efficiency. Here, the solution-processed recipe is advanced with BiI3 dopant for the printed deposition with controllable crystal growth. The resultant BiVO4 films prefer (001) orientation with nanorod feature on substrate, allowing a faster charge transfer and improved photocurrent. The BiVO4 photoanode in tandem with perovskite solar module delivers an operating photocurrent density of 5.88 mA cm-2 at zero bias in 3.11 cm2 active area under AM 1.5 G illumination, yielding a solar-to-hydrogen efficiency as high as 7.02% for unbiased water splitting. Equally important, the stability of the aged BiVO4 rods has been addressed to distinguish phase segregation at surface. The photocatalysis degradation composes of vanadium loss and Bi2 O3 enriching at the surface, opening a lid on the long-term stability of BiVO4 photoanodes.

Construction of Core-shell Sb2 s3 @Cds Nanorod with Enhanced Heterointerface Interaction for Chromium-Containing Wastewater Treatment

How to collaboratively reduce Cr(VI) and break Cr(III) complexes is a technical challenge to solve chromium-containing wastewater (CCW) pollution. Solar photovoltaic (SPV) technology based on semiconductor materials is a potential strategy to solve this issue. Sb2 S3 is a typical semiconductor material with total visible-light harvesting capacity, but its large-sized structure highly aggravates disordered photoexciton migration, accelerating the recombination kinetics and resulting low-efficient photon utilization. Herein, the uniform mesoporous CdS shell is in situ formed on the surface of Sb2 S3 nanorods (NRs) to construct the core-shell Sb2 S3 @CdS heterojunction with high BET surface area and excellent near-infrared light harvesting capacity via a surface cationic displacement strategy, and density functional theory thermodynamically explains the breaking of SbS bonds and formation of CdS bonds according to the bond energy calculation. The SbSCd bonding interaction and van der Waals force significantly enhance the stability and synergy of Sb2 S3 /CdS heterointerface throughout the entire surface of Sb2 S3 NRs, promoting the Sb2 S3 -to-CdS electron transfer due to the formation of built-in electric field. Therefore, the optimized Sb2 S3 @CdS catalyst achieves highly enhanced simulated sunlight-driven Cr(VI) reduction (0.154 min-1 ) and decomplexation of complexed Cr(III) in weakly acidic condition, resulting effective CCW treatment under co-action of photoexcited electrons and active radicals. This study provides a high-performance heterostructured catalyst for effective CCW treatment by SPV technology.

Synthesis of Layered Lead-Free Perovskite Nanocrystals with Precise Size and Shape Control and Their Photocatalytic Activity

Halide perovskites have attracted enormous attention due to their potential applications in optoelectronics and photocatalysis. However, concerns over their instability, toxicity, and unsatisfactory efficiency have necessitated the development of lead-free all-inorganic halide perovskites. A major challenge in designing efficient halide perovskites for practical applications is the lack of effective methods for producing nanocrystals with precise size and shape control. In this work, a layered perovskite, Cs4ZnSb2Cl12 (CZS), is found from calculations to exhibit size- and facet-dependent optoelectronic properties in the nanoscale, and thus, a colloidal method is used to synthesize the CZS nanoparticles with size-tunable morphologies: zero- (nanodots), one- (nanowires and nanorods), two- (nanoplates), and three-dimensional (nanopolyhedra). The growth kinetics of the CZS nanostructures, along with the effects of surface ligands, reaction temperature, and time were investigated. The optoelectronic properties of the nanocrystals varied with size due to quantum confinement effects and with shape due to anisotropy within the crystals and the exposure of specific facets. These properties could be modulated to enhance the visible-light photocatalytic performance for toluene oxidation. In particular, the 9.7 nm CZS nanoplates displayed a toluene to benzaldehyde conversion rate of 1893 μmol g-1 h-1 (95% selectivity), 500 times higher than the bulk synthesized CZS, and comparable with the reported photocatalysts. This study demonstrates the integration of theoretical calculations and synthesis, revealing an approach to the design and fabrication of novel, high-performance colloidal perovskite nanocrystals for optoelectronic and photocatalytic applications.

Enhance the stability of oxygen vacancies in SrTiO3 via metallic Ag modification for efficient and durable photocatalytic NO abatement

Oxygen vacancy engineering is an appealing strategy in the direction of photocatalytic pollutant purification. Unfortunately, the short lifetime of oxygen vacancies significantly limits photocatalytic efficiencies and their application. Herein, we report that such a scenario can be resolved via plasmonic silver metal modification SrTiO₃ containing oxygen vacancies, which can achieve a high NO removal rate of 70.0% and long stability. This outstanding photocatalytic activity can be attributed to the increased optical response range and carrier separation by metallic Ag with the unique character of localized surface plasmonic resonance (LSPR) effect. Moreover, the intrinsic mechanism of how the plasmonic metal could enhance the stability of oxygen vacancies is proposed. The plasmon-driven hot carriers inject SrTiO₃ support that promotes the regeneration of oxygen vacancies around the interface, meanwhile, the introduction of Ag nanoparticles prevents the oxygen vacancies from being filled by the reactant. This work elucidates the unique role of plasmonic metal in photocatalysis, providing an innovative idea for improving catalytic stability.

Multifunctional Ti3C2 decorated perovskite La1-xSrxCoO3 nanorods for efficient energy conversion

The exploitation of functional materials is paramount for the development of renewable energy to alleviate the storage of freshwater and energy. Herein, a series of perovskites, La_1-xSr_xCoO₃ (LSC), were prepared by a facile hydrothermal and calcination method, in which the oxygen evolution reaction (OER) activity was facilitated with the composition of x = 0.1. Moreover, the two-dimensional (2D) Ti₃C₂ MXene dopant was introduced to boost the functions of electrocatalytic oxygen evolution capability and solar thermal evaporation performance. Strong interfacial interaction and prominent charge-transfer between the La_1-xSr_xCoO₃ and Ti₃C₂ MXene accelerate the redox process of perovskite La_1-xSr_xCoO₃. The obtained La_0.9Sr_0.1CoO₃/Ti₃C₂ MXene (LSM) composite acquired an overpotential of 330 mV at 10 mA cm^-2 in 1 M KOH electrolyte while maintaining remarkable durability. The lower Tafel slope of 83.9 mV per decade for the OER was also achieved, comparable to that of the commercial RuO₂ catalyst. In addition, the LSM exhibited a high solar-evaporation conversion efficiency of 96.8% under 1 sun irradiation, which demonstrated the multi-functionality of this composite. Hence, by presenting high performance in energy conversion of perovskite-derived materials, this work demonstrates their great potential in practical applications for solar driven desalination and highly active electrocatalysis technologies.

Boosting visible light photocatalysis in BiOI/BaFe12O19 magnetic heterojunction

Many previous studies have underestimated the role of magnetic components in improving photocatalytic performance. It is significance to explore the migration mechanism of photoinduced carriers in magnetic heterojunction. Here, a magnetic heterojunction, BiOI/BaFe₁₂O₁₉, was synthesized by a simple preparation method. The optimal synthesis conditions and photocatalytic reaction conditions were explored. The growth mechanism of bismuth iodide oxide (BiOI) was elaborated by introducing a micromagnetic field stemming from barium ferrite (BaFe₁₂O₁₉). The electrochemical impedance spectroscopy (EIS), Mott-Schottky curve (MS), transient fluorescence spectrometer (PL), and photocurrent response plot (i ~ t) tests indicated that the BiOI/BaFe₁₂O₁₉ possessed a higher transfer capacity of electrons, higher separation efficiency of photoinduced carriers, stronger photocurrent response, and higher carriers density, compared with pure BiOI. The ultraviolet-visible diffuse reflectance spectrophotometer (UV-vis DRS), electron paramagnetic resonance spectrometer (EPR), MS, and quenching experiments revealed band structure configuration and migration mechanism of photoinduced carriers. The enhancement mechanism of photocatalysis and photocatalytic reaction mechanism was clearly proclaimed in BiOI/BaFe₁₂O₁₉ catalytic system.

Research progresses on the application of perovskite in adsorption and photocatalytic removal of water pollutants

The problem of global water pollution and scarcity of water resources is becoming increasingly serious. Multifunctional perovskites can well drive adsorption and photocatalytic reactions to remove water pollutants. There are many advantages of perovskites, such as abundant oxygen vacancies, easily tunable structural morphology, stable crystal state, highly active metal sites, and a wide photo response range. However, there are few reviews on the simultaneous application of perovskite to adsorption and photocatalytic removal of water pollutants. Thus, this paper discusses the preparation methods of perovskite, the factors affecting the adsorption of water environmental pollutants by perovskite, and the factors affecting perovskite photocatalytic water pollutants. The particle size, specific surface area, oxygen vacancies, electron-hole trapping agents, potentials of the valence band, and conduction band in perovskites are significant influencing factors for adsorption and photocatalysis. Strategies for improving the performance of perovskites in the fields of adsorption and photocatalysis are discussed. The adsorption behaviors and catalytic mechanisms are also investigated, including adsorption kinetics and thermodynamics, electrostatic interaction, ion exchange, chemical bonding, and photocatalytic mechanism. It summarizes the removal of water pollutants by using perovskites. It provides the design of perovskites as high-efficiency adsorbents and catalysts for developing new technologies.

Fabrication of black NiO/Sr2FeTaO6 heterojunctions with rapid interface charge transfer for efficient photocatalytic hydrogen evolution

Series of black NiO/Sr₂FeTaO₆ (NiO/SFT) composites were synthesized by the combined processes of hydrothermal method and calcination treatment. The formed NiO was deposited on the surface of Sr₂FeTaO₆ to form a closely interfacial contact, leading to the formation of NiO/Sr₂FeTaO₆ heterojunction. The resulted samples were fully characterized by XRD, TEM, XPS, and UV-Vis DRS to gain their microstructure, crystal phase, atomic states and optical absorption properties. Introducing narrow-bandgap semiconductor of black NiO in NiO/Sr₂FeTaO₆ heterojunctions exhibits two major advantages. On the one hand, coupling with black NiO can significantly increase the light harvesting capacity of Sr₂FeTaO₆. On the other hand, the formed NiO/Sr₂FeTaO₆ heterojunctions benefited the separation and transfer of photogenerated charge carriers, which was confirmed by photo-electrochemical measurement, PL and TR-PL spectra. The activity of as-prepared samples was evaluated by photocatalytic hydrogen (H₂) evolution (PHE) under visible light irradiation. The resulted NiO/SFT composites showed the improved PHE efficiency than that of NiO and Sr₂FeTaO₆, owing to the synergistic effects of synergistic effects of heterojunction formation for the efficient charge carrier transfer/separation and increased light harvesting capacity. However, the excess amount of NiO loaded in NiO/SFT composites will restrain the light harvesting of Sr₂FeTaO₆ component and decrease, leading to the decreased PHE activity. Our work provided an insight on the construction of high-efficiency heterojunction photocatalysts for PHE reaction.

Constructing NCuS Interface Chemical Bonds over SnS2 for Efficient Solar-Driven Photoelectrochemical Water Splitting

The restricted charge transfer and slow oxygen evolution reaction (OER) dynamics tremendously hamper the realistic implementation of SnS₂ photoanodes for photoelectrochemical (PEC) water splitting. Here, a novel strategy is developed to construct interfacial NCuS bonds between NC skeletons and SnS₂ (CuNC@SnS₂ ) for efficient PEC water splitting. Compared with SnS₂ , the PEC activity of CuNC@SnS₂ photoelectrode is tremendously heightened, obtaining a current density of 3.40 mA cm² at 1.23 V_RHE with a negatively shifted onset potential of 0.04 V_RHE , which is 6.54 times higher than that of SnS₂ . The detailed experimental characterizations and theoretical calculation demonstrate that the interfacial NCuS bonds enhance the OER kinetic, reduce the surface overpotential, facilitate the separation of photon-generated carriers, and provide a fast transmission channel for electrons. This work presents a new approach for modulating charge transfer by interfacial bond design in heterojunction photoelectrodes toward promoting PEC performance and solar energy application.

Induced abundant oxygen vacancies in Sc2VO5-δ /g-C3N4 heterojunctions for enhanced photocatalytic degradation of levofloxacin

Sc₂VO_5-δ /g-C₃N₄ heterojunctions (SVCs) with abundant oxygen vacancies (OVs) were synthesized by ultrasonic exfoliation combined with the thermal etching method. The structures, OVs and spatial separation of the photogenerated carriers were systematically characterized. The results manifested that the SVCs were successfully constructed via the strong interaction between g-C₃N₄ (CN) and Sc₂VO_5-δ (SV). The SVCs possessed a higher concentration of OVs than that of pristine CN and SV. The formation of the SVC heterostructures and the optimization of the OVs were the two major factors to accelerate the separation of the charge carriers and finally to improve the photocatalysis performance. The as-prepared 10%SVC (containing 10 wt% of SV) catalyst exhibited the highest OV concentration and the best photocatalytic performance. The levofloxacin (LVX) photodegradation activity showed a positive correlation with the OV concentration. The photocatalytic degradation efficiencies were 89.1, 98.8 and 99.0% on 10%SVC for LVX, methylene blue (MB) and rhodamine B (RhB), respectively. These photodegradation processes followed the pseudo first order kinetic equation. The apparent rate constant (k _app) of LVX degradation on 10%SVC was 11.0 and 7.5 times that of CN and SV. The h⁺, ˙OH and ˙O₂ ^- were the major reactive species in the photodegradation process.

Boosting the photocatalytic properties of NaTaO3 by coupling with AgBr

AgBr/NaTaO3 composites, with different molar % of NaTaO3 (Br/NTO(X%)), have been synthesized by simple precipitation methods; bare NaTaO3 was synthesized by hydrothermal procedure, while AgBr was synthesized by a precipitation procedure using cetyl-tri-methyl-ammonium bromide (CTAB) and AgNO3. Samples have been characterized by X-ray diffraction (XRD), N2 adsorption, UV–vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the as-prepared photo-catalysts was evaluated through photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and caffeic acid (CAFA) under UV and visible illumination. Single AgBr material and Br/NTO(X%) composites displayed the ability to absorb light in the visible region, while NaTaO3 is only photoactive under UV irradiation. Based on the position of conduction and valence bands of AgBr and NaTaO3, the heterojunction between these two photo-catalysts corresponds to a type II junction. In the case of photocatalytic degradation of RhB and CAFA, Br/NTO(x%) composites have highest photocatalytic activity than that obtained by both parental materials under the same operational conditions. AgBr and Br/NTO(x%) composites achieve a fast degradation of MO, together with a considerable adsorption capacity, attributed to the presence of a remaining amount of residual CTAB on the AgBr surface. In summary, coupling AgBr with NaTaO3 improves the photocatalytic activity under both UV and visible illumination with respect to the parental components, but the performance of the composites is highly dependent on the type of substrate to be degraded and the illumination conditions.

Fluid Field Modulation in Mass Transfer for Efficient Photocatalysis

Mass transfer is an essential factor determining photocatalytic performance, which can be modulated by fluid field via manipulating the kinetic characteristics of photocatalysts and photocatalytic intermediates. Past decades have witnessed the efforts and achievements made in manipulating mass transfer based on photocatalyst structure and composition design, and thus, a critical survey that scrutinizes the recent progress in this topic is urgently necessitated. This review examines the basic principles of how mass transfer behavior impacts photocatalytic activity accompanying with the discussion on theoretical simulation calculation including fluid flow speed and pattern. Meanwhile, newly emerged viable photocatalytic micro/nanomotors with self-thermophoresis, self-diffusiophoresis, and bubble-propulsion mechanisms as well as magnet-actuated photocatalytic artificial cilia for facilitating mass transfer will be covered. Furthermore, their applications in photocatalytic hydrogen evolution, carbon dioxide reduction, organic pollution degradation, bacteria disinfection and so forth are scrutinized. Finally, a brief summary and future outlook are presented, providing a viable guideline to those working in photocatalysis, mass transfer, and other related fields.

Development of heterogeneous photocatalysts via the covalent grafting of metal complexes on various solid supports

To date, remarkable progress has been achieved in the development of photocatalysts owing to their high activity, selectivity, and tunable light absorption in the visible light range. Recently, heterogeneous photocatalytic systems have emerged as potential candidates due to their beneficial attributes (e.g., high surface area, ease of functionalization and facile separation). Herein, we provide a concise overview of the rational design of heterogeneous photocatalysts by grafting photoactive complexes on heterogeneous support matrices via covalent grafting and their detailed characterization techniques, which have been followed by the landmark examples of their applications. Also, major challenges and opportunities in the forthcoming progress of these appealing areas are emphasised.

Recent Advancements in Photocatalysis Coupling by External Physical Fields

Photocatalysis is one of the most promising green technologies to utilize solar energy for clean energy achievement and environmental governance, such as artificial photosynthesis, water splitting, pollutants degradation, etc. Despite decades of research, the performance of photocatalysis still falls far short of the requirement of 5% solar energy conversion efficiency. Combining photocatalysis with the other physical fields has been proven to be an efficient way around this barrier which can improve the performance of photocatalysis remarkably. This review will focus on the recent advances in photocatalysis coupling by external physical fields, including Thermal-coupled photocatalysis (TCP), Mechanical-coupled photocatalysis (MCP), and Electromagnetism-coupled photocatalysis (ECP). In this paper, coupling mechanisms, materials, and applications of external physical fields are reviewed. Specifically, the promotive effect on photocatalytic activity by the external fields is highlighted. This review will provide a detailed and specific reference for photocatalysis coupling by external physical fields in a deep-going way.

Solid-State Synthesis of ZnO/ZnS Photocatalyst with Efficient Organic Pollutant Degradation Performance

To improve the separation efficiency of photogenerated carriers in ZnS, constructing a ZnS-based heterostructure with ZnO is assessed to be an efficient strategy, and a ZnO/ZnS photocatalyst was prepared by a solid-phase approach, and the structure and morphology were systematically studied. The ZnO/ZnS photocatalyst showed excellent photocatalytic properties on methyl orange, rhodamine B and tetracycline under UV light irradiation, indicating that the photocatalyst exhibited efficient broad-spectrum photocatalytic performance. Compared with ZnS, the degradation rates of ZnO/ZnS photocatalysts for methyl orange, rhodamine B and tetracycline under UV light increased from 21%, 9% and 32% to 96%, 94% and 93%, respectively, higher than the reported ZnO/ZnS composites synthesized by a novel wet chemical route, attributing to the improvement of light absorption ability and the effective separation of carriers. In addition, the influence of the sacrificial agent on the reaction system was investigated, and the synergistic mechanism of ZnO and ZnS in the catalytic process was analyzed according to the fluorescence spectra, photocurrent and first-principles calculation results, and a possible catalytic mechanism was put forward.

A Review of Performance Prediction Based on Machine Learning in Materials Science

With increasing demand in many areas, materials are constantly evolving. However, they still have numerous practical constraints. The rational design and discovery of new materials can create a huge technological and social impact. However, such rational design and discovery require a holistic, multi-stage design process, including the design of the material composition, material structure, material properties as well as process design and engineering. Such a complex exploration using traditional scientific methods is not only blind but also a huge waste of time and resources. Machine learning (ML), which is used across data to find correlations in material properties and understand the chemical properties of materials, is being considered a new way to explore the materials field. This paper reviews some of the major recent advances and applications of ML in the field of properties prediction of materials and discusses the key challenges and opportunities in this cross-cutting area.

Machine Learning for Electrocatalyst and Photocatalyst Design and Discovery

Electrocatalysts and photocatalysts are key to a sustainable future, generating clean fuels, reducing the impact of global warming, and providing solutions to environmental pollution. Improved processes for catalyst design and a better understanding of electro/photocatalytic processes are essential for improving catalyst effectiveness. Recent advances in data science and artificial intelligence have great potential to accelerate electrocatalysis and photocatalysis research, particularly the rapid exploration of large materials chemistry spaces through machine learning. Here a comprehensive introduction to, and critical review of, machine learning techniques used in electrocatalysis and photocatalysis research are provided. Sources of electro/photocatalyst data and current approaches to representing these materials by mathematical features are described, the most commonly used machine learning methods summarized, and the quality and utility of electro/photocatalyst models evaluated. Illustrations of how machine learning models are applied to novel electro/photocatalyst discovery and used to elucidate electrocatalytic or photocatalytic reaction mechanisms are provided. The review offers a guide for materials scientists on the selection of machine learning methods for electrocatalysis and photocatalysis research. The application of machine learning to catalysis science represents a paradigm shift in the way advanced, next-generation catalysts will be designed and synthesized.

Monochromatic light-enhanced photocatalytic CO2 reduction based on exciton properties of two-dimensional lead halide perovskites

Converting CO₂ into valuable solar fuels through photocatalysis has been considered a green and sustainable technology that is promising for alleviating global warming and providing energy in an environmentally friendly manner. However, traditional photocatalysts generally suffer from low surface-reactive reaction sites, inefficient light harvesting and rapid recombination of electron-hole pairs. Lead halide perovskite materials have been considered ideal semiconductor photocatalysts for photocatalytic CO₂ reduction due to their tunable band gaps, strong light absorption, and low cost. Herein, a series of L₂Cs_n-1Pb_nX_3n+1 (L = ba, ha, oa; X = Cl, Br, I; n = 1, 2) 2D layered perovskites were synthesized by a facile solvothermal method. The effects of alkyl amine chain length, halogen atoms and inorganic layer number on their properties were studied. More importantly, these 2D materials were used as photocatalysts for CO₂ reduction without any sacrificial agents. These 2D perovskites exhibited markedly increased performance in comparison with 3D bulk materials, benefitting from the larger surface-area-to-volume ratio and faster and more efficient exciton dissociation, which achieved the highest CO yield of 158.69 μmol g^-1 h^-1 and CH₄ yield of 6.9 μmol g^-1 h^-1 through the design of the photocatalytic system. In addition, the influence of light source conditions on photocatalysis was studied systematically, including light source intensity and wavelength. The experimental results indicated that an appropriate solvent, high light intensity and monochromatic light source matching the wavelength of exciton absorption can effectively improve the photocatalytic efficiency.

FeVO4 nanowires for efficient photocatalytic CO2 reduction

Band structures of the FeVO4 semiconductor were investigated by first-principles calculations, and FeVO4 nanowires can greatly improve the performance of photocatalytic CO2 reduction.