Amino-Assisted Anchoring of CsPbBr3 Perovskite Quantum Dots on Porous g-C3 N4 for Enhanced Photocatalytic CO2 Reduction

p-Thiocresol Functionalized Cesium Lead Bromide (PTC@CsPbBr3): A Fluorometric Sensing Probe for the Detection of Cholesterol

Inorganic halide-based perovskites (e.g., cesium lead bromide) are tremendously useful semiconducting materials due to their unique optoelectronic properties. However, degradation of these perovskites under humid conditions is one of the major drawbacks to prevent their wide applications. Herein, passivated cesium lead bromide nanoparticles are synthesized using p-thiocresol as a passivating ligand, and this stable version of perovskite is later applied successfully as a sensor probe towards cholesterol detection. The designed sensor can detect cholesterol with a lower detection limit of 0.24 ppm and a fast response time of 10 s. The mechanism of quenching PTC@CsPbBr3 upon the gradual addition of cholesterol is discussed. Further, the sensor is successfully applied in the detection of cholesterol in real samples (blood serum). This work presents PTC@CsPbBr3 as a novel sensing platform for detecting cholesterol well in biomedical applications.

Halogen-Site Regulation in Cs3Bi2X9 Quantum Dots for Efficient and Selective Oxidation of Benzyl Alcohol Driven by Solar Light

Sluggish charge kinetics and low selectivity limit the solar-driven selective organic transformations under mild conditions. Herein, an efficient strategy of halogen-site regulation, based on the precise control of charge transfer and molecule activation by rational design of Cs3Bi2X9 quantum dots photocatalysts, is proposed to achieve both high selectivity and yield of benzyl-alcohol oxidation. In situ PL spectroscopy study reveals that the Bi─Br bonds formed in the form of Br-associated coordination can enhance the separation and transfer of photoexcited carriers during the practical reaction. As the active center, the exclusive Bi─Br covalence can benefit the benzyl-alcohol activation for producing carbon-centered radicals. As a result, the Cs3Bi2Br9 with this atomic coordination achieves a conversion ratio of 97.9% for benzyl alcohol and selectivity of 99.6% for aldehydes, which are 56.9- and 1.54-fold higher than that of Cs3Bi2Cl9. Combined with quasi-in situ EPR, in situ ATR-FTIR spectra, and DFT calculation, the conversion of C6H5-CH2OH to C6H5-CH2* at Br-related coordination is revealed to be a determining step, which can be accelerated via halogen-site regulation for enhancing selectivity and photocatalytic efficiency. The mechanistic insights of this research elucidate how halogen-site regulation in favor of charge transfer and molecule activation toward efficient and selective oxidation of benzyl alcohol.

W-N heteroatom-interface in melon carbon nitride/N-doped tungsten oxide Z-Scheme photocatalyst toward improved photocatalytic hydrogen generation activity

The construction of heterointerface in photocatalyst is an efficient approach to boost the separation and utilization efficiency of charge carriers, which is challenging and crucial in photocatalysis. Here, the construction of melon-structured carbon nitride/N-doped WO3 (MCN/NWx) heterojunction photocatalyst was achieved by a method of prealcoholysis combined with thermal polymerization, where N-doping of WO3 was achieved in-situ in the formation of heterojunction. The promoted charge separation efficiency was realized through the charge transfer from the conduction band of N-doped WO3 to the valence band of the MCN. Density functional theory calculation results showed that the formation of the W-N heteroatom-interface led to the increase of density of states at the heterointerface and decrease of the band gap. The MCN/NWx nanocomposite featured a metallic band structure of the nanocomposite photocatalysts, resulting in the enhanced photocatalytic activity. The photocatalytic hydrogen evolution activity of the MCN/NW2 was enhanced about 2.5 times than that of MCN. This research provides a novel insight into the construction of a novel heteroatom-junction that boosts the separation efficiency of charge carriers, and thereby improves the photocatalytic activity.

Hydrogenation of CO2 into Value-added Chemicals Using Solid-Supported Catalysts

Reducing CO2 emissions is an urgent global priority. In this context, several mitigation strategies, including CO2 tax and stringent legislation, have been adopted to halt the deterioration of the natural environment. Also, carbon recycling procedures undoubtedly help reduce net emissions into the atmosphere, enhancing sustainability. Utilizing Earth's abundant CO2 to produce high-potential green chemicals and light fuels opens new avenues for the chemical industry. In this context, many attempts have been devoted to converting CO2 as a feedstock into various value-added chemicals, such as CH4 , lower methanol, light olefins, gasoline, and higher hydrocarbons, for numerous applications involving various catalytic reactions. Although several CO2 -conversion methods have been used, including electrochemical, photochemical, and biological approaches, the hydrogenation method allows the reaction to be tuned to produce the targeted compound without significantly altering infrastructure. This review discusses the numerous hydrogenation routes and their challenges, such as catalyst design, operation, and the combined art of structure-activity relationships for the various product formations.

Polymer-enhanced perovskite oxide-based photocatalysts: a review

Oxide perovskites (OPs) have emerged as promising photocatalysts for numerous applications, such as energy conversion, renewable fuels, and environmental remediation. Although OPs are gaining traction, their efficacies are still hindered by low charge carrier mobility and poor stability. This study investigated the function of polymers actively participating in OP structures to improve the overall characteristics. An overview of the polymer-enhanced perovskite oxide photocatalyst (PEPOP) field was effectively reviewed. These PEPOPs were demonstrated in photovoltaics, pollutant degradation, and gas conversion and reduction. Nonetheless, additional research is needed to explore the potential of PEPOPs to establish their efficacy in photocatalytic applications. The technological improvements of PEPOPs were hindered by significant challenges related to stability and sensitivity. The urgency of this review was apparent due to the fast-paced nature of research in the field of photocatalysis. Recent breakthroughs and emerging applications highlight the need for a comprehensive overview of PEPOPs and their enhanced catalytic capabilities. Consequently, a broad outlook was provided for the current state of PEPOP-related studies, highlighting the potential of these materials for future applications.

Insight on the structural, electronic and optical properties of Zn, Ga-doped/dual-doped graphitic carbon nitride for visible-light applications

The density functional theory (DFT) was applied for the first time to study the doping and co-doping of Ga and Zn metals on graphitic carbon nitride (g-C3N4). The doping of these metal impurities into g-C3N4 leads to a significant decrease in the bandgap energy. Moreover, the co-doping leads to even lower bandgap energy than either individual Zn or Ga-doped g-C3N4. The theoretical electronic and optical properties including the density of state (DOS), energy levels of the frontier orbital, excited state lifetime, and molecular electrostatic potential of the doped and co-doped g-C3N4 support their application in UV-visible light-based technologies. The quantum mechanical parameters (energy band gap, binding energy, exciton energy, softness, hardness) and dipole moment exhibit higher values (ranging from 1.36 to 4.94 D) compared to the bare g-C3N4 (0.29 D), indicating better solubility in the water solvent. The time-dependent DFT (TD-DFT) calculations showed absorption maxima in between the UV-Vis region (309-878 nm). Additionally, charge transfer characteristics, transition density matrix (TDM), excited state lifetime and light harvesting efficiency (LHE) were investigated. Overall, these theoretical studies suggest that doped and co-doped g-C3N4 are excellent candidates for electronic semiconductor devices, light-emitting diodes (LEDs), solar cells, and photodetectors.

In Situ Growth of Lead-Free Cs2CuBr4 Perovskite Quantum Dots in KIT-6 Mesoporous Molecular Sieve for CO2 Adsorption, Activation, and Reduction

Metal halide perovskites (MHPs) are emerging as promising candidates for photocatalytic CO₂ conversion. However, their practical application is still restricted by the poor intrinsic stability and weak adsorption/activation toward CO₂ molecules. The rational design of MHPs-based heterostructures with high stability and abundant active sites is a potential solution to this obstacle. Herein, we report the in situ growth of lead-free Cs₂CuBr₄ perovskite quantum dots (PQDs) in KIT-6 mesoporous molecular sieve, obtaining remarkable photocatalytic CO₂ reduction activity and durable stability. The optimized Cs₂CuBr₄@KIT-6 heterostructure exhibits the photocatalytic CO and CH₄ evolution rates of 51.6 and 17.2 μmol g^-1 h^-1, respectively, far exceeding those of pristine Cs₂CuBr₄. On the basis of in situ diffuse reflectance infrared Fourier transform spectra and theoretical investigations, the detailed CO₂ photoreduction pathway is systematically revealed. This work provides a new route for the rational construction of perovskite-based heterostructures with strong CO₂ adsorption/activation and good stability for photocatalytic CO₂ reduction.

Research status, challenges and future prospects of renewable synthetic fuel catalysts for CO2 photocatalytic reduction conversion

In recent years, with global climate change, the utilization of carbon dioxide as a resource has become an important goal of human society to achieve carbon peaking and carbon neutrality. Among them, the catalytic conversion of carbon dioxide to generate renewable fuels has received great attention. As one of these methods, photocatalysis has its unique properties and mechanism, which can only rely on sunlight without inputting other energy. It is an emerging discipline with great development prospects. The core of photocatalysis lies in the development of photocatalysts with high activity, high selectivity, low cost, and high durability. This review first introduces the background and mechanism of photocatalysis, then introduces various types of photocatalysts based on different substrates, and analyzes the methods and mechanisms to improve the activity and selectivity of photocatalysts. Finally, combining the plasmon effect with photocatalysis, the review analyzes the promoting effect of the plasmon effect on the photocatalytic carbon dioxide synthesis of renewable fuels, which provides a new idea for it.

Perovskite Photocatalytic CO2 Reduction or Photoredox Organic Transformation?

Metal-halide perovskites have been explored as photocatalysts for CO₂ reduction. We report that perovskite photocatalytic CO₂ reduction in organic solvents is likely problematic. Instead, the detected products (i.e., CO) likely result from a photoredox organic transformation involving the solvent. Our observations have been validated using isotopic labeling experiments, band energy analysis, and new control experiments. We designed a typical perovskite photocatalytic setup in organic solvents that led to CO production of up to ≈1000 μmol g^-1  h^-1 . CO₂ reduction in organic solvents must be studied with extra care because photoredox organic transformations can produce orders of magnitude higher rate of CO or CH₄ than is typical for CO₂ reduction routes. Though CO₂ reduction is not likely to occur, in situ CO generation is extremely fast. Hence a suitable system can be established for challenging organic reactions that use CO as a feedstock but exploit the solvent as a CO surrogate.

In-Situ Anchoring Pb-Free Cs3 Bi2 Br9 @BiOBr Quantum Dots on NHx -Rich Silica with Enhanced Blue Emission and Satisfactory Stability for Photocatalytic Toluene Oxidation

All-inorganic metal halide perovskite quantum dots (QDs) have attracted attention from researchers with their fascinating optoelectronic properties. However, blue-emitting perovskite QDs typically have low photoluminescence quantum yield (PLQY). For potential commercial applications, it is preferable to replace Pb with an element having low toxicity. Here, Pb-free Cs₃ Bi₂ Br₉ @BiOBr perovskite QDs were anchored on the surface of NH_x -rich monodisperse silica (A-SiO₂ ) via N-Bi chemical bonding to isolate QDs from each other, thus enhancing efficient surface passivation and suppressing optical decay. Compared to unanchored QDs, Cs₃ Bi₂ Br₉ @BiOBr QDs/A-SiO₂ composites exhibited significantly enhanced blue emission performance, the PLQY of which increased from 16.62 % to 77.26 %, in addition to good water and environmental stability. Finally, the novel composites as photocatalysts were used to drive the oxidation of toluene, a template reaction of C(sp³ )-H bond activation and demonstrated astonishing conversion rates (4317 μmol g^-1  h^-1 ) with high selectivity (around 87 %).

Chemically Bonded α-Fe2 O3 /Bi4 MO8 Cl Dot-on-Plate Z-Scheme Junction with Strong Internal Electric Field for Selective Photo-oxidation of Aromatic Alcohols

Inferior contact interface and low charge transfer efficiency seriously restrict the performance of heterojunctions. Herein, chemically bonded α-Fe₂ O₃ /Bi₄ MO₈ Cl (M=Nb, Ta) dot-on-plate Z-scheme junctions with strong internal electric field are crafted by an in situ growth route. Experimental and theoretical results demonstrate that the internal electric field provides a powerful driving force for vectorial migration of photocharges between Bi₄ MO₈ Cl and α-Fe₂ O₃ , and the interfacial Fe-O bond not only serves as an atomic-level charge flow highway but also lowers the charge transfer energy barrier, thereby accelerating Z-scheme charge transfer and realizing effective spatial charge separation. Impressively, α-Fe₂ O₃ /Bi₄ MO₈ Cl manifests a significantly improved photocatalytic activity for selective oxidation of aromatic alcohols into aldehydes (Con. ≥92 %, Sel. ≥96 %), with a performance improvement of one to two orders of magnitude. This work presents atomic-level insight into interfacial charge flow steering.

Metal Halide Perovskite Based Heterojunction Photocatalysts

With fascinating photophysical properties and a strong potential to utilize solar energy, metal halide perovskites (MHPs) have become a prominent feature within photocatalysis research. However, the effectiveness of single MHP photocatalysts is relatively poor. The introduction of a second component to form a heterojunction represents a well-established route to accelerate carrier migration and boost reaction rates, thus increasing the photoactivity. Recently, there have been several scientific advances related to the design of MHP-based heterojunction photocatalysts, including Schottky, type II, and Z-scheme heterojunctions. In this Review, we systematically discuss and critically appraise recent developments in MHP-based heterojunction photocatalysis. In addition, the techniques for identifying the type of active heterojunctions are evaluated and we conclude by briefly outlining the ongoing challenges and future directions for promising photocatalysts based on MHP heterojunctions.

Atom manufacturing of photocatalyst towards solar CO2reduction

Photocatalytic CO₂reduction reaction (CO₂RR) is believed to be a promising remedy to simultaneously lessen CO₂emission and obtain high value-added products, but suffers from the thwarted activity of photocatalyst and poor selectivity of product. Over the past decade, aided by the significant advances in nanotechnology, the atom manufacturing of photocatalyst, including vacancies, dopants, single-atom catalysts, strains, have emerged as efficient approaches to precisely mediate the reaction intermediates and processes, which push forward in the rapid development of highly efficient and selective photocatalytic CO₂RR. In this review, we summarize the recent developments in highly efficient and/or selective photocatalysts toward CO₂RR with the special focus on various atom manufacturing. The mechanisms of these atom manufacturing from active sites creation, light absorbability, and electronic structure modulation are comprehensively and scientifically discussed. In addition, we attempt to establish the structure-activity relationship between active sites and photocatalytic CO₂RR capability by integrating theoretical simulations and experimental results, which will be helpful for insights into mechanism pathways of CO₂RR over defective photocatalysts. Finally, the remaining challenges and prospects in this field to improve the photocatalytic CO₂RR performances are proposed, which can shed some light on designing more potential photocatalysts through atomic regulations toward CO₂conversion.

CdSe 1D/2D Mixed-Dimensional Heterostructures: Curvature-Complementary Self-Assembly for Enhanced Visible-Light Photocatalysis

Mixed-dimensional heterostructures (MDHs), which combine nanomaterials of different dimensionalities deliver on the promise to bypass intrinsic limitations of a given low-dimensional material. Here, a strategy to engineer MDHs between two low-dimensional materials by curvature-complementary self-assembly is described. CdSe nanotubes rolled from 2D nanosheets and 1D CdSe nanorods, with negative and positive curvatures, respectively, are selected to illustrate complementary curvature self-assembly. The assembly process, optical, and photoelectrical properties of the CdSe MDHs are thoroughly investigated. Several remarkable features of CdSe MDHs, including increased light absorption, efficient charge separation, and appropriate bandgap structure are confirmed. The MDHs significantly alleviate the sluggish kinetics of electron transfer in the quantum sized CdSe subunits (onset potential of 0.21 V vs RHE for MDHs; 0.4 V lower than their low-dimensional building blocks), while the spatial nano-confinement effect in the CdSe MDHs also assists the interfacial reaction kinetics to render them ideal photocatalysts for benzylamine oxidation (conversion > 99% in 4 h with a two times higher rate than simple mixtures). The results highlight opportunities for building MDHs from low-dimensional building blocks with curvature-complementary features and expand the application spectrum of low dimensional materials in artificial photosynthesis.

Boosting Photocatalytic Activity and Stability of Lead-Free Cs3Bi2Br9 Perovskite Nanocrystals via In Situ Growth on Monolayer 2D Ti3C2Tx MXene for C-H Bond Oxidation

Light-driven selective oxidation of saturated C-H bonds with molecular oxygen, as an alternative to conventional thermochemical catalysis, allows a sustainable and eco-friendly manner to convert solar energy into highly value-added oxygenates. However, the photocatalytic oxidation of hydrocarbons still remains a great challenge owing to the low efficiency in the separation and transfer of photogenerated charge of the currently available photocatalytic materials. Herein, we report a novel perovskite-based heterostructure photocatalyst, in which ligand- and lead-free all-inorganic perovskite Cs₃Bi₂Br₉ nanocrystals (NCs) with uniform crystal size and high crystallinity were homogeneously distributed on the surface of ultrathin two-dimensional (2D) monolayer Ti₃C₂T_x MXene nanosheets in an in situ growth manner. The resultant heterostructure featured with intimate interface between Cs₃Bi₂Br₉ NCs and Ti₃C₂T_x MXene and strong visible-light adsorption not only exhibits significant enhancement in the performance of photocatalytic oxidation of challenging aromatic and aliphatic alkanes under visible-light irradiation but also greatly improves the stability of Cs₃Bi₂Br₉ NCs under a reaction environment. Comprehensive characterizations reveal that the formation of an intimate interface between Cs₃Bi₂Br₉ NCs and highly conductive ultrathin 2D Ti₃C₂T_x MXene nanosheets via strong interaction markedly accelerates the separation and transfer efficiency of photogenerated electron-hole pairs and simultaneously suppresses their recombination, resulting in improved utilization of the excited charges, which account for the highly enhanced photocatalytic performance.

Surface modification for improving the photoredox activity of CsPbBr3 nanocrystals

In recent years inorganic lead halide perovskite nanocrystals (PNCs) have been used in photocatalytic reactions. The surface chemistry of the PNCs can play an important role in the excited state interactions and efficient charge transfer with redox molecules. In this work, we explore the impact of CsPbBr₃ nanocrystal surface modification on the excited state interactions with the electron acceptor benzoquinone (BQ) for three different ligand environments: as oleic acid/oleylamine (OA/OAm), oleic acid (OA)/trioctylphosphine (TOP), and oleic acid (OA)/oleylamine (OAm)/trioctylphosphine (TOP) ligands. Our finding concludes that amine-free PNCs (OA/TOP capped) exhibit the best excited state interactions with benzoquinone compared to the conventional oleylamine ligand environment. The photoinduced electron transfer (PET) rate constants were measured from PL-lifetime decay measurement. The amine-free PNCs show the highest PET which is 9 times higher than that of conventional ligand capped PNCs. These results highlight the impact of surface chemistry on the excited-state interactions of CsPbBr₃ NCs and in photocatalytic applications. More importantly, this work concludes that amine-free PNCs maintain a redox-active surface with a high photoinduced electron transfer rate which makes them an ideal candidate for photocatalytic applications.

Coupling CsPbBr3 Quantum Dots with Covalent Triazine Frameworks for Visible-Light-Driven CO2 Reduction

Photocatalytic reduction of CO₂ into value-added chemical fuels is an appealing approach to address energy crisis and global warming. CsPbBr₃ quantum dots (QDs) are good candidates for CO₂ reduction because of their excellent photoelectric properties, including high molar extinction coefficient, low exciton binding energy, and defect tolerance. However, the pristine CsPbBr₃ QDs generally have low photocatalytic performance mainly due to dominant charge recombination and lack of efficient catalytic sites for CO₂ adsorption/activation. Herein, we report a new photocatalytic system, in which CsPbBr₃ QDs are coupled with covalent triazine frameworks (CTFs) for visible-light-driven CO₂ reduction. In this hybrid photocatalytic system, the robust triazine rings and periodical pore structures of CTFs promote the charge separation in CsPbBr₃ and endow them with strong CO₂ adsorption/activation capacity. The resulting photocatalytic system exhibits excellent photocatalytic activity towards CO₂ reduction. This work presents a new photocatalytic system based on CTFs and perovskite QDs for visible-light-driven CO₂ reduction, which highlights the potential of perovskite-based photocatalysts for solar fuel applications.

Anchoring of Formamidinium Lead Bromide Quantum Dots on Ti3C2 Nanosheets for Efficient Photocatalytic Reduction of CO2

Metal halide perovskite with a suitable energy band structure and excellent visible-light response is a prospective photocatalyst for CO₂ reduction. However, the reported inorganic halide perovskites have undesirable catalytic performances due to phase-sensitive and severe charge carrier recombination. Herein, we anchor the FAPbBr₃ quantum dots (QDs) on Ti₃C₂ nanosheets to form a FAPbBr₃/Ti₃C₂ composite within a Schottky heterojunction for photocatalytic CO₂ reduction. Upon visible-light illumination, the FAPbBr₃/Ti₃C₂ composite photocatalyst exhibits an appealing photocatalytic performance in the presence of deionized water. The Ti₃C₂ nanosheet acts as an electron acceptor to promote the rapid separation of excitons and supply specific catalytic sites. An optimal electron consumption rate of 717.18 μmol/g·h is obtained by the FAPbBr₃/0.2-Ti₃C₂ composite, which has a 2.08-fold improvement over the pristine FAPbBr₃ QDs (343.90 μmol/g·h). Meanwhile, the FAPbBr₃/Ti₃C₂ photocatalyst also displays a superior stability during photocatalytic reaction. This work expands a new insight and platform for designing superb perovskite/MXene-based photocatalysts for CO₂ reduction.

Lead-Free Metal Halide Perovskites for Hydrogen Evolution from Aqueous Solutions

Metal halide perovskites (MHPs) exploitation represents the next big frontier in photovoltaic technologies. However, the extraordinary optoelectronic properties of these materials also call for alternative utilizations, such as in solar-driven photocatalysis, to better address the big challenges ahead for eco-sustainable human activities. In this contest the recent reports on MHPs structures, especially those stable in aqueous solutions, suggest the exciting possibility for efficient solar-driven perovskite-based hydrogen (H₂) production. In this minireview such works are critically analyzed and classified according to their mechanism and working conditions. We focus on lead-free materials, because of the environmental issue represented by lead containing material, especially if exploited in aqueous medium, thus it is important to avoid its presence from the technology take-off. Particular emphasis is dedicated to the materials composition/structure impacting on this catalytic process. The rationalization of the distinctive traits characterizing MHPs-based H₂ production could assist the future expansion of the field, supporting the path towards a new class of light-driven catalysts working in aqueous environments.

Glycine-Functionalized CsPbBr3 Nanocrystals for Efficient Visible-Light Photocatalysis of CO2 Reduction

Capping ligands are indispensable for the preparation of metal-halide-perovskite (MHP) nanocrystals (NCs) with good stability; however, the long alkyl-chain capping ligands in conventional MHP NCs will be unfavorable for CO₂ adsorption and hinder the efficient carrier separation on the surface of MHP NCs, leading to inferior catalytic activity in artificial photosynthesis. Herein, CsPbBr₃ nanocrystals with short-chain glycine as ligand are constructed through a facile ligand-exchange strategy. Owing to the reduced hindrance of glycine and the presence of the amine group in glycine, the photogenerated carrier separation and CO₂ uptake capacity are noticeably improved without compromising the stability of the MHP NCs. The CsPbBr₃ nanocrystals with glycine ligands exhibit a significantly increased yield of 27.7 μmol g^-1  h^-1 for photocatalytic CO₂ -to-CO conversion without any organic sacrificial reagents, which is over five times higher than that of control CsPbBr₃ NCs with conventional long alkyl-chain capping ligands.

Metal halide perovskites as an emergent catalyst for CO2 photoreduction: a minireview

The present minireview summarizes recent advances in the application of metal halide perovskite for CO₂ photoreduction.

Photocorrosion at Irradiated Perovskite/Electrolyte Interfaces

Metal-halide perovskites transformed optoelectronics research and development during the past decade. They have also gained a foothold in photocatalytic and photoelectrochemical processes recently, but their sensitivity to the most commonly applied solvents and electrolytes together with their susceptibility to photocorrosion hinders such applications. Understanding the elementary steps of photocorrosion of these materials can aid the endeavor of realizing stable devices. In this Perspective, we discuss both thermodynamic and kinetic aspects of photocorrosion processes occurring at the interface of perovskite photocatalysts and photoelectrodes with different electrolytes. We show how combined in situ and operando electrochemical techniques can reveal the underlying mechanisms. Finally, we also discuss emerging strategies to mitigate photocorrosion (such as surface protection, materials and electrolyte engineering, etc.).

Direct Z-Scheme Heterojunction of Semicoherent FAPbBr3/Bi2WO6 Interface for Photoredox Reaction with Large Driving Force

Metal halide perovskites with direct band gap and strong light absorption are promising materials for harvesting solar energy; however, their relatively narrow band gap limits their redox ability when used as a photocatalyst. Adding a second semiconductor component with the appropriate band structure offsets can generate a Z-scheme photocatalytic system, taking full advantage of the perovskite's intrinsic properties. In this work, we develop a direct Z-scheme photocatalyst based on formamidinium lead bromide and bismuth tungstate (FAPbBr₃/Bi₂WO₆) with strong redox ability for artificial solar-to-chemical energy conversion. With desirable band offsets and strong joint redox potential, the dual photocatalyst is shown to form a semicoherent heterointerface. Ultrafast transient infrared absorption studies employing selective excitation reveal synergetic photocarrier dynamics and demonstrate Z-scheme charge transfer mechanisms. Under simulated solar irradiation, a large driving force photoredox reaction (∼2.57 eV) of CO₂ reduction coupled with benzyl alcohol oxidation to benzaldehyde is achieved on the Z-scheme FAPbBr₃/Bi₂WO₆ photocatalyst, harnessing the full synergetic potential of the combined system.

Recent Developments in Lead and Lead-Free Halide Perovskite Nanostructures towards Photocatalytic CO2 Reduction

Perovskite materials have been widely considered as emerging photocatalysts for CO2 reduction due to their extraordinary physicochemical and optical properties. Perovskites offer a wide range of benefits compared to conventional semiconductors, including tunable bandgap, high surface energy, high charge carrier lifetime, and flexible crystal structure, making them ideal for high-performance photocatalytic CO2 reduction. Notably, defect-induced perovskites, for example, crystallographic defects in perovskites, have given excellent opportunities to tune perovskites' catalytic properties. Recently, lead (Pb) halide perovskite and their composites or heterojunction with other semiconductors, metal nanoparticles (NPs), metal complexes, graphene, and metal-organic frameworks (MOFs) have been well established for CO2 conversion. Besides, various halide perovskites have come under focus to avoid the toxicity of lead-based materials. Therefore, we reviewed the recent progress made by Pb and Pb-free halide perovskites in photo-assisted CO2 reduction into useful chemicals. We also discussed the importance of various factors like change in solvent, structure defects, and compositions in the fabrication of halide perovskites to efficiently convert CO2 into value-added products.

The high photocatalytic efficiency and stability of LaNiO3/g-C3N4 heterojunction nanocomposites for photocatalytic water splitting to hydrogen

A binary direct Z-scheme LaNiO₃/g-C₃N₄ nanocomposite photocatalyst consisted with LaNiO₃ nanoparticles and g-C₃N₄ nanosheets was successfully synthesized by means of mechanical mixing and solvothermal methods in order to improve the photocatalytic water splitting activity. The as-prepared materials were characterized by powder X-ray diffraction (XRD), Scanning Electron microscope (SEM), Transmission Electron microscope (TEM), X-ray photoelectron spectroscope (XPS), Fourier Transform Infrared Spectroscopy (FT-IR) and N₂ adsorption–desorption experiments, respectively, demonstrating the formation of interfacial interaction and heterogeneous structure in LaNiO₃/g-C₃N₄ nanocomposites. Under UV-light irradiation, the LaNiO₃/g-C₃N₄ samples which without the addition of any noble metal as co-catalyst behaved enhanced photocatalytic water splitting activity compared with pure LaNiO₃ and g-C₃N₄, owing to the Z-scheme charge carrier transfer pathway. Especially, the LaNiO₃/70%g-C₃N₄ nanocomposite reach an optimal yield of up to 3392.50 µmol g⁻¹ in 5 h and held a maximum H₂ evolution rate of 678.5 µmol h⁻¹ g⁻¹ that was 5 times higher than that of pure LaNiO₃.

Recent Advances in Photocatalytic CO2 Utilisation Over Multifunctional Metal–Organic Frameworks

The efficient conversion of carbon dioxide (CO2) to high-value chemicals using renewable solar energy is a highly attractive but very challenging process that is used to address ever-growing energy demands and environmental issues. In recent years, metal–organic frameworks (MOFs) have received significant research attention owing to their tuneability in terms of their composition, structure, and multifunctional characteristics. The functionalisation of MOFs by metal nanoparticles (NPs) is a promising approach used to enhance their light absorption and photocatalytic activity. The efficient charge separation and strong CO2 binding affinity of hybrid MOF-based photocatalysts facilitate the CO2 conversion process. This review summarises the latest advancements involving noble metal, non-noble-metal, and miscellaneous species functionalised MOF-based hybrid photocatalysts for the reduction of CO2 to carbon monoxide (CO) and other value-added chemicals. The novel synthetic strategies and their corresponding structure–property relationships have also been discussed for solar-to-chemical energy conversion. Furthermore, the current challenges and prospects in practical applications are also highlighted for sustainable energy production.

Revealing the A-Site Effect of Lead-Free A3 Sb2 Br9 Perovskite in Photocatalytic C(sp3 )-H Bond Activation

The lead-free halide perovskite A₃ Sb₂ Br₉ is utilized as a photocatalyst for the first time for C(sp³ )-H bond activation. A₃ Sb₂ Br₉ nanoparticles (A₃ Sb₂ Br₉ NPs) with different ratios of Cs and CH₃ NH₃ (MA) show different photocatalytic activities for toluene oxidation and the photocatalytic performance is enhanced when increasing the amount of Cs. The octahedron distortion caused by A-site cations can change the electronic properties of X-site ions and further affect the electron transfer from toluene molecules to Br sites. After the regulation of A-site cations, the photocatalytic activity is higher with A₃ Sb₂ Br₉ NPs than that with classic photocatalysts (TiO₂ , WO₃ , and CdS). The main active species involved in photocatalytic oxidation of toluene are photogenerated holes (h⁺ ) and superoxide anions (^. O₂ ^- ). The octahedron distortion by A-site cations affecting photocatalytic activity remains unique and is also a step forward for understanding more about halide-perovskite-based photocatalysis. The relationship between octahedron distortion and photocatalysis can also guide the design of new photocatalytic systems involving other halide perovskites.

Charge Transfer in the Heterostructure of CsPbBr3 Nanocrystals with Nitrogen-Doped Carbon Dots

Heterostructures of inorganic halide perovskites with mixed-dimensional inorganic nanomaterials have shown great potential not only in the field of optoelectronic energy devices and photocatalysis but also for improving our fundamental understanding of the charge transfer across the heterostructure interface. Herein, we present for the first time the heterostructure integration of the CsPbBr₃ nanocrystal with an N-doped carbon dot. We explore the photoluminescence (PL) and photoconductivity of the heterostructure of CsPbBr₃ nanocrystals and N-doped carbon dots. PL quenching of CsPbBr₃ nanocrystals with the addition of N-doped carbon dots was observed. The photoexcited electrons from the conduction band of CsPbBr₃ are trapped in the N-acceptor state of N-doped carbon dots, and the charge transfer occurs via quasi type II-like electronic band alignment. The charge transfer in the halide perovskite-based heterostructure should motivate further research into the new heterostructure synthesis with perovskites and the fundamental understanding of the mechanism of charge/energy transfer across the heterostructure interface.

Oxygen Doping in Graphitic Carbon Nitride for Enhanced Photocatalytic Hydrogen Evolution

The incorporation of oxygenic groups could remarkably enhance the light absorption and charge separation of graphitic carbon nitride (g-C₃ N₄ ). The intrinsic role of oxygenic species on photocatalytic activity in g-C₃ N₄ has been intensively studied, but it is still not fully explored. Herein, the essential relationships between oxygenic functionalities and the catalytic performance are revealed. Results demonstrate that C-O-C functionality as an electron trap could help to increase the resistance of conduction transfer (R_ct ) by limiting electrons transfer in CNx. In contrast, N-C-O functionality between different tri-s-triazine unites could promote the electrons transfer, leading to a reduced R_ct in CNx. The best H₂ production rate (3.70 mmol h^-1  g^-1 , 12.76-fold higher than that of CN) is obtained over CN3, because of the highest N-C-O ratio (r_N-C-O ). The apparent quantum efficiency (AQE) of CN3 at 405 nm, 420 nm, 450 nm, 500 nm and 550 nm is 33.90 %, 20.88 %, 8.25 %, 3.66 % and 1.01 %, respectively.

Recent Progress in Engineering Metal Halide Perovskites for Efficient Visible-Light-Driven Photocatalysis

Artificial photosynthesis has attracted increasing attention due to recent environmental and energy concerns. Metal halide perovskites (MHPs) demonstrating excellent optoelectronic properties have currently emerged as novel and efficient photocatalytic materials. Herein, the structural features of MHPs that are responsible for the photoinduced charge separation and charge migration properties are briefly introduced, and then important and necessary photophysical and photochemical aspects of MHPs related to photoredox catalysis are summarized. Subsequently, the applications of MHPs for solar energy harvesting and photocatalytic conversion, including H₂ evolution, CO₂ reduction, degradation of organic pollutants, and photoredox organic synthesis, are extensively demonstrated, with a focus on strategies for improving the performance (e.g., selectivity, activity, stability, recyclability, and environmental compatibility) of these MHP-based photocatalytic systems. To conclude, existing challenges and prospects on the future development of MHP-based materials towards photoredox catalysis applications are detailed.