Perovskite-based Photocatalysts Research Articles

G-C3N4 as ballistic electron transport “Tunnel” in CsPbBr3-based ternary photocatalyst for gas phase CO2 reduction

Perovskite CsPbBr3 quantum dot shows great potential in artificial photosynthesis, attributed to its outstanding optoelectronic properties. Nevertheless, its photocatalytic activity is hindered by insufficient catalytic active sites and severe charge recombination. In this work, a CsPbBr3@Ag-C3N4 ternary heterojunction photocatalyst is designed and synthesized for high-efficiency CO2 reduction. The CsPbBr3 quantum dots and Ag nanoparticles are chemically anchored on the surface of g-C3N4 sheets, forming an electron transfer tunnel from CsPbBr3 quantum dots to Ag nanoparticles via g-C3N4 sheets. The resulting CsPbBr3@Ag-C3N4 ternary photocatalyst, with spatial separation of photogenerated carriers, achieves a remarkable conversion rate of 19.49 μmol·g−1·h−1 with almost 100 % CO selectivity, a 3.13-fold enhancement in photocatalytic activity as compared to CsPbBr3 quantum dots. Density functional theory calculations reveal the rapid CO2 adsorption/activation and the decreased free energy (0.66 eV) of *COOH formation at the interface of Ag nanoparticles and g-C3N4 in contrast to the g-C3N4, leading to the excellent photocatalytic activity, while the thermodynamically favored CO desorption contributes to the high CO selectivity. This work presents an innovative strategy of constructing perovskite-based photocatalyst by modulating catalyst structure and offers profound insights for efficient CO2 conversion.

All-Inorganic Perovskite NiTiO3 /Cs3 Sb2 I9 Heterostructure for Photocatalytic CO2 Reduction to CH4 with High Selectivity.

Developing efficient and stable halide perovskite-based photocatalysts for highly selectivity reduction CO2 to valuable fuels remains a significant challenge due to their intrinsic instability. Herein, a novel heterostructure featuring 2D Cs3 Sb2 I9 nanosheets on a 3D flower-like mesoporous NiTiO3 framework using a top-down stepwise membrane fabrication technique is constructed. The unique bilayer heterostructure formed on the 3D mesoporous framework endowed NiTiO3 /Cs3 Sb2 I9 with sufficient and close interface contact, minimizing charge transport distance, and effectively promoting the charge transfer at the interface, thus improving the reaction efficiency of the catalyst surface. As revealed by characterization and calculation, the coupling of Cs3 Sb2 I9 with NiTiO3 facilitates the hydrogenation process during catalytic, directing reaction intermediates toward highly selective CH4 production. Furthermore, the van der Waals forces inherent in the 3D/2D heterostructure with face-to-face contact provide superior stability, ensuring the efficient realization of photocatalytic CO2 reduction to CH4 . Consequently, the optimized 3D/2D NiTiO3 /Cs3 Sb2 I9 heterostructure demonstrates an impressive CH4 yield of 43.4µmolg-1 h-1 with a selectivity of up to 88.6%, surpassing most reported perovskite-based photocatalysts to date. This investigation contributes to overcoming the challenges of commercializing perovskite-based photocatalysts and paves the way for the development of sustainable and efficient CO2 conversion technologies.

Photocatalysis Based on Metal Halide Perovskites for Organic Chemical Transformations.

Heterogeneous photocatalysts incorporating metal halide perovskites (MHPs) have garnered significant attention due to their remarkable attributes: strong visible-light absorption, tuneable band energy levels, rapid charge transfer, and defect tolerance. Additionally, the promising optical and electronic properties of MHP nanocrystals can be harnessed for photocatalytic applications through controlled crystal structure engineering, involving composition tuning via metal ion and halide ion variations, dimensional tuning, and surface chemistry modifications. Combination of perovskites with other materials can improve the photoinduced charge separation and charge transfer, building heterostructures with different band alignments, such as type-II, Z-scheme, and Schottky heterojunctions, which can fine-tune redox potentials of the perovskite for photocatalytic organic reactions. This review delves into the activation of organic molecules through charge and energy transfer mechanisms. The review further investigates the impact of crystal engineering on photocatalytic activity, spanning a diverse array of organic transformations, such as C-X bond formation (X = C, N, and O), [2 + 2] and [4 + 2] cycloadditions, substrate isomerization, and asymmetric catalysis. This study provides insights to propel the advancement of metal halide perovskite-based photocatalysts, thereby fostering innovation in organic chemical transformations.

Synergistic effect of multiferroicity in GdFeO3 nanoparticles for significant hydrogen production through photo/electrocatalysis

Due to chemical stability and visible-light driven features, perovskite-based photocatalysts and electrocatalysts are potential candidates for implementation of water-splitting hydrogen production to help tackle the present fuel crisis. In this study, it is shown that multiferroic GdFeO3 nanoparticles can help meet this need. GdFeO3 nanoparticles were solvothermally produced in pristine form, and the chemical purity of these particles was evaluated by powder X-ray diffraction, while the morphology and average particle size of 71 nm were determined by scanning and transmission electron microscopy techniques. Oxygen vacancies and grain-mediated two-dimensional planar defects in GdFeO3 nanoparticles were identified with high-resolution transmission electron microscopy along with Raman and X-ray photoelectron spectroscopies. Magnetization and electric polarization studies confirmed the multiferroic nature of the nanoparticles. Without the use of a co-catalyst, GdFeO3 nanoparticles exhibited a hydrogen evolution rate of 685 μmol h−1g−1 and an apparent quantum yield of 14% which was attributed to electric-polarization-induced band bending. The effect of sacrificial agents in H2 production was also evaluated to find the true hydrogen evolution. Moreover, in contrast to other cutting-edge oxygen evolution reaction electrocatalysts as Ba0.5Sr0.5Co0.8Fe0.2O3−δ, GdFeO3 nanoparticles showed a very low overpotential of 320 mV in an alkaline media with favorable chemical stability.

Self-supported CsPbBr3/Ti3C2Tx MXene aerogels towards efficient photocatalytic CO2 reduction

Aerogels, especially MXene aerogels, are an ideal multifunctional platform for developing efficient photocatalysts for CO2 reduction because they are featured by abundant catalytic sites, high electrical conductivity, high gas absorption ability and self-supported structure. However, the pristine MXene aerogel has almost no ability to utilize light, which requires additional photosensitizers to assist it in achieving efficient light harvesting. Herein, we immobilized colloidal CsPbBr3 nanocrystals (NCs) onto the self-supported Ti3C2Tx (where Tx represents surface terminations such as fluorine, oxygen, and hydroxyl groups) MXene aerogels for photocatalytic CO2 reduction. The resultant CsPbBr3/Ti3C2Tx MXene aerogels exhibit a remarkable photocatalytic activity toward CO2 reduction with total electron consumption rate of 112.6 μmol g-1h-1, which is 6.6-fold higher than that of the pristine CsPbBr3 NC powders. The improvement of the photocatalytic performance is presumably attributed to the strong light absorption, effective charge separation and CO2 adsorption in the CsPbBr3/Ti3C2Tx MXene aerogels. This work presents an effective perovskite-based photocatalyst in aerogel form and opens a new avenue for their solar-to-fuel conversions.

Wastewater treatment with perovskite-based photocatalysts: Environmental sustainability from a green perspective

Persistent organic compounds in wastewater are seriously harming the environment and living beings, which have a negative impact on ecosystems. In this context, perovskite oxides have received significant attention owing to their unique structural properties, high stability, versatile composition, and excellent catalytic activity. Organic pollutants from wastewater can be removed with the help of perovskite oxide through photocatalytic degradation. Here, this review compiles the most recent information on the preparation of perovskite oxide nanostructures and their potential application in wastewater treatment by photocatalysis. Challenges, prospects, and barriers to their widespread usage have also been examined. The photocatalytic efficiency of perovskite oxides and their modified form for wastewater treatment has been discussed here. Perovskite oxides have been modified to decrease their band gap for enhanced visible region activity, charge transfer segregation for a long lifetime, and fast photocatalyst reaction. It has been thoroughly investigated how doping and heterojunction formation influence the corresponding perovskite oxides.

A Lead-Free 0D/2D Cs3Bi2Br9/Bi2WO6 S-Scheme Heterojunction for Efficient Photoreduction of CO2.

Photocatalytic reduction of CO2 into valuable hydrocarbon fuels is one of the green ways to solve the energy problem and achieve carbon neutrality. Exploring photocatalyst with low toxicity and high-efficiency is the key to realize it. Here we report a lead-free halide perovskite-based 0D/2D Cs3Bi2Br9/Bi2WO6 (CBB/BWO) S-scheme heterojunction for CO2 photoreduction, prepared by a facile electrostatic self-assembly approach. The CBB/BWO shows superior photoreduction of CO2 under visible light with CO generation rate of 220.1 μmol·g-1·h-1, which is ∼115.8 and ∼18.5 times higher than that of Cs3Bi2Br9 perovskite quantum dots (CBB PQDS) and Bi2WO6 nanosheets (BWO NS), respectively. The improved photocatalytic activity can be attributed to the tight 0D/2D structure and S-scheme charge transfer pathway between the Cs3Bi2Br9 PQDS and atomic layers of the Bi2WO6 NS, which shortens transmission distance of photogenerated carriers and boosts efficient separation and transfer of the carriers. This work provides insight in manufacturing potential lead-free perovskite-based photocatalysts for achieving carbon neutrality.

Efficient Exciton Dissociation through the Edge Interfacial State in Metal Halide Perovskite-Based Photocatalysts

Metal halide perovskites (MHPs) with superior optoelectronic properties have recently been actively pursued as catalysts in heterogeneous photocatalysis. Dissociating excitons into charge carriers holds the key to enhancing the photocatalytic performance of MHP-based photocatalysts, especially for those with strong quantum-confinement effects. However, attaining efficient exciton dissociation has been rather challenging. Herein, we propose a novel concept that the edge interfacial state can trigger anisotropic electron transfer to promote exciton dissociation. By taking Cs4PbBr6/TiO2 mesocrystal heterojunction as a proof-of-concept, we demonstrate that the unique interfacial state at the edge of the system is generated by the defect-mediated chemical interaction and acts as a trap state, which brings on a directionally favored electron transfer from the center to edge regions, thereby significantly enhancing the desired exciton dissociation. Consequently, such a system achieves an excellent performance in photocatalytic CO2 reduction. This paradigmatic work sheds light on the excitonic aspects for rational design of advanced photocatalysts toward high performance.

Efficient Charge Transfer and Effective Active Sites in Lead-Free Halide Double Perovskite S-Scheme Heterojunctions for Photocatalytic H2 Evolution.

The practical application of lead-free double perovskite Cs2 AgBiBr6 in photocatalytic H2 evolution is still restricted due to the low activity and poor stability. The rational design of lead-free halide double perovskites heterojunctions with efficient charge transfer and effective active sites is a potential route to achieve the ideal prospect. Herein, in this work an S-scheme heterojunction of Cs2 AgBiBr6 with enriched Br-vacancies and WO3 nanorods (VBr -Cs2 AgBiBr6 /WO3 ) obtaining excellent visible-light responsive photocatalytic H2 evolution performance and durable stability is reported. The S-scheme heterojunction driven by the unaligned Fermi levels of these two semiconductors ensures the efficient charge transfer at the interface, and density functional theory calculations reveal the enriched Br vacancies on Cs2 AgBiBr6 (022) surfaces introduced by atom thermal vibration provide effective active sites for hydrogen evolution. The optimized VBr -Cs2 AgBiBr6 /WO3 S-scheme photocatalyst exhibits the photocatalytic hydrogen evolution rate of 364.89µmol g-1 h-1 which is 4.9-fold of bare VBr -Cs2 AgBiBr6 (74.44µmol g-1 h-1 ) and presents long-term stability of 12h continuous photocatalytic reaction. This work provides deep insights into the photocatalytic mechanism of VBr -Cs2 AgBiBr6 /WO3 S-scheme heterojunctions, which emerges a new strategy in the applications of perovskite-based photocatalysts.

Fabricating a type II heterojunction by growing lead-free perovskite Cs2AgBiBr6in situ on graphite-like g-C3N4 nanosheets for enhanced photocatalytic CO2 reduction.

Perovskite-based photocatalysts have received significant attention for converting CO2 into fuels, such as CO, CH4 or long alkyl chains. However, the use of these catalysts is plagued by several limitations, such as poor stability, lead toxicity, and inadequate conversion efficiency due to the rapid recombination of carriers. Herein, a g-C3N4@Cs2AgBiBr6 (CABB) type II heterojunction photocatalyst has been prepared by growing lead-free CABB nanocrystals (10-14 nm) on the graphite-like carbon nitride (g-C3N4) nanosheet using the in situ crystallization method. The resulting nanocomposite, g-C3N4@CABB, demonstrated an efficient charge transfer pathway via a typical type II heterojunction. With formation rates of 10.30 μmol g-1 h-1 for CO and 0.88 μmol g-1 h-1 for CH4 under visible light irradiation, the nanocomposite exhibited enhanced photocatalytic efficiency in CO2 reduction compared to CABB and g-C3N4. The improved photocatalytic performance of the g-C3N4@CABB nanocomposite was attributed to the fabricated type II heterojunction, which boosted the interfacial charge transfer from g-C3N4 to CABB. This work will inspire the design of heterojunction-based photocatalysts and increase the fundamental understanding of perovskite-based catalysts in the CO2 photoreduction process.

Recent progress in metal halide perovskite-based photocatalysts: physicochemical properties, synthetic strategies, and solar-driven applications

Metal halide perovskite (MHP) materials have garnered significant interest in the realm of energy conversion and storage amid the push for carbon-neutral energy solutions due to the tunable band gap, high light collection efficiency, high photogenerated carrier mobility, and high defect tolerance.

Recent progress in metal halide perovskite photocatalysts for hydrogen evolution

The basic design principles and recent progress in halide perovskite-based photocatalysts are summarized, aiming to achieve efficient and stable photocatalytic hydrogen production.

Recent Progress in Halide Perovskite Nanocrystals for Photocatalytic Hydrogen Evolution.

Due to its environmental cleanliness and high energy density, hydrogen has been deemed as a promising alternative to traditional fossil fuels. Photocatalytic water-splitting using semiconductor materials is a good prospect for hydrogen production in terms of renewable solar energy utilization. In recent years, halide perovskite nanocrystals (NCs) are emerging as a new class of fascinating nanomaterial for light harvesting and photocatalytic applications. This is due to their appealing optoelectronic properties, such as optimal band gaps, high absorption coefficient, high carrier mobility, long carrier diffusion length, etc. In this review, recent progress in halide perovskite NCs for photocatalytic hydrogen evolution is summarized. Emphasis is given to the current strategies that enhance the photocatalytic hydrogen production performance of halide perovskite NCs. Some scientific challenges and perspectives for halide perovskite photocatalysts are also proposed and discussed. It is anticipated that this review will provide valuable references for the future development of halide perovskite-based photocatalysts used in highly efficient hydrogen evolution.

A Review on Halide Perovskite-Based Photocatalysts: Key Factors and Challenges.

A growing number of research articles have been published on the use of halide perovskite materials for photocatalytic reactions. These articles extend these materials' great success from solar cells to photocatalytic technologies such as hydrogen production, CO2 reduction, dye degradation, and organic synthesis. In the present review article, we first describe the background theory of photocatalysis, followed by a description on the properties of halide perovskites and their development for photocatalysis. We highlight key intrinsic factors influencing their photocatalytic performance, such as stability, electronic band structure, and sorption properties. We also discuss and shed light on key considerations and challenges for their development in photocatalysis, such as those related to reaction conditions, reactor design, presence of degradable organic species, and characterization, especially for CO2 photocatalytic reduction. This review on halide perovskite photocatalysts will provide a better understanding for their rational design and development and contribute to their scientific and technological adoption in the wide field of photocatalytic solar devices.

Multiple chemical valences induced interface regulation in perovskite nickelate/carbon nitride for boosting photocatalytic hydrogen evolution

Recent developments in transition metal-based photocatalysts have heightened the need for superior solar utilization. Evidence suggests that properly adjusting the chemical valence of the transition metal elements could simultaneously achieve broad-spectrum absorption and efficient charge separation for the photocatalysts. However, the understanding and application of this strategy remain a significant challenge. Herein, a series of La0.9Ni0.8Co0.2O3-α/g-C3N4 (LNCO/CN) composites were synthesized employing a mild reduction procedure in the H2/Ar atmosphere. Experimental studies reveal that the composites regulated by interfacial coordination unsaturation Ni2+ and metal Ni0 possess accelerated Z-scheme charge transfer through the interfacial bond between Ni2+ and N. Besides, the localized-surface-plasmon-resonance-induced “hot electrons” injection process of in situ grown Ni0 nanoparticle is confirmed, which can efficiently quench the photoinduced holes and create hole vacancies around the interface. Due to the synergistic effect between Ni2+ and Ni0, the lifetime of the photo-excited electrons is prolonged with inhibited recombination behavior. After modulation, optimal LNCO/CN Z-scheme hybrid exhibits 9-fold promotion of photocatalytic hydrogen evolution rate compared to pristine LNCO/CN. This study gives valuable insight into the purposeful utilization of the chemical valence modulating strategy, which alters the chemical valence of transition metal elements to enhance the performance of perovskite-based photocatalysts dramatically.

Solar Light-Induced Photocatalytic Degradation of Ciprofloxacin Antibiotic Using Biochar Supported Nano Bismuth Ferrite Composite

Research on advanced materials for environmental remediation and pollutant degradation is rapidly progressing because of their numerous applications. Biochar is an excellent material support for the catalytic activity of bismuth ferrite (BiFeO3), which is one of the best perovskite-based photocatalysts in this work for diverse pollutant degradation when exposed to direct sunlight. Biochar was produced by pyrolyzing oil palm empty fruit bunches (OPEFBs) and then integrate with BiFeO3 in the presence of cross-linked chitosan to create a BFO/biochar coupled magnetic photocatalyst (CBB). This research was conducted to examine the performance of the photocatalytic activity of CBB towards the degradation of ciprofloxacin antibiotics. To determine the optimal condition, two operational parameters that are photocatalyst dosage and initial pollutant concentrations, were evaluated. The results of the powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope-energy dispersive X-ray (SEM-EDX) analyses confirmed the high purity of the rhombohedral BiFeO3 with a high surface area, as well as the successful coupling of BiFeO3 and biochar at a ratio of 1:1. The most effective conditions for the various variables are 1.5 g/L CBB dosage at 10 ppm with 77.08% photodegradation under direct sunlight for 2 h. Further, a pseudo-first-order kinetic reaction was followed and observed with decreasing k values as the initial concentration increased. This shows that the system performs best at low concentrations. This finding confirms that the catalytic parameters improved the efficiency of photocatalysts with biochar assistance in removing antibiotic pollutants.

Lattice-matched in-situ construction of 2D/2D T-SrTiO3/CsPbBr3 heterostructure for efficient photocatalysis of CO2 reduction

The elaborate regulation of heterostructure interface to accelerate the interfacial charge separation is one of practicable approaches to improve the photocatalytic CO2 reduction performance of halide perovskite (HP) materials. Herein, we report an in-situ growth strategy for the construction of 2D CsPbBr3 based heterostructure with perovskite oxide (SrTiO3) nanosheet as substrate (CsPbBr3/SrTiO3). Lattice matching and matchable energy band structures between CsPbBr3 and SrTiO3 endow CsPbBr3/SrTiO3 heterostructure with an efficient interfacial charge separation. Moreover, the interfacial charge transfer rate can be further accelerated by etching SrTiO3 with NH4F to form flat surface capped with Ti−O bonds. The resultant 2D/2D T-SrTiO3/CsPbBr3 heterostructure exhibits an impressive photocatalytic activity for CO2 conversion with a CO yield of 120.2 ± 4.9 µmol g−1 h−1 at the light intensity of 100 mW/cm2 and water as electron source, which is about 10 and 7 times higher than those of the pristine SrTiO3 and CsPbBr3 nanosheets, surpassing the reported halide perovskite-based photocatalysts under the same conditions.

Aromatic bromination with hydrogen production on organic-inorganic hybrid perovskite-based photocatalysts under visible light irradiation

Aromatic bromides are important chemicals in nature and chemical industries. However, their traditional synthesis routes suffer from low atomic economy and pollutant formation. Herein, we show that organic–inorganic hybrid perovskite methylammonium lead bromide (MAPbBr3) nanocrystals stabilized in aqueous HBr solution can achieve simultaneous aromatic bromination and hydrogen evolution using HBr as the bromine source under visible light irradiation. By hybridizing MAPbBr3 with Pt/Ta2O5 and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as electron- and hole-transporting motifs, aromatic bromides were achieved from aromatic compounds with high yield (up to 99%) and selectivity (up to 99%) with the addition of N,N-dimethylformamide or its analogs. The mechanistic studies revealed that the bromination proceeds via an electrophilic attack pathway and that HOBr may be the key intermediate in the bromination reaction.

Highly crystalline lead-free Cs3Sb2Br9 perovskite microcrystals enable efficient and selective photocatalytic oxidation of benzyl alcohol

Selective oxidation of alcohols to the corresponding aldehydes constitutes a great challenge in organic and green chemistry, which typically requires environmentally unfriendly oxidants/catalysts or relatively harsh conditions (high temperature & pressure). Herein, we report an eco-friendly perovskite-based photocatalyst, in which all-inorganic perovskite Cs3Sb2Br9 microcrystals with high crystallinity were prepared using a facile antisolvent method at various temperatures. For the photocatalytic oxidation of benzyl alcohol, the Cs3Sb2Br9 microcrystal photocatalysts exhibited up to 77% conversion and 88% selectivity toward benzaldehyde under oxygen atmosphere and visible-light illumination. More significantly, the comparative experimental results in air were close to those in oxygen, with the observation of 96% conversion and 94% selectivity for the optimized conditions under air atmosphere. Notably, the conversion of our best-performing photocatalyst was 32 and 6.4 times higher than that of the lead-based CsPbBr3 and FAPbBr3 (FA: formamidinium) perovskites, respectively. Furthermore, the underlying photocatalytic oxidation mechanism was proposed by the electron spin resonance (ESR) and the controlled experiments using specific scavengers. This study sheds light on promising new photocatalytic applications of the lead-free metal halide perovskites.

Synthesis and Characterization of Fe-Doped CaTiO3 Polyhedra Prepared by Molten NaCl Salt

CaTiO3 as one of the perovskite-based photocatalysts has a band gap energy of 3.5 eV (~354 nm), thus will work at the ultraviolet light region. One of the strategies to decrease the band gap energy is doping metal. In this research, CaTiO3 was doped by Fe element as purposes to decreasing its band gap energy. Fe doped CaTiO3 compounds were synthesized using molten NaCl salt method. The diffractogram samples showed that the Fe-doped CaTiO3 crystal was successfully prepared. Meanwhile, the SEM images showed that the particle shape was regular polyhedral morphology, and doping Fe3+ caused the particle size to decrease and agglomerated. The UV-Vis DRS spectra showed that the Fe-dopant revealed the absorption light at visible range wavelength.