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[Display omitted] • Pr-modified MnCeO x catalysts exhibited excellent SCR performance and SO 2 tolerance. • The SCR reaction pathways based on both L-H and E-R mechanisms were investigated. • The ad-NH 3 species on MnCePrO x -0.3 showed superior reactivity. • Abundant of O ads and Mn4+ on MnCePrO x -0.3 catalysts promoted the "fast SCR". Using a one-step impregnation method, a series of Pr-modified MnCeO x catalysts with different Pr molar ratios were created to manufacture an efficient and effective catalyst for low-temperature NH 3 -SCR. It was demonstrated that the Pr modification could extensively boost the MnCeO x catalysts' de-NO x activity and SO 2 resistance and led to the formation of a unique broom-like morphology, especially when the molar ratio of Pr/Mn = 0.3, the MnCePrO x -0.3 exhibited above 90 % NO conversion at 250 °C with the existence of 100 ppm SO 2. According to the characterization results, the enhancement of Pr doping for MnCeO x catalysts was mainly manifested by the expanded specific surface area, the improved dispersion of active components, the enhanced surface acidity and redox ability, and the generated more chemisorbed oxygen (O ads) species. All these characteristics allowed the NH 3 -SCR reaction over MnCePrO x -0.3 catalysts to proceed through the both Eley-Rideal (E-R) and Langmuir-hinshelwood (L-H) mechanism. [ABSTRACT FROM AUTHOR]

• Novel flower spherical-like Bi-Bi 7 O 9 I 3 /Ag-AgI S-scheme heterojunction was synthesized. • Dual plasmons (Bi, Ag) enhance the visible light absorption and photothermal effect. • The synergistic role of S-scheme heterojunction, SPR effect and photothermal effect contributed to the excellent phenol photodegradation and removal activity. • Theoretical calculation expressed Fermi energy levels and work function. The flower spherical-like S-scheme Bi 7 O 9 I 3 /AgI heterostructure was successfully fabricated through hydrothermal as well as calcination reduction method. The Ag and Bi nanoparticles generated during calcination reduction process are tightly fixed on surface of Bi 7 O 9 I 3 and AgI, severally, which was distinctly beneficial to the charge transfer. On account of the enhanced light absorption and surface plasma resonance of Ag and Bi, Bi-Bi 7 O 9 I 3 /Ag-AgI possessed conspicuous photothermal effect. The results show that Bi-Bi 7 O 9 I 3 /Ag-AgI possessesed the optimal photodegradation efficiency and TOC removal rate of phenol, which are 100% and 95.38% within 80 min and 120 min. The light-induced carriers could be efficaciously separated by establishing an S-scheme photocatalytic system. A possible photocatalytic degradation mechanism of the as-constructed samples was investigated by free radical capture experiment as well as EPR technique. In addition, the photocatalyst exhibited the high stability. This work will supply a new perspective with the synthesis of novel S-scheme heterostructure. [ABSTRACT FROM AUTHOR]

An efficient carbon quantum dot (CQD)-modified TiO 2 /SrTiO 3 heterojunction was constructed for photocatalytic CO 2 reduction in this paper. Photogenerated electrons of SrTiO 3 transferred to TiO 2 via the transfer channel of CQDs for electron-hole recombination, while the photogenerated electrons migrated from TiO 2 to CQDs to participate in the photocatalytic CO 2 reduction reaction. Meanwhile, the up-conversion of CQDs enhanced the light harvesting ability of the catalyst and the CQDs enriched the active reaction sites. Due to the above advantages, the CO and CH 4 produce rate over 0.1-CTS reached 54.9 and 35.9 μmol g−1 h−1, respectively, which was dramatically increased compared with pure TiO 2 and pure SrTiO 3. This work proposes a feasible strategy for integrating CQDs with TiO 2 and SrTiO 3 for the optimistic cooperative effect to obtain an effective catalyst for photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

Photocatalytic reduction of CO 2 is a considerable method to alleviate global warming and energy shortage. In this work, CoAl-LDH/Ni 1 Cu NP nitrogen-doped carbon composites (CA/Ni 1 Cu NP N-C) can efficiently reduce CO 2 into CO, CH 4 , and C 2 H 6 under visible light. In situ characterization techniques and theoretical calculations were employed to investigate the CO 2 evolution pathway and photocatalytic mechanism. The synergistic interaction of Cu nanoparticles and Ni single-atom sites accelerated the photogenerated charge separation and facilitated the adsorption properties of key intermediates. As a result, the yields of CH 4 and C 2 H 6 on CA/Ni 1 Cu NP N-C were achieved up to 35.245 and 25.328 μmol g−1 h−1 with electron selectivity of 40.24% and 50.61%, respectively. This work is instructive for using metal nanoparticles to optimize single-atom catalysts to promote their catalytic activity. [Display omitted] • CoAl-LDH/Ni 1 Cu NP N-C single-atom photocatalysts were synthesized. • The yields of CH 4 and C 2 H 6 were 35.245 (40.24%) and 25.328 (50.61%) μmol g−1 h−1. • The charge transfer mechanism and CO 2 evolution path were investigated. • Synergistic interaction of Cu NP and Ni 1 sites optimized the photocatalytic mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrons are redistributed as Mg&MoP/CN loaded at a reverse interfacial position. • Interfacial MoP behaves as the electron collecting sites to improve the activity. • Exterior Mg functions as the catalyzing sites to tackle the selectivity challenge. • Selective and efficient CH 4 evolution are achieved by a Z-scheme reaction pathway. Constructing photocatalysts with dual-function active sites can coordinate the photogenerated electrons transfer and the adsorption energy of key intermediates, thereby converting CO 2 into valuable methane with high efficiency. However, the role that the interfacial position of functional catalysts played in determining the activity and selectivity of CO 2 photoreduction remains unclear. Herein, we regulated the action interface and synergistic effect of magnesium nitrate hydroxide and molybdenum phosphide (Mg & MoP) to modify polymeric carbon nitride (PCN), and found the function-oriented Mg-MoP/PCN exhibits superior performance for catalyzing CO 2 -to-CH 4 in pure water, with a rate of 24.45 μmol h−1 g−1 and 95.3 % selectivity. Theoretical and experimental studies reveal that interfacial layer of MoP promotes the evolutionary activity by facilitating the electron transfer while exterior layer of Mg functions as the catalyzing sites to tackle the selectivity challenge by promoting CO 2 adsorption and CO* stabilization. The synergistic interaction of function-oriented Mg&MoP realizes selective CH 4 evolution with high efficiency via a Z-scheme pathway. The interfacial position of bifunctional catalysts is vital for regulating CO 2 photoreduction activity and product selectivity. [ABSTRACT FROM AUTHOR]

• NO is removed by using persulfate/limestone slurry. • NO removal process is optimized by RSM. • The maximum value of NO removal efficiency was 85.7%. • Reaction temperature is the most significant factor for NO removal. In this work, NO removal process by using sodium persulfate/limestone slurry was investigated. Based on the response surface methodology, the effects of operation parameters, including reaction temperature, sodium persulfate concentration, initial concentration of NO and the concentration of transition metal ions, on NO removal efficiency were investigated. It was found that reaction temperature was the determining factor in NO removal process among all the variables studied, another significant parameter was the persulfate concentration in the mixed slurry. Moreover, the interaction of the reaction temperature with the persulfate concentration also played an important role for their double activation on the removal process. The proposed model equation using response surface methodology had shown good agreement with the experimental data, with a correlation coefficient (R2) of 0.9511. Through the analysis, it was found that the maximum value of NO removal efficiency (85.7%) could be obtained at the specific reaction temperature (58.3 °C) and sodium persulfate concentration (0.066 mol/L), respectively. Therefore, persulfate/limestone slurry is suitable for efficient NO removal. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The MoP/CN samples exhibit superior activity in CO 2 reduction and H 2 evolution. • The CO 2 adsorption and conversion progress is well revealed in the photoreaction. • The efficient co-catalyst MoP facilitates the separation and transfer of charges. Abstract Photoreduction CO 2 to hydrocarbons and photosplitting water for H 2 production are the most promising, sustainable approaches for environmental pollution alleviation and solar-to-chemical energy conversion. However, developing low-cost, high efficient and stable photocatalysts remains a great challenge. Herein, we reported a novel visible-light activated MoP co-catalyst loaded g-C 3 N 4 photocatalyst for CO 2 reduction and water splitting under simulated irradiation firstly. Experimental results demonstrated that the composites were highly active and exhibited superior stability. The maximum CO and H 2 evolution rates of 0.92 μmol h−1 and 40.38 μmol h−1 were achieved on MoP/CN-15% catalyst, which were 4.5-fold and 74.5-fold higher than the pure g-C 3 N 4 , and the corresponding apparent quantum efficiencies (AQE) were 3.5% and 18.3% at 420 nm, respectively. In situ FTIR analysis disclosed the CO 2 adsorption and conversion progress, in which the COO− acted as a major intermediate. Furthermore, comprehensive characterization analysis revealed the introduction of MoP facilitated the separation and transfer of photogenerated electron-hole pairs, and the theoretical calculation by density functional theory (DFT) also confirmed that MoP could effectively separate the photoexcited charges from g-C 3 N 4. Combining with experimental and DFT calculations results, a new way to design cost-effective photocatalysts has been enlightened. [ABSTRACT FROM AUTHOR]

Sb was used as the additive to enhance the NH 3 -SCR performance of MnTiO x catalyst. Experimental results revealed that MnSbTiO x -0.2 demonstrated outstanding NH 3 -SCR activity in a wide temperature window (100–400 ℃) and high resistance to SO 2 . Characterization results indicated the introduction of Sb into MnTiO x catalyst could improve the dispersity of active species and generate more surface acid sites, Mn 4+ and surface adsorbed oxygen species. In situ DRIFT spectra proved that the presence of Sb in MnSbTiO x -0.2 catalyst could form new Brønsted acid sites, along with the increased surface Lewis acidity. The improved adsorption of NH 3 and NO x species over MnSbTiO x -0.2 catalyst had a stimulating effect on the NH 3 -SCR reaction over it through Langmuir−Hinshelwood (L-H) route. Moreover, Sb species in MnSbTiO x -0.2 could improve the reactivities of ad-NH 3 and ad-NO x species in SCR reaction. All these factors contributed to the excellent performance of MnSbTiO x -0.2 catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • The formation of N–C–S–Ni bonds and N–C–O–Ni–S bonds in NiS/SO-PCN composites provided the rapid charge transfer pathways. • The loading of NiS on O-PCN could extend the light absorption to the near-infrared region for photocatalytic hydrogen evolution. • The reduced metallic Ni0 from Ni2+ species acted as the charge transfer mediators to constitute the Z-scheme mechanism. In this study, both narrow band-gap semiconductor NiS and S and O defects modification were introduced into the design of PCN photocatalyst to enhance its photocatalytic performance. The O and S defects, on one hand, provided the higher specific area and more charge separation sites, and constituted the dual fast charge transfer pathways with NiS through the N–C–S–Ni bonds and N–C–O–Ni–S bonds, which greatly increased the carrier transfer kinetics at the interface and restricted the carrier recombination. On the other hand, the midgap level derived from S and O defects also enhanced the absorption of visible light and accommodated more excited electrons. Furthermore, Z-scheme mode could form as Ni2+ species were reduced to metallic Ni0 to acts as charge transfer mediator under irradiation. As such, a maximum hydrogen evolution rate of 1239.3 μmol/g/h was achieved over 5%NiS/SO-Melon composite, nearly 31.4 times the rate of pristine PCN. [ABSTRACT FROM AUTHOR]

Effectively harnessing solar energy for the conversion of CO 2 into valuable chemical energy presents a viable solution to address energy scarcity and climate change concerns. Nonetheless, the limited light absorption and sluggish charge kinetics significantly hinder the photoreduction of CO 2 . In this study, we employed a facile sol-gel method combined with wetness impregnation to synthesize Cu-doped TiO 2 coated with NiO x nanoparticles. Various characterizations verified the successful incorporation of Cu ions into the TiO 2 crystal lattice and the formation of NiO x co-catalysts within the composites. The optimal performance attained with CTN-0.5 demonstrates an output of 11.85 μmol h -1 g -1 for CO and 9.51 μmol h -1 g -1 for CH 4 , which represent a 4.4-fold and 15.6-fold increase, respectively, compared to those achieved with pure TiO 2 . The induced Cu defect band broadens the light absorption by decreasing the conduction band edge of TiO 2 , while NiO x upshifts the valence band of TiO 2 because of the interaction of valence orbitals. Light irradiation EPR and FTIR tests suggest that the collaboration of CuO x and NiO x promotes the formation of oxygen vacancies/defects and a rapid charge transfer pathway, thereby provides numerous active sites and electrons to enhance CO 2 photoreduction performance.

MOF-based photoelectrocatalysis (PEC) using CO 2 as an electron donor offers a green, clean, and extensible way to make hydrocarbon fuels under more tolerant conditions. Herein, basic principles of PEC reduction of CO 2 and the preparation methods and characterization techniques of MOF-based materials are summarized. Furthermore, three applications of MOFs for improving the photoelectrocatalytic performance of CO 2 reduction are described: (i) as photoelectrode alone; (ii) as a co-catalyst of semiconductor photoelectrode or as a substrate for loading dyes, quantum dots, and other co-catalysts; (iii) as one of the components of heterojunction structure. Challenges and future wave surrounding the development of robust PEC CO 2 systems based on MOF materials are also discussed briefly.

Transforming CO 2 into renewable fuels or valuable carbon compounds could be a practical means to tackle the issues of global warming and energy crisis. Photocatalytic CO 2 reduction is more energy-efficient and environmentally friendly, and offers a broader range of potential applications than other CO 2 conversion techniques. Ferroelectric materials, which belong to a class of materials with switchable polarization, are attractive candidates as catalysts due to their distinctive and substantial impact on surface physical and chemical characteristics. This review provides a concise overview of the fundamental principles underlying photocatalysis and the mechanism involved in CO 2 reduction. Additionally, the composition and properties of ferroelectric materials are introduced. This review expands on the research progress in using ferroelectric materials for photocatalytic reduction of CO 2 from three perspectives: directly as a catalyst, by modification, and construction of heterojunctions. Finally, the future potential of ferroelectric materials for photocatalytic CO 2 reduction is presented. This review may be a valuable guide for creating reasonable and more effective photocatalysts based on ferroelectric materials.

Solar-energy-driven CO 2 hydrogenation is a promising strategy to alleviate the climate crisis. Methane is a desirable derivative of CO 2 reduction. However, developing a photocatalyst for highly active and selective CH 4 generation remains challenging. Herein, we report a double Z-scheme Bi 3 O 4 Cl/g-C 3 N 4 /Cd 0.5 Zn 0.5 S photocatalyst for efficient reduction of CO 2 to CH 4 . In situ characterization techniques confirmed that the charge migration mechanism in Bi 3 O 4 Cl/g-C 3 N 4 /Cd 0.5 Zn 0.5 S promotes charge separation through double internal electric fields. As a result, the optimized C0.01B0.02C catalyst displayed a formation rate high up to 25.34 μmol g -1 h -1 and a selectivity of 96.52% of CH 4 . Moreover, the AQY of CO 2 conversion on C0.01B0.02C (1.84%) was almost 41 times higher than that of the bare CN. This study provides a novel perspective to develop heterojunction photocatalysts for selective CO 2 conversion to CH 4 .

Converting CO 2 into chemicals and fuels by solar energy can alleviate global warming and solve the energy crisis. In this work, CoAl-LDO/MoO 3-x (LDO/MO) composites were successfully prepared and achieved efficient CO 2 reduction under visible light. The CoAl-layered double oxides (CoAl-LDO) evolved from CoAl-layered double hydroxide (CoAl-LDH) exhibited a more robust structure, broader light absorption, and improved CO 2 adsorption ability. The local surface plasmon resonance (LSPR) effect excited by nonstoichiometric MoO 3-x broadened the photo-response range of CoAl-LDO/MoO 3-x . In addition, constructing step-scheme (S-scheme) heterojunctions could simultaneously optimize the migration mechanism of photogenerated electrons and holes, and retain carriers with strong redox ability. Therefore, the production rates of CO and CH 4 on the optimal LDO/MO composite were 7 and 9 times higher than the pristine CoAl-LDH, respectively. This work hybridizes oxidation photocatalysts and LDO-based materials to optimize the charge separation and migration mechanisms, which guides the modification of LDO-based materials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Covalent organic frameworks (COFs) are one type of porous organic materials linked by covalent bonds. COFs materials exhibit many outstanding characteristics such as high porosity, high chemical and thermal stability, large specific surface area, efficient electron transfer efficiency, and the ability for predesigned structures. These exceptional advantages enable COFs materials to exhibit remarkable performance in photocatalysis. Additionally, the activity of COFs materials as photocatalysts can be significantly upgraded by ion doping and the formation of heterojunctions. This paper summarizes the latest research progress on COF-based materials applied in photocatalytic systems. Initially, typical structures and preparation methods of COFs are analyzed and compared. Moreover, the essential principles of photocatalytic reactions over COFs-based materials and the latest research developments in photocatalytic hydrogen production, CO 2 reduction, pollutants elimination, organic transformation, and overall water splitting are indicated. At last, the outlook and challenges of COF-based materials in photocatalysis are discussed. This review is intended to permit instructive guidance for the efficient use of photocatalysis based on COFs in the future., (© 2023 Wiley-VCH GmbH.)

In this research, a ternary Cu-CuTCPP/Cu 2 O/CoAl-LDH composite with a dual Z-scheme heterostructure was fabricated based on a Cu 2 O photocatalyst and applied in photocatalytic CO 2 reduction. The physicochemical properties of the prepared catalysts and the possible reaction mechanism in CO 2 reduction were analyzed and studied by various characterization methods. The activity of CO 2 reduction significantly increased, especially forming C2 products. The optimal yield of C 2 H 4 and C 2 H 6 reached 1.56 and 1.92 μmol g -1 h -1 respectively, which was 14.45 and 17.45 times that from using the Cu 2 O monomer. In addition, the selectivity of C2 products reached 37.4%. The satisfactory C2 yield was mainly due to the fact that Cu 1+ δ 2 (COO) 3 nodes in Cu-CuTCPP contained adjacent Cu sites, which effectively promoted the C-C coupling reaction. Moreover, the dual Z-scheme heterojunction stimulated the separation of photogenerated electron-hole pairs and diminished the recombination rate. This work contributes to the development of novel photocatalysts with a dual Z-scheme heterojunction and facilitates the generation of valuable C2 products.

Photocatalytic CO 2 reduction to valuable fuels is a promising way to alleviate anthropogenic CO 2 emissions and energy crises. Perovskite oxides have attracted widespread attention as photocatalysts for CO 2 reduction by virtue of their high catalytic activity, compositional flexibility, bandgap adjustability, and good stability. In this review, the basic theory of photocatalysis and the mechanism of CO 2 reduction over perovskite oxide are first introduced. Then, perovskite oxides' structures, properties, and preparations are presented. In detail, the research progress on perovskite oxides for photocatalytic CO 2 reduction is discussed from five aspects: as a photocatalyst in its own right, metal cation doping at A and B sites of perovskite oxides, anion doping at O sites of perovskite oxides and oxygen vacancies, loading cocatalyst on perovskite oxides, and constructing heterojunction with other semiconductors. Finally, the development prospects of perovskite oxides for photocatalytic CO 2 reduction are put forward. This article should serve as a useful guide for creating perovskite oxide-based photocatalysts that are more effective and reasonable., (© 2023 Wiley-VCH GmbH.)

Energy shortage and global warming caused by the extensive use of fossil fuels are urgent problems to be solved at present. Photoreduction of CO 2 is considered to be a feasible solution. The ternary composite catalyst g-C 3 N 4 /Ti 3 C 2 /MoSe 2 was synthesized by hydrothermal method, and its physical and chemical properties were studied by an array of characterization and tests. In addition, the photocatalytic performance of this series of catalysts under full spectrum irradiation was also tested. It is found that the CTM-5 sample has the best photocatalytic activity, and the yields of CO and CH 4 are 29.87 and 17.94 μmol g -1  h -1 , respectively. This can be ascribed to the favorable optical absorption performance of the composite catalyst in the full spectrum and the establishment of S-scheme charge transfer channel. The formation of heterojunctions can effectively promote charge transfer. The addition of Ti 3 C 2 materials provides plentiful active sites for CO 2 reaction, and its superior electrical conductivity is also favorable for the migration of photogenerated electrons., (© 2023 Wiley-VCH Verlag GmbH.)

Ammonia selective catalytic reduction (NH 3 -SCR) of nitrogen oxides is an effective and well-established technology for NO x removal, but current commercial denitrification catalysts based on V 2 O 5 -WO 3 /TiO 2 have some obvious disadvantages, including narrow operating temperature windows, toxicity, poor hydrothermal stability, and unsatisfied SO 2 /H 2 O tolerance. To overcome these drawbacks, it is imperative to investigate new types of highly efficient catalysts. In order to design catalysts with outstanding selectivity, activity, and anti-poisoning ability, core-shell structured materials have been widely applied in the NH 3 -SCR reaction, which exhibits numerous advantages including the large surface area, the strong synergy interaction of core-shell materials, the confinement effect, and the shielding effect from the shell layer to protect the core. This review summarizes recent developments of core-shell structured catalysts for NH 3 -SCR, including basic classification, synthesis methods, and a detailed description of the performance and mechanisms of each type of catalyst. It is hoped that the review will stimulate future developments in NH 3 -SCR technology, leading to novel catalyst designs with improved denitrification performance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Photocatalysis driven by solar energy is a feasible strategy to alleviate energy crises and environmental problems. In recent years, significant progress has been made in developing advanced photocatalysts for efficient solar-to-chemical energy conversion. Single-atom catalysts have the advantages of highly dispersed active sites, maximum atomic utilization, unique coordination environment, and electronic structure, which have become a research hotspot in heterogeneous photocatalysis. This paper introduces the potential supports, preparation, and characterization methods of single-atom photocatalysts in detail. Subsequently, the fascinating effects of single-atom photocatalysts on three critical steps of photocatalysis (the absorption of incident light to produce electron-hole pairs, carrier separation and migration, and interface reactions) are analyzed. At the same time, the applications of single-atom photocatalysts in energy conversion and environmental protection (CO 2 reduction, water splitting, N 2 fixation, organic macromolecule reforming, air pollutant removal, and water pollutant degradation) are systematically summarized. Finally, the opportunities and challenges of single-atom catalysts in heterogeneous photocatalysis are discussed. It is hoped that this work can provide insights into the design, synthesis, and application of single-atom photocatalysts and promote the development of high-performance photocatalytic systems., (© 2023 Wiley-VCH GmbH.)

A photocatalytic system driven by solar light is one of the promising strategies for converting CO 2 into valuable energy. The reduction of CO 2 to CH 4 is widely studied since CH 4 has a high energy density as the main component of nonrenewable natural gas. Therefore, it is necessary to develop semiconductor materials with high photocatalytic activity and CH 4 selectivity. Graphitic carbon nitride (g-C 3 N 4 /CN) has attracted widespread attention for photocatalytic CO 2 reduction due to its excellent redox ability and visible light response. A hybrid system constructed by loading cocatalysts on g-C 3 N 4 can significantly improve the yield of target products, and serve as a general platform to explore the mechanism of the CO 2 reduction reaction. Herein, we briefly introduce the theory of selective CO 2 photoreduction and the basic properties of cocatalysts. Then, several typical configurations and modification strategies of cocatalyst/CN systems for promoting CH 4 selective production are presented in detail. In particular, we systematically summarize the application of cocatalyst/CN composite photocatalysts in the selective reduction of CO 2 to methane, according to the classification of cocatalysts (monometal, bimetal, metal-based compound, and nanocarbon materials). Finally, the challenges and perspectives for developing cocatalyst/g-C 3 N 4 systems with high CH 4 selectivity are presented to guide the rational design of catalysts with high performance in the future.

The photocatalytic reduction of CO 2 to hydrocarbons is expected to simultaneously alleviate the energy crisis and greenhouse effect. Herein, the ternary BiOCl/C/Cu 2 O catalysts with different mass ratios were compounded using a simple hydrothermal method, revealing better photocatalytic activity than the monomer. In the absence of sacrificial agents and photosensitizers, 25% BiOCl/C/Cu 2 O showed optimal photocatalytic performance. The CO and CH 4 yields over 25% BiOCl/C/Cu 2 O reached 26.77 and 9.86 μmol g -1 h -1 , which is 2.9 and 8.7 times higher than that of the pristine Cu 2 O, respectively. The ameliorative activity can be attributed to the construction of the Z-scheme heterostructure and carbon layer, which are conducive to the transfer and separation of photogenerated carriers. This study offers valuable references for the design and investigation of a Z-scheme heterojunction using a carbon layer as an electron transfer medium.

Converting CO 2 into value-added products by photocatalysis, electrocatalysis, and photoelectrocatalysis is a promising method to alleviate the global environmental problems and energy crisis. Among the semiconductor materials applied in CO 2 catalytic reduction, Cu 2 O has the advantages of abundant reserves, low price and environmental friendliness. Moreover, Cu 2 O has unique adsorption and activation properties for CO 2 , which is conducive to the generation of C 2+ products through CC coupling. This review introduces the basic principles of CO 2 reduction and summarizes the pathways for the generation of C 1 , C 2 , and C 2+ products. The factors affecting CO 2 reduction performance are further discussed from the perspective of the reaction environment, medium, and novel reactor design. Then, the properties of Cu 2 O-based catalysts in CO 2 reduction are summarized and several optimization strategies to enhance their stability and redox capacity are discussed. Subsequently, the application of Cu 2 O-based catalysts in photocatalytic, electrocatalytic, and photoelectrocatalytic CO 2 reduction is described. Finally, the opportunities, challenges and several research directions of Cu 2 O-based catalysts in the field of CO 2 catalytic reduction are presented, which is guidance for its wide application in the energy and environmental fields is provided., (© 2023 Wiley-VCH GmbH.)

In recent years, three-dimensionally ordered macroporous (3DOM) materials have attracted tremendous interest in the field of photocatalysis due to the periodic spatial structure and unique physicochemical properties of 3DOM catalysts. In this review, the fundamentals and principles of 3DOM photocatalysts are briefly introduced, including the overview of 3DOM materials, the photocatalytic principles based on 3DOM materials, and the advantages of 3DOM materials in photocatalysis. The preparation methods of 3DOM materials are also presented. The structure and properties of 3DOM materials and their effects on photocatalytic performance are briefly summarized. More importantly, 3DOM materials, as a supported catalyst, are extensively employed to combine with various common materials, including metal nanoparticles, metal oxides, metal sulfides, and carbon materials, to enhance photocatalytic performance. Finally, the prospects and challenges for the development of 3DOM materials in the field of photocatalysis are presented., (© 2023 Wiley-VCH GmbH.)

Photocatalytic CO 2 conversion into solar fuels is a promising technology to alleviate CO 2 emissions and energy crises. The development of core-shell structured photocatalysts brings many benefits to the photocatalytic CO 2 reduction process, such as high conversion efficiency, sufficient product selectivity, and endurable catalyst stability. Core-shell nanostructured materials with excellent physicochemical features take an irreplaceable position in the field of photocatalytic CO 2 reduction. In this review, the recent development of core-shell materials applied for photocatalytic reduction of CO 2 is introduced . First, the basic principle of photocatalytic CO 2 reduction is introduced. In detail, the classification and synthesis techniques of core-shell catalysts are discussed. Furthermore, it is also emphasized that the excellent properties of the core-shell structure can greatly improve the activity, selectivity, and stability in the process of photocatalytic CO 2 reduction. Hopefully, this paper can provide a favorable reference for the preparation of efficient photocatalysts for CO 2 reduction., (© 2022 Wiley-VCH GmbH.)

Photocatalytic reduction of CO 2 to high-energy products is an effective way to utilize solar energy and mitigate the greenhouse effect. In this paper, a series of CQDs/Bi 12 O 17 Cl 2 /NiAl-LDH (C/BOC/LDH) photocatalysts were prepared via a one-pot hydrothermal method, demonstrated excellent photocatalytic CO 2 reduction performance. In the case of only water without any photosensitizer and sacrificial agent, the CO production rate on C/0.3BOC/LDH reached 16.4 μmol·g -1 h -1 , which is 6.7 times higher than that of the original LDH. The construction of Z-scheme heterojunctions inhibited the recombination of electrons with holes. The unique up-conversion PL behavior of CQDs benefitted the absorption of energy in the NIR by the photocatalyst. This study provides meaningful assistance for the design and construction of a ternary photocatalytic system with Z-scheme heterojunction and carbon-based co-catalyst., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Photocatalytic CO 2 reduction technology has a broad potential for dealing with the issues of energy shortage and global warming. As a widely studied material used in the photocatalytic process, titanium dioxide (TiO 2 ) has been continuously modified and tailored for more desirable application. Recently, the defective/reduced titanium dioxide (TiO 2- x ) catalyst has attracted broad attention due to its excellent photocatalytic performance for CO 2 reduction. In this perspective review, we comprehensively present the recent progress in TiO 2- x -based materials for photocatalytic CO 2 reduction. In detail, the review starts with the fundamentals of CO 2 photocatalytic reduction. Then, the synthesis of a defective TiO 2 structure is introduced for the regulation of its photocatalytic performance, especially its optical properties and dissociative adsorption properties. In addition, the current application of TiO 2- x -based photocatalysts for CO 2 reduction is also highlighted, such as metal-TiO 2- x , oxide-TiO 2- x and TiO 2- x -carbon-based photocatalysts. Finally, the existing challenges and possible scope of photocatalytic CO 2 reduction over TiO 2- x -based materials are discussed. We hope that this review can provide an effective reference for the development of more efficient and reasonable photocatalysts based on TiO 2- x .

As a renewable green energy, hydrogen has received widespread attention due to its huge potential in solving energy shortages and environment pollution. In this paper, a one-step solvothermal method was applied to grow ultra-thin g-C 3 N 4 (UCN) nanosheets and NiS nanoparticles on the surface of ZnIn 2 S 4 (ZIS). A ternary NiS/ZnIn 2 S 4 /ultra-thin-g-C 3 N 4 composite material with dual high-speed charge transfer channels was constructed for the advancement of the photocatalytic H 2 generation. The optimal ternary catalyst 1.5wt.%NiS/ZnIn 2 S 4 /ultra-thin-g-C 3 N 4 (NiS/ZIS/UCN) achieved a H 2 evolution yield reached to 5.02 mmolg -1 h -1 , which was 5.23 times superior than that of pristine ZnIn 2 S 4 (0.96 mmolg -1 h -1 ) and even outperform than that of the best precious metal modified 3.0 wt%Pt/ZnIn 2 S 4 (4.08 mmolg -1 h -1 ). The AQY at 420 nm could be achieved as high as 30.5%. The increased photocatalytic performance of NiS/ZIS/UCN could be ascribed to the type-I heterojunctions between intimated ZIS and UCN. In addition, NiS co-catalyst with large quantity of H 2 evolution sites, could result in efficient photo-induced charges separation and migration. Furthermore, the NiS/ZIS/UCN composite exhibited excellent H 2 evolution stability and recyclability. This work would also offer a reference for the design and synthesis of ternary co-catalyst with heterojunction composite for green energy conversion., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Selective catalytic reduction with NH 3 (NH 3 -SCR) was the most efficient approach to mitigate the emission of nitrogen oxides (NO x ). Although the conventional manganese oxide-based catalyst had gradually become a kind of principal catalyst for the low-temperature NH 3 -SCR reaction, there were still numerous defects. The growing demands for extensive operation temperature scope, strong SO 2 tolerance, and excellent catalytic activity had boosted the development of novel manganese oxide-based catalysts. In this review, three forms of manganese oxide-based catalysts were introduced in detail, including single manganese oxide catalysts, composite manganese oxide-based catalysts, and supported manganese oxide-based catalysts. The surface acidity and redox properties of manganese oxide-based catalysts could be strengthened by optimizing the preparation methods, exposing specific crystal planes, and constructing multiple active centers and sacrificial sites, which improved the SCR performance and anti-poisoning properties of catalysts. Secondly, we briefly summarized the NH 3 -SCR reaction mechanism of manganese oxide-based catalysts, including the Eley-Rideal (E-R) mechanism and the Langmuir-Hinshelwood (L-H) mechanism. Finally, several overtures were proposed for the future research directions of manganese oxide-based catalysts for NH 3 -SCR reaction, hoping to narrow the gap between the novel manganese oxide-based catalysts and the actual demands and realize commercialized application in the nearest future.

Converting CO 2 to renewable fuels or valuable carbon compounds is an effective way to solve the global warming and energy crisis. Compared with other CO 2 conversion methods, photocatalytic reduction of CO 2 is more energy-saving, environmentally friendly, and has a broader application prospect. Layered double hydroxide (LDH) has attracted widespread attention as a two-dimensional material, composed of metal hydroxide layers, interlayer anions and water molecules. This review briefly introduces the basic theory of photocatalysis and the mechanism of CO 2 reduction. The composition and properties of LDH are introduced. The research progress on LDH in the field of photocatalytic reduction of CO 2 is elaborated from six aspects: directly as a catalyst, as a precursor for a catalyst, and by modification, intercalation, supporting with other materials and construction of a heterojunction. Finally, the development prospects of LDH are put forward. This review could provide an effective reference for the development of more efficient and reasonable photocatalysts based on LDH.

Promoting the separation of photogenerated electron-hole pairs and enhancing the charge carrier transfer are critical in photocatalysis. In our work, a ball-flower-like NiS/Zn 3 In 2 S 6 /g-C 3 N 4 photocatalyst fabricated by a hydrothermal method exhibited superior performance for photocatalytic water splitting. The optimized 2.0% NiS/Zn 3 In 2 S 6 /g-C 3 N 4 rivaled noble metal based Pt/g-C 3 N 4 and showed an apparent quantum efficiency (AQE) of 24.3% at 420 nm, with a H 2 yield of 4.135 mmol g -1 h -1 , which was 30.4 and 9.51 times that of pure g-C 3 N 4 and binary Zn 3 In 2 S 6 /g-C 3 N 4 composites, respectively. The experimental and characterization results suggested that the heterojunction formed between Zn 3 In 2 S 6 /g-C 3 N 4 and the decorating NiS co-catalyst cooperatively suppressed the electron-hole recombination and facilitated the charge carrier transfer, thus resulting in significant improvement of the H 2 evolution performance. Moreover, the increased specific surface area and the enhanced visible-light absorption also contributed to superior water splitting performance. The prepared ternary catalytic system with the heterojunction and non-noble metal co-catalyst has great potential as an alternative to noble metals for achieving cost-efficient water splitting systems.

The Cu/TiO 2 catalysts with the addition of Eu were developed by the sol-gel way for the selective catalytic reduction (SCR) of NO x by NH 3 . Activity tests revealed that CuEu/TiO 2 -0.15 catalyst showed the optimal de-NO x performance in a wide temperature range (150-300 °C), along with an admirable SO 2 tolerance. According to characterization analysis, the relationship between the NH 3 -SCR performance and physicochemical characters of samples was explored. The adjunction of Eu on Cu/TiO 2 catalyst can contribute to the formation of a large amount of Cu 2+ , adsorbed oxygen, and acid sites on the catalyst surface. Moreover, the Eu addition on Cu/TiO 2 is favorable to the generation of activated NO x and NH 3 substances adsorbed on the catalyst surface, which would conduce to the NH 3 -SCR process by Langmuir-Hinshelwood (L-H) mechanism effectively.

In this study, it was found that the CeVO 4 -CeO 2 nanocomposite possessed remarkably selective catalytic reduction (SCR) performance and wider active temperature scope. And, the promotion principle was explored based on BET, XRD, XPS, H 2 -temperature-programmed reduction, NH 3 -temperature-programmed desorption, and in situ diffuse reflectance infrared Fourier transform (DRIFT) techniques. The characterization outcomes manifested that the CeVO 4 -CeO 2 nanocomposite could inhibit its crystallinity and enhance the concentrations of chemisorbed oxygen species and Ce 3+ , which was advantageous to the SCR process. Moreover, the in situ DRIFT technique manifested that the NH 3 -SCR reaction over Ce 0.75 V 0.25 O y was enhanced effectively through the mechanism of L-H.

CO pretreatment was found to effectively improve the SCR performance of CeO 2 , with over 90% at about 300 °C. The larger specific area and the decrease of CeO 2 crystallization indicated the modification of the surface structure after CO pretreatment. Abundant Ce 3+ species and active oxygen, better reducibility, and the higher surface adsorption capacity were mainly responsible for its enhanced SCR performance. DRIFT analysis revealed the presumed coexistence of two reaction routes that the L-H mechanism was related to the reaction temperature, while the reaction rate of E-R route was almost directly proportional to the NO concentration at a certain temperature, based on the kinetic calculation. In addition, the CO-pretreated CeO 2 also exhibited a better poisoning tolerance for SO 2 and H 2 O and excellent thermal stability and circularity. Graphical abstract The process of NH 3 -SCR reaction over CeO 2 -CO catalyst.

Bi 2 O 3 /g-C 3 N 4 nanoscale composites with a Z-scheme mechanism were successfully synthesized by high temperature calcination combined with a hydrothermal method. These synthesized composites exhibited excellent photocatalytic performance, especially the 40 wt% Bi 2 O 3 /g-C 3 N 4 composite, which produced about 1.8 times the CO yield of pure g-C 3 N 4 . The obtained products were characterized by X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and so on. Characterization results revealed that Bi ions had well covered the surface of g-C 3 N 4 , thus restraining the recombination of electron-hole pairs and resulting in a stronger visible-light response and higher CO yield. In addition, the electron transfer process through the Z-scheme mechanism also promoted the photocatalytic activity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Z-Scheme MoS2/g-C3N4 heterojunction photocatalysts were fabricated using a hydrothermal deposition procedure together with a calcination route, and then applied for CO2 photoreduction. Experimental results indicated that the 10% MoS2/g-C3N4 heterojunction displayed the best photocatalytic performance. Furthermore, the maximum CO yields of 58.59 μmol (g-cat)-1 under 7 h-visible light irradiation was up to 2.94 times that of the unadulterated g-C3N4. The enhanced photocatalytic performance of 10% MoS2/g-C3N4 catalyst was due to the favored visible light response, the efficient separation of photogenerated electron-hole pairs as well as its larger specific surface area.

It was well recognized that Pb had a poisoning effect on a SCR catalyst. In this study, the deactivation mechanism of Pb on the Ce/TiO 2 catalyst was investigated based on the characterization results of TPD and in situ DRIFT studies. It was found that the addition of Pb on the Ce/TiO 2 catalyst not only inhibited the adsorption and activation of NH 3 species, but also led to the decrease of the activity of adsorbed NH 3 species in the SCR reaction. The adsorption of NOx species and the oxidation of NO by O 2 over the Ce/TiO 2 catalyst were also suppressed by the addition of Pb, while the reactivity of adsorbed NO 2 species did not decrease. Moreover, the results revealed that the NH 3 -SCR reaction over the Ce/TiO 2 catalyst followed both the E-R and L-H mechanisms, while the NH 3 -SCR reaction over Ce/TiO 2 -Pb was mainly controlled by the L-H mechanism. The contributions of the L-H mechanism to the SCR reactions over Ce/TiO 2 and Ce/TiO 2 -Pb decreased with increasing reaction temperature. The deactivation of Ce/TiO 2 -Pb was mainly attributed to the suppressed NH 3 adsorption and activation, accompanied by the inhibited NO oxidation and the decrease of Brønsted acid sites.

CeO2-CuO/Al2O3 catalysts were prepared by three different methods and their activities for selective catalytic reduction (SCR) of NO with NH3 were investigated. As can be seen from the experimental results, the catalyst prepared by the single-step sol-gel (SG) method showed the best SCR activity and resistance to SO2 and H2O. In order to investigate the relationship between the preparation method and the performance of SCR catalysts, the catalysts were characterized by using Brunauer-Emmett-Teller, X-ray diffraction, temperature programmed reduction with hydrogen, temperature programmed desorption with ammonia, X-ray photoelectron spectroscopy, Fourier transform infrared and thermo-gravimetric analysis techniques. It was found that the excellent performance of CeO2-CuO/Al2O3 catalyst prepared by the single-step SG method should be resulted from its large surface area, low crystallinity, high oxygen storage capacity, high NH3 adsorption capacity, high concentration of surface chemisorbed oxygen, weak sulphation process and weak water absorption.