Adsorption Behavior of Ammonia on Strontium Bromide Surface: First-Principles Study.

Thermochemical heat storage based on a gas-solid interaction is an effective long-term energy storage technology and is considered as one of the important technologies for the recovery of industrial waste heat and renewable energy sources such as solar energy. There are many working pairs used for thermochemical heat storage, among which ammonium halides are widely trusted for their good thermodynamic properties. It has attracted a lot of attention in the past decade, but it is still in the laboratory-scale research stage. In this study, the adsorption behavior of strontium bromide surfaces on the atomic scale is investigated using density functional theory with SrBr2/NH3 as the working pair. The optimal adsorption location of ammonia molecules on the strontium bromide surface is determined. Meanwhile, different metal atoms were doped to explore the microscopic factors affecting the adsorption. The energy barrier of the SrBr2/NH3 reaction was 4.507 kcal/mol, which was reduced to 4.145 kcal/mol after doping Mg. The thermodynamics of the Ca atoms doped with SrBr2 were significantly improved, with a reduction in the energy barrier to 0.727 kcal/mol. Comparing the three energy barrier results, Ca doping has a significant optimization effect on the thermal storage process. The results could provide relevant information for the investigation of thermochemical adsorption heat storage, provide insight into the adsorption mechanism of ammonium molecules on strontium bromide, and also facilitate the design of efficient composite adsorbents.

Bi3O4Cl/g-C3N4/Cd0.5Zn0.5S Double Z-Scheme Heterojunction Photocatalyst for Highly Selective CO2 Reduction to Methane.

Solar-energy-driven CO2 hydrogenation is a promising strategy to alleviate the climate crisis. Methane is a desirable derivative of CO2 reduction. However, developing a photocatalyst for highly active and selective CH4 generation remains challenging. Herein, we report a double Z-scheme Bi3O4Cl/g-C3N4/Cd0.5Zn0.5S photocatalyst for efficient reduction of CO2 to CH4. In situ characterization techniques confirmed that the charge migration mechanism in Bi3O4Cl/g-C3N4/Cd0.5Zn0.5S 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 CH4. Moreover, the AQY of CO2 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 CO2 conversion to CH4.

Recent Progress of Single-Atom Photocatalysts Applied in Energy Conversion and Environmental Protection.

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 (CO2 reduction, water splitting, N2 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.

Recent Progress of Covalent Organic Frameworks-Based Materials in Photocatalytic Applications: A Review.

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, CO2 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.

Recent Progress of Three-dimensionally Ordered Macroporous (3DOM) Materials in Photocatalytic Applications: A Review.

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.

Recent Advances and Perspectives of Core-Shell Nanostructured Materials for Photocatalytic CO2 Reduction.

Photocatalytic CO2 conversion into solar fuels is a promising technology to alleviate CO2 emissions and energy crises. The development of core-shell structured photocatalysts brings many benefits to the photocatalytic CO2 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 CO2 reduction. In this review, the recent development of core-shell materials applied for photocatalytic reduction of CO2 is introduced . First, the basic principle of photocatalytic CO2 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 CO2 reduction. Hopefully, this paper can provide a favorable reference for the preparation of efficient photocatalysts for CO2 reduction.

Converting CO2 into Value-Added Products by Cu2 O-Based Catalysts: From Photocatalysis, Electrocatalysis to Photoelectrocatalysis.

Converting CO2 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 CO2 catalytic reduction, Cu2 O has the advantages of abundant reserves, low price and environmental friendliness. Moreover, Cu2 O has unique adsorption and activation properties for CO2 , which is conducive to the generation of C2+ products through CC coupling. This review introduces the basic principles of CO2 reduction and summarizes the pathways for the generation of C1 , C2 , and C2+ products. The factors affecting CO2 reduction performance are further discussed from the perspective of the reaction environment, medium, and novel reactor design. Then, the properties of Cu2 O-based catalysts in CO2 reduction are summarized and several optimization strategies to enhance their stability and redox capacity are discussed. Subsequently, the application of Cu2 O-based catalysts in photocatalytic, electrocatalytic, and photoelectrocatalytic CO2 reduction is described. Finally, the opportunities, challenges and several research directions of Cu2 O-based catalysts in the field of CO2 catalytic reduction are presented, which is guidance for its wide application in the energy and environmental fields is provided.

Research Progress on Photocatalytic CO2 Reduction Based on Perovskite Oxides.

Photocatalytic CO2 reduction to valuable fuels is a promising way to alleviate anthropogenic CO2 emissions and energy crises. Perovskite oxides have attracted widespread attention as photocatalysts for CO2 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 CO2 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 CO2 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 CO2 reduction are put forward. This article should serve as a useful guide for creating perovskite oxide-based photocatalysts that are more effective and reasonable.

Catalytic Oxidation of Acetone on SmMn2O5: Effect of Acid Etching and Loading Treatment.

The key of catalytic oxidation technology is to develop a stable catalyst with high activity. It is still a serious challenge to achieve high conversion efficiency of acetone with an integral catalyst at low temperature. In this study, the SmMn2O5 catalyst after acid etching was used as the support, and the manganese mullite composite catalyst was prepared by loading Ag and CeO2 nanoparticles on its surface. By means of SEM, TEM, XRD, N2-BET, XPS, EPR, H2-TPR, O2-TPD, NH3-TPD, DRIFT, and other characterization methods, the related factors and mechanism analysis of acetone degradation activity of the composite catalyst were discussed. Among them, the CeO2-SmMn2O5-H catalyst has the best catalytic activity at 123 and 185 °C for T50 and T100, respectively, and shows excellent water and thermal resistance and stability. In essence, the surface and lattice defects of highly exposed Mn sites were formed by acid etching, and the dispersibility of Ag and CeO2 nanoparticles was optimized. Highly dispersed Ag and CeO2 nanoparticles have a highly synergistic effect with the support SmMn2O5, and the reactive oxygen species provided by CeO2 and the electron transfer brought by Ag further promote the decomposition of acetone on the carrier SMO-H. In the field of catalytic degradation of acetone, a new catalyst modification method of high-quality active noble metals and transition metal oxides supported by acid-etched SmMn2O5 has been developed.

Research Progress of a Composite Metal Oxide Catalyst for VOC Degradation.

Volatile organic compounds (VOCs) are atmospheric pollutants that have been of concern for researchers in recent years because they are toxic, difficult to remove, and widely sourced and easily cause damage to the environment and human body. Most scholars use low-temperature plasma biological treatment, catalytic oxidation, adsorption, condensation, and recovery techniques to treat then effectively. Among them, catalytic oxidation technology has the advantages of a high catalytic efficiency, low energy consumption, high safety factor, high treatment efficiency, and less secondary pollution; it is currently widely used for VOC degradation technology. In this paper, the catalytic oxidation technology for the degradation of multiple types of VOCs as well as the development of a single metal oxide catalyst have been briefly introduced. We also focus on the research progress of composite metal oxide catalysts for the removal of VOCs by comparing and analyzing the metal component ratio, preparation method, and types of precursors and the catalysts' influence on the catalytic performance. In addition, the reason for catalyst deactivation and a correlation between the chemical state of the catalyst and the electron distribution are discussed. Development of a composite metal oxide catalyst for the catalytic oxidation of VOCs has been proposed.

Recent progress of low-temperature selective catalytic reduction of NOx with NH3 over manganese oxide-based catalysts.

Selective catalytic reduction with NH3 (NH3-SCR) was the most efficient approach to mitigate the emission of nitrogen oxides (NOx). Although the conventional manganese oxide-based catalyst had gradually become a kind of principal catalyst for the low-temperature NH3-SCR reaction, there were still numerous defects. The growing demands for extensive operation temperature scope, strong SO2 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 NH3-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 NH3-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.

DetectFormer: Category-Assisted Transformer for Traffic Scene Object Detection.

Object detection plays a vital role in autonomous driving systems, and the accurate detection of surrounding objects can ensure the safe driving of vehicles. This paper proposes a category-assisted transformer object detector called DetectFormer for autonomous driving. The proposed object detector can achieve better accuracy compared with the baseline. Specifically, ClassDecoder is assisted by proposal categories and global information from the Global Extract Encoder (GEE) to improve the category sensitivity and detection performance. This fits the distribution of object categories in specific scene backgrounds and the connection between objects and the image context. Data augmentation is used to improve robustness and attention mechanism added in backbone network to extract channel-wise spatial features and direction information. The results obtained by benchmark experiment reveal that the proposed method can achieve higher real-time detection performance in traffic scenes compared with RetinaNet and FCOS. The proposed method achieved a detection performance of 97.6% and 91.4% in AP50 and AP75 on the BCTSDB dataset, respectively.

The deactivation mechanism of Pb on the Ce/TiO2 catalyst for the selective catalytic reduction of NOx with NH3: TPD and DRIFT studies.

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/TiO2 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/TiO2 catalyst not only inhibited the adsorption and activation of NH3 species, but also led to the decrease of the activity of adsorbed NH3 species in the SCR reaction. The adsorption of NOx species and the oxidation of NO by O2 over the Ce/TiO2 catalyst were also suppressed by the addition of Pb, while the reactivity of adsorbed NO2 species did not decrease. Moreover, the results revealed that the NH3-SCR reaction over the Ce/TiO2 catalyst followed both the E-R and L-H mechanisms, while the NH3-SCR reaction over Ce/TiO2-Pb was mainly controlled by the L-H mechanism. The contributions of the L-H mechanism to the SCR reactions over Ce/TiO2 and Ce/TiO2-Pb decreased with increasing reaction temperature. The deactivation of Ce/TiO2-Pb was mainly attributed to the suppressed NH3 adsorption and activation, accompanied by the inhibited NO oxidation and the decrease of Brønsted acid sites.

Low-temperature selective catalytic reduction of NO on CeO2-CuO/Al2O3 catalysts prepared by different methods.

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.

Mechanism and anti-corrosion measures of carbon dioxide corrosion in CCUS: A review.

Carbon capture, utilization, and storage (CCUS) technology is widely recognized as a key solution for mitigating global climate change. Consequently, it has received significant attention from countries worldwide. However, carbon dioxide corrosion poses a significant challenge to CCUS and represents a bottleneck to the large-scale development and application of this technology. To mitigate this issue, this review starts with a discussion of corrosion problems in CCUS. Later, the fundamentals of the carbon dioxide corrosion mechanism are introduced. Then, the influences of various factors that affect the corrosion are highlighted, such as water content, pH, flow rate, etc. Afterward, we summarize the commonly used methods for corrosion protection, with a particular focus on inhibitor, given their eco-friendly and effective nature. Lastly, challenges and prospects are discussed to motivate future studies on developing novel, high-performance green inhibitor and studying the corresponding protection mechanisms, hoping to make some contributions to carbon emission reduction.

Research progress on photocatalytic reduction of CO2 based on ferroelectric materials.

Transforming CO2 into renewable fuels or valuable carbon compounds could be a practical means to tackle the issues of global warming and energy crisis. Photocatalytic CO2 reduction is more energy-efficient and environmentally friendly, and offers a broader range of potential applications than other CO2 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 CO2 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 CO2 from three perspectives: directly as a catalyst, by modification, and construction of heterojunctions. Finally, the future potential of ferroelectric materials for photocatalytic CO2 reduction is presented. This review may be a valuable guide for creating reasonable and more effective photocatalysts based on ferroelectric materials.

Metal-organic frameworks (MOFs) for photoelectrocatalytic (PEC) reducing carbon dioxide (CO2) to hydrocarbon fuels.

MOF-based photoelectrocatalysis (PEC) using CO2 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 CO2 and the preparation methods and characterization techniques of MOF-based materials are summarized. Furthermore, three applications of MOFs for improving the photoelectrocatalytic performance of CO2 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 CO2 systems based on MOF materials are also discussed briefly.

Constructing Cu defect band within TiO2 and supporting NiOx nanoparticles for efficient CO2 photoreduction.

Effectively harnessing solar energy for the conversion of CO2 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 CO2. In this study, we employed a facile sol-gel method combined with wetness impregnation to synthesize Cu-doped TiO2 coated with NiOx nanoparticles. Various characterizations verified the successful incorporation of Cu ions into the TiO2 crystal lattice and the formation of NiOx 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 CH4, which represent a 4.4-fold and 15.6-fold increase, respectively, compared to those achieved with pure TiO2. The induced Cu defect band broadens the light absorption by decreasing the conduction band edge of TiO2, while NiOx upshifts the valence band of TiO2 because of the interaction of valence orbitals. Light irradiation EPR and FTIR tests suggest that the collaboration of CuOx and NiOx promotes the formation of oxygen vacancies/defects and a rapid charge transfer pathway, thereby provides numerous active sites and electrons to enhance CO2 photoreduction performance.

Recent progress of cocatalysts loaded on carbon nitride for selective photoreduction of CO2 to CH4.

A photocatalytic system driven by solar light is one of the promising strategies for converting CO2 into valuable energy. The reduction of CO2 to CH4 is widely studied since CH4 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 CH4 selectivity. Graphitic carbon nitride (g-C3N4/CN) has attracted widespread attention for photocatalytic CO2 reduction due to its excellent redox ability and visible light response. A hybrid system constructed by loading cocatalysts on g-C3N4 can significantly improve the yield of target products, and serve as a general platform to explore the mechanism of the CO2 reduction reaction. Herein, we briefly introduce the theory of selective CO2 photoreduction and the basic properties of cocatalysts. Then, several typical configurations and modification strategies of cocatalyst/CN systems for promoting CH4 selective production are presented in detail. In particular, we systematically summarize the application of cocatalyst/CN composite photocatalysts in the selective reduction of CO2 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-C3N4 systems with high CH4 selectivity are presented to guide the rational design of catalysts with high performance in the future.

Recent advances in core-shell structured catalysts for low-temperature NH3-SCR of NOx.

Ammonia selective catalytic reduction (NH3-SCR) of nitrogen oxides is an effective and well-established technology for NOx removal, but current commercial denitrification catalysts based on V2O5-WO3/TiO2 have some obvious disadvantages, including narrow operating temperature windows, toxicity, poor hydrothermal stability, and unsatisfied SO2/H2O 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 NH3-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 NH3-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 NH3-SCR technology, leading to novel catalyst designs with improved denitrification performance.