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Photocatalytic CO2reduction (PCO2RR) is regarded as a promising means to mitigate the effects of climate change and current energy shortage. However, photocatalysis is not very effective because of the rapid recombination of photogenerated electron–hole pairs. S-scheme heterojunctions can effectively separate photogenerated carriers and significantly improve the redox ability of photocatalysts. In recent years, S-scheme heterojunction photocatalysts have become a popular topic of research because of their superior photocatalytic performance. This review examines the recent research advancements in S-scheme heterojunction photocatalysts. First, the principle of PCO2RR is briefly introduced. Various types of heterojunctions are introduced, the charge transfer mechanisms and characterization methods of S-scheme heterojunctions are described, and the applications of metal oxides, metal sulfides, and other S-scheme photocatalysts in CO2reduction are discussed and reviewed, respectively. In conclusion, the limitations and prospective directions of S-scheme heterojunction photocatalysts in CO2photoreduction are discussed to provide direction for the design of high-performance S-scheme heterojunction photocatalysts.

Excessive greenhouse gas emissions have led to a series of environmental problems, such as the increasing greenhouse effect, rising sea levels, and melting glaciers at the poles, threatening the global environment for human existence. In view of this, the development of CO2capture technologies with commercialization potential is imperative, as CO2is the primary contributor to greenhouse gases. In recent years, chemical absorption techniques founded on sterically hindered amines, such as 2-amino-2-methyl-1-propanol (AMP), have garnered escalating interest owing to their benefits of large absorption capacity and diminished energy consumption for regeneration as compared to traditional amine-based methods. In this review, the steric hindrance effect of a sterically hindered amine and its reaction mechanism with CO2are reviewed. Subsequently, sterically hindered amine absorbents are classified into four kinds, single amine absorbents, blended amine absorbents, biphasic amine absorbents, and nonaqueous amine absorbents, and recent advancements in investigating the kinetic and thermodynamic characteristics of carbon dioxide sequestration through the utilization of sterically hindered amine sorbents are comprehensively evaluated. Technical-economic analysis and life cycle assessment of the CO2capture processes based on sterically hindered amine absorbents have been comprehensively reviewed. Furthermore, future work for CO2capture technologies based on sterically hindered amines is suggested.

With the continuous expansion of the industrial production scale and the rapid development of urbanization, ecological damage and environmental pollution caused by air pollutants have become a non-negligible problem in human society. Catalytic technology is one of the most promising and environmentally friendly measures in the past few decades to deal with airborne pollutants. The exploitation and research of efficient and low-cost catalysts is the determining element for the development of the catalytic oxidation process. One-dimensional (1D) manganese oxide shows high activity, selectivity, and stability, which gives credit to the excellent redox ability and surface acidy of MnOx. Additionally, the defect sites, acid–base characteristics, and valence state of the element are all modulated by the 1D morphologies of these catalysts. As a result, they have been widely employed to reduce air pollution. In this paper, the fabrication process of manganese oxide nanowires, nanorods, and nanosheets is reviewed in detail. Second, we briefly summarize the application of 1D manganese oxide nanostructures for the removal of nitrogen oxides, volatile organic compounds, carbon monoxide, ozone, and other pollutants. Finally, several approaches were proposed for the future research directions of one-dimensional manganese oxide nanostructures, hoping to narrow the gap between the novel manganese oxide-based catalysts and the actual demands and to realize commercialized application in the nearest future.

There is no time to delay reducing CO2to mitigate the greenhouse effect. For this purpose, electrochemical CO2reduction has rapidly developed and become an essential means of producing CO2derivatives. In recent years, two-dimensional materials have become the preferred choice as catalysts for electrochemical CO2reduction due to their superior properties. In this review, the fundamentals of electrochemical CO2reduction are introduced first. Then we discuss five typical two-dimensional materials, such as TMOs and TMDs, and explain the basic concept of electrochemical CO2reduction and the role of electrolytes. Finally, the development prospects of two-dimensional materials for electrochemical CO2reduction are put forward.

In this work, a ternary BiOCl/g-C3N4/Ag2CrO4composite with a dual Z-scheme heterojunction was prepared based on a g-C3N4photocatalyst and applied in the photocatalytic reduction of CO2. The optimal CH4and CO yields of the ternary composite catalyst could be achieved on BOC/CN/ACO-1% with 81.21 and 30.20 μmol g–1for 6 h, respectively, which was considerably enhanced compared to that for pure g-C3N4. The apparent quantum efficiency was achieved to be 2.68% for the BOC/CN/ACO-1% catalyst in the photoreduction of CO2at 420 nm. This performance enhancement resulted from constructing the dual Z-scheme and the improved light response, which had efficient charge migration and an excellent response to sunlight. This study provides a vital reference for developing dual Z-scheme heterojunction catalysts for the photocatalytic reduction of CO2.

The selective catalytic reduction (SCR) of NOxwith ammonia is an effective method to remove NOxfrom stationary and mobile sources. Cerium oxides (CeOx) have been studied extensively as low-temperature SCR catalysts since they manifest prominent oxygen storage capacity in catalysis. This paper reviews the recent progress on the Ce-based catalysts for low-temperature SCR de-NOxwith NH3, including three categories, single CeOx, Ce-based multimetal oxide, and Ce-based multimetal oxides with support. In the section on single CeOx, the reasons for the significant catalytic activity and the function of CeOxin the catalytic reactions are systematically reviewed. For multimetal oxide catalysts, the various roles played by the components of catalysts are summarized from several aspects. In the introduction of supported metal oxide catalysts, according to the type of support, the function of each support in the reaction is analyzed methodically. Additionally, we investigated the reaction mechanism of low-temperature SCR of NOx, including Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms. Finally, the development outlook and direction of the application of cerium oxide-based catalysts in the field of low-temperature SCR of NOxis prospected.

In this study, MnO2nanotubes, nanowires, and nanoparticles were synthetized by a hydrothermal method, after which the NO removal process with sodium persulfate solution catalyzed by MnO2of different shapes was studied and compared. It could be verified that MnO2nanowires showed the best NO removal efficiency of 91.2% with the catalyst concentration of 0.06 mol/L. As illustrated from the XRD, SEM, TEM, and XPS analysis results, the relatively higher activity of MnO2nanowires could be attributed to its low crystallinity and the presence of more lattice oxygen. The reaction mechanism was further confirmed by using the electron paramagnetic resonance technique, which verified the promotional effect by capturing the signal of hydroxyl (•OH) and sulfate (SO4–•) radicals. Additionally, free radical-quenching experiments also verified the decisive impacts of these two radicals on the removal system, where sulfate (SO4–•) radicals played a major role.

The photocatalytic CO2reduction technology can effectively decrease the CO2content in air while converting CO2into high-value-added chemicals and turning waste into treasure. In this study, Cu2O with a concave cubic structure was fabricated by selective etching, and ZnIn2S4nanosheets were successfully loaded on it uniformly, which significantly elevated its catalytic activity. The maximum CO yield of 9.98 μmol/g/h was obtained on the Z-scheme ZIS/Cu2O-0.3 photocatalyst, which was 3.7 and 4.3 times as high as the bare Cu2O concave cube and ZnIn2S4, respectively. The excellent photocatalytic performance could be attributed to the construction of Z-scheme heterojunction which facilitated the efficient separation of electron–hole pairs, a large specific surface area that provided an abundance of reactive sites, and positive visible light response.

Converting CO2into valuable energy and chemicals is an effective way to solve environmental problems and energy crises. Compared with other CO2conversion methods, electrocatalytic CO2conversion can be combined with clean energy, enhancing its energy efficiency, environmental friendliness, and sustainability; the process can be improved significantly. In recent years, the self-assembly of metal ions/clusters and organic ligands to form crystalline compounds, known as metal–organic frameworks (MOFs), has attracted considerable attention. These materials have gained prominence due to their diverse range of potential applications and distinctive properties. This Review briefly introduces the basic principles of electrocatalytic reduction of CO2and the composition and properties of MOF materials. It summarizes the research progress of MOFs in the field of electrocatalytic CO2reduction from the following aspects: pristine MOF catalysts, MOF-based composites, and MOF-derived electrocatalysts. Finally, the development prospects of MOFs are discussed in combination with the current research status, providing a reference for the development of more efficient and stable MOF electrocatalysts.

Constructing heterostructures and designing excellent structures to simulate natural photosynthesis are effective ways to efficiently and selectively convert CO2into products with high energy. Herein, a novel 0D/3D heterostructure composed of Cd0.5Zn0.5S quantum dots and CdIn2S4nano-octahedron was resoundingly fabricated via a simple solvothermal–coprecipitation method. The optimal yields of CO2photoreduction to CO and CH4over the Cd0.5Zn0.5S/CdIn2S4composite material could reach up to 14.07 and 4.23 μmol/g/h, respectively, which was primarily due to the synergistic effect of the 0D/3D heterostructure and unique morphology, thus accelerating the transfer of light-induced carriers. In addition, the as-fabricated composite exhibited excellent stability and weaker photocorrosion. Hence, this work could provide a simple and efficient route for the design and construction of photocatalysts with superior activity for CO2photoreduction.

In this work, an urchinlike W18O49/g-C3N4composite was fabricated via a simple hydrothermal process. The photocatalytic CO2conversion reaction was applied to evaluate the photocatalytic behavior of this catalytic system, and the WOCN-20 wt % heterojunction displayed superior photocatalytic behavior under full spectrum light irradiation, which was 6.46 μmol·h–1·g–1for CO and 3.97 μmol·h–1·g–1for CH4, respectively. Furthermore, in the near-infrared region, the composite photocatalysts also displayed excellent photocatalytic performance. A large number of characterizations and testing measures were carried out to study the components, morphology, and physicochemical properties of W18O49/g-C3N4photocatalyst, which were helpful to exploring and understanding the reasons for the improvement of catalytic performance. The boosted activity resulted from the tight contact between W18O49and g-C3N4and the formation of a Z-scheme heterojunction. The local surface plasmonic resonance (LSPR) of W5+also contributed to the realization of efficient photocatalysis under near-infrared light. The Z-scheme electron transport model could realize the efficient separation of light-induced e––h+pairs and reduce the recombination rate, thereby boosting the CO2photocatalytic reduction process.

Photoreduction of CO2can effectively alleviate the troublesome global energy crisis and environmental problems by converting CO2into hydrocarbons. Due to the discovery of photocatalysts that can respond to infrared light, the application of full spectrum in photocatalysis has attracted many researchers. This review comprehensively summarizes the progress in CO2photocatalytic reduction based on full-spectrum photocatalytic systems, and the basic theory of photoresponse, the mechanism of photocatalysis and photoreduction of CO2, and the representative photocatalytic materials working under ultraviolet, visible, and infrared irradiation are discussed. The strategies and related mechanisms of realizing full-spectrum photocatalysis are introduced, and the contribution of photoreactors to CO2photocatalytic reduction is also mentioned. Finally, the application prospects of light-driven reactions in CO2reduction are prospected. It is hoped that this review can offer clearer guidance for CO2reduction and construction of full spectrum-driven photocatalyst for efficient photocatalytic CO2reduction in the future.

In this study, novel Schottky-junction photocatalysts Bi-metal-deposited g-C3N4were constructed via a one-step solvothermal process for photocatalytic CO2reduction under simulated irradiation. The photocatalytic performance illustrated that the nanohybrid catalysts have extreme activity and excellent stability. The maximum CO yield of 3.78 μmol h–1g–1was reached on the BiCN-0.6 hybrid, which was about 3 times as much as that of pure g-C3N4. The phase, microstructure, and optical and photoelectrochemical properties were demonstrated by related characterization methods. The improvement mechanism could be ascribed to the enhanced photon absorption capacity and the decreased recombination rate of photoinduced carriers arising from the Schottky barrier in the system. This work may provide a meaningful approach to enhance the photocatalytic activity through a simple and green strategy.