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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]

The Eu-doped TiO 2 nanoparticles were successfully prepared by a simple sol-gel method. The properties of the catalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS), N 2 adsorption-desorption, UV–vis diffuse reflectance and photoluminescence (PL) spectroscopy. The results indicated that Eu-TiO 2 catalysts had a high specific surface area, enhanced visible light response and low recombination rate of electron-hole pairs. The photocatalytic performances of Eu-TiO 2 catalysts for CO 2 reduction were investigated under 9 h irradiation of a 300 W Xe arc lamp. The maximum yields of CH 4 and CO over the optimized Eu-TiO 2 catalyst were 65.53 μmol/g.cat and 42.91 μmol /g.cat, respectively, which were approximately 13 times and 1 times higher than that of pure TiO 2 . The enhanced photocatalytic performance could be ascribed to the high-efficiency separation of photo-generated electron-hole pairs. [ABSTRACT FROM AUTHOR]

Photocatalytic reduction of CO 2 into hydrocarbon fuels, utilizing inexhaustible solar energy to simulate natural photosynthesis, is a promising approach to simultaneously alleviate environmental issues and energy crises. Among the developed photocatalysts, bismuth (Bi)-based materials have been extensively applied for photocatalytic CO 2 reduction due to their unique electronic configuration and excellent physicochemical properties. Various approaches have been investigated to enhance the photocatalytic performance of Bi-based photocatalysts for CO 2 reduction, among which constructing direct or indirect Z-scheme by coupling Bi-based materials with matching semiconductors is an effective method. In this review, the latest major advancements in the design of high-efficient Bi-based Z-scheme photocatalysts for photocatalytic CO 2 reduction are summarized, including structural engineering strategies for direct Z-scheme and several patterns of indirect Z-scheme construction. Moreover, the proposed S-scheme structure based on the Z-scheme structure is also briefly discussed. Finally, the current challenges and prospects of the future development of the Bi-based Z-scheme structure for CO 2 photoreduction are also presented and discussed. [Display omitted] • The progress on photocatalytic CO 2 reduction over Bi-based Z-scheme photocatalysts are summarized. • The relationship between Bi-based Z-scheme structure and the photocatalytic CO2 reduction activity was investigated. • The future development of the Bi-based Z-scheme structure for CO 2 photoreduction is discussed. [ABSTRACT FROM AUTHOR]

In this study, Er3+/Yb3+ co-doped NiAl-LDH (LDH:Er3+,Yb3+) photocatalysts were successfully fabricated through a solvothermal process. The results revealed that the LDH:Er3+,Yb3+ displayed promoted photoreduction CO 2 activity under Vis/NIR light irradiation. A maximum CO yield of 13.2 μmolg−1h−1 had been obtained on LDH:1%Er,2%Yb, which was 9.4 and 1.5 times higher as high as the pure LDH and the LDH:1%Er, respectively. The improved photocatalytic activity can be ascribed to the expanded photoresponse range to NIR light region caused by the upconversion effect of Er3+/Yb3+, and the improved photogenerated charge separation efficiency with Er3+/Yb3+ serving as an electron trap. The NIR photocatalytic activity and the improved light absorption of LDH: Er3+,Yb3+ indicate that the upconversion mechanism is involved in the whole photocatalytic process. Therefore, this result presents new insights for the rational construction of Vis-NIR light-driven photocatalysts with high-efficient solar energy utilization and practical application prospects in the future. • LDH:Er3+;Yb3+ was prepared via a solvothermal method. • The photocatalyst exhibited enhanced visible and NIR photoreduction activity. • The mechanism of Vis/NIR photocatalytic reaction on LDH:Er3+;Yb3+ was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • NH 2 -UiO-66/CdIn 2 S 4 composite exhibited superior CO 2 photoreduction activity. • NH 2 -UiO-66/CdIn 2 S 4 could achieve the rapid separation of photoexcited e−/h+ pairs. • High CO 2 molecules adsorption activity of NH 2 -UiO-66/CdIn 2 S 4 composite. Solar-driven carbon dioxide (CO 2) photoreduction has been considered as an environmentally friendly and promising strategy to utilize solar energy and mitigate the impact of greenhouse effect. Designing novel cost-effective photocatalytic system with high CO 2 molecules adsorption activity is an efficient avenue to enhance CO 2 photoreduction performance. Herein, a series of NH 2 -UiO-66/CdIn 2 S 4 (NU66/CIS) photocatalysts with different NU66 contents were constructed via facile in-situ hydrothermal route and displayed graceful morphology. According to a series of characterization results, porous octahedron NU66 were deeply anchored on flowerlike 3D-microspheres CIS, and a part of the small-sized CIS were evenly dispersed on the surface of NU66. Without any sacrificial agent, the optimized 8% NU66/CIS heterojunctions still exhibited the satisfactory photocatalytic efficiency for CO 2 conversion, whose CO and CH 4 yields reached up to 11.24 μ mol g−1 h−1 and 2.92 μ mol g−1 h−1, respectively, which were 2.87 and 3.31 folds higher than that of pristine CIS. The remarkably boosted activity of NU66/CIS was originated from the high specific surface area and the formation of heterostructure between the well-dispersed NU66 and CIS, which could promote the electron transfer during CO 2 photocatalytic reduction. [ABSTRACT FROM AUTHOR]

• S-scheme Bi-BiOCl/MgIn 2 S 4 marigold microflower heterostructure. • 6 % Bi-BiOCl/MgIn 2 S 4 sample behaved the optimal photocatalytic performance for CO 2 photoreduction into CH 4. • Metal Bi acted as the bridge connecting the BiOCl and MgIn 2 S 4 to facilitate the charge transfer. Step-scheme (S-scheme) Bi-BiOCl/MgIn 2 S 4 heterostructure (BBOC/MIS) was successfully fabricated via NaBH 4 reduction and facile in-situ hydrothermal process and applied in photocatalytic CO 2 reduction. A part of BBOC ultrathin nanosheets processed by ultrasonication exfoliation was grown on the surfaces of MIS marigold microflower. Another part of BBOC and MIS exhibited as the core and shell of BBOC/MIS, respectively. The morphology, band alignment, optical and electronic characteristics of photocatalysts were comprehensively studied via diverse characterization methods. The S-scheme BBOC/MIS heterojunction possessed superior photocatalytic performance and well reusability to primarily convert CO 2 into CH 4 with high efficiency under the simulated solar light irradiation without using any sacrificial agent in water. Experimental results displayed that the 6% BBOC/MIS sample behaved the optimal photocatalytic performance in photocatalytic reduction of CO 2 , and its maximum CH 4 production rate could reach up to 4.29 μmol g−1 h−1, which was about 7.56 times as high as that of unadulterated MIS. The enhanced photocatalytic performance of BBOC/MIS could be attributed to the improved visible light response and highly-efficient separation of the photogenerated electron-hole pairs between BBOC and MIS through the S-scheme heterojunction interface. In addition, the metal Bi acted as the bridge connecting the BOC and MIS to facilitate the charge transfer, which greatly promoted the CO 2 photocatalytic reduction to CH 4. [ABSTRACT FROM AUTHOR]

• 20 % BiO 2- x/g-C 3 N 4 composites exhibited the best photocatalytic activity. • BiO 2-x narrowed the band gap and expanded the visible light range. • The separation and migration of photogenerated carriers are promoted. Photoreduction CO 2 to hydrocarbons are the sustainable and green methods to solve energy shortages and environmental pollution problems. Therefore, the development of efficient and environment-friendly photocatalysts remains a huge challenge, while coupling co-catalyst on traditional photocatalysts is a potential approach for improving photocatalytic activity. Here, a novel BiO 2-x co-catalyst coupled g-C 3 N 4 photocatalyst was prepared by a simple hydrothermal approach for the photocatalytic reduction of CO 2. The experimental results proved that BiO 2-x /g-C 3 N 4 composites played a vital part for promoting the photocatalytic capability. The 20 % BiO 2-x /g-C 3 N 4 composites exhibited the best photocatalytic capability under the simulated visible-light. A maximum yield of CO (42.29 μmol/gcat) and CH 4 (7.2 μmol/gcat) were obtained, which were 3.8 and 2.5 times that over pure g-C 3 N 4 , and its apparent quantum yield (AQY) was 1.5 % at 420 nm. According to the characterization results, the significantly increased photocatalytic activity could be ascribed to larger specific surface area, stronger visible-light absorption properties and more effective separation and transfer of photogenerated electron-hole pairs. Our finding provides a certain reference for the development and application of novel co-catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] 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. [ABSTRACT FROM AUTHOR]

• Co 2 B/CN triggered the water splitting reaction from visible to NIR regions. • "SPR effect" that noble metal featured was fabricated in the amorphous Co 2 B nanosheets. • Optimized Co 2 B/CN catalyst showed the activity for H 2 evolution outperformed Pt/CN. • Amorphous featured Co 2 B nanosheets provided massive active sites for reaction. • The promoted charge transfer and the inhibited e-/h+ recombination are available on Co 2 B/CN. Developing noble-metal-free photocatalysts to address the challenges of high recombination rate of electrons and holes and poor optical response is high desirable for water splitting. Herein, cobalt boride (Co 2 B) nanosheets with amorphous phases ordered in short-range but disordered in long-range was fabricated, and coupled with graphic carbon nitride (CN) photocatalysts in the form of B(δ−)–Co(δ+)–N(δ−) bonding states through an in-situ chemical reduction method. The optimized Co 2 B/CN nanohybrids exhibited a H 2 evolution rate of 56.86 μmol/h with the highest AQY up to 22.8 %, outperforming than that of Pt decorated CN. Theoretical calculation by DFT verify the characterization results and show that Co active sites on Co 2 B have better performance of adsorbing H atoms and desorbing hydrogen. The disordered structure of Co 2 B nanosheets contributed to water splitting performance by providing abundant active sites while metallic nature of Co 2 B facilitated electrons transfer and inhibited the recombination of electrons and holes. Moreover, theoretical calculation suggested that the high concentration of free carriers endowed Co 2 B with an resembled SPR effect, thereby increasing the light response of CN and triggering the reaction from visible-light region extended to the near-infrared region up to 800 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] 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-1h−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. [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]

• The B-TiO 2 /CuInS 2 Z-scheme heterojunction with visible light response was prepared. • B-TiO 2 /CuInS 2 could convert CO 2 into CO and CH 4 with the yields 21.39 and 4.83 µmol g−1 h−1. • Both boron doping and CuInS 2 sensitization can effectively improve the utilization of visible light. • The synergistic effect of B doping Z-scheme heterojunction optimized the separation and migration of photogenerated carriers. Photocatalytic reduction CO 2 into valuable solar fuels is a promising strategy to alleviate the greenhouse effect and the energy crisis on Earth. In this work, a B-TiO 2 /CuInS 2 photocatalyst has been synthesized through a simple hydrothermal-calcination method for efficient reducing CO 2 into CO and CH 4. Boron doping and sensitization of CuInS 2 ensure the excellent visible light response capacity of the composite catalyst. The synergistic effect between oxygen vacancies and Z-scheme heterojunction also endow the photocatalyst with strong carrier separation capability. Consequently, the optimized B-TO/CIS-2.5 sample exhibited the best CO (21.39 μmol g−1 h−1) and CH 4 (4.83 μmol g−1 h−1) production, approximately 9 and 14 times higher than that of TO and B-TO, respectively. This study provides a reliable approach for developing photocatalysts with boosted CO 2 reduction activity and high stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CoAl-LDH/CGCNN-Metal NPs ternary photocatalysts with visible light response were prepared. • CoAl-LDH/CGCNN-Au NPs could convert CO 2 into CO, CH 4 , C 2 H 4 , and C 2 H 6 with the yields of 5.93, 17.68, 1.25 and 2.15 µmol g−1h−1. • The synergistic effect between S-scheme heterojunction and metal NPs could improve the light absorption capacity and the separation of photogenerated electron-hole pairs. Converting CO 2 into high-value products by photocatalysis can alleviate the global greenhouse effect and energy crisis. In this work, CoAl-LDH/CGCNN-Metal NPs (AC-M) ternary photocatalysts were synthesized by calcination, hydrothermal, and ultrasonic self-assembly methods. In pure water, the best sample AC-Au could convert CO 2 into CO, CH 4 , C 2 H 4 , and C 2 H 6 with the yields of 5.93, 17.68, 1.25 and 2.15 µmol g−1h−1, respectively, and exhibited good stability within 5 cycles (30 h). The synergistic effect between S-scheme heterojunction and metal NPs could broaden the composite's photo-response range and promote the separation of photogenerated carriers. Furthermore, the metal NPs could also serve as the electron-rich centers to improve the chemisorption of CO 2 and convert it into C 1 and C 2 products under visible light. This work can provide meaningful guidance for studying the efficient reduction of CO 2 to C 1 and C 2 products by S-scheme heterojunction/metal NPs ternary photocatalytic system. [ABSTRACT FROM AUTHOR]

A series of flaked Mg/g-C 3 N 4 catalysts were synthesized via an in-situ hydrothermal deposition method and measured their photocatalytic activity for CO 2 reduction. The characterization results indicated that the obtained Mg/pCN catalysts had high surface area and massive active sites for CO 2 absorption. The introduction of Mg species had a positive effect to extend the spectral response property and increased the separation rate of photogenerated electron-holes pairs. Mg-doped g-C 3 N 4 catalysts showed much higher photocatalytic performance than pCN. The maximum CH 4 and CO yields of 17.09 and 4.13 μmol/g-cat, respectively, had been obtained for CO 2 reduction after 6 h reaction. [ABSTRACT FROM AUTHOR]

Using photocatalysis to reduce carbon dioxide to hydrocarbons is a promising way to mitigate the greenhouse effect and the energy crisis simultaneously. However, conventional photocatalytic technology is inefficient due to its low utilization of the full spectrum. Photothermal effect can combine the advantages of photocatalysis and thermocatalysis to overcome inherent defects and elevate the catalytic activity by one order of magnitude compared with single photocatalysis. This review focuses on the generation and promotion mechanism of photothermal effect on photocatalytic reduction of CO 2. In addition, the developments of several practical catalysts with photothermal effect are presented, including non-precious metal-based catalysts, precious metal-based catalysts, and oxygen vacancy-riched catalysts. Eventually, the prospects and challenges of the applications of the photothermal effect are in consideration, which is instructive for the discovery of non-expensive and efficient photothermal catalysts for photocatalytic reduction of CO 2. [Display omitted] • The photothermal effect is particularly beneficial to CO 2 photocatalytic process. • The origin of photothermal effect is explained. • The promoting mechanism of photothermal effect on CO 2 reduction is summarized. • Several excellent photothermal catalysts for CO 2 reduction are presented. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct Z-scheme FeWO 4 /NiAl-LDH heterostructure was fabricated. • The 10%FWLDH possessed the optimal photocatalytic CO yield. • The effective separation of the light-induced e-/h+ pairs was available on FWLDH composite. In recent years, photocatalytic reduction of carbon dioxide technology has been considered as an effective approach to moderate the energy crisis. In order to achieve efficient reduction of CO 2 , direct Z-scheme heterostructure composed of NiAl-LDH flower-like sphere and FeWO 4 nanoflakes (FWLDH) were obtained through a facile hydrothermal strategy. The prepared FWLDH photocatalysts revealed outstanding performance for CO 2 photoreduction to CO under the irradiation of visible light. The 10%FWLDH possessed the optimal photocatalytic CO yield (5 μmol· g−1·h−1), reaching up to 2.4 folds higher than that of pristine LDH (2.1 μmol·g−1·h−1). In addition, the CO selectivity was more than 93% over hydrogen evolution from the side reaction of water reduction. Finally, EPR characterization indicated that the electron transfer mechanism of FWLDH catalyst conformed to the Z-scheme pattern. The effective separation of the light-induced electron-hole pairs and the enhancement of the photoelectron reduction ability at the NiAl-LDH conduction band were the reasons for the prominent improvement of the photocatalytic performance of NiAl-LDH. This research could provide a novel perspective for designing photocatalyst with high efficiency for CO 2 photoreduction. [ABSTRACT FROM AUTHOR]

• Cs x WO 3 /g-C 3 N 4 catalyst shows full spectrum CO 2 photoreduction activity. • Improved charge separation efficiency is realized on Cs x WO 3 /g-C 3 N 4 catalyst. • LSPR effect is responsible for the NIR photocatalytic activity. Full spectrum-driven Cs x WO 3 /g-C 3 N 4 catalyst was successfully synthesized by the combination of solvothermal and ultrasonication methods and used in CO 2 photocatalytic reduction. The experimental results suggested that 20 wt% Cs x WO 3 /g-C 3 N 4 catalyst possessed the best yield of CH 4 under NIR and full spectrum light irradiation, which were 1.72 and 6.79 μmol·g−1·h−1, respectively. This outstanding photocatalytic activity could be attributed to the localized surface plasmonic resonance effect and the formation of heterojunction structure, which led to the improved charge separation efficiency, good light-harvesting ability and broadened light response. [ABSTRACT FROM AUTHOR]

• 30% In 2 S 3 /NiAl-LDH exhibited the best photocatalytic performance. • Efficient separation of photogenerated electron-hole pairs. • A perfect band matching and efficient internal charge transfer within the n-n junction. A novel ball-flower In 2 S 3 /NiAl-LDH heterojunction photocatalyst was synthesized via a simple one-step hydrothermal approach for the first time and applied for CO 2 photocatalytic reduction. The In 2 S 3 /LDH composites exhibited excellent photocatalytic performance and stability in CO 2 photoreduction in water under the irradiation of simulated solar light. Experimental results indicated that the 30% In 2 S 3 /NiAl-LDH heterojunction photocatalyst exhibited the best photocatalytic performance. And the maximum CH 4 yields of 36.1 μmol/(h·g-cat) under 7 h visible light irradiation was about 2.5 and 3.5 times of unadulterated LDH and In 2 S 3. The enhanced photocatalytic performance of 30% In 2 S 3 /NiAl-LDH catalyst was due to the highly-efficient separation of photogenerated electron-hole pairs, its larger specific surface area and stronger visible-light absorption capacity. [ABSTRACT FROM AUTHOR]