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The preparation of heterojunction photocatalysts with staggered energy band structures and proper interfacial contacts is an effective way to improve CO 2 conversion. This study adopted a simple hydrothermal method to form Cu 2 O on the surface of BiOBr, and s scheme BiOBr/Cu 2 O heterojunctions with close contacts were constructed. The rate of CO 2 reduction over the catalyst was tested in a gas-solid reactor simulating sunlight. The results show that the BiOBr/Cu 2 O composite moderately yields CH 4 with an efficiency of 22.78 μmol g−1h−1 for conversion from CO 2 to CH 4 in visible light, while pure BiOBr yields only CO. In addition, Transient photocurrent response, Electrochemical impedance spectroscopy, and Photoluminescence measurements demonstrated that the BiOBr/Cu 2 O had a strong photogenerated carrier transfer and separation and high photo-availability, while key intermediates favoring CH 4 yield were found by in situ IR. Finally, the possible photocatalytic mechanism was explored based on the energy band structures of BiOBr and Cu 2 O in the characterization. [Display omitted] • BiOBr/Cu 2 O with S-scheme heterostructure was synthesized using a simple approach. • Cu 2 O as an active site adjusting the photoreduction of CO 2 to CH 4. • Possible photocatalytic reaction mechanism for CO 2 reduction by 20%-BiOBr/Cu 2 O proposed. [ABSTRACT FROM AUTHOR]

The electron density on the catalyst surface has a great influence on the multi-electron transport process of photocatalytic reduction of CO 2. In this work, hierarchical Cu 2 O/Ni-MOF composite photocatalyst with local surface plasmon resonance (SPR) properties was prepared by simple hydrothermal and water bath methods. Through DRS, XPS and AES tests found that the SPR of Cu0 expanded the light absorption, provided hot electrons for the reaction system, and greatly improved the photocatalytic activity in coordination with the hierarchical structure and heterostructure. In the absence of sacrificial agent, the CO yield of 30%-Cu 2 O/Ni-MOF was 4.1 times of Cu 2 O (5.32 μmol/g) and 11.1 times of Ni-MOF (1.95 μmol/g), respectively. Then, the possible photocatalytic reaction path was simply speculated based on in-situ FT-IR. In conclusion, the hierarchical structure, heterostructure and SPR effect accelerate the kinetics of Cu 2 O/Ni-MOF photocatalytic reaction, thus improving its photocatalytic activity. [Display omitted] • The 3D hierarchical heterogeneous Cu 2 O/Ni-MOF with SPR effect was synthesized by a simple strategy. • Cu 2 O was uniformly dispersed due to heterogeneous nucleation sites provided by 3D Ni-MOF. • SPR effect of Cu0 provides additional electrons for the reaction system to participate in the CO 2 reaction. [ABSTRACT FROM AUTHOR]

The special S-scheme heterostructure of 40%-ZIS/Cu 2 S possesses a strong redox capacity and improves the light trapping ability, increases the active surface area and reaction sites for charge transfer and separation, and greatly improves the CO 2 conversion efficiency. As shown, the CB and VB of ZIS are −1.52 eV and +1.14 eV, respectively, and those of Cu 2 S are −0.15 eV and +1.24 eV, respectively. According to the conduction band/valence band theory, the catalysts are excited to generate sunlight-driven electron-hole pairs, which are distributed on their respective CBs and VBs and waiting to participate in the reaction. Due to the special transfer path of the S-scheme heterojunction, the electrons on the CB of Cu 2 S were transferred to the VB of ZIS. This increases the active surface area and reaction sites for charge transfer and separation and improves the CO 2 conversion efficiency. ZIS with more electrons can more efficiently reduce CO 2 moderately to CO. This special electron transfer method with controllable in-built electric field strength and stable interfacial carrier transport process ensures the maximisation of photoelectron-hole separation efficiency. [Display omitted] • ZIS/Cu 2 S with S-scheme heterostructure was synthesized using a simple approach. • Snowflake-like two-dimensional structures as carriers mainly providing active sites for photocatalytic reduction of CO 2. • Possible photocatalytic reaction mechanism for CO 2 reduction by 40 %-ZIS/Cu 2 S proposed. Designing S-scheme heterojunctions has become a powerful strategy to enhance photocatalytic activity and improve the localization of catalyst surface charge. Therefore, more and more research has been devoted to S-scheme heterojunctions. In this work, we employed a simple two-step hydrothermal method to fabricate S-scheme ZnIn 2 S 4 /Cu 2 S (ZIS/Cu 2 S) heterojunctions. The results show that the composites exhibit good performance in the photoreduction of CO 2 to CO and CH 4. Especially, at 40 %-ZIS/Cu 2 S, the release rates of CO and CH 4 were 13.35 μmol g−1 and 34.81 μmol g−1 under the condition of a 4 h reaction, and the selectivity of CH 4 reached 80 %. In addition, the in situ FTIR test revealed that the catalyst promoted the formation of the key intermediates COOH* and CH 3 O* under the effect of light interaction, which was favorable to the photoreduction of CO 2. This indicates that the electron transfer path of S-type not only promotes the separation of carriers for conversion but also has a strong redox ability to selectively convert CO 2 to CH 4 , which provides some thoughts for the design of S-scheme heterojunction photocatalysts. This provides some thoughts for the design of S-scheme heterojunction photocatalysts. [ABSTRACT FROM AUTHOR]

Designing S-scheme heterojunctions is an effective method to improve the charge localization on the surface of photocatalysts. Their effective charge transport routes can be enhanced with the help of interfacial noble metal nanoparticles. Herein, an Ag/CuO@ZnIn 2 S 4 plasma S-scheme heterojunction with heterogeneous interfacial covalent bonds was successfully designed. The 15% Ag/CuO@ZnIn 2 S 4 has promising photocatalytic performance and stability with the highest CO and CH 4 yields of 6.9 and 54.4 µmol g−1 h−1 and CH 4 selectivity of 92.8%. It is evidenced that the photogenerated charge can be efficiently separated and transported due to the influence of both the S-scheme electron migration mode and the Cu-S covalent bond. The process is further accelerated by using precious metals as cocatalysts, which can then selectively convert CO 2 into CH 4. This research is expected to provide helpful information for engineering S-scheme heterojunction photocatalysts and investigating their charge transfer kinetics. [Display omitted] • Design of a S-scheme heterojunction to promote the separation of carriers. • Built the Cu-S bonds to accelerate the transfer of charges. • Utilizing the LSPR effect to generate hot electrons and enhance light absorption. • The Ag/CuO@ZnIn 2 S 4 photocatalysts can selectively reduce CO 2 to CH 4. [ABSTRACT FROM AUTHOR]

• SnS 2 atomic layer with Pt 3 Co nanoclusters have been successfully prepared. • Nanoclusters can enrich electrons, reduce barriers, and promote proton transport. • The photoelectric properties of catalysts is significantly enhanced. • The CO 2 photoreduction efficiency of the SnS 2 /Pt 3 Co catalyst is markedly improved. Poor capability of charge-holes separation and slower surface CO 2 reaction kinetics hinder photocatalytic performance. Here, SnS 2 atomic layer with Pt 3 Co alloy nanoclusters have been successfully prepared. Nanoclusters could be used as highly catalytic active sites, which not only facilitates the carrier separation and transport kinetics, but enriches electrons lowered the reaction barrier. As expected, the CO evolution rate of the champion SnS 2 /Pt 3 Co catalyst was 13.6 times higher than that of the original SnS 2 catalyst under white light irradiation. In-situ DRIFTS identifies key intermediate in the photoreduction process. In-situ XPS and DFT calculation further verifies the electron transport direction and charge density distribution at the SnS 2 /Pt 3 Co interface. Our work uncovers the role of nanoclusters in carrier separation and transport as well as proton transport, opening new chances for obtaining efficient photoreduction CO 2 property. [ABSTRACT FROM AUTHOR]

The interfacial regulation strategy between semiconductors can effectively promote the separation efficiency of photogenerated carriers and enhance photocatalytic activity under the synergistic effect. Herein, AgInS 2 QDs-MoS 2 /GO (AIS-MS/GO) composites were prepared by interfacial coupling of AgInS 2 QDs (AIS), hierarchical MoS 2 and ultrathin GO. Ultrathin GO successfully solved the agglomeration problem of AIS and hierarchical MoS 2. Moreover, the photogenerated carriers were effectively separated and transferred under the synergistic effect of the AIS-MS heterojunction and ultrathin GO, thus promoting tetracycline (TC) degradation and CO 2 reduction performance. The degradation rate of tetracycline (TC) reached 96.5 %, and the yields of CO and CH 4 in the CO 2 reduction products reached 52.6 and 28.5 μmol g–1, respectively, when using the optimized photocatalyst. In-situ FTIR analysis indicated that TC is gradually degraded by small molecules on the composite surface, and has excellent dissociation ability of water molecules during the CO 2 reduction process. This work provides a new vision for the rational design of heterojunction-based photocatalysts using the interfacial regulation strategy for enhancing interfacial charge separation and photocatalytic performance. [Display omitted] • AIS-MS/GO composites were prepared via the interfacial regulation strategy. • The photogenerated carriers were effectively separated and transferred under synergistic and interfacial effects. • The aggregation problem of AIS and hierarchical MoS 2 was effectively solved. • AIS-MS/GO composites achieve a 96.5 % TC degradation rate and 35.1 % selectivity for CH 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • The UCN@ZIS/SWNTs composite with different V Zn concentrations was constructed for photocatalytic CO 2 reduction. • The UCN was acidified to regulate the surface-active site for CO 2 activation and H 2 O dissociation. • The SWNTs further improves the separation efficiency of photogenerated electron-hole pairs by providing charge transfer channels. • The UCN@rZIS/SWNTs composite displays excellent photocatalytic performance and CH 4 selectivity. Zinc vacancy (V Zn) concentrations were successfully regulated on the hierarchical flower spherical ZnIn 2 S 4 (ZIS) by controlling the hydrothermal temperature. The photo-electrochemical experiments indicated that the carrier separation efficiency of ultrathin-g-C 3 N 4 @ZIS/SWNTs (UCN@ZIS/SWNTs) composite with different V Zn concentrations (poor-V Zn ZIS (pZIS) and rich-V Zn ZIS (rZIS)) had an efficient improvement because of the construction of UCN@ZIS heterojunction and the multiple channels for charge transfer provided by SWNTs. In-situ FTIR results indicate that the presence of V Zn and the enriched surface-active site on UCN contributes to CO 2 activation and H 2 O dissociation. Additionally, the yield of CO and CH 4 over UCN@rZIS/SWNTs composite reached 33.7 µmol g−1 and 39.8 µmol g−1, respectively, and the selectivity of CH 4 reached 54.1 % under the synergistic effect of V Zn , the surface-active site of UCN and charge-transfer channels. This work established an ideal defect model for enhancing CO 2 photocatalytic reduction performance and product selectivity, which may provide a new way to improve photocatalytic efficiency and a better understanding of the photocatalytic reaction mechanisms. [ABSTRACT FROM AUTHOR]

The 15D/R achieve near 99.6% selectivity at the gas–solid interface for UV–Vis light-driven CO 2 reduction to CO, with a rate of 42.41 μmol·g−1. The high conductivity of RGO and the strong interaction with DUT-67 enhanced the electron coupling effect, which was conducive to the separation of carriers. The rapid formation of HCOO− and the rapid desorption of CO are responsible for the high CO yield and selectivity. [Display omitted] • The DUT-67/RGO aerogel are first prepared for CO 2 reduction in a gas–solid system. • 15D/R achieve near 99.6% selectivity for UV–Vis light-driven CO 2 reduction to CO. • Separation efficiency of carriers is the main reason for the improvement of CO yield. Herein, DUT-67/RGO aerogel photocatalysts with three-dimensional (3D) macroscopic morphology were first prepared by a facile hydrothermal and freeze-drying process. It was observed that DUT-67 endowed aerogels with strong adsorption/activation capacity for CO 2 molecules. Besides, RGO not only dispersed DUT-67 as a macroscopic carrier, but also improved the utilization rate of light energy. The high conductivity of RGO and the strong interaction with DUT-67 enhanced the electron coupling effect, which was conducive to the separation of carriers. 15D/R achieved near 99.6% selectivity at the gas–solid interface for UV–Vis light-driven CO 2 reduction to CO, with a rate of 42.41 μmol·g−1. The adsorption behavior of products at the interface and formation process of intermediates were monitored based on CO-TPD and in situ Fourier transform infrared spectra. The extremely high selectivity for CO came from the weak adsorption of CO on the surface of 15D/R and formation of CH 4 required more complex intermediates. [ABSTRACT FROM AUTHOR]

rGO modified g-C 3 N 4 /R-CeO 2 Multi-interface contact S-scheme heterojunction photocatalyst maximizes the transfer efficiency of photogenerated electron and the CO 2 adsorption ability, thus greatly improving the CO 2 photoreduction performance. [Display omitted] • 2D-1D-2D g-C 3 N 4 /R-CeO 2 /rGO photocatalyst has been prepared for CO 2 photoreduction. • 2D-1D-2D multi-interface contact structure is of help for carrier transfer process. • π-π conjugation effect and Ce4+/Ce3+ transformation facilitate electron transmission. • In-situ FTIR and 13C isotope tracer tests analysis the CO 2 photoreduction mechanism. Construction of multi-interface contact step-scheme (S-scheme) photocatalyst is a promising pathway to achieve high-electron transfer efficiency for photocatalytic CO 2 reduction. In this paper, g-C 3 N 4 nanosheets were selected as the main photocatalyst, rod-like CeO 2 (R-CeO 2) with unique Ce4+→Ce3+ conversion property and rGO were loaded on the g-C 3 N 4 surface to construct 2D-1D-2D sandwich photocatalyst. The yields of CO and CH 4 were about 63.18 and 32.67 μmol/g after 4 h when the rGO/R-CeO 2 /g-C 3 N 4 was used as catalyst, which were about 4 and 6 times higher than that of pure CN, respectively. Cyclic experiments proved that the composite had excellent photocatalytic and material stability. Photoelectrochemical tests showed that the construction of S-scheme electron transfer model and the introduction of rGO can great enhance the electron transmission and separation of photogenerated electron-hole pairs. CO 2 adsorption test identified that the loading of R-CeO 2 and rGO obviously enhanced the CO 2 adsorption ability of pure g-C 3 N 4. Density functional theory (DFT) calculations used to analyze the electron transfer path and the formation of the build-in electric field at the semiconductor interface. In-situ FTIR and 13CO 2 element-tracer detection carried out to research the process of CO 2 photoreduction. A possible multi-interface contact S-scheme electron transfer mechanism for enhanced CO 2 photoreduction activity has been discussed. [ABSTRACT FROM AUTHOR]

• LSPR effect enhanced Z-scheme ZnO/Au/g-C 3 N 4 micro needles film (3-ZAC) has been prepared for the photoreduction of CO 2 into CO under UV–vis light irradiation. • Au NPs at the interface of ZnO/g-C 3 N 4 not only act as the electron-transfer bridge, but also as LSPR excited source to speed up the separation of electron-hole pairs photogenerated in the semiconductors. • DFT calculation and FDTD simulation methods has been used to prove the transfer processes of photogenerated electron. The photoproduction of CO from the photocatalytic CO 2 reduction process has been evidenced from 13C isotope tracer tests. • This work demonstrates the importance of the build-in electric field formed at g-C 3 N 4 /ZnO interface and local electromagnetic field of Au NPs for the photoreduction process, providing an inspiring concept for future advancement in this area. Local Surface Plasma Resonance (LSPR) effect enhanced Z-scheme ZnO/Au/g-C 3 N 4 micro-needles film (3-ZAC) has been prepared for the photoreduction of CO 2 into CO under UV–vis light irradiation. Photoreduction experiments show that 3-ZAC has the excellent photocatalytic performance and reusability. The CO production can be achieved 689.7 μmol/m2 after 8 h reaction time, which is 4.5 higher than that of the pure ZnO film. 13C isotope test shows that CO is produced from CO 2 by photoreduction. DFT calculations confirm that build-in electric field formed at g-C 3 N 4 /ZnO interface effectively promoted the electron transfer efficiency in Z-scheme interface. FDTD simulations prove that Au NPs not only act as electron-transfer bridge, but also as LSPR excited source to speed up the separation of electron-hole pairs. In-situ FTIR technique was used to investigate the CO 2 photoreduction process. The above characteristics together maximize the electron transfer efficiency, which causes the material has enhanced photocatalytic performance. [ABSTRACT FROM AUTHOR]

Energy band location and charge separation mechanism of SnS 2 /Au/g-C 3 N 4 system during photoreduction under sunlight irradiation. • The catalyst is prepared by facile thermal treatment and chemical deposition method. • The SnS 2 /Au/g-C 3 N 4 composites show a superior optical adsorption under UV–vis light. • The Au nanoparticle and the Z-type scheme jointly improve the separation of carrier. • The SnS 2 /3ml-Au/g-C 3 N 4 displays the best photoreduction activity and durability. The use of semiconductor photocatalytic reduction technology has higher efficiency and lower energy consumption for CO 2 reduction, but its existence of some mismatched energy band positions and relatively slow charge-hole separation greatly limits its practical application. In this paper, a SnS 2 /Au/g-C 3 N 4 embedded structure model with carbon and nitrogen hybridization is proposed to gain an in-depth understanding of the role of hybridization and precious metal modification in photocatalysis. Carriers were investigated from the perspective of kinetics through photocurrent, LSV curve, and FL spectroscopy. After modification of Au nanoparticles, the photo-excited electrons showed a slower decay process, indicating that the separation of carriers was enhanced, which was further confirmed by impedance and PL spectroscopy. SEM, AFM and TEM analysis confirmed that the 2D face-to-face SnS 2 /Au/g-C 3 N 4 embedded structure was successfully prepared and the Au nanoparticles were evenly distributed. Au nanoparticles not only act as a bridge for electron transport in 2D semiconductor materials to accelerate electron transport, but generate more excited electrons by themselves under the radiation of sunlight, which effectively improves the separation efficiency of electron-hole pairs and enhances the photocatalyst activity. DFT calculations show that the Z-type mechanism and the intercalated energy level of the SnS 2 /Au/g-C 3 N 4 embedded structure expand the light absorption and improve the carrier separation efficiency. As expected, the photocatalyst activity with CO and CH 4 the evolution rate of up 93.81 µmol·g−1·h−1 and 74.98 µmol·g−1·h−1 under visible light irradiation, respectively, while the photocatalytic activity is negligible loss after 30 h photoreduction. This work reveals the role of embedded structure and precious metal modification in the separation and transmission of electron-hole, opening up new perspective for achieving high-efficiency solar CO 2 reduction performance. [ABSTRACT FROM AUTHOR]