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Interfacial coupling of two-dimensional semiconductor materials is an effective option to construct heterojunction for enhancing photocatalytic activity. In this paper, a g-C3N4/SnS2 type-II heterojunction was constructed using an electrostatic self-assembly method. The g-C3N4/SnS2-60 showed a CO yield of 2.54 µmol g−1, which was 2.96 and 22.1 times that of the g-C3N4 and SnS2 nanosheets, respectively. The efficient carrier separation efficiency of the composites is mainly derived from the type-II heterojunction structure and the interfacial synergy of the two-dimensional (2D) structure. In addition, the high light response intensity of the g-C3N4/SnS2 composite also had excellent electron excitation and transfer ability. This work provides a new vision for the rational design of 2D heterojunction-based photocatalysts for the study of CO2 reduction. [ABSTRACT FROM AUTHOR]

Improved photogenerated carrier separation efficiency is of importance for improving photocatalytic activity. Herein, the photocatalytic CO2 reduction of a 3D/0D ZnIn2S4/NiS ohmic‐junction photocatalyst under simulated sunlight is studied. The ZnIn2S4–2%NiS sample has the best excellent photoreduction CO2 performance facilitated by triethanolamine (TEOA) reagents, the ZnIn2S4–2%NiS sample with a CO yield of 12.63 μmol g−1 h−1, which is two times that for pure ZnIn2S4 (6.37 μmol g−1 h−1). It is demonstrated that NiS nanoparticles not only improve the efficiency of electron generation and charge separation by constructing a tight contact ohmic‐junction, but also act as a cocatalyst to extend the photoreaction range and lower the reaction barrier, which effectively accelerates the photocatalytic reduction reaction. Additionally, the 3D structure of ZnIn2S4 has an excellent specific surface area that facilitates the dispersion of NiS. The generation, separation, and migration of photogenerated electron holes are studied from the kinetics perspective through transient photocurrent response, linear sweep voltammetry curve and photoluminescence spectroscopy. In situ Fourier transform infrared spectroscopy is applied to study the CO2 photoreduction process. Herein, the important role of cocatalyst and ohmic‐junction in improving photocatalytic activity is revealed and a new idea for the construction of efficient photocatalysts is provided. [ABSTRACT FROM AUTHOR]

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]

Highlights • CdTe nanoparticles modifying leafy CdS on N-rGO photocatalysts were prepared. • CdTe/CdS/N-rGO exhibited extensively enhanced photocatalytic activity and stability. • Homologous heterojunctions, solar spectrum response promote degradation of 2,4-DCP. • The mechanism for photodegrading 2,4-DCP was proposed. Abstract CdTe nanoparticles modifying leafy CdS homologous semiconductor heterojunctions on nitrogen-doped reduced graphene oxide with solar full spectrum response is synthesized by a simple hydrothermal method and solvothermal method, and investigate their photocatalystic degradation of 2,4-dichlorophenol (2,4-DCP). The obtained CdTe/CdS/N-rGO composites show stronger intensity of photocurrent and longer lifetime of photon-generated carrier than CdTe/CdS and raw CdS, especially by which 70% 50 mg/L 2,4-DCP could be decomposed under visible light irradiation within 6 h. These result from those CdTe nanoparticles have good optical absorption coefficient to effectively absorb more photons and form electronic traps on its surface atoms, and construct homologous semiconductor heterojunctions between CdTe and leafy CdS to change movement pathway of photogenerated charge carriers, further prolonging the lifetime of electrons and holes, and loading nitrogen-doped reduced graphene oxide (N-rGO) could not contribute to electrons transfer, but also provide more active sites to improve the whole photocatalytic ability. These are further confirmed by those that high-resolution transmission electron microscopy (HRTEM) shows that crystal lattices of CdTe and CdS are staggered and the diffuse reflectance spectra (DRS) demonstrated absorption edge of CdTe/CdS/N-rGO get tremendous improved, even ternary composites could response in solar full spectrum. The new approach may provide some inspirations for constructing homologous heterojunctions structure on materials as support with efficient photocatalytic performance. Graphical abstract Image, graphical abstract A proposed photocatalytic mechanism for photodegrading 2,4-DCP. [ABSTRACT FROM AUTHOR]

In this work, efficient NiO nanoparticles/TiO 2 nanorods p-n heterojunction structure photocatalyst is constructed by reasonable design of two-step calcination technology and examined for hydrogen production activity from methanol-water mixture. In the NiO/TiO 2 heterojunction structure small NiO nanoparticles are evenly distributed on the surface of TiO 2 and tightly connected together with TiO 2 , as it was determined by microscope characterization techniques, which conducive to the interface transport of photogenerated carriers. The novelty of this paper is the detailed characterization of NiO/TiO 2 photocatalysts by electrochemical technics as Transient photocurrent response, Mott-Schottky plots, linear sweep voltammograms and Electrochemical impedance spectroscopy and their correlation with photoactivity. The rationally designed NiO/TiO 2 p-n heterojunction promotes the transfer of photogenerated electrons and inhibits carrier recombination. The highest hydrogen production was exhibited in the presence of the 2-NiO/TiO 2 composite during 3 h of UV irradiation (701 μmol/g cat.), which exceeded the activity of pure TiO 2 by more than 1.3 times. The loss of photocatalytic hydrogen yield is negligible after repeating cycle reactions. Finally, a possible p-n heterojunction photocatalytic reduction mechanism has been discussed and apparent quantum yield was calculated. [Display omitted] • NiO nanoparticles/TiO 2 nanorods p-n heterojunction photocatalyst was constructed. • NiO/TiO 2 exhibited higher photoactivity for H 2 production in comparison with TiO 2. • Correlation of photoelectrochemical measurements with photoactivity of NiO/TiO 2. • NiO/TiO 2 p-n heterojunction inhibits carrier recombination. • Apparent Quantum Yields were calculated. [ABSTRACT FROM AUTHOR]

Wide-light absorption performance and efficient carrier separation ability are the necessary conditions for excellent photocatalytic materials. In this research, g-C 3 N 4 QDs (CN QDs) and Au nano-particles (NPs) co-modified CeO 2 /Fe 3 O 4 micro-flowers (MFs) photocatalyst (CACeF) has been prepared. CO 2 photoreduction experiments showed that the composite had obviously enhanced photoreduction activity and photocatalytic stability. The yields of CO and CH 4 over it as catalyst in 4 h is about 5 and 8 times greater than that of pure CeO 2. Photoelectrochemical tests showed that the heterojunction between CN QDs and Au NPs can greatly improve the carrier separation ability and the light-utilization efficiency of photocatalysts. Besides, the excellent electronic transmission performance of Au NPs provided a specific channel for the electron transmission, and the strong local surface plasmon resonance (LSPR) of Au NPs resulted in a lot of hot-electrons can directly take part in the CO 2 photoreduction. The synergistic effect between CN QDs and Au NPs can further enhance the photocatalytic activity of the photocatalyst. Fe 3 O 4 QDs can ensure the effective recovery and reuse of the composite without affecting the photocatalytic performance of composite. Finally, a potential photoreduction mechanism of CN QDs and Au NPs co-modified CeO 2 /Fe 3 O 4 MFs photocatalyst were discussed in total. [Display omitted] • g-C3N4 QDs/Au NPs/CeO2/Fe3O4 has been prepared for the CO2 photoreduction. • Light-absorption performance of photocatalyst has been greatly enhanced. • Au efficiently speeds up the electrons' generation efficiency in semiconductors. • Synergistic effect of CN QDs/Au NPs enhanced the photoreduction performance. • Fe3O4 QDs can ensure the recovery without affecting the photocatalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dual-plasma enhanced g-C 3 N 4 /Pd/MoO 3-x heterojunction was fabricated for high-selectivity photocatalytic CO 2 reduction. • The g-C 3 N 4 /Pd/MoO 3-x composites revealed excellent near-infrared absorption ability. • The carrier separation efficiency was effectively improved under the synergistic effect of MoO 3-x and Pd nanosheets. • The g-C 3 N 4 /Pd/MoO 3-x S-scheme heterojunction displayed high photocatalytic performance and CO selectivity. • The S-scheme charge transfer mechanism was proposed based on UPS and ESR results. The localized surface plasmon resonance (LSPR) effect has shown significant progress in enhancing the efficiency of light absorption and separating photogenerated carriers. Herein, the dual-plasma enhanced 2D/2D/2D g-C 3 N 4 /Pd/MoO 3-x (CPM) S-scheme heterojunction photocatalysts were synthesized using the method of hydrothermal and electrostatic self-assembly for high-selectivity photocatalytic reduction of CO 2 to produce CO. The dual LSPR effect of MoO 3-x and ultrathin Pd nanosheets synergistically broadened the optical response range of the CPM composites and successfully improved the photocatalytic activity and near-infrared (NIR) performance. The optimized CPM-30 photocatalysts exhibited CO yields of 18.55 μmol g−1 with a selectivity of 96.3%. In addition, the CO yield reached 3.92 μmol g−1 after 4 h of NIR light photoirradiation. The electron spin resonance (ESR) and ultraviolet photoelectron spectroscopy (UPS) tests showed that the S-scheme heterojunctions were constructed by coupling g-C 3 N 4 /Pd nanosheets and MoO 3-x. This work will provide a reference for improving product selectivity through the design of two-dimensional composites and the utilization of plasma materials. [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]

S-scheme heterojunction of In 2 O 3 /H 1.5 CN/2Au was prepared by hydrothermal, acidizing and calcination methods. The two-dimensional thin layer H 1.5 CN avoided the aggregation of In 2 O 3 and completed the S-scheme charge transfer with In 2 O 3. Moreover, Au not only enhanced the visible light absorption capacity of composites but also provided more active sites for CO 2 reduction. [Display omitted] • S-scheme heterojunction of In 2 O 3 /H 1.5 CN/2Au achieve CO 2 photocatalytic conversion to CO and CH 4. • The enhanced photocatalytic activity results from effective interfacial charge migration and separation and increased active sites. • The LSPR effect of Au improves the utilization of visible light. The construction of S-scheme heterojunction is of great significance for the photocatalytic reduction of CO 2. Here, we prepared two-dimensional (2D) ultra-thin g-C 3 N 4 by acidifying the carbon nitride precursor, and used In 2 O 3 to construct a S-scheme heterojunction with 2D g-C 3 N 4 , and finally In 2 O 3 /H 1.5 CN was modified with Au nanoparticles. The physicochemical properties of the prepared materials were studied by SEM/TEM, XPS, DRS, PL and photochemical test. Meantime, the S-scheme charge transfer mechanism was demonstrated by UPS and ESR. As a result, on the one hand, S-scheme heterojunction accelerated the transfer of electrons on the CB of In 2 O 3 to the VB of g-C 3 N 4 , avoided the recombination of photon-generated carrier. On the other hand, Au, as an effective cocatalyst, promoted photoinduced electron transfer and provided more active sites for CO 2 reduction and the local surface plasmon resonance phenomenon caused by Au NPs enhanced the visible light absorption capacity of the composite material. Moreover, 2D thin layer of g-C 3 N 4 played a carrier effect to disperse In 2 O 3 cube. Therefore, In 2 O 3 /H 1.5 CN/2Au had stable CO 2 reduction products, and the yields of CO/CH 4 reached 141.24/77.05 μmol/g. [ABSTRACT FROM AUTHOR]

The 3D hierarchical structure of CdS/Ni-MOF inhibits the agglomeration of CdS, improve light harvesting, increase active surface area, reaction sites, promote charge transfer and separation, which greatly improves the efficiency of CO 2 conversion. However, when the CdS is overloaded and its hierarchical structure is destroyed, the heterostructure plays a major role in improving the performance. Based on the above results, we propose the preliminary mechanism of 20%-CdS/Ni-MOF photocatalytic reduction of CO 2. Firstly, under UV–Vis illumination, Ni-MOF and CdS are excited to produce electrons (e−) and holes (h+). Then, because of the tight interface contact, the e- excited by Ni-MOF could be transferred to CdS with more positive CB, and CdS as the active site could reduce CO 2 to CO more effectively. At the same time, the h+ in the VB of Ni-MOF and CdS participate in the oxidation reaction to produce O 2 and H 2 O 2 , which achieving the elimination of holes. Such charge separation and transfer of the electron-hole pairs facilitate enhanced photocatalytic activity. [Display omitted] • The 3D hierarchical heterostructure was synthesized by a simple strategy. • 20%-CdS/Ni-MOF showed excellent performance in the vapor–solid reaction system. • The hierarchical structure and heterostructure of CdS/Ni-MOF play a synergistic role. Fabricating the hierarchical heterostructure is efficient way for enhancing CO 2 conversion of semiconductor photocatalysts. Herein, a simple strategy has been employed to prepare several 3D hierarchical CdS/Ni-MOF heterostructure photocatalysts, and the selective photoreduction of CO 2 to CO under simulated sunlight in the gas–solid phase reactor. Among the prepared photocatalysts, 20%-CdS/Ni-MOF shows the best CO yield, which was 16 times and 7 times that of Ni-MOF and CdS, respectively. By controlling the morphology of the catalyst, we found that the significant improvement in photocatalytic activity can be ascribed to the synergistic effect of heterostructure in CdS/Ni-MOF and its unique hierarchical structure, which can improve the efficiency of charge transmission and provides abundant active sites, etc. Finally, the preliminary photocatalytic mechanism was discussed by in situ FTIR and liquid ultraviolet spectrophotometer. [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]

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]

Pt@CeO 2 /3DCN heterojunction are prepared by calcination method and photoreduction technology. The enhanced photoreduction of CO 2 performance can be ascribed to the synergistic effects of the oxygen vacancies in CeO 2 for CO 2 activation and heterojunction for electron separation. Besides, Pt nanoparticles (NPs) on CeO 2 /3DCN can further promote the transfer of electrons, resulting in higher photocatalytic activity. • The Pt@CeO 2 /3DCN photocatalyst was successfully synthesized. • Pt@45CeO 2 /3DCN exhibit best ability of CO 2 photoreduction under UV light. • The synergy of CeO 2 and 3DCN improves the photocatalytic performance. The conversion of CO 2 into high value-added carbon-based compounds through photocatalytic reduction technology is considered as one of the more promising strategies to solve the greenhouse effect. And construction of heterojunction photocatalysts can promote the separation of photoelectron-hole pairs, so as to achieve higher activity of photocatalytic CO 2 reduction. Hence, Pt@CeO 2 /3DCN heterojunction are prepared by calcination method and photoreduction technology. The photocatalytic results revealed that Pt@CeO 2 /3DCN show better photocatalytic activity for reducing CO 2 into CO and CH 4 , compared with 3DCN. Especially, Pt@45CeO 2 /3DCN shows the maximum photocatalytic activity of 4.69 and 3.03 μmol·h−1·g−1 for CO and CH 4 under UV light irradiation, respectively, and the reduction activity did not decrease significantly after five cycles. The enhanced photoreduction of CO 2 performance can be ascribed to the synergistic effects of the oxygen vacancies in CeO 2 for CO 2 activation and heterojunction for electron separation. Besides, Pt nanoparticles (NPs) on CeO 2 /3DCN can further promote the transfer of electrons, resulting in higher photocatalytic activity. [ABSTRACT FROM AUTHOR]