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[Display omitted] • Cu-porphyrin (CuPor)/Ru-pincer complex (RuN 3) polymer are in-situ coupled on Cs 0.33 WO 3. • Organic-inorganic Z-scheme heterojunction formed via ester bond and H-bond interactions. • A cascade Z-scheme charge transfer mechanism proceeds in the CoPor-RuN 3 /CsWO composite. • CsWO's electrons can combine with the polymer's holes via the interfacial heterojunction. • Cu/Ru sites of CoPor-RuN 3 polymer promote electrons enriching on Ru center for CO 2 RR. The photocatalytic system that simulates the principle of photosynthesis is considered one of the most promising technologies for converting CO 2 into chemical fuels. Herein, copper tetra(4-carboxyphenyl)porphyrin (CuPor)-ruthenium 2,6-bis(5-amino-benzimidazol-2-yl)pyridine pincer complex (RuN 3) coupled polymer (CuPor-RuN 3) is in-situ polymerized on hexagonal tungsten bronze Cs 0.33 WO 3 (CsWO) nanoparticles to construct a novel CuPor-RuN 3 /CsWO composite photocatalyst with cascade charge transfer mechanism, where the inorganic–organic Z-scheme heterojunction at the CuPor-RuN 3 /CsWO interface and the Z-scheme molecular junction (-[CuPor-RuN 3 ]-) within the polymer facilitate photoexcited electrons transferring from CuPor units to RuN 3 ones, and finally enriching on Ru sites for boosting the CO 2 reduction reaction (CO 2 RR). Under visible light irradiation and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole serving as electron donor, the resultant CuPor-RuN 3 /CsWO delivers average CO/CH 4 yields up to 4645/89 μmol g-1h−1, corresponding to an overall photoactivity of 10002 μmol g-1h−1, which is 20 times higher than that of the single polymer. These results provide new ideas for exploring high-performance artificial photosynthesis system to convert CO 2 into chemical fuels. [ABSTRACT FROM AUTHOR]

An in-situ topotactic transformation strategy is proposed for constructing CuO/Cu 2 O S-scheme hetero-nanosheets with abundant interfacial Cu(II)-O-Cu(I) bridges for boosted CO 2 photoreduction. The interfacial Cu(II)-O-Cu(I) bridges are found to provide fast transfer channels for photogenerated carriers transporting from CuO to Cu 2 O in an S-scheme pathway, leading to enhanced separation of photogenerated carriers. [Display omitted] • Cu 2 O/CuO HNSs are prepared by an in-situ topotactic transformation strategy. • The interfacial Cu(II)-O-Cu(I) bridges can provide fast transfer channels for photogenerated carriers. • The bond bridges can tune the kinetic and thermodynamic processes of the CO 2 -to-CO conversion. • Cu 2 O/CuO HNSs exhibit a high conversion rate of 22.14 μmol g−1 h−1 with a CO selectivity of 94.4%. Efficient charge transfer across interfaces is highly desirable, but remains challenging in engineering semiconductor heterojunctions for photocatalysis. In this work, hybrid hetero-nanosheets (HNSs) of CuO/Cu 2 O bridged with interfacial Cu(II)-O-Cu(I) have been constructed via an in-situ topotactic transformation strategy, in which CuO nanosheets are partially reduced by ascorbic acid and transformed into Cu 2 O. The interfacial Cu(II)-O-Cu(I) bridges are found to provide fast transfer channels for photogenerated carriers transporting from CuO to Cu 2 O in an S-scheme pathway, leading to enhanced separation of photogenerated carriers. Furthermore, the bond bridges can tune the kinetic and thermodynamic processes of the CO 2 -to-CO conversion at interfacial Cu(I) catalytic sites by altering the rate-determined step and shifting downwards d -band center of the Cu(I) sites. Owing to the interfacial Cu(II)-O-Cu(I) bridges, the optimized CuO/Cu 2 O HNSs significantly expedite the CO 2 photoreduction to CO, delivering a CO 2 conversion rate of 22.14 μmol g−1 h−1 with a CO selectivity of 94.4%, outperforming the state-of-the-art copper oxide-based photocatalysts. This work demonstrates an effective in-situ topotactic transformation strategy to create interfacial bond bridges at heterogeneous interfaces for boosted photocatalysis as well as the critical roles of interface catalytic sites for CO 2 conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pd, Rh, Cu ions modify the SrMoO 4 in form of surface species. • Pd, Rh, Cu-modified SrMoO 4 catalysts show enhanced photocatalytic activity. • Metal ion modifications increase adsorption sites and active surface regions. • Introduced species' energy levels match the potential of water oxidation. • Band engineering strategy enables selective photoreduction of CO 2 to CH 4. Photocatalytic CO 2 reduction holds promise as a strategy to mitigate the energy crisis and greenhouse effects. However, devising cost-effective photocatalysts capable of efficiently and selectively converting CO 2 to CH 4 remains challenging. This study presents the synthesis of Pd, Rh, and Cu-modified SrMoO 4 photocatalysts via a one-step solvothermal method. Our findings demonstrate increased CH 4 activity and controlled selectivity through the modification with Pd, Rh, or Cu ions. It was determined that Pd, Rh, or Cu ions modified the SrMoO 4 surface as -O-Pd-O-, -O-Rh-O-, or -O-Cu–O- species, increasing the adsorption sites and active regions on the catalyst surface. Moreover, these introduced -O-Pd-O-, -O-Rh-O-, or -O-Cu–O- species' energy level enhances visible light absorption and photogenerated charge carrier separation, and regulates the band structure for better alignment with water oxidation potential. This leads to greater water oxidation half-reaction efficiency and increased H+ generation in photocatalytic CO 2 reduction. Consequently, more protons (H+) participate in CO 2 photocatalytic reduction, thus promoting CH 4 production and selectivity. These insights may guide the design of highly-selective photocatalysts for effective CO 2 photoreduction through bandgap engineering strategies. [ABSTRACT FROM AUTHOR]

Structural reorganization is developed for preparing highly polymerized ultrathin g-C 3 N 4 nanosheets, which have a great potential in visible-light-driven CO 2 photoreduction. [Display omitted] • Highly polymerized ultrathin g-C 3 N 4 nanosheets are synthesized via structural reorganization. • The bridged N-(C) 3 provides more electron transfer channels with extended conjugate π → π* system as well as distorts the plane structure with activated n → π* electronic transition. • The prepared g-C 3 N 4 shows rapid and effective photoexcited carriers transfer and separation as well as extensional visible light absorption, resulting in highly active CO 2 photoreduction in a wide spectral range. • This work offers new design ideal for highly active g-C 3 N 4 materials in visible-light‐driven CO 2 photoreduction. Graphitic carbon nitride (g-C 3 N 4) exhibits moderate CO 2 photoreduction due to fast recombination of photoexcited charges and low-grade visible light absorption. Herein, we synthesized highly polymerized ultrathin g-C 3 N 4 nanosheets by structural reorganization. Both experimental and theoretical calculations indicate that amino groups stabilized by hydrogen bonding networks are the easiest to remove to form a more stable bridged N-(C) 3. This procedure provides additional electron transfer channels with an extended conjugated π → π* system and buckled plane structure with activated n → π* electronic transitions. This new configuration significantly improves the separation efficiency of photoexcited charges and widens the light absorption range. As a result, the prepared g-C 3 N 4 shows efficient CO 2 -to-CO conversion with a CO production rate of 12.95 μmol g-1 h−1 under λ ≥ 420 visible light and 2 μmol g-1 h−1 under λ ≥ 500 visible light, respectively. This work offers a new design idea for highly active visible-light-driven g-C 3 N 4 for CO 2 photoreduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-TiO 2 NFs/MoSe 2 heterojunctions were fabricated through the solvothermal method for the UV–vis light active photocatalytic CO 2 reduction. • Integration of copper coupled with a highly conductive phase of 1 T MoSe 2 (80%) accelerated the separation and migration of photogenerated carriers. • Reaction intermediates are directly detected and analyzed by in-situ FTIR spectra. • A 2 wt% MoSe 2 loaded on one-dimensional Cu-doped TiO 2 showed the highest CO 2 photoreduction activity (H 2 ; 81 µmol/g, CO; 396 µmol/g, and CH 4 ; 92 µmol/g) with CO 2 selectivity of 90%. • A possible S-scheme mechanism for CO 2 photoreduction over Cu-TiO 2 NFs/MoSe 2 was proposed. Efficient solar-driven conversion of CO 2 into valuable chemical energy offers a promising way to address the issues of energy shortage and climate change. However, the weak and slow charge kinetics severely impede CO 2 photoreduction. Herein, hybrid-phase MoSe 2 (1 T-2H MoSe 2) nanosheet-coated Cu-doped TiO 2 nanofibers (Cu-TiO 2 NFs) were prepared using a solvothermal method. Different characterizations confirmed the successful doping of Cu into a TiO 2 crystal lattice and the generation of stable 1 T-2H MoSe 2 in the composite samples. The developed internal electric field drives electrons from the Cu-TiO 2 NFs to MoSe 2 , demonstrating the presence of a Step-scheme (S-scheme) charge transfer path in the Cu-TiO 2 NFs/1T-2H MoSe 2 heterostructure, which allows efficient and selective CO 2 photoreduction. In addition, the optimum sample contains an abundant 1 T MoSe 2 coupled with Cu+/Cu0 which offers copious active sites to improve CO 2 adsorption and subsequent conversion to CO and CH 4. The optimum sample exhibits a remarkable CO 2 selectivity of 90%. These findings provide new possibilities for improving the preparation of efficient photocatalysts for the photoreduction of CO 2. [ABSTRACT FROM AUTHOR]

The adsorption configuration of CO 2 on the catalysts changed from monodentate to bidentate after the introduction of bridging oxygen vacancies into SnTa 2 O 6 , which is beneficial for CO 2 adsorption and activation. The good stability of SnTa 2 O 6−x can be attributed to the distinct molecular configuration of CO 2 , which avoids filling and consuming of the oxygen vacancies. [Display omitted] • The bridging oxygen vacancies were constructed in SnTa 2 O 6−x by an improved flame reduction method. • 40-SnTa 2 O 6−x showed 7.5 times improved visible light catalytic activity with a CO yield of 21.1 μmol h−1 g−1. • The transition of adsorption configuration of CO 2 on the catalysts boosts adsorption and activation. • The bidentate configuration avoids filling of oxygen vacancies and ensures its stability. Construction of oxygen vacancies is a common strategy to improve the performance of metal oxide photocatalysts. However, the oxygen vacancies can be easily filled and consumed by the oxygen atoms of CO 2 molecules during CO 2 photoreduction reactions, resulting in deactivation of the catalyst. In this study, bridging oxygen vacancies were introduced into SnTa 2 O 6 nanosheets, which remarkably enhanced the photocatalytic performance with good stability. The SnTa 2 O 6−x obtained after 40 s of flame reduction treatment showed 7.5 times higher visible-light-activity than pristine SnTa 2 O 6 (21.1 μmol h−1 g−1 of CO), and sustained good stability even after five cycles. Accompanied by a positive shift in the d-band center, the adsorption configuration of CO 2 on the catalysts changed from monodentate to bidentate after the introduction of bridging oxygen vacancies into SnTa 2 O 6 , which is beneficial for CO 2 adsorption and activation. Furthermore, the bridging oxygen vacancies in SnTa 2 O 6−x can reduce the Gibbs free energy of COOH*, and facilitate the photo conversion of CO 2 by receiving photogenerated electrons. The good stability of SnTa 2 O 6−x can be attributed to the distinct molecular configuration of CO 2 , which avoids filling and consuming the oxygen vacancies. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Bi 2 WO 6 nanosheets loaded with PtO x nanoparticles were synthesized by photoreduction. • Optimal CH 4 yield was achieved with a content of 0.5% PtO x loading. • PtO x loading boosted the process of carrier separation and water oxidation. Abstract Solar CO 2 photoreduction into hydrocarbons is promising and significative. However, many conventional catalysts reported usually suffer from poor photocatalytic activities. Herein, ultrathin Bi 2 WO 6 nanosheets with a thickness of about 4.8 nm have been synthesized by hydrothermal method, which exhibited a CH 4 production rate of 19 ppm g−1 h−1 under a low CO 2 concentration of 400 ppm. PtO x nanoparticles with a size of about 2 nm were then loaded on the Bi 2 WO 6 nanosheets as excellent co-catalysts by photoreduction in aqueous solution, and an optimal CH 4 yield of 108.8 ppm g−1 h−1 was achieved, which was about 5.7 times than that of pristine Bi 2 WO 6 nanosheets. Further analyses of photocurrent curves, electrochemical impedance spectroscopy and polarization curves of water oxidation indicated that the improved photocatalytic activity was suggested to result from the enhanced carrier separation and accelerated water oxidation by PtO x nanoparticles. The work will likely give a deeper insight of PtO x nanoparticles and provide a new idea to design catalysts for CO 2 photoreduction to CH 4. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Eu could facilitate the separation and transfer of photogenerated electron-hole pairs. • The Eu/C 3 N 4 composites have superior photocatalytic performance in both CO 2 reduction and H 2 evolution. • In-situ FTIR analysis indicates that the HCOOH is a major intermediate during the CO 2 conversion progress. • Massive photogenerated carriers existed in Eu/g-C 3 N 4 are favorable to the CO 2 photoconversion to CH 4. Abstract The high-efficiency photocatalytic CO 2 reduction and H 2 evaluation performance are quite attractive and desired for clean energy utilization and environmental pollution alleviation. Herein, the novel visible-light activated Eu (III) doped g-C 3 N 4 composites with different contents (2%, 4%, 6%, 8% and 10%) were successfully synthesized for the first time. The Eu (III) species acted as the Lewis acids could trap photoexcited electrons with superior ability. The photocatalytic activity of Eu/g-C 3 N 4 catalysts exhibited superior performance and stability in both CO 2 photoreduction and H 2 production with the presence of water under the visible light irradiation. A maximum CH 4 and H 2 yields of 22.8 μmol/(h·g-cat) and 78.1 μmol/(h·g-cat), respectively, had been obtained on 8% Eu/g-C 3 N 4 catalyst, which was about 2.2 and 7.3 times as high as the pure g-C 3 N 4. In situ FTIR analysis discloses that HCOOH is a major intermediate during the CO 2 conversion progress. The Mott–Schottky method also indicated massive photogenetated carriers existed in Eu/g-C 3 N 4 catalysts that in favor of the CO 2 conversion to CH 4. The origin of such remarkable photocatalytic activities could be explained as follows: (i) Eu3+ species captured photogenerated electrons and inhibited the recombination of photogenerated electron-hole pairs; (ii) the doped Eu3+ narrowed the band gap and enhanced the visible-light absorption capacity; (iii) the introduction Eu3+ increased the activated specific surface area. This work may provide meaningful guidelines for rare earth mental application on improving the performance of photocatalyst. [ABSTRACT FROM AUTHOR]

Graphical abstract Hydrogen bonding between the amino groups in CdS-EF and carboxyl groups in FeTCPP can provide efficient channels for electron transfer from CdS-EF to FeTCPP, resulting in greatly enhanced catalytic activity of the CdS-EF/FeTCPP hybrid photocatalyst for CO 2 reduction. Highlights • CdS with and without ethylenediamine (CdS-EF and CdS) have been synthesized. • CdS-EF and CdS have been coupled respectively with FeTCPP for CO 2 photoreduction. • CdS-EF/FeTCPP shows higher photocatalytic activity than CdS/FeTCPP. • Amino groups in CdS-EF can facilitate electron transfer from CdS-EF to FeTCPP. • H-bonds are present between amino groups in CdS-EF and carboxyl groups in FeTCPP. Abstract The hybrid coupling between inorganic semiconductor and molecular catalyst can provide a promising approach for the construction of highly efficient and selective photocatalytic CO 2 reduction systems. This hybrid system can take full advantage of the strong light harvesting capability of semiconductor and high selectivity of molecular catalyst. The interaction linker bridging the semiconductor and molecular catalyst plays an important role in supplying efficient electron transfer channels. In this study, both CdS with and without ethylenediamine functionalization (i.e., CdS-EF and CdS) have been successfully synthesized and further respectively coupled with tetra(4-carboxyphenyl)porphyrin iron(III) chloride (FeTCPP) for CO 2 photoreduction. It is found that CdS-EF exhibits inferior photocatalytic activity to CdS, while CdS-EF/FeTCPP hybrid photocatalyst shows much higher activity than CdS/FeTCPP. This is because hydrogen bonding exists between the amino groups in CdS-EF and carboxyl groups in FeTCPP, which can act as electron transfer channels from CdS to FeTCPP in the obtained hybrid system. [ABSTRACT FROM AUTHOR]

[Display omitted] • We have grown the first octahedral NiSe 2 on one-dimensional NiTiO 3 NFs using a one-pot solvothermal method. • The composite NiTiO 3 NFs/NiSe 2 presented an improved CO 2 photoreduction efficiency compared to the pristine NiTiO 3 NFs photocatalyst. • The optimal sample (0.09 wt% NTNs) can perform UV–vis light-driven CO 2 reduction to CO and CH 4 with a selectivity of 88.8% at a rate of 459.96, 269.02 μmol g−1h−1 respectively. • The high CO 2 photoreduction is attributed to the improved light absorbance and prolonged lifetime of photogenerated carriers due to metallic NiSe 2. • In situ FT-IR (DRIFT) revealed the selective CO 2 → COOH ∗ → CO ∗ / C O → CHO ∗ → CH 3 O ∗ → CH 4 conversion on the optimal sample. Excessive CO 2 concentrations in the atmosphere have a range of adverse effects, including climate change and the rise in sea levels. One approach to mitigate these issues is to utilize artificial photosynthesis, which transforms CO 2 into valuable fuels. In this study, a unique octahedral nickel selenide (NiSe 2) structure supported on one-dimensional (1D) nickel titanate nanofibers (NiTiO 3 NFs) was created through a one-pot solvothermal process. The optimized NiTiO 3 NFs/NiSe 2 nanostructure exhibits exceptional CO 2 photoreduction performance across a broader range of the solar spectrum (UV–vis). At a 0.09 wt% NiSe 2 concentration, the yields of CH 4 and CO were 3.14 and 1.47 times higher, respectively, than those produced by pure NiTiO 3 NFs. The exceptional photocatalytic activity can be attributed to the efficient electron extraction and transfer from NiTiO 3 NFs to NiSe 2 , as well as the enhanced light harvesting capacity. Furthermore, the introduction of NiSe 2 generates more oxygen vacancies (O V) that can promote the adsorption and activation of CO 2 and water, considerably reducing the free energy barrier for COOH* formation and accelerating the reaction kinetics. The results of this study are expected to create new opportunities for synthesizing efficient photocatalysts based on transition metal dichalcogenides that can be utilized in energy conversion applications. [ABSTRACT FROM AUTHOR]

The COF-366-Fe@CeO 2 core – shell Z-scheme heterostructure is fabricated by Schiff base reaction with an in-situ reaction strategy and exhibits an excellent photocatalytic CO 2 production rate under the visible light irradiation without any additional photosensitizers or sacrificial agents. [Display omitted] • The COF-366-Fe@CeO 2 core–shell Z-scheme heterostructure is fabricated through Schiff base reaction with an in-situ reaction strategy. • The Z-scheme heterostructure dramatically boosts the separation of photogenerated carriers, as confirmed by the results of comprehensive characterizations. • The Fe active sites and strong oxidation ability of CeO 2 endow COF-366-Fe@CeO 2 efficient photocatalytic CO 2 reduction activity under the visible light irradiation without any additional photosensitizers or sacrificial agents. The porphyrin-based covalent organic frameworks (COFs) are promising candidates for photocatalytic CO 2 conversion account for their long-range ordered mesopores and excellent semiconducting properties, but the insufficient oxidative capacity of valence band is less efficient for photooxidation of H 2 O, which hinders the photocatalytic performance. Herein, the stable organic–inorganic Z-scheme heterostructure was constructed through covalently connecting COF-366-Fe consisting of Fe-porphyrin and terephthaldehyde units with CeO 2 by Schiff base reaction with an in-situ reaction strategy. The COF-366-Fe@CeO 2 core–shell Z-scheme heterojunction not only effectively integrated the light-harvesting capability, active metal centers of COF-366-Fe and strong oxidation ability of CeO 2 , but also promoted the separation and transfer of photoexcited carriers. The as-prepared COF-366-Fe@CeO 2 exhibited a photocatalytic CO yield of 66.2 μmol g−1 in 8 h with a 99 % selectivity under the visible light irradiation without additional photosensitizers and sacrificial agents, which was far superior to COF-366-Fe and CeO 2. The remarkable promoted performance is ascribed to the covalently contact Z-scheme heterojunction interface, which benefited to facilitate the separation of photoexcited electron-hole pairs, as confirmed by the results of electronic paramagnetic resonance, time-resolved photoluminescence and in-situ XPS. This study provides an idea for designing highly-effective COF-based photocatalysts for artificial photosynthesis. [ABSTRACT FROM AUTHOR]

A cascade Z-scheme g-C 3 N 4 /BiVO 4 heterojunction with dual modification of phosphates and Ag nanoclusters for selective CO 2 photoreduction. [Display omitted] • A Z-scheme CN/BVO heterojunction is tailored by the phosphates and Ag nanoclusters. • Optimal catalyst shows a high CO 2 to CO conversion rate with 97% selectivity. • PO-bridged 2D interfaces and Ag nanoclusters endow the cascade charge transfer. • The mechanism of high CO selectivity brought by the decorated Ag is disclosed. Artificial Z-scheme heterojunctions by mimicking photosynthesis have been widely investigated for photoreduction of CO 2 , yet the activity is hindered by the weak interfacial interactions and insufficient CO 2 activation sites. Here, a cascade Z-scheme g-C 3 N 4 /BiVO 4 (CN/BVO) heterojunction has been tailored by the dual modification of phosphates and Ag nanoclusters for CO 2 reduction in pure water, in which phosphates are modified in the interface of CN/BVO by a facile impregnation method, while Ag nanoclusters are anchored on the surface of CN by a light induced in-situ deposition strategy under a low-temperature environment created by liquid N 2. The optimal Ag-CN/PO-BVO heterojunction delivers a ca.48 μmol g−1h−1 CO generation rate with 97 % selectivity, which exhibits a 24-fold increment in CO production rate compared with that of pristine BVO. The improved photoactivity is mainly ascribed to the accelerated Z-scheme charge transfer from the built PO-bridged dimension-matched 2D interfaces and from the introduced Ag nanoclusters with preferable catalytic functions for CO 2 reduction mainly by means of the time-resolved surface photovoltage responses and fluorescence spectra. Moreover, temperature-programmed desorption curves and in-situ DRIFTS results demonstrate that the introduced Ag is favorable for CO 2 activation and CO desorption with COOH intermediates, responsible for the high CO selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A direct Z-scheme heterojunction of NU/CC was fabricated for CO 2 photoreduction. • The heterojunction of NH 2 -UiO-66/CeCO 3 OH was featured with O-Zr-CO 3 2- bond. • The rate of electron consumption of NU/CC is 152.8 μmol/g h, 5-fold of that of NU. NH 2 -UiO-66 is recently regarded as a potential photocatalyst for CO 2 reduction reaction due to the high CO 2 adsorption capacity, high UV–vis light absorption capacity and chemical stability. Aiming to further improve its activity, in this paper, a composite of NH 2 -UiO-66 and CeCO 3 OH (NU/CC) was fabricated via an in-situ growth method of NH 2 -UiO-66 on CeCO 3 OH. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) characterizations indicated that a direct Z-scheme heterojunction between CeCO 3 OH and NH 2 -UiO-66 was formed via the formation of O-Zr-CO 3 2- bond. The CO 2 adsorption measurement, UV–vis DRS spectra and photo(electro)chemical measurements indicated that the optimal composite NU/CC-1.6–90 exhibited the higher CO 2 adsorption capacity, stronger respond and wider absorption range to UV–vis light, as well as the significantly delayed recombination of photogenerated electron-hole pairs, compared with other control samples. As a result, NU/CC-1.6–90 delivered the obviously enhanced photocatalytic activity of CO 2 to both CO and CH 4 , and the rate of electron consumption reached 152.8 μmol/g h, 5-fold of that of NH 2 -UiO-66. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solar-driven CO 2 reduction by g-C 3 N 4 -based photocatalyst with Pt-Fe 3 O 4 bimetals. • Fe 3 O 4 doping results in forming Fe 3 O 4 /Pt/g-C 3 N 4 , with high capability of CO 2 adsorption. • The synergistic effect of the bimetals promotes selective and efficient CO 2 conversion. • CH 4 yield over optimized Fe 3 O 4 /Pt co-decorated g-C 3 N 4 is 38 times of pure g-C 3 N 4. • The selective reduction pathway and intermediate species are investigated. In this study, we report the effects of co-catalysts of Pt nanoparticles and Fe 3 O 4 clusters on photocatalytic behaviors of g-C 3 N 4 (CN) and the use of the resulting photocatalyst for CO 2 photoreduction to solar fuels in a flow reactor operated at room-temperature. In presence of H 2 O vapors, the selectivity of photogenerated electrons was emphasized, and found that the yield rate and selectivity of CH 4 were improved by deposition of Pt on CN. With further inclusion of Fe 3 O 4 over Pt/g-C 3 N 4 (PtCN), the CH 4 yield rate was significantly enhanced and H 2 formation inhibited simultaneously, resulting in improved CH 4 selectivity. Results show that the optimized Fe 3 O 4 /Pt co-decorated CN (0.50 %FPtCN) heterostructure possesses significantly enhanced CO and CH 4 yield rates of 1.83 μmolg−1h−1 and 0.532 μmolg−1h−1, respectively, which were 9 and 38 times superior to pure CN, attributed predominantly synergistic effects of Pt, Fe 3 O 4 , and CN. Owing to exceptional conductivity and electron-sink function, Pt NPs are an excellent electron transporter, which facilitates interfacial charges transfer and prohibits their recombination, while, the Fe 3 O 4 clusters can synergistically promote the CO 2 photoreduction by effectively using electrons as the oxidation − reduction center. Finally, insight obtained from results is used to propose a possible underlying mechanism for superior photocatalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Double-shelled hollow spheres with spatially separated active sites were fabricated. • Photoinduced charge transfer and separation were greatly accelerated. • Visible-light harvesting was significantly enhanced in heterostructured hybrid. • Spatially separated active sites improved yield and selectivity in CO 2 conversion. Heterostructured hybrids with hollow configuration and efficient charge separation are very promising for CO 2 photoreduction. This study demonstrates the design and fabrication of hierarchical double-shelled CeO 2 @SnS 2 hollow spheres with spatially separated active sites (MnO x /CeO 2 @SnS 2 /Ni 2 P DSHSs) for efficient CO 2 photoreduction. In this catalyst system, MnO x and Ni 2 P cocatalysts are selectively anchored on the CeO 2 and SnS 2 shells, respectively, forming spatially separated active sites. The confinement effect of outer-surface SnS 2 nanosheets offers more opportunities for Ni 2 P cocatalyst to react with CO 2 molecules. Owing to the desired hierarchical double-shelled hollow architecture and spatially-separated cocatalysts, the MnO x /CeO 2 @SnS 2 /Ni 2 P DSHSs possess the advantages of abundant spatially-separated active sites, enhanced visible-light harvesting, and accelerated charge separation. As expected, the optimized MnO x /CeO 2 @SnS 2 /Ni 2 P DSHSs sample exhibits remarkable CO 2 photoreduction activity. The CO yield and selectivity reach 29.67 μmol g−1 h−1 and 90.1%, respectively, which are remarkably higher than the control samples. This study demonstrates a promising strategy to construct well-defined hierarchical hybrid catalysts for maximizing CO 2 photoreduction performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 photocatalytic reduction employing an amorphous TiO 2 catalyst. • Photoreduction by amorphous TiO 2 modified with SiO 2 supported on ITO-PET. • Experimental and theoretical analysis of the catalyst behavior phenomena. • Reaction medium acid-base behavior by DFT-Koopmańs theorem. • Affinity trends between surfaces, target molecules and water. In this contribution, the behavior of a photocatalytic CO 2 reduction (PCO 2 R) employing an amorphous-TiO 2 modified with silica (SiO 2) supported on polyethylene terephthalate film-coated with indium tin oxide (AM-TiO 2 -SiO 2 /ITO-PET) catalyst was studied. The AM-TiO 2 -SiO 2 /ITO-PET synthesized via soft method exhibited a high performance toward the production of CH 4 , H 2 and CO gases, a decrease of the gases production after being used once. This behavior was analyzed and explained from surface phenomenon approaches employing experimental and theoretical means XRD (experimental and theoretical), Raman, FTIR, PL, binding energies (E binding), DFT-Koopman descriptors and theoretical Gibbs free energy. The analysis proposes that surfaces with superficial SiO 2 groups are more affine to some target molecules (T-M). This affinity promotes faster adsorption and reaction, but contributes to the obstruction in the mechanizing reaction. The formation of second-order links (Van der Waals and Hydrogen bonds) between affine T-M and catalytic surfaces will result in molecular blocking and will lead to catalyst deactivation. Finally, the production of CO on AM-TiO 2 -SiO 2 /ITO-PET is kinetically favorable due to the disorder on the AM-TiO 2 surface. This specific chemical photoreduction pathway, promoted by the superficial disorder, is also assisted by second-order links (Van der Waals and Hydrogen bonds). [ABSTRACT FROM AUTHOR]

[Display omitted] • Sub-nanometer Pt NCs were obtained by tuning the amount of Pt integrated on P25. • Pt-NC/P25 exhibited prominent CO 2 reduction activity for selective CH 4 generation. • Activity and selectivity of Pt-NC/P25 for CO 2 photoreduction depend on Pt-NC size. • Pt-NC/P25 had high stability during multiple CO 2 photoreduction test runs. • High proportion of edge/corner sites of Pt-NC/P25 led to high CH 4 selectivity. Integration of sub-nanometer–sized Pt cocatalysts on semiconductor materials is a promising approach to improve the activity and selectivity of CO 2 photoreduction. However, the practical realization of such an integrated catalyst is a challenging task. We rationally integrated sub-nanometer Pt nanoclusters (Pt NCs) on the surface of commercial P25 catalyst by adjusting the amount of Pt loading. The lateral reduction in the size of Pt NCs resulted in high metal dispersion, increased active metal surface area, better CO 2 adsorption, and hindered photoexcited charge-carrier recombination. The sub-nanometer Pt NCs integrated with P25 with a weight percentage of 0.5% (Pt-NC/P25-0.5) exhibited exceptional CO 2 photoreduction activity for CH 4 production and excellent stability during successive test runs. This catalyst outperformed its counterparts with larger Pt NCs and several previously reported state-of-the-art photocatalysts in terms of CH 4 generation. Importantly, compared to its counterparts, Pt-NC/P25-0.5 had a higher proportion of edge and corner sites, which have a strong affinity for CO molecules, resulting in a high CH 4 selectivity of 95% against H 2. The size-dependent selectivity and activity of Pt NCs for CO 2 reduction demonstrated in this study offer insights into the development of sub-nanometer metal-based catalysts for photocatalytic energy applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Indium hydroxide (In(OH)3) with mesoporous structure was synthesized via a sol–gel hydrothermal treatment. [•] Mesoporous In(OH)3 obtained larger surface area and exhibited higher activity in adsorption of CO2. [•] Photoreduction of CO2 into renewable hydrocarbon fuels over mesoporous In(OH)3 was successfully realized. [•] The evolution rate of CH4 over the mesoporous In(OH)3 is 19 times higher than that of n-In(OH)3. [ABSTRACT FROM AUTHOR]

Highlights: [•] We propose a novel photocatalyst for the photoreduction of CO2 to CH4. [•] The plasmonic properties of Ag NPs enhanced the photoactivity. [•] Final CH4 yield rates up to 2.64μmol(gcatal h). [Copyright &y& Elsevier]

[Display omitted] • A hybrid of highly-configured TiO 2 hollow spheres and N-doped carbon dots was developed. • The hybrid endowed large surface area and high CO 2 adsorption and light absorption abilities. • The hybrid demonstrated remarkable CO 2 photoreduction activity for methane generation. • Multiple roles of CD and notable surface structure of TiO 2 enabled effective and selective CO 2 reduction. • The hybrid displayed high stability and durability during consecutive test cycles. Transforming CO 2 into solar fuel using renewable solar energy and a catalyst is an effective approach that simultaneously addresses energy scarcity and climate deterioration. Therefore, it is necessary, albeit challenging, to design a catalyst that works effectively for this purpose. Herein, we have rationally developed a hybrid catalyst composed of highly-configured TiO 2 hollow spheres (TOH) and N-doped carbon dots (CD), referred to as CD/TOH, and use this hybrid as a catalyst for photocatalytic CO 2 reduction to produce CH 4 under simulated sunlight. The electron microscopy results revealed that the CD/TOH hybrid possesses a porous hollow sphere structure uniformly adorned with N-doped carbon dots. Moreover, the CD/TOH hybrid demonstrates many beneficial properties for CO 2 photoreduction reactions, including a large surface area, effective light-harvesting capability, high CO 2 adsorption, and, most importantly, significantly enhanced separation of photoexcited charges. Consequently, the CD/TOH containing 2 wt% CD achieves an optimum CH 4 formation rate of 26.8 μmol h−1 g−1, corresponding to 98% CH 4 selectivity against competitive H 2 production. Further, the hybrid also demonstrated stable CO 2 reduction activity during consecutive test runs. Thus, the insights gained from this study may aid in the development of effective catalysts for CO 2 photoreduction. [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]

Nitrogen and oxygen vacancies were fabricated to increase the adsorption and activation capacity of CO 2 and promote Z-scheme charge carrier transfer process in g-C 3 N 4 /TiO 2 heterostructure, this greatly enhances visible light photocatalytic activity of CO 2 reduction. [Display omitted] • Z-scheme CN/TiO 2 heterostructure with nitrogen and oxygen dual vacancies were fabricated. • Dual vacancies can increase the adsorption and activation capacity of CO 2 on CN/TiO 2. • Dual vacancies can promote the Z-scheme charge transfer and the oxidation ability. • V N -CN/V O -TiO 2 heterostructure exhibits excellent photocatalytic CO 2 reduction performance. Z-scheme heterostructure of nitrogen-vacancy rich g-C 3 N 4 nanoparticles (V N -CN) confined in oxygen-vacancy rich TiO 2 nanotube arrays (V O -TiO 2) were fabricated to enhance CO 2 photoreduction under visible light irradiation. Dual vacancies mediated V N -CN/V O -TiO 2 heterostructure exhibits excellent photocatalytic CO 2 reduction performance, and the CO and CH 4 evolution rate are about 1.5 times and 3 times higher than that of pristine CN/TiO 2 , respectively. Possible reasons for the improvement of photocatalytic activity are as follows: (1) the adsorption and activation capacity of CO 2 on the surface of CN/TiO 2 are obviously improved due to the construction of nitrogen and oxygen dual vacancies; (2) the construction of dual vacancies are beneficial for enhancing the visible light absorption, promoting separation and transfer of photogenerated carriers due to intimate contact interface between V N -CN and V O -TiO 2 ; (3) Z-scheme heterostructure could boost oxidation ability of V N -CN/V O -TiO 2 and promote the production of more hydroxyl radical, which can react with CO 2 − to form HCO 3 −, leading to a new pathway to CO 2 photoreduction compared to pristine CN/TiO 2. [ABSTRACT FROM AUTHOR]

• DFT calculations unravel the productivity and selectivity of CO 2 photoreduction on SiC. • Hydrogen source from proton or hydroxylated SiC affect the CO 2 reduction. • Reverse water-gas shift (RWGS) mechanism has lower limiting potential than others. Photocatalysis of CO 2 into CH 4 and O 2 on marigold-like SiC@MoS 2 has recently been reported with high product yield of 323 and 621 μL·g−1·h−1, respectively, where protons produced from MoS 2 were directly used as hydrogen source for CO 2 reduction on the SiC surfaces (JACS, 2018, 140, 14595). However, the yields are only 98.1 and 26.9 μL·g−1·h−1 for CH 4 and CO, respectively, if the hydrogen source is from the hydroxylated SiC (ChemComm, 2019, 55, 1572). To unravel the productivity and selectivity of the reaction, we first provide that the limiting potential of CO 2 to CH 4 on SiC(1 1 1) surface is ∼0.7 V lower than that of hydroxylated SiC(1 1 1) surface. Due to the Δ G des (1.68 eV) of CO is close to the ΔG max (1.33 eV) of the hydroxylated SiC(1 1 1) surface, a small amount of CO are produced. Furthermore, we found the reverse water-gas shift (RWGS) mechanism has much lower limiting potential than those proposed in the experiments. [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]

• A novel TiO 2 -CZTS heterostructure nanocomposite is designed and synthesized. • Photoreduction of CO 2 over TiO 2 -CZTS is conducted in CO 2 + H 2 O vapor. • TiO 2 -CZTS shows strong absorption in whole visible light region. • CZTS decorated TiO 2 synergistically enhances CO 2 reduction rate. • A possible photocatalytic mechanism of CO 2 reduction is proposed. Owing to human activities and intensive utilization of modern technology, the CO 2 concentration in the environment increases which concomitantly leads to global warming. In order to overcome this issue, photocatalytic reduction of CO 2 aims to develop new cost-effective catalytic chemistries with the ability to efficiently utilize the CO 2 and convert into sustainable alternative feedstock for commercial commodity chemicals. In this context, a series of TiO 2 -Cu 2 ZnSnS 4 nanocomposites are directly prepared by one-step hydrothermal method. The nanocomposites are intensively characterized as photocatalysts for photoreduction of CO 2 to gaseous hydrocarbons (CO and CH 4), under visible-light illumination. In comparison to TiO 2 for one hour of irradiation, the maximum generation-rates of CO and CH 4 over nanocomposite are 33 and 6 times as high, respectively. Excellent stability with almost similar generation-rate after 4 cycles shows that heterostructure nanocomposites may offer a potential approach to stimulate the efficiency of hybrid materials in photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

• Zn 0.2 Cd 0.8 S/g-C 3 N 4 heterojunction was fabricated via a combined facile sonication and hydrothermal method. • The formed heterojunction improved the charge transfer and separation efficiency. • Improved photocatalytic activity can be achieved by the heterostructured material. • Zn 0.2 Cd 0.8 S/g-C 3 N 4 exhibited excellent stability and recyclability. • Reasons for high efficiency photocatalytic performance were discussed in detail. Herein, a type-Ⅱ heterojunction of Zn 0.2 Cd 0.8 S/g-C 3 N 4 (ZnCdS/CN) nanocomposites for CO 2 photoreduction to produce CH 3 OH is prepared via a combined simple sonication and hydrothermal method. After introducing g-C 3 N 4 into Zn 0.2 Cd 0.8 S, it is found that the amorphous powder g-C 3 N 4 is coated on the surface of Zn 0.2 Cd 0.8 S. The HRTEM and XPS results illustrate the heterostructure formation. The i-t curve, EIS and PL results suggest that the formed type-Ⅱ heterojunction improves the charge separation and transfer efficiency, and inhibits the recombination of photoinduced electron-hole pairs. Because of the improved photoelectric performance brought by the heterojunction, an optimized sample with g-C 3 N 4 to ZnCdS/CN mass ratio of 30% displays high CH 3 OH production rate of 11.5 ± 0.3 μmol·g−1·h−1, which is 2.6 and 2.7 times greater than that of Zn 0.2 Cd 0.8 S solid solution (4.4 ± 0.2 μmol·g−1·h−1) and g-C 3 N 4 (4.2 ± 0.1 μmol·g−1·h−1), respectively. Moreover, under the protection of g-C 3 N 4 , the crystal structure and reaction activity of the composite are almost maintained even after four cycles, showing excellent stability. This work can provide guidance for synthesis of other heterojunction photocatalysts with excellent activity and stability. [ABSTRACT FROM AUTHOR]

• Co and Ni metalloporphyrin complexes were synthesized and used as catalyst for CO 2 photocatalytic reduction. • Whether Co or Ni metalloporphyrin complexes exhibit better photocatalytic performance is elucidated. • The performance comparison was carried out for the mechanism illustration of performance difference in Co and Ni metal sites. • The relative strength of activity and CO 2 adsorption ability in Co and Ni sites is clarified. Porphyrin based MOFs have exhibited excellent photocatalytic properties in photocatalytic CO 2 reduction and metal sites in porphyrin units play an important role in the reactions. For investigating the mechanism of different photocatalytic performance of metals sites in porphyrin units, metalloporphyrin complexes with Co and Ni metal sites (Co-POR, Ni-POR) were prepared by a short term method and used for visible-light drived CO 2 photoreduction conversion with water vapor as sacrificial agent. PL spectra indicates that the fluorescence intensity of Co-POR was obviously lower than that of Ni-POR and DFT calculation indicates that CO 2 adsorption energy on Co-POR (17.92 kJmol−1) is higher than that on Ni-POR (16.37 kJmol−1). The efficient separation of charge carries and the strong CO 2 adsorption ability are main advantages of Co-POR compared with Ni-POR. As a direct result, the experimental results showed that 0.40 μ m o l g - 1 h - 1 CO was produced over Co-POR after 4 h reaction, which is about equivalent to a 1.7-fold enhancement compared to Ni-POR under the same reaction condition. [ABSTRACT FROM AUTHOR]