Photocatalysts For CO2 Conversion Research Articles

Construction of Co1-xZnxFe2xGa2-2xO4 (0

Solid solutions are garnering substantial attention in the realm of solar energy utilization due to their tunable electronic properties, encompassing band edge positions and charge-carrier mobilities. In this study, we designed and synthesized Co1-xZnxFe2xGa2-2xO4 (0<x≤0.6) as a photocatalyst for CO2 conversion using H2O. Careful optical and photo/electrochemical characterizations unveiled that the relative content of CoGa2O4 and ZnFe2O4 not only substantially influences light absorption in the full solar spectrum but also modulates valence and conduction band positions. We thoroughly assessed the photocatalytic activity of Co1-xZnxFe2xGa2-2xO4 and found that when x=0.35, the solid-solution catalyst achieved a remarkable CO2 reduction rate to CH4 and CO (31.5 μmol g-1 h-1). Furthermore, this optimized solid-solution catalyst demonstrated impressive photostability. Characterization and DFT calculations revealed that the formation of a solid solution not only reduces the band gap and promotes the separation of electron-hole pairs to accelerate efficient CO2 photoreduction, but also the introduction of more FeO6 octahedral active sites in Co1-xZnxFe2xGa2-2xO4 solid solutions enhanced the effective photoreduction of CO2. This design results in high conversion efficiencies for producing solar fuels through CO2 reduction with H2O.

Investigation of the Performance of Heterogeneous MOF-Silver Nanocube Nanocomposites as CO2 Reduction Photocatalysts by In Situ Raman Spectroscopy

Here, we fabricated two different heterogeneous nanocomposites, core-shell MOF-AgNC and corner MOF-AgNC, as photocatalysts for CO2 conversion by generating metal-organic frameworks (MOFs) on silver nanocube templates. These MOF-AgNC nanocomposites showed good CO2 adsorption features and high CO2 reduction reactivity. The performances of these MOF-AgNC nanocomposites in CO2 adsorption and CO2 reduction reactions can be characterized by in situ Raman spectrum measurement. The corner MOF-AgNC nanocomposite exhibited a faster CO2 adsorption rate than the core-shell MOF-AgNC nanocomposite, which was due to the higher surface area/volume ratio of the MOF in corner MOF-AgNC. The CO2 reaction reactivity and mechanisms (products of the reaction) of CO2 reduction also depended on the morphologies of MOF-AgNC nanocomposites, which were caused by different reaction environments at the interface between the MOF and AgNCs. The CO2 reduction reactivity of MOF-AgNC nanocomposites also exhibited high sensitivity to the irradiation intensity and wavelength, which was caused by the variation of the number of hot electrons and their positions in AgNCs with the irradiation intensity and irradiation wavelength, respectively. This method for the synthesis of heterogeneous nanocomposites should make it possible to design photocatalysts for various reactions by carefully designing the morphology and composition of nanocomposites.

Construction and engineering of an interfacial structure in a Cux/FeMgOy catalyst for the photoreduction of CO2 to ethylene

An FeMgOy-modified Cu interfacial structure is constructed as a photocatalyst for CO2 conversion with H2O via the structural topological transformation of layered double hydroxides.

Photocatalytic CO2 Conversion Using Anodic TiO2 Nanotube-CuxO Composites

Nanosized titanium dioxide (TiO2) is currently being actively studied by the global scientific community, since it has a number of properties that are important from a practical point of view. One of these properties is a large specific surface, which makes this material promising for use in photocatalysts, sensors, solar cells, etc. In this work, we prepared photocatalysts based on TiO2 nanotubes for converting carbon dioxide (CO2) into energy-intensive hydrocarbon compounds. Efficient gas-phase CO2 conversion in the prepared single-walled TiO2 nanotube-CuxO composites was investigated. Parameters of defects (radicals) in composites were studied. Methanol and methane were detected during the CO2 photoreduction process. In single-walled TiO2 nanotubes, only Ti3+/oxygen vacancy defects were detected. The Cu2+ centers and O2− radicals were found in TiO2 nanotube-CuxO composites using the EPR technique. It has been established that copper oxide nanoparticles are present in the TiO2 nanotube-CuxO composites in the form of the CuO phase. A phase transformation of CuO to Cu2O takes place during illumination, as has been shown by EPR spectroscopy. It is shown that defects accumulate photoinduced charge carriers. The mechanism of methane and methanol formation is discussed. The results obtained are completely original and show high promise for the use of TiO2-CuxO nanotube composites as photocatalysts for CO2 conversion into hydrocarbon fuel precursors.

The Graphitic Carbon Nitride (g-C3N4): A Promising Material for Photocatalytic CO2 Reduction

The excess use of fossil fuel and rapid industrialization increase of CO2 level in the atmosphere. Efficient conversion of CO2 to value added chemicals and fuels are the best method to reduce CO2 level as well as to maintain sustainability. To overcome the kinetic and thermodynamic barrier in CO2, a suitable heterostructure composite is necessary. Among different types of materials carbon based materials and their composites are shown their suitability electrochemical, thermal and photo-assisted method of CO2 conversion. Among different carbon based materials, graphitic carbon nitrite (g-C3N4) is a sustainable, inexpensive photocatalyst for CO2 conversion. This present article tries to summarize recent works based on conversion of CO2 in presence of solar light using g-C3N4 based composites. This provides an outlook for the future development of new catalysts to reduce CO2 effectively and save our earth from CO2 pollution.

Novel Cerium-Based Sulfide Nano-Photocatalyst for Highly Efficient CO2 Reduction.

To address the environmental crisis caused by excessive emissions of CO2 , the development of effective photocatalysts for the conversion of CO2 into chemicals has emerged as one of the most promising strategies. Herein, beyond those well-studied materials, a rare-earth sulfide-based nanocrystal NaCeS2 is fabricated and investigated for efficient and selective conversion of CO2 into CO, where the role of Ce ions is crucial. Firstly, the hybridization of Ce 4f and Ce 5d orbitals contributes to the photoresponsive band structure of NaCeS2 . Secondly, due to the charge rearrangement supplied by the incompletely filled 4f orbitals of Ce ions, NaCeS2 exhibits excellent charge separation efficiency and CO2 adsorption affinity, reducing the energy barrier for the conversion from CO2 to CO. Moreover, a NaCeS2 -MoS2 heterostructure is also designed to further boost the electron transfer from the Mo site to the Ce site, which results in an improvement of the catalytic reduction yield from 7.24 to 23.42µmol g-1 within 9 h (both better than TiO2 controls). This work offers a platform for the development of rare-earth-based photocatalysts for CO2 conversion.

Construction of the Sn-doped defect pyrochlore oxide KNbMoO6·H2O/g-C3N4 composite and its photocatalytic reduction of CO2

The Sn-doped defect pyrochlore oxide KNbMoO6·H2O/g-C3N4 composite can be used as a photocatalyst for conversion of CO2 in order to deal with energy and environmental issues.

2d/2dtio2/G-C3n4 Ultrathin Nanosheet as an Efficient Biomimetic Photocatalyst for Conversion of Co2 and Ch4

2d/2dtio2/G-C3n4 Ultrathin Nanosheet as an Efficient Biomimetic Photocatalyst for Conversion of Co2 and Ch4

Improved Photoactivities of Large‐surface‐area g‐C3N4 for CO2 Conversion by Controllably Introducing Co‐ and Ni‐Species to Effectively Modulate Photogenerated Charges

AbstractSimultaneously modulating photogenerated electrons and holes by introducing transitional metals species on carbon nitride (g‐C3N4) are highly desired for effectively photocatalytic converting CO2. Herein, a cyanuric acid‐melamine preassembled approach is developed to obtain large‐surface‐area g‐C3N4 with high photoactivity for CO2 conversion, and its photoactivity is improved by controllably modifying Co‐species during the synthetic process of g‐C3N4, attributed to its hole capture capability and catalytic capability for water oxidation. Moreover, the photoactivity is further improved by decorating Ni‐species on g‐C3N4, attributed to its electron capture capability and catalytic capability for CO2 reduction. Noticeably, simultaneously modulating holes and electrons displays a noticeable synergy on improving photocatalytic activities. Interestingly, the photoactivity of amount‐optimized Co and Ni co‐modified g‐C3N4 is 3.1‐time higher than that of pristine g‐C3N4, with the quantum efficiency improvement of 4.5 time at 405 nm. This work will provide a feasible way of simultaneously modulating electrons and holes to fabricate high‐performance g‐C3N4‐based nano‐sized photocatalysts for CO2 conversion.

Ternary ZnO/ZnAl2O4/ Al2O3 composite nanofiber as photocatalyst for conversion of CO2 and CH4

Electrospinning is a flexible synthesis method which not only facilitates the preparation of the nanofibers with dramatically improved surface area, but also takes advantage of the structural defects to form heterojunctions with photocatalytic activities. In this study for the first time, a continuous layer of composite ceramic nanofiber was fabricated by employing two-nozzle electrospinning method to make the nanofiber from a 12: 3: 3: 13: 87 (percent ratio) solution of aluminum acetate: boehmite nanoparticle: zinc acetate: polyacrylonitrile: dimethylformamide respectively. The step by step thermal post-processing was performed on the nanofiber to decompose the polymeric part and achieve a pure ceramic phase. Characterization of the ceramic nanofiber was conducted using Fe-SEM, FTIR, XRD, TGA-DTA, BET and UV–Vis techniques. The SEM and XRD results confirmed that the ceramic nanofiber with average diameter of 160 nm was composed of ZnO, Al2O3 and ZnAl2O4 phases. The resultant nanofiber was used as a photocatalyst for conversion of CO2 in presence of CH4 as the reductant and UV–A irradiation under mild conditions. The maximum conversion percentages of CO2 and CH4 after 240 min were 20% and 11.7% respectively.The present study proposes a method for preparing a ternary nanofiber of Al2O3, ZnO, and ZnAl2O4 with the potential to be used as a photocatalyst for conversion of CO2 in presence of CH4.

Improved photoactivities for CO2 conversion and phenol degradation of α-Fe2O3 nanoparticles by co-coupling nano-sized BiPO4 and CuO to modulate electrons

It's highly desired to design and fabricate effective α-Fe2O3-based photocatalysts by increasing the surface area, promoting the charge separation and providing catalytic function. Herein, specific surface area-enlarged α-Fe2O3 (SE-FO) nanoparticles have been successfully synthesized by a functional molecule-modulated phase-separated hydrothermal method, with high photocatalytic activities for CO2 conversion and phenol degradation. The photocatalytic activities of SE-FO could be greatly improved by coupling nano-sized BiPO4 via an in-situ introduction method. This is attributed to the coupled BiPO4 as a high-energy platform to accept photogenerated electrons from α-Fe2O3 so as to enhance the charge separation mainly by means of surface photovoltage spectra and fluorescence spectra-related to the amount of produced •OH species. Moreover, the photocatalytic activities are further improved by introducing a proper amount of nanocrystalline CuO via a simple impregnation process. It is confirmed based on the temperature-programmed desorption and electrochemical reduction measurements that the improved photoactivity is attributed to the introduced CuO as the co-catalyst for promoting electron-induced reduction reactions. Remarkably, the optimized α-Fe2O3 nanocomposite exhibits about 3-time photoactivity improvement compared with the pristine α-Fe2O3. This work would provide a feasible route to fabricate high-activity α-Fe2O3-based photocatalysts for CO2 conversion and phenol degradation.

Germanium-substituted Zn2TiO4 solid solution photocatalyst for conversion of CO2 into fuels

Photocatalytic CO2 reduction conjugated with H2O oxidation is regarded as a promising artificial photosynthesis system because it can simultaneously solve energy and environment problems. Here, a novel solid solution, Zn2Ti1−xGexO4 (0 ≤ x ≤ 0.15), with high photocatalytic activity for the reaction was successfully synthesized via a facile molten salts route. The Zn-based solid solutions with size about 200 nm have a homogeneous inverted cubic spinel structure (Fd3m) and a continuously modulated band gap with the Ge content. For the CO2 reduction reaction with H2O under simulated solar irradiation, the Zn2Ti1−xGexO4 solid solutions display not only high activity for the conversion of CO2 into CH4 and CO fuels, but also long-term stability (>60 h of catalytic reaction). Experimental results and theoretical calculations indicated that the conduction and the valence bands of the cubic spinel Zn2TiO4 are positively shifted by introducing Zn2GeO4 with a pseudocubic inverse spinel structure, but the band gaps of solid solutions are simultaneously modulated with the introduction of germanium. Nevertheless, the Zn2TiO4 affords a light-carrier effective mass and strong electron delocalization by forming a solid solution with Zn2GeO4, which is beneficial to improving migration of photogenerated electrons and holes. As a synergistic result of band gap narrowing and high carrier diffusion, good conversion efficiencies for production of solar fuels through the reactions of CO2 reduction with H2O are achieved.