Photocatalysts For CO2 Photoreduction Research Articles

ZnIn2S4/TiO2 photocatalyst for CO2 photoreduction: Advancing sustainable energy conversion to renewable solar fuels

The rapid increase in CO2 concentration in the atmosphere raised global climate challenges, which creates attention for the researcher to mitigate CO2 from the atmosphere so that the environment can be sustained for generations. From the photocatalysis perspective, reducing CO2 into carbon monoxide (CO) and methane (CH4) is a promising pathway for sustainable solar fuel production. Here, we fabricated a heterojunction nanocomposite photocatalyst of ZnIn2S4 and TiO2. The photocatalyst was highly efficient for CO2 reduction with 1754 and 481 μmol/g yields of CO and CH4, respectively. The photocatalyst had excellent photocatalytic activity and was stable for five consecutive experiments without significant activity loss. The potential of ZnIn2S4/TiO2 photocatalyst to revolutionize carbon monoxide production for various applications underscores its significance in advancing sustainable carbon mitigation strategies.

A CuI Cluster-Based Covalent Metal-Organic Framework as a Photocatalyst for Efficient Visible-Light-Driven Reduction of CO2.

The application of solar energy to convert CO2 into high-value chemicals and fuels has been considered a highly desirable approach to relieving the greenhouse effect and energy crisis. However, the exploration of appropriate photocatalysts remains a major challenge. Combining the respective advantages of covalent organic frameworks and metal-organic frameworks to construct covalent metal-organic frameworks (CMOFs) can be a valid strategy to provide efficient, reliable, and eco-friendly photocatalysts. In this study, a CuI cluster-based CMOF (JNM-2) is used as a photocatalyst for CO2 photoreduction under visible-light irradiation. JNM-2 exhibits remarkable efficiency in photocatalytic CO2 reduction with high production rates of HCOOH (9019 μmol g-1 h-1 ) and CO (835 μmol g-1 h-1 ). The active center, reaction intermediates, and product generation pathways are elucidated by in situ DRIFTS and DFT calculations. This work demonstrates the tremendous possibilities of CMOFs as photocatalysts for CO2 reduction and provides profound insights into the mechanism of CO2 conversion into HCOOH/CO by using a molecularly accurate structural model.

Novel CeOx-modified In2O3 with stabilized Ce3+ states as a highly efficient photocatalyst for photoreduction of CO2 with CH4 or H2O

In this work, CeOx/In2O3 containing mass ratios of 0.1, 0.2 and 0.3 CeOx were prepared via a simple wet impregnation method and their photoactivity was evaluated for CO2 photoreduction with CH4 or H2O. HRTEM verified the formation of an oxide-oxide interface in CeOx/In2O3. XPS analysis revealed the presence of trivalent Ce3+ as the predominant species in CeOx/In2O3 that were formed due to the stabilization of Ce3+ states by In2O3. The presence of a higher content of Ce3+ reflected a strong interfacial contact between CeOx and In2O3. The optimized CeOx/In2O3 showed 4–7 times enhancement as compared to the unmodified In2O3 for CO2 photoreduction with CH4 or H2O reactions. The selectivity of CO and H2 were dependent on the reductant used. The selectivity of CO and H2 for CO2 photoreduction with CH4 remained at 33 % and 66 % after CeOx addition. Contrarily, the selectivity of H2 showed a gradual drop from 61 % to 18 % with an increase in CeOx loading when H2O was used as reductant. The improved activity of CeOx/In2O3 was because of (i) promoted charge transfer and separation due to strong interfacial contact and Type II band alignment, (ii) enhanced light absorption, and (iii) increased basic sites for CO2 adsorption.

Ions-exchange anchoring Cu7S4 cocatalyst on K2Ti8O17 nanowires assembly for enhanced CO2 photoreduction through efficient charge separation

Photocatalytic CO2 reduction into solar fuels has received increasing attention because it is a promising approach to tackle the environment and energy issues we are currently facing. Herein, the composite of K2Ti8O17 nanowires assembly coupled with Cu7S4 cocatalyst has been successfully prepared by an ion exchange method, in which the CuCl is employed as the copper source to convert CdS to Cu7S4. The photocatalytic performance of the integrated K2Ti8O17-Cu7S4 composite is evaluated by CO2 photoreduction, and it exhibits superior photoreduction capability than pristine K2Ti8O17 nanowires assembly. In particular, the K2Ti8O17-Cu7S4-0.2 sample displays the highest CH4 (6.02 μmol g−1 h−1) and CO (0.89 μmol g−1 h−1) yield within 4 h light irradiation, which is 3.83 and 12.71 times higher than that of K2Ti8O17 sample, respectively. Based on the photo/electrochemical test results, the anchoring of Cu7S4 cocatalyst can promote the photogenerated electron-hole pairs separation and charge transfer of the K2Ti8O17, which contributes to more photogenerated electrons participating in the process of photocatalytic CO2 reduction to CH4. This work offers a promising approach to design efficient noble-cocatalyst-free photocatalyst for CO2 photoreduction.

Zinc porphyrin and rhenium complex-based donor-acceptor conjugated porous polymer for visible-light-driven conversion of CO2 to CO

Visible-light-driven photocatalytic conversion of CO2 into valuable chemicals and fuels is highly desirable but challenging. Herein, we report a donor-acceptor type conjugated porous polymer (ZnPor@Re) consisting of zinc porphyrin as the donor and rhenium complex as the acceptor as an ideal platform for visible-light-driven photocatalytic conversion of CO2 into CO. As expected, ZnPor@Re shows excellent photocatalytic activity for reduction of CO2 under white LED irradiation, achieving up to CO production of 66.2 mmol g–1, selectivity of 99.8% and apparent quantum yield of 1.3% at 420 nm. Time-resolved photoluminescence decay experiment indicates that donor-acceptor structure within the skeleton of ZnPor@Re affords an oriented electron transfer channel of the excited electrons from zinc porphyrin donor to rhenium complex acceptor, thus facilitating separation and transfer of photogenerated charge carries. The current work highlights the great potential of amorphous conjugated porous polymer as photocatalyst for CO2 photoreduction.

A multifunctional anionic metal-organic framework for high proton conductivity and photoreduction of CO2 induced by cation exchange.

Metal-organic frameworks (MOFs) provide an ideal platform for loading various guests owing to their available space, and can be developed as a class of multifunctional materials. Herein, we cover the design and synthesis of two kinds of exchanged frameworks with multifunctional applications based on H3ImDC and In(NO3)3·2H2O through guest exchange inside the framework. The guest ammonium ion (NH4+) and [Ru(2,2'-bipyridine)3]2+ (Rubpy) are selected to exchange the dimethylammonium cation (Me2NH2+) encapsulated within In-MOF, giving birth to two kinds of new MOFs, named NH4+@In-MOF and Rubpy@In-MOF respectively. The proton conduction of NH4+@In-MOF and the CO2 photoreduction of Rubpy@In-MOF are investigated. Under different test conditions, the proton conductive behaviors of NH4+@In-MOF are evaluated and the best proton conductive value can reach up to 9.81 × 10-3 S cm-1. Compared to the original In-MOF, Rubpy@In-MOF exhibits a significantly enhanced CO2 photoreduction performance under a pure CO2 atmosphere. Furthermore, its photocatalytic activity is retained even under a 10% CO2 gas atmosphere, displaying a synergistic effect between Rubpy and In-MOF24 within Rubpy@In-MOF.

Hollow TiO2 Microsphere/Graphene Composite Photocatalyst for CO2 Photoreduction

In an attempt to improve the photocatalytic activity of anatase TiO2, we developed a composite photocatalyst composed of hollow TiO2 microspheres (hTS) and graphene. The hTS were prepared through a two-step hydrothermal process, where SiO2 microspheres with desirable diameters of 100–400 nm were used as sacrificial templates. Accordingly, the effect of the hTS cavity size on the activity of the catalyst in wet CO2 photoreduction (CO2PR) was studied. Furthermore, it was established that the hydrothermal pH value crucially influences the photocatalytic activity of the hTS photocatalyst, as well as its composition and microstructure. The hTS photocatalyst was also combined with graphene (0–90 wt%) to improve its photocatalytic activity. This study provides insight into the optimal microsphere diameter, hydrothermal pH value, and graphene/hTSx ratio required for designing hollow microsphere-based photocatalysts with enhanced CO2PR performances.

Hierarchical hyper-branched titania nanorods with tuneable selectivity for CO2 photoreduction.

Utilising captured CO2 and converting it into solar fuels can be extremely beneficial in reducing the constantly rising CO2 concentration in the atmosphere while simultaneously addressing energy crisis issues. Hence, many researchers have focused their work on the CO2 photoreduction reaction for the last 4 decades. Herein, the titania hyper-branched nanorod (HBN) thin films, with a novel hierarchical dendritic morphology, revealed enhanced CO2 photoreduction performance. The HBNs exhibited enhanced photogenerated charge production (66%), in comparison with P25 (39%), due to the unique hyper-branched morphology. Furthermore, the proposed HBN thin films exhibited a high degree of control over the product selectivity, by undergoing a facile phase-altering treatment. The selectivity was shifted from 91% towards CO, to 67% towards CH4. Additionally, the HBN samples showed the potential to surpass the conversion rates of the benchmark P25 TiO2 in both CO and CH4 production. To further enhance the selectivity and overall performance of the HBNs, RuO2 was incorporated into the synthesis, which enhanced the CH4 selectivity from 67% to 74%; whereas the incorporation of CuO revealed a selectivity profile comparative to P25.

Varied proton conductivity and photoreduction CO2 performance of isostructural heterometallic cluster based metal–organic frameworks

A family of isostructural heterometallic MOFs based on Fe2M clusters serve as potential proton conductors and photocatalysts for CO2 photoreduction.

Hydrocarbon production by addition of Cu‐ZnO on g‐C3N4 for CO2 conversion

AbstractIn this study, copper/zinc oxide/graphite nitrogen carbide (Cu/ZnO/g‐C3N4) is prepared using a hydrothermal method and applied as a photocatalyst for CO2 photoreduction. The morphology and structural properties of the obtained Cu/ZnO/g‐C3N4 are systematically characterized through X‐ray powder diffraction, ultraviolet–visible absorption spectroscopy, transmission electronic microscopy, and photoluminescence spectroscopy. A 3 wt% Cu/ZnO/g‐C3N4 photocatalyst exhibits high CH4 (40.7 μmol g−1 hr−1), CO (65.1 μmol g−1 hr−1), and CH3OH (92.5 μmol g−1 hr−1) production rates, which are 38.3, 77.1, and 58.1 fold higher than the pure g‐C3N4. The production rate is higher than those for bulk g‐C3N4 and ZnO/g‐C3N4. Finally, the reaction mechanism of Cu/ZnO/C3N4 is proposed in this study.

Immobilizing perovskite CsPbBr3 nanocrystals on Black phosphorus nanosheets for boosting charge separation and photocatalytic CO2 reduction

Direct conversion CO2 to useful chemical fuels by photocatalysis has been considered to be a promising strategy for renewable energy production. The realization of this goal relies mainly on the development of photocatalysts with ideal charge separation efficiency. Here, we use all-inorganic perovskite nanocrystals (CsPbBr3) immobilized on two-dimensional (2D) black phosphorus nanosheets (BP), resulting in a new and effective CsPbBr3/BP photocatalyst for CO2 photoreduction. Compare to pristine CsPbBr3, the introduction of BP generates more active sites for facilitating CO2 activation and trapped the excited electrons from CsPbBr3 with high charge separation efficiency. Time-resolved photoluminescence and transient absorption measurements together with density functional theory calculations provide a clear elucidation of the charge separation pathways that contribute to the enhanced CO2 conversion rate. This significant feature provides a new venue for constructing all-inorganic perovskite-based photocatalyst by combining with BP for solar energy conversion and artificial photosynthesis.

Bi-Quantum-Dot-Decorated Bi4V2O11 Hollow Nanocakes: Synthesis, Characterization, and Application as Photocatalysts for CO2 Reduction

Bi-quantum-dot-modified Bi4V2O11 (BQDs/Bi4V2O11) hollow nanostructures were prepared via a two-step hydrothermal process and used as photocatalysts for CO2 photoreduction under simulated sunlight i...

SrCO3-modified brookite/anatase TiO2 heterophase junctions with enhanced activity and selectivity of CO2 photoreduction to CH4

Utilizing the abundant solar energy to chemically convert CO2 into high-energy chemical fuels such as CO, CH4 or CH3OH offers a way to address the serious concerns about the increasing atmospheric CO2 levels and the depletion of fossil fuels. Herein, a series of SrCO3-modified TiO2 composites have been synthesized by adding SrCl2 into a TiCl4 hydrothermal reaction solution. It is found that brookite TiO2quasi nanocubes with high phase purity (denoted as pristine TiO2) can be derived from the TiCl4 reaction solution, and the additive Sr2+ ions lead to the formation of SrCO3-modified TiO2 heterophase junctions (HPJs) containing brookite nanorods and anatase nanoparticles. When used the SrCO3-modified TiO2 HPJs (hereafter denoted as SrCO3/HPJs) as photocatalyst for CO2 photoreduction, significantly enhanced activity and selectivity for CO2 photoreduction to CH4 can be achieved as compared to the pristine TiO2. Especially, 1.0% SrCO3/HPJs composite shows CH4/CO production activities of 19.66/2.64 μmol g−1 h−1 with an overall photoactivity of 162.6 μmol g−1 h−1, which is 12.3 times of the pristine TiO2 that shows an overall photoactivity of 13.2 μmol g−1 h−1 with CH4/CO production activities of 0.79/3.46 μmol g−1 h−1. The brookite/anatase TiO2 HPJs can effectively promote the photogenerated charge separation and restrain the interfacial charge recombination, and the SrCO3 species on the TiO2 HPJs can act as an efficient synergistic catalyst to improve the CO2 adsorption and activation abilities, and thus cause the enhanced activity and selectivity for CO2 photoreduction to CH4. This work represents the first example of coupling TiO2 HPJs with alkaline earth metal carbonates for efficient CO2 photoreduction.

A review of nanostructured non-titania photocatalysts and hole scavenging agents for CO2 photoreduction processes

Non-titania photocatalysts, including metal sulphides, oxides, oxynitrides and nitrides, have been deployed as the photocatalyst for CO2 photoreduction since last century. The nanostructured non-titania photocatalysts and the introduction of hole scavenging agents into the CO2 photoreduction system have revealed some key characteristics to stimulate the conversion of CO2 to hydrocarbons.

Photocatalytic reduction of carbon dioxide by strontium titanate nanocube-dispersed mesoporous silica

Strontium titanate nanocube-dispersed mesoporous silica (STO(NC)-MPS) nanocomposite was examined as a photocatalyst for the photoreduction of CO2. Copper (Cu) was examined as a co-catalyst, and the results showed that it was effective for the production of CO under a flow of CO2 and UV irradiation in water. As confirmed by gas chromatography–mass spectrometry, 13CO was produced in the presence of 13CO2, thus demonstrating that CO was generated upon photoreduction of CO2. Simultaneous formation of O2 suggested that water acted as a reductant in the photocatalysis process. Moreover, Cu supported on STO(NC)-MPS showed higher selectivity toward CO2 reduction when compared with Cu-supported composite prepared from mesoporous silica and SrTiO3 that was synthesized by conventional solid state reaction. Thus, the current findings highlight the characteristics and advantages of SrTiO3 nanocubes and their nanocomposites with mesoporous silica as photocatalysts for CO2 photoreduction.

Polymeric g-C3N4Coupled with NaNbO3Nanowires toward Enhanced Photocatalytic Reduction of CO2into Renewable Fuel

Visible-light-responsive g-C3N4/NaNbO3 nanowires photocatalysts were fabricated by introducing polymeric g-C3N4 on NaNbO3 nanowires. The microscopic mechanisms of interface interaction, charge transfer and separation, as well as the influence on the photocatalytic activity of g-C3N4/NaNbO3 composite were systematic investigated. The high-resolution transmission electron microscopy (HR-TEM) revealed that an intimate interface between C3N4 and NaNbO3 nanowires formed in the g-C3N4/NaNbO3 heterojunctions. The photocatalytic performance of photocatalysts was evaluated for CO2 reduction under visible-light illumination. Significantly, the activity of g-C3N4/NaNbO3 composite photocatalyst for photoreduction of CO2 was higher than that of either single-phase g-C3N4 or NaNbO3. Such a remarkable enhancement of photocatalytic activity was mainly ascribed to the improved separation and transfer of photogenerated electron–hole pairs at the intimate interface of g-C3N4/NaNbO3 heterojunctions, which originated from the...

Cu2s/Cu1.96S /Graphite Oxide Composite As Photocatalyst for CO2 Photoreduction

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A critical review of CO2 photoconversion: Catalysts and reactors

Photocatalytic conversion of CO2 to either a renewable fuel or valuable chemicals, using solar energy has attracted more and more attention, due to the great potential to provide an alternative clean fuel and solve the problems related to the global warming. This review covers the current progress of photocatalytic conversion of CO2 by photocatalysis over the metal oxides. A brief overview of the fundamental aspects for artificial photosynthesis has been given and the development of novel photocatalysts for CO2 photoreduction has been discussed. Several key factors for high-efficiency CO2 photoreduction and the recent development of photocatalytic reactor design for this artificial photosynthesis have also been highlighted.

Comparison of catalytic activity of carbon-based AgBr nanocomposites for conversion of CO2 under visible light

The catalytic activities of carbon-based AgBr nanocomposites (AgBr/CNT, AgBr/GP, AgBr/EG, and AgBr/AC) for CO2 reduction to hydrocarbons under visible light were investigated in this study. The carbon-based AgBr nanocomposites were prepared on carbon-based supporting materials (CNT, GP, EG, and AC) by the deposition–precipitation method in the presence of cetyltrimethylammonium bromide (CTAB). The photocatalytic activities of AgBr nanocomposites on different supporting materials (CNT, GP, EG, and AC) were investigated by CO2 reduction yield in the presence of water under visible light (λ > 420 nm). The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that AgBr nanoparticles were well dispersed on the surface of supporting materials. AgBr/CNT and AgBr/GP had a relatively higher reduction yield under visible light due to the transfer of photoexcited electrons from the conduction band of well-dispersed AgBr to carbon supporting materials. In addition, the carbon-based AgBr nanocomposites were stable in the repeated uses under visible light. The total product yields of carbon-based AgBr nanocomposites after the 5 repeated uses almost remained about 83% of the first run. Therefore, carbon-based AgBr nanocomposite is an effective and stable visible-light-driven photocatalyst for CO2 photoreduction.