Photocatalytic Conversion Of CO2 Research Articles

Reinforcing the efficiency of photocatalytic CO2 conversion with H2O vapor through the integration of photothermal Cu/C@Bi/C supported on 3D g-C3N4 under full-spectrum solar irradiation

Developing an efficient photocatalyst for CO2 conversion to chemical fuels that maximizes the utilization of solar energy, particularly near-infrared light, remains a persistent challenge. Meanwhile, it is difficult to suppress the H2 evolution during the photocatalytic process. Herein, Cu/C@Bi/C grafted on the surface of 3D g-C3N4 (NCN) can serve as a highly durable and active catalyst for photothermal synergistic catalytic CO2 reduction under full-spectrum solar irradiation in solid-liquid-gas three-phase interfaces, wherein the Cu/C@Bi/C serves as a harvesting-near-infrared light nanoreactor and an electron transport bridge for the enhancement of the interface local temperature and the efficient transfer of photoinduced electrons. As a result, the hybrid catalyst shows excellent photothermal catalytic activity of CO2 to CO (169.26 μmol·g−1·h−1) and CO2 to CH4 (1.94 μmol·g−1·h−1), outperforming the majority of the conventional photocatalysts, whereas the competitive reaction of H2 evolution can be inhibited. This study presents a feasible approach for the efficient utilization of solar energy by harnessing near-infrared light through nano-reactors, thereby providing a viable strategy for photothermal catalytic CO2 reduction.

Enhanced charge separation of Cu-BTC@CuSe@TiO2 hollow octahedrons for efficient CO2 photoreduction with superior CO selectivity

Solar-driven photocatalytic conversion of CO2 into high-value-added fuels has attracted widespread attention. However, the relatively low conversion efficiency and product yield severely limited photocatalytic applications. In this work, binary Cu-BTC@TiO2 catalysts with adjustable inner cavity were prepared using copper-based metal organic framework (Cu-BTC) octahedrons as substrate via a solvothermal reaction. In this process, the inner Cu-BTC octahedrons can be controllably etched into a hollow octahedral structure in the presence of HF. Subsequently, the Cu-BTC@CuSe@TiO2 hollow octahedrons (HOs) were fabricated by selenization reaction and exhibited various properties such as abundant active sites for CO2 adsorption and reduction reactions, shortened charge transfer distance to prevent electron-hole recombination, and internal reflection/scattering effects to improve solar light utilization. Moreover, the formed dual p-n heterostructures between p-type CuSe and n-type semiconductors (Cu-BTC and TiO2) effectively promote spatial separation and migration of charge carriers. The synergistic effect of these advantages makes the optimized Cu-BTC@CuSe@TiO2 HO catalyst exhibit remarkable CO2 photoreduction performance with a CO production rate of 72.3 μmol h−1 g−1 and near 100 % selectivity. This work opens a new pathway for designing highly active photocatalysts with excellent product selectivity.

Synergistic CdS@CeO2 nanocomposites: Harnessing Z-scheme electron transfer for enhanced photocatalytic CO2 conversion and aqueous Cr(VI) reduction

The present work describes the fabrication of CdS-D@CeO2 Z-scheme heterojunctions as highly stable, efficient and recyclable photocatalysts for the visible light assisted reduction of CO2 to methanol as well as Cr(VI) to Cr(III). The bare CeO2 produced methanol with the rate of 111 μmolh−1g−1 that is much lower in comparison to CdS-D@CeO2 (501 μmolh−1g−1). In addition, the photocatalytic efficiency remained nearly same for three successive runs, indicating the higher stability and recycling ability of the heterojunctions CdS-D@CeO2. It was also observed that under direct sunlight irradiation, CdS-D@CeO2 efficiently reduced 100% Cr(VI) to Cr(III) in an aqueous medium in just 40 minutes. Moreover, >95% removal was maintained even after 5 catalytic cycles. Additionally, for mimicking real contaminated water samples, the influence of the foreign ions on Cr(VI) reduction was evaluated by using lake water sample and no adverse effects on the result were observed. Thus, this work showed a way to develop cost-effective, easily synthesized, durable and recyclable composite photocatalysts for CO2 utilization and proficient removal of waste water pollutants by employing the clean, green, and renewable solar energy.

Enhanced CO2 photoreduction over bismuth-rich Bi4O5Br2: Optimized charge separation and intrinsic barriers

Photocatalytic CO2 conversion into chemicals is one of effective strategies to overcoming the energy crisis and global warming. However, the CO2 photoreduction efficiency is hindered by poor charge separation and CO2 activation. The composition regulation of photocatalyst is a promising strategy to solve these issues. Herein, we constructed the Bi4O5Br2 in ionic liquid through a solvothermal approach. The electronic structure of photocatalyst has been regulated over Bi4O5Br2 through Bi-rich strategy, achieving enhanced charge separation and long carrier lifetime. Density-functional theory (DFT) calculations found that the intrinsic barriers for CO2 adsorption-activation can be effectively optimized over Bi4O5Br2, promoting the CO2 dissociation and facilitating the generation of *COOH. Therefore, Bi4O5Br2 possesses improved evolution rates of 23.81 and 1.33 μmol g−1 for CO and CH4 under irradiation of 300 W Xe lamp for 4 h. This work demonstrates a valuable strategy for the rational construction of efficient materials towards CO2 photoreduction.

CO2 Photoreduction Over Semiconducting 2D Materials with Supported Single Atoms: Recent Progress and Challenges.

In the face of the growing energy crisis and environmental challenges, substantial efforts are now directed toward sustainable clean energy as a replacement for traditional fossil fuels. CO2 photoreduction into value-added chemicals and fuels is widely recognized as a promising approach to mitigate current energy and environmental concerns. Photocatalysts comprising single atoms (SAs) supported on two-dimensional (2D) semiconducting materials (SAs-2DSemi) have emerged as a novel frontier due to the combined merits of SA catalysts and 2D materials. In this study, we review advancements in metal SAs confined on 2DSemi substrates, categorized into four groups: (1) metal oxide-based, (2) g-C3N4-based, (3) emerging, and (4) hybridized 2DSemi, for photocatalytic CO2 conversion over the past few years. With a particular focus on highlighting the distinct advantages of SAs-2DSemi, we delve into the synthesis of state-of-the-art catalysts, their catalytic performances, and mechanistic elucidation facilitated by experimental characterizations and theoretical calculations. Following this, we outline the challenges in this field and offer perspectives on harnessing the potential of SAs-2DSemi as promising photocatalysts. This comprehensive review aims to provide valuable insights for the future development of 2D photocatalytic materials involving SAs for CO2 reduction.

Metal doped TiO2 decorated carbon nanostructured materials as an emerging photocatalysts for solar fuels production

The concept of photocatalytic CO2 and H2O conversion to solar fuels and value-added products provides simultaneous solution for increased energy demands and environmental problems. However, the lack of efficient photocatalysts restrains the large-scale development of photocatalytic technology. In the present study, noble (Pt and Au) and transition metal (Ni) doped nanoflakes assembled on TiO2@carbon microrods with high surface area and rutile crystal structure is prepared via fast, versatile solvothermal method. The photocatalytic performance of the prepared nanocomposites was evaluated in two photocatalytic systems: CO2 reduction and hydrogen production via photoreforming. Pt-doped catalyst showed enhanced hydrogen production efficiency and increased CH4 selectivity, while Ni-doped catalyst exhibited remarkable CO2 reduction activity with higher selectivity towards CO. The mechanism of Pt-promoted CH4 formation and Ni- and Au-promoted CO formation was thoroughly discussed regarding kinetic and thermodynamic parameters.

Spiral-template from waste tea-leaf to design hierarchical dispersed zinc oxide nanocatalyst for boosting their photocatalytic carbon dioxide reduction

The utilization of cellulose-based templates to enhance the dispersion of zinc oxide (ZnO) nanoparticles represents an effective approach for enhancing their photocatalytic carbon dioxide (CO2) reduction activity. However, the limited availability of surface active sites on linear cellulose fiber has posed a significant challenge for loading ZnO nanoparticles. The present study introduces a technique for segregating spiral vessel (SV) from waste tea-leaves and employing them as templates for in-situ self-assembled ZnO nanoparticles. Due to the inherent three-dimensional (3D) stability of the spiral structure, ZnO nanoparticles exhibit excellent dispersion and maintain a stable hierarchical spiral morphology even after template removal. With the help of a field emission scanning electron microscope (FE-SEM), it could be observed that SV-loaded ZnO nanospheres extracted from waste Pu 'er tea-leaves retained the best spiral morphology after removing the template. The photocatalytic CO2 conversion over spheroidal ZnO with SV as templates (ZnOSS) significantly enhanced yields of CO and CH4, reaching 6.700 and 1.666 μmol·g−1h−1, respectively, surpassing those of other synthesized catalysts. The results obtained from the free radical scavenging experiment and electron paramagnetic resonance (EPR) test demonstrate the pivotal involvement of superoxide radicals (∙O2−) and hydroxyl radicals (∙OH) in the photocatalytic reduction of CO2. Quantum mechanical simulation further verified that the ZnO (0 0 2) crystal face was the best reaction interface with CO2. The design of a cellulose-based spiral template not only facilitates the valorization of waste biomass but also offers a novel perspective for the synthesis of efficient photocatalysts.

S‑scheme heterojunction of thin-layer O-modified graphitic carbon nitride/cobalt porphyrin to promote photocatalytic CO2 conversion

The emissions of CO2 are increasing year by year, which have led to serious environmental problems. Converting CO2 into valuable fuels through photocatalysis is a promising strategy. In this research, oxygen atoms were successfully innovated into graphitic carbon nitride (CN). Additionally, cobalt porphyrin (CoTPP) was successfully loaded onto the modified carbon nitride (Co/CN). The generation of interfacial electric fields and bending bands between CN and CoTPP was demonstrated experimentally. The electrons in the CN and the holes in the CoTPP were combined to form a unique S-scheme heterojunction structure, and efficient separation of carriers was promoted. As a result, the CO conversion under visible light irradiation reached an impressive 100.70 μmol g−1 h−1. By integrating theoretical and experimental findings, this study underscores the critical role of catalyst design in enabling efficient photocatalytic CO2 reduction.

A covalent organic framework integrating photocatalytic center and electron reservoir for photocatalytic CO2 reduction to HCOOH

Direct and efficient photocatalytic conversion of CO2 into fuels and high value-added chemicals under sunlight is of great significance in alleviating the energy crisis and environmental issues. Covalent organic frameworks (COFs) have attracted much attention in the photocatalytic field as materials that can be pre-designed on demand. Taking advantage of the pre-designable properties of COFs materials, the integration of organic building blocks with photocatalytic activity and photoelectron-resident properties into frameworks can improve the electron-hole separation efficiency and photocatalytic performance. Here, we report a newly designed COF (COF-TVBT-N) with triazine and alkenyl groups that can be used as a photocatalyst to accomplish the photoreduction of CO2 to HCOOH under simulated sunlight without the assistance of metal sites and photosensitizers. Furthermore, we unambiguously reveal that the photocatalytic active center in COF-TVBT-N is TVBT through the combination of experiments and theoretical calculations. DFT calculations suggest that the adsorption of H near the active center is beneficial for the adsorption and photoreduction of CO2 in this photocatalytic system. The photoexcitation process and photocatalytic CO2 reduction mechanism of COF-TVBT-N are also reasonably deduced based on DFT calculations. This work provides ideas for the design of COFs as photocatalysts for CO2 reduction and gives insights into the mechanism of CO2 conversion to HCOOH.

Non-trivial topological surface states regulation of 1 T-OsCoTe2 enables selective C―C coupling for highly efficient photochemical CO2 reduction toward C2+ hydrocarbons

Despite ongoing research, the rational design of non-trivial topological semimetal surface states for the selective photocatalytic CO2 conversion into valuable products remains full of challenges. Herein, we present the synthesis of lattice-matched 1 T-OsCoTe2 for the photoreduction upgrading of CO2 to tri-carbon (C3) alkane (propane, C3H8) by the integration of experimental work and theory prediction/calculation. Experimental studies suggested a high electron-based selectivity of 71.2 % for C3H8 and an internal quantum efficiency of 54.6 % at 380 nm. In-situ X-ray photoelectron spectroscopy and X-ray absorption fine structure spectroscopy demonstrated that Co and Os atoms coordinated with Te atoms enable an efficient Os―Te―Co electron transfer to activate the generation of *CH3, *CHOCO and *CH2OCOCO. Density functional theory calculations further confirmed Os―Te―Co electron bridging on the improved CO2 conversion kinetics. To our knowledge, this is the first report suggesting the role of Os atoms in accelerating the photocatalytic CO2 conversion activity of the topological semimetal 1 T-OsCoTe2.

Size‐Dependent Multi‐Electron Donation in Metal‐Complex Quantum Dots Hybrid Catalyst for Photocatalytic Carbon Dioxide Reduction

AbstractThe effective conversion of carbon dioxide (CO2) into valuable chemical fuels relies significantly on the donation of multiple electrons. Its efficiency is closely linked to both the density and lifetime of excited charge carriers. In this study, a hybrid catalyst system comprising covalently bonded InP/ZnS quantum dots (QDs) and Re‐complexes is showcased. The electronic band alignment between the QDs and the Re‐complexes is revealed to dominate the multi‐electron transfer process for photocatalytic conversion to methane (CH4). Notably, the size of the QDs is found to be a determining parameter. Among the three QD sizes investigated, transient absorption spectroscopy studies unveil that rapid multi‐electron transfer from the QDs to the Re‐catalyst occurs in smaller QDs (2.3 nm) due to the substantial driving force. Consequently, the photocatalytic conversion of CO2 to CH4 is significantly enhanced with a turnover number of 6, corresponding to the overall apparent quantum yield of ≈1%. This research underscores the possibilities of engineering multi‐electron transfer by manipulating the electronic band alignment within a catalytic system. This can serve as a guide for optimizing photocatalytic CO2 reduction.

2D Copper–Porphyrin Metal–Organic Framework Nanosheet‐Photosensitized TiO2 for Efficiently Broadband Light‐Driven Conversion of CO2 to CH4

The effective utilization of light is crucial in the use of the solar energy for CO2 conversion into valuable fuels and chemicals, in which improving the photocatalytic materials’ capacity to absorb light is a key. Herein, a 2D copper–porphyrin metal−organic framework (MOF)‐photosensitized titania, TiO2/Zn–CuTCPP, is reported, which can absorb wide range of light and photoreduce CO2 with high efficiency under full spectrum irradiation. Fluorescence spectral analysis elucidates the relationship between the photocatalytic activity and the electron–hole separation efficiency. In addition, mechanistic information obtained from electron paramagnetic resonance and in situ infrared analyses demonstrates that the presence of Cu–N4 site in the MOF structure is conducive to the generation of hydrogen free radicals (•H), which plays a key role in the formation of intermediates, thus facilitating the hydrogenation in the reaction process. Consequently, TiO2/Zn–CuTCPP significantly enhances the photocatalytic conversion of CO2 into CH4 with a yield 14 times higher than that of P25.

Metal–oxygen hybridization in Agcluster/TiO2 for selective CO2 photoreduction to CH4

Selective photocatalytic reduction of CO2 to CH4 is one of the most efficient ways to achieve carbon neutralization. However, the formation of methane remains a challenge due to the slow multiple-proton-coupled electron transfer process and the involvement of various C1 intermediates. Herein, an Agcluster/TiO2 catalyst with Ag-O hybridization was synthesized by supporting Ag clusters on anatase phase TiO2 microspheres for photocatalytic CO2 methanation. The Agcluster/TiO2 sample presents an electron selectivity of 86 % for CH4 production with a yield of 25.25 μmol g–1 h−1. Mechanistic study reveals that Ag clusters accelerate the separation and migration of photogenerated carriers, and enhance the adsorption of CO2. Moreover, the Ag-O hybridization promotes the multiple-proton–electron coupling transfer process by effectively stabilizing intermediates and facilitating *CO hydrogenation to *CHO, resulting in selective CO2 reduction to CH4. This work provides a new insight into the development of selective photocatalytic conversion of CO2 to methane by constructing supported cluster catalysts.

Effect of the Ti content and pore size of mesoporous catalysts on CO2 photoreduction

The photocatalytic conversion of CO2 into chemicals and fuels is a promising approach for reducing atmospheric CO2 and addressing energy demands. This study investigates the impact of titanium (Ti) content and pore size in mesoporous silica on CO2 photoreduction (CO2PR) efficiency. Ordered mesoporous silica with a large surface area and stability is used as a matrix for Ti dispersion. Two sets of photocatalysts with varying Ti contents and pore sizes are synthesized and assessed for their microstructures, photoelectric properties, and CO2PR efficiency in both solid–gas and liquid–gas modes. The results reveal that photocatalysts with only 3.0 wt% Ti perform comparably to commercial TiO2 (P25) and can be recycled and reused. Moreover, an enhancement in photocatalytic activity with increasing pore sizes of the photocatalysts is observed. Notably, a photocatalyst with 3.0 wt% Ti and about 8 nm pore size significantly outperforms P25, producing much higher CH4, CO, and CH3OH yields. These findings are crucial for optimizing photocatalyst efficiency and are applicable across various compositions.

Dipole increase synergistic frustrated Lewis pairs induced by Sn dopant boosts ultrathin layered bismuth oxychloride for CO2 photoreduction

Photocatalytic conversion of CO2 into valued chemicals is limited by the CO2 adsorption and activation capability on catalyst surface. In this work, Sn element was successfully doped in ultrathin BiOCl with oxygen vacancies. The dipole moment of catalyst efficient increased due to the Sn doping, leading to a stronger internal electric field. In addition, the surface frustrated Lewis pairs were simultaneously constructed near the oxygen vacancies due to Sn dopant. The formed region of frustrated Lewis pairs-oxygen vacancies as active sites enable an improved CO2 adsorption, and the enhanced internal electric field intensity promoted the charge carrier separation and transfer, leading to the enhanced CO2 reduction performances. This work provides light on enhancing internal electric field by increasing dipole moment and presents feasible tunability of catalytic active sites at atom-scale, providing fundamental insights for understanding of mechanism of element doping in catalyst for improving CO2 photoreduction performance.

Photocatalytic conversion of CH4 and CO2 to acetic acid over Cu/ZnO catalysts under mild conditions

The conversion of methane (CH4) and carbon dioxide (CO2) into high-value products under mild conditions is crucial for addressing the greenhouse effect and advancing C1 chemistry. In this study, Cu/ZnO catalysts were prepared through a one-step wet reduction process, and the catalytic conversion of CH4 and CO2 into acetic acid molecules (CH3COOH) was achieved via photon activation at ambient temperature. The yield of acetic acid was 411.6 μmol/Lgcat−1h−1 with a selectivity of 89.5 % under optimal conditions (100 mWcm−2 light intensity, 25 ± 2 °C, 2 MPa pressure, and a 1:1 CH4:CO2 volume ratio). Enhanced solubility of CH4 in aqueous under increased pressure and temperature was observed to improve acetic acid production. Additionally, the catalytic mechanism involved surface chemisorption of CH4 and CO2, facilitated by ZnO and Cu in the catalyst, leading to C-C coupling and subsequent acetic acid formation, driven by photogenerated electron-hole migration. This study provides a foundational understanding for the synthesis of value-added chemicals through CH4 and CO2 conversion via C-C coupling in mild environments.

The A-site and B-site regulation of LaCoO3 nanofiber based on electrospinning for boosting photocatalytic CO2 conversion

Photocatalytic CO2 reduction with perovskite can effectively address both energy and environmental issues. Nevertheless, it remains challenging to prepare photocatalysts with suitable hollow tubular structures in rational. Herein, the La1-xSrxCo1-δFeδO3 nanofiber with a hollow tubular structure was fabricated through an electrospinning method. The hollow nanofiber structure was constructed by doping Sr atoms in the A-site and Fe atoms in the B-site of LaCoO3 perovskite. The characterization of TEM proved that the hollow tubular structural La1-xSrxCo1-δFeδO3 nanofiber exhibited an external diameter of about 95 nm and an internal diameter of about 50 nm. The hollow tubular structural La1-xSrxCo1-δFeδO3 nanofiber showed superior carrier separation ability which could exhibit significant advantages for photocatalytic CO2 reduction. The CH3OH generation rate over the optimized La0.8Sr0.2Co0.7Fe0.3O3 nanofiber could reach 5.25 µmol⋅g−1⋅h−1. This work highlighted an electrospinning strategy to build a hollow tubular structural La1-xSrxCo1-δFeδO3 nanofiber for enhancing photoreduction CO2.

Integrating CO2 reduction, H2O oxidation and H2 evolution catalysts into a dual S-scheme artificial photosynthetic system for tunable syngas production

It remains a challenge to achieve overall photocatalytic conversion of CO2 with H2O into tunable syngas and O2. Herein, by inserting BiVO4 into the heterointerface of hollow core-shell CdS@T-COF S-scheme photocatalyst, an innovative CdS/BiVO4@T-COF dual S-scheme heterojunction is developed, which gives an almost stoichiometric evolution of syngas (453.6 μmol gcat−1 h−1) and O2 (230.5 μmol gcat−1 h−1). Moreover, the CO output and selectivity only decline by around 20% when pure CO2 is replaced by diluted CO2 (15%) atmosphere. The BiVO4 embedding not only augments the internal electric field and band bending, upgrading the separation efficiency of active carriers, but also alters the roles of the components involved, separating the occurrence of CO, O2 and H2 evolution on T-COF, BiVO4 and CdS in lower energy barriers. Besides, varying the T-COF thickness can modulate the availability of CO2, H2O and photon to different sites, thereby adjusting the CO/H2 ratio in a wide window. This work opens an avenue for customizing three-in-one artificial photosynthetic systems for coupling three half reactions.

Dual catalytic system: Cu2O@Bi2WO6 2D nano-chips nanocomposite for CO2 photoreduction with amine promotion towards sustainable energy and chemicals

The pursuit of sustainable energy and chemical synthesis propels the development of advanced catalytic systems in photocatalytic CO2 conversion and pharmaceutical chemicals production. The present study demonstrated the decorated Cu2O nanoparticles on a Bi2WO6 surface with effective contact that improved the optical properties of the nanocomposite photocatalyst. The nanocomposite was synthesized via hydrothermal method and achieved ∼7 nm nanoparticle size of Cu2O with a high surface area, refers many active sites at the photocatalyst surface. The photocatalyst efficiently reduced CO2 into CO (2315 μmol-g−1) and CH4 (965 μmol-g−1) under visible light irradiation; simultaneously, the coupling of amines produced chemicals necessary for the pharmaceuticals. In addition, the amine behaves like a sacrificial electron donor in the process; thus, it makes the photocatalytic system prominent in energy conversion.

Oxygen vacancies-tuned BiOBr nanosheets for accelerating CO2 and Cr(VI) photoreduction

Unsatisfactory charge separation ability and insufficient active sites are the main factors leading to low efficiency for photocatalytic CO2 conversion and Cr(VI) reduction. Constructing surface defects to accelerate charge separation is an effective strategy for promoting photocatalytic process. Herein, the oxygen vacancies modulated BiOBr nanosheets were constructed by NaBH4 solution treatment. Density functional theory calculation results found that the formed oxygen vacancies would increase the electron density around Bi atoms near the oxygen vacancies, and inhibiting recombination of the photoinduced carriers. Besides, abundant oxygen vacancies can effectively enhance the adsorption of CO2 molecules. Therefore, the BiOBr with rich oxygen vacancies (BiOBr-ROV) shows higher evolution rates for CO (15.66 μmol g−1) and CH4 (0.22 μmol g−1) under irradiation of 300 W Xe lamp for 4 h compared with pristine BiOBr nanosheets (BiOBr) and BiOBr with deficient oxygen vacancies (BiOBr-DOV). The intermediate products in the CO2 reduction process have been detected by in-situ Fourier-transform infrared spectroscopy. Besides, the photodegradation activity of Cr(VI) over BiOBr-ROV is 98.65% under 80 min of irradiation, which is higher than that of BiOBr (78.01%) and BiOBr-DOV (53.67%). The work provides a new possibility to construct photocatalysts with high-performance for solar energy conversion.