Photoreduction Of Carbon Dioxide Research Articles

Perovskite Nanocrystals In Situ Encapsulated in TiO2 Microspheres for Stable CO2 Photoreduction in Water.

Photoreduction of carbon dioxide (CO2) into fuels presents a promising approach to mitigate global warming and energy crises. Halide perovskite nanocrystals (NCs) with prominent optoelectronic properties have triggered substantial attention as photocatalysts but are limited by the charge recombination and instability. Here, we develop stable CsPbBr3/titania microspheres (TMs) by in situ growth of CsPbBr3 NCs inside mesoporous TMs through solid-state sintering, which significantly improves the stability of perovskite NCs, making them applicable in water with efficient CO2 photoreduction performance. Notably, the CsPbBr3/TMs demonstrates a 6.73- and 9.23-fold increase in the rate of CH4 production compared to TMs and CsPbBr3, respectively. The internal electric field facilitates S-scheme charge transfer, enhancing the separation of electron-hole pairs, as evidenced by X-ray photoelectron spectroscopy and electron paramagnetic resonance analysis, which is pivotal for the selective photoreduction of CO2. These insights pave the way for the design of CsPbBr3-based photocatalysts with superior efficiency and stability.

Vacancy modulation on NiTi-layered double hydroxides towards highly selective CO2 photoreduction

Photoreduction of carbon dioxide (CO2) is a promising way to achieve sustainable energy production and alleviate environmental problems. Herein, we report a NiTi-layered double hydroxides photocatalyst with bivalent and trivalent metal vacancies (denoted as NiVTiV-LDHs) via alkali-etching amphoteric metal cations (Zn and Al) from NiZnTiAl-LDHs precursor. The NiVTiV-LDHs attains a CH4 selectivity of 94% with a production rate of 2398 µmol g−1 h−1, which is preponderant to the state-of-the-art photocatalysts. Operando X-ray absorption fine structure (XAFS) and Fourier-transform infrared spectroscopy (FT-IR) characterizations combined with density functional theory (DFT) calculations corroborate that Ni2+δ−O(H)−Ti3+ζ sites modulated by adjacent vacancies exhibits a declined 3d-orbital occupancy, accelerating the charge transfer for boosting CH4 formation. Moreover, the unique adsorption configuration (Ni2+δ/Ti3+ζ−CO) not only stabilizes the key intermediate *CO for further protonation, but also induces a decreased energy barrier of the rate-determining step (hydrogenation of *OCH3), accounting for the robust photocatalytic CO2 reduction towards CH4.

Effect of copper and silver modification of NH2-MIL-125(Ti) on the photoreduction of carbon dioxide to formic acid over this framework under visible-light irradiation

Cu and Ag enhance the photocatalytic activities of metal–organic frameworks (MOFs) toward CO2 conversion because of their CO2 adsorption capacities and effects on the lowest unoccupied molecular orbital (LUMO) overpotentials of MOFs. However, to date, targeted introduction of metals into MOFs to achieve visible (Vis)-light-active photocatalysts for CO2 photoconversion has not been realized. Herein, a series of amine-functionalized Ti MOF (NH2-MIL-125(Ti))-based photocatalysts were successfully synthesized using metalation, incorporation, and photodeposition, allowing Cu and Ag incorporation into NH2-MIL-125(Ti) and attainment of ultraviolet- and Vis-light-active photocatalysts. Notably, the most active photocatalyst obtained by post-synthetic metalation of NH2-MIL-125(Ti) by Cu2+ (MOF_met_0.5%Cu) demonstrated excellent performance in photoreducing CO2 to HCOOH: a conversion rate of 30.1 umolg−1h−1 and quantum yield of 1.18% at 380 nm. Photoconversion of CO2 to HCOOH was further confirmed using 13CO2. The novel approach proposed herein is a significant step toward clean energy production and environmental pollutant elimination.

Synthetic Leaves Based on Crystalline Olefin-Linked Covalent Organic Frameworks for Efficient CO2 Photoreduction with Water.

We report, for the first time, a new synthetic strategy for the preparation of crystalline two-dimensional olefin-linked covalent organic frameworks (COFs) based on aldol condensation between benzodifurandione and aromatic aldehydes. Olefin-linked COFs can be facilely crystallized through either a pyridine-promoted solvothermal process or a benzoic anhydride-mediated organic flux synthesis. The resultant COF leaf with high in-plane π-conjugation exhibits efficient visible-light-driven photoreduction of carbon dioxide (CO2) with water (H2O) in the absence of any photosensitizer, sacrificial agents, or cocatalysts. The production rate of carbon monoxide (CO) reaches as high as 158.1 μmol g-1 h-1 with near 100% CO selectivity, which is accompanied by the oxidation of H2O to oxygen. Both theoretical and experimental results confirm that the key lies in achieving exceptional photoinduced charge separation and low exciton binding. We anticipate that our findings will facilitate new possibilities for the development of semiconducting COFs with structural diversity and functional variability.

Nitrogen Doping-Roused Synergistic Active Sites in Perovskite Enabling Highly Selective CO2 Photoreduction into CH4.

The intricate protonation process in carbon dioxide reduction usually makes the product unpredictable. Thus, it is significant to control the reactive intermediates to manipulate the reaction steps. Here, we propose that the synergistic La-Ti active sites in the N-La2Ti2O7 nanosheets enable the highly selective carbon dioxide photoreduction into methane. In the photoreduction of CO2 over N-La2Ti2O7 nanosheets, in situ Fourier transform infrared spectra are utilized to monitor the *CH3O intermediate, pivotal for methane production, whereas such monitoring is not conducted for La2Ti2O7 nanosheets. Also, theoretical calculations testify to the increased charge densities on the Ti and La atoms and the regulated formation energy barrier of *CO and *CH3O intermediates by the constructed synergistic active sites. Accordingly, the methane formation rate of 7.97 μL h-1 exhibited by the N-La2Ti2O7 nanosheets, along with an electron selectivity of 96.6%, exceeds that of most previously reported catalysts under similar conditions.

Construction of Au-modified CN-based donor-acceptor system coupled with dual photothermal effects for efficient photoreduction of carbon dioxide

Conversion of CO2 into high value-added fuels through the photothermal effect is an effective approach for utilizing solar energy. In this study, we prepared the CN-based photocatalyst Py-CTN-Au with both donor-acceptor (D-A) system and dual photothermal effects using a simple two-step method involving calcination and photo-deposition. Real-time monitoring with a thermal imaging camera revealed that Py-CTN-Au0.5 achieved a maximum stable temperature of 180 °C, which was approximately 1.2 times higher than that of Py-CTN (155 °C) and 1.9 times higher than that of g-CN (95 °C) under the same reaction conditions. Under the optimized reaction conditions, Py-CTN-Au0.5 exhibited a CO release rate of 30.59 umol g−1 after 4 h of reaction, which was 7.3 times higher than that of pure g-CN (4.18 umol g−1). The D-A system not only facilitated the separation and transformation of charge carriers but also induced a photothermal effect to accelerate the photoreduction of CO2. Additionally, the cocatalyst Au nanoparticles (Au NPs) further enhanced the charge carrier dynamics and photothermal effect by increasing the built-in electric field intensity and localized surface plasmon resonance (LSPR) effect, respectively. The dual photothermal effects resulting from the non-radiative photon conversion of the D-A structure and the Au NPs LSPR effect, along with the enhanced charge carrier dynamics, catalyzed the efficient photoreduction of CO2. DFT simulations were used to confirm the effect of D-A system and Au NPs. In-situ FTIR results demonstrated that the synergistic photothermal effect promoted the formation of the key intermediate species COOH*, which is beneficial for the photocatalytic reduction of CO2. This study provides valuable insights into the multiple photothermal synergistic effects in photocatalytic reactions.

Efficient and Selective Photoreduction of Carbon Dioxide to Methane Using Nanopolyoxomolybdate Supported by Ar-g-C3N4 on Dendritic Fibrous Nanotitanium

Efficient and Selective Photoreduction of Carbon Dioxide to Methane Using Nanopolyoxomolybdate Supported by Ar-g-C3N4 on Dendritic Fibrous Nanotitanium

Efficient CO2 photoreduction enabled by the one-dimensional (1D) porous structured NiTiO3 nanorods

In this study, porous, and hollow nanorods of NiTiO3 (NiTiO3 NRs-p: 2–3 μm in length and 400 nm in diameter) are successfully prepared using an ethylene glycol-mediated approach at room temperature (25 °C), followed by calcination at 700 °C in air environment. Their rough surfaces and accumulated holes are advantageous for adsorption and subsequent photoreduction of carbon dioxide (CO2) under UV–vis irradiation. The NiTiO3 NRs-p exhibit superior performance in terms of photoconversion of CO2 (purity 99.999 %, 100 mL/min) into gaseous CO (57.833 μmolg−1 h−1) and CH4 (24.33 μmolg−1 h−1) with an overall CO2 selectivity (SCO2) of 89 %. In contrast, the solid NiTiO3 nanorods (NiTiO3 NRs) exhibit moderate performance in CO2 reduction, producing CO (30.33 μmolg−1 h−1) and CH4 (11.50 μmolg−1 h−1) with a CO2 selectivity of SCO2 = 60 %. NiTiO3 NRs-p exhibits superior photocatalytic activity against CO2 over other NiTiO3 morphologies with similar physical and chemical properties (such as nanoparticles (NPs) and nanofibers (NFs). This enhancement in photocatalytic activity can be attributed to the porous texture and hollow rod-like structure of NiTiO3 NRs-p, which provides a larger number of active sites to promote rapid mass transport. This unique one-dimensional (1D) structure also facilitates the separation of photogenerated electron-hole pairs, as demonstrated experimentally. This study opens a new room for a simple and facile routes for the photocatalytic conversion of CO2 into solar fuels.

Interfacial electron interactions governed photoactivity and selectivity evolution of carbon dioxide photoreduction with spinel cobalt oxide based hollow hetero-nanocubes

In this work, an efficient CO2 photoreduction catalyst based on Co3O4/ZnIn2S4 hollow hetero-nanocubes is precisely constructed via an in-situ transformation of cobalt-organic framework followed by a solvothermal reaction. Comprehensive in-situ spectroscopic analyses and theoretical calculations have revealed that the critical interfacial electron interactions (IEIs) effects on both photoactivity evolution and selectivity modulation in the Co3O4/ZnIn2S4 hetero-structure. As the content of ZnIn2S4 increases in the hetero-structure, the photoactivity exhibits a volcano-like evolution profile but the CH4 selectivity reduces monotonously. The improved photoactivity is attributed to the IEIs-promoted charge separation as well as the specific-surface-area effect in terms of electron unitization rate, and the electronic structure of Co3O4 is tuned and the energy barrier for the key reaction intermediate *CHO is reduced, leading to improved CH4 selection in comparison with bare Co3O4. The IEIs-mediated production selectivity is further verified by a Co3O4/CeO2 heterojunction, indicating a certain universality of the IEI effect.

Selective Photoreduction of CO2 to CH4 Triggered by Metal-Vacancy Pair Sites.

Selectively achieving the photoreduction of carbon dioxide (CO2) to methane (CH4) remains a significant challenge, which primarily arises from the complexity of the protonation process. In this work, we designed metal-vacancy pair sites in defective metal oxide semiconductors, which anchor the reactive intermediates with a bridged linkage for the selective protonation to produce CH4. As an example, oxygen-deficient Nb2O5 nanosheets are synthesized, in which the niobium-oxygen vacancy pair sites are demonstrated by X-ray photoelectron spectroscopy and electron paramagnetic resonance spectra. In situ Fourier transform infrared spectroscopy monitors the *CH3O intermediate, a key intermediate for CH4 production, during the CO2 photoreduction in oxygen-deficient Nb2O5 nanosheets. Importantly, the built metal-vacancy pair sites regulate the *CH3O formation step as a spontaneous process, making the reduction of CO2 to CH4 the preferred method. Therefore, the oxygen-deficient Nb2O5 nanosheets exhibit a CH4 formation rate of 19.14 μmol g-1 h-1, with an electron selectivity of ∼94.1%.

Ab initio investigation of hot electron transfer in CO2 plasmonic photocatalysis in the presence of hydroxyl adsorbate.

Photoreduction of carbon dioxide (CO2) on plasmonic structures is of great interest in photocatalysis to aid selectivity. While species commonly found in reaction environments and associated intermediates can steer the reaction down different pathways by altering the potential energy landscape of the system, they are often not addressed when designing efficient plasmonic catalysts. Here, we perform an atomistic study of the effect of the hydroxyl group (OH) on CO2 activation and hot electron generation and transfer using first-principles calculations. We show that the presence of OH is essential in breaking the linear symmetry of CO2, which leads to a charge redistribution and a decrease in the OCO angle to 134°, thereby activating CO2. Analysis of the partial density of states (pDOS) demonstrates that the OH group mediates the orbital hybridization between Au and CO2 resulting in more accessible states, thus facilitating charge transfer. By employing time-dependent density functional theory (TDDFT), we quantify the fraction of hot electrons directly generated into hybridized molecular states at resonance, demonstrating a broader energy distribution and an 11% increase in charge-transfer in the presence of OH groups. We further show that the spectral overlap between excitation energy and plasmon resonance plays a critical role in efficiently modulating electron transfer processes. These findings contribute to the mechanistic understanding of plasmon-mediated reactions and demonstrate the importance of co-adsorbed species in tailoring the electron transfer processes, opening new avenues for enhancing selectivity.

Efficient photoreduction of carbon dioxide to ethanol using diatomic nitrogen-doped black phosphorus.

Successful conversion of CO2 into C2 products requires the development of new catalysts that overcome the difficulties in efficient light harvesting and CO-CO coupling. Herein, density functional theory (DFT) is used to assess the photoreduction properties of nitrogen-doped black phosphorus. The geometric structure, redox potential, first step of hydrogenation activation, CO desorption, and CO-CO coupling are systematically calculated, based on which the diatomic nitrogen-doped black phosphorus (N2@BPV) stands out. The calculated results of the CO2RR pathway demonstrate that N2@BPV has excellent selectivity and high activity for CH3CH2OH production. The results of the time-dependent ab initio nonadiabatic molecular dynamics simulation show that the diatomic N active sites of N2@BPV facilitate charge separation and inhibit electron-hole recombination. In addition, the activation mechanism of CO2 is studied. The main reason for CO2 activation is attributed to the imbalance in electron transfer that destroys the symmetry of CO2. We expect that our study will offer some theoretical guidance in CO2 conversion.

Enhanced photocatalytic CO2 reduction by controlled oxygen vacancy generation and co-constructed heterojunction strategy for Pd/CeO2

Artificial photoreduction of carbon dioxide (CO2) into useful chemicals using solar energy requires stable photocatalysts with efficient charge separation and effective CO2 adsorption. Herein, the CeO2-supported Pd catalysts (Vo-R-Pd/CeO2) with...

Plasmonic Au nanoparticles enhance the photogenerated electron efficiency for carbon dioxide photoreduction

We prepared a Aux/BaTiO3 plasmonic photocatalyst where Au NPs promote the separation of photogenerated electron–hole pairs and provide hot-electron injection through the LSPR effect, thus enhancing the Aux/BaTiO3 photocatalytic reduction of CO2 performance.

Efficient photoreduction of carbon dioxide to acetaldehyde on monatomic defective black phosphorus

Conversion of CO2 into C2 products has been challenging, largely due to the insufficient electron deliverability of catalyst. Here we proposed latent monatomic defective black phosphorus (BPV), on which the efficient photoreduction of CO2 to CH3CHO was confirmed by density functional theory (DFT) calculations. The electrostatic potential difference between the upper and lower atoms of the BPV was found responsible for the enhanced separation of electrons and holes. The COCO coupling was studied, the charge transfer from BPV to CO (0.38 |e|) was found contributes to the enhanced CO2 reduction reaction (CO2RR) activity and promoted COCO coupling process. This work provides theoretical guidelines on the design of defect catalyst for CO2 photoreduction.

NH3 plasma synthesis of amino modified NiCo layered double hydroxide nanoflowers for carbon dioxide photoreduction

Photoreduction as the paramount ingredient of CO2 catalytic conversion plays an eminent role in greenhouse gas treatment. As a promising catalyst, layered double hydroxide has been widely studied because of its rich variety, low hazard and easy availability. In an effort to improve the productivity of photocatalytic CO2 reduction, the preparation of efficient photocatalysts becomes the key to solve this challenge. Thin nickel-cobalt bimetallic hydroxides (NiCo LDH) were prepared by the hydrothermal method of glycerol and methanol. Amino groups were grafting onto NiCo LDH nanosheets in an ammonia atmosphere by low-temperature plasma. The photocatalytic reduction performance of NH2-NiCo LDH was optimized by adjusting the time of plate dielectric barrier discharge plasma treatment. This work provides theoretical basics for modification of layered double hydroxide.

Core@shell-structured catalysts based on Mg-O-Cu bond for highly selective photoreduction of carbon dioxide to methane

Core@shell-structured catalysts based on Mg-O-Cu bond for highly selective photoreduction of carbon dioxide to methane

Water-activation-facilitated photocatalytic CO2 reduction by a heterogeneous synergetic single-atomic Zn sites and Pd nanocrystals

Enhancing the photoreduction of carbon dioxide (CO2) to produce valuable chemicals, such as carbon monoxide (CO), is of significant importance. The bottleneck in developing advanced catalysts lies in the rational design of catalytic centers with efficient CO2 activation and hydrogen proton production. In this work, palladium nanoparticles (Pd NPs) were successfully modified on UiO-66-NH2-Zn SAs (UN-Zn SAs) by a photo-deposition method. The optimized photocatalyst, 4 Pd NPs-UN-0.7Zn SAs, demonstrated exceptional performance in converting CO2 to CO, exhibiting approximately 1.4-fold and 7.8-fold enhancements compared to UN-0.7Zn SAs and UN, respectively. A combination of time-resolved photoluminescence spectroscopy and electron paramagnetic resonance results unveiled that the introduction of Pd NPs effectively promoted the photogenerated charge separation and facilitated water activation to produce more hydrogen protons. The generated hydrogen protons were subsequently coupled with nearby CO2 that was activated by Zn SAs, thus achieving the facile water-activation-induced CO2 reduction process. Theoretical calculations further confirmed that the heterogeneous synergistic effects between Zn SAs and Pd NPs lowered the energy barrier for the rate-limiting step of CO2 conversion to COOH* , thereby achieving efficient photocatalytic CO2 reduction reactions. This work provides a new perspective on the development of efficient catalysts for the effective conversion of CO2.

Manipulating the Optically Active Defect–Defect Interaction of Colloidal Quantum Dots for Carbon Dioxide Photoreduction

Manipulating the Optically Active Defect–Defect Interaction of Colloidal Quantum Dots for Carbon Dioxide Photoreduction

Adaptive lattice-matched MOF and COF core-shell heterostructure for carbon dioxide photoreduction

Adaptive lattice-matched MOF and COF core-shell heterostructure for carbon dioxide photoreduction