Catalytic Reduction Of CO2 Research Articles

Infrared analysis of catalytic CO2 reduction in hydrogenated germanium.

The oxidation and carbisation kinetics of porous amorphous and nano-crystalline hydrogenated germanium (a-Ge:H and nc-Ge:H) films exposed to ambient air and deionized water have been studied using vibration modes observed by infrared spectroscopy. Based on infrared analysis, a two-step process of first oxidation by water and secondly carbisation by carbon dioxide (CO2) is proposed that partly mimics the (photo-)catalytic processes in artificial (photo)synthesis. It is shown that water acts like the precursor for oxidation of porous a-Ge:H and nc-Ge:H in the first step. The incorporation of oxygen in a-Ge:H and nc-Ge:H alloys occurs preferentially at Ge-dangling bonds and not at the Ge–Ge back bonds like in hydrogenated silicon alloys (next of kin IV-valence element). The formation of germanium oxide (GeO) tissue at void surfaces locally creates Ge alloys with significantly lower energy levels for the valence band that can align with the half reaction for water reduction. The heterogeneous nature of a-Ge:H and nc-Ge:H oxidation will result in local catalytic generation of electrons and protons. It is proposed that these charge carriers and ions act as precursors for the second-step reaction based on carbisation that includes both the adsorption of CO2 and formation of CO and formaldehyde.

1d / 0d H-Bs Nts/Czs-X Heterojunction with Strong Interfacial Electric Field Coupling Enhanced Mass Transfer Based on Gas-Liquid-Solid Micro Interface Contact for Efficient Photothermal Synergistic Catalytic Co2 Reduction to Syngas

1d / 0d H-Bs Nts/Czs-X Heterojunction with Strong Interfacial Electric Field Coupling Enhanced Mass Transfer Based on Gas-Liquid-Solid Micro Interface Contact for Efficient Photothermal Synergistic Catalytic Co2 Reduction to Syngas

Significantly Enhanced Photothermal Catalytic Co2 Reduction Over Tio2/G-C3n4 Composite with Full Spectrum Solar Light

Significantly Enhanced Photothermal Catalytic Co2 Reduction Over Tio2/G-C3n4 Composite with Full Spectrum Solar Light

Photothermal Functional Material and Structure for Photothermal Catalytic Co2 Reduction: Recent Advance, Application and Prospect

Photothermal Functional Material and Structure for Photothermal Catalytic Co2 Reduction: Recent Advance, Application and Prospect

Reaction Mechanism of the Enhanced Reaction Activity and Rate of N-Doped CoO Photocatalysts for Photoreduction of CO2 in Air

The use of light to directly reduce CO2 in the atmosphere is the actual development trend of photocatalysis applications in the future. However, it is still in the initial stage of exploration. In this work, oleylamine is used as a template in a one-step hydrothermal method to obtain the N-doped CoO catalyst that can be used to efficiently reduce CO2 in air. N-doped CoO achieves ultrahigh CO2 conversion efficiency (about 75%), amazing CO yield (2.902 mmol g–1 h–1), and superior CO conversion frequency (TOFCO > 300) in air. However, in a 0.03% simulated atmosphere (Ar/CO2), the CO precipitation rate drops by 18 times, while the H2 precipitation rate increases significantly. Quasi-in situ spectroscopy and experimental studies show that O2 in the CO2 reduction process will promote the formation of an amorphous layer with a small number of hydroxyl groups on the surface of N-doped CoO. This amorphous/crystalline interface will effectively promote the catalytic reduction of CO2. This work has inspired further research on the photoreduction process of low-concentration CO2 in the future.

Non-synergistic photocatalysis of CO2-to-CO conversion by a binuclear complex of rigidly linking two cobalt catalytic centers

A novel binuclear cobalt complex C1 of rigidly linking two [Co(TPA)Cl]Cl moieties at meta positions of a benzene was synthesized and characterized as a catalyst for homogeneous photocatalytic CO2 reduction. Different from state-of-the-art binuclear catalyst catalyzing CO2 reduction with a synergistic catalysis mechanism, C1 catalyses CO2-to-CO conversion independently at each cobalt catalytic center. At an optimal condition, system of C1 produced CO with a TON of 721 (based on C1, corrsoponding to TON 360 per cobalt center) and a high selectivity of 91.5%. Electrochemistry and steady state spectroscopy studies revealed that a CoICoI species, generated via successive photoinduced electron transfer from excited photosensitizer to C1, is the active species of CO2 conversion. No synergistic effect of two cobalt centers exists for CO2 reduction because of larger Co-Co distance and rigid structure of C1.

S‐Scheme Heterojunction and Defect Site Engineering on CuxIn5S8−Cu2‐ySe for Highly Efficient Photoreduction of CO2 to methanol

AbstractThe conversion and utilization of CO2 is imminent. Herein, the CuxIn5S8−CuySe S‐scheme heterojunction catalyst was successfully synthesized by the MOF‐derived method and the strategy of surface hydrogenation. In a photocatalytic performance test, Cu1.5In4.5S7.5−Cu1.45Se has excellent catalytic activity, and the production rate of methanol is 5.250 umol g−1 h−1, and the methanol selectivity is about 100 %. In addition, through DFT calculation and in situ FT‐IR, a new mechanism for the catalytic reduction of CO2 to methanol by bimetallic sites or variable valence metal sites is revealed, which opens up a new strategy to conversion of CO2 into energy fuel. This research couples charge accumulation centers, active sites and adsorption sites on the exposed active interface to enhance the visible light‐driven photocatalytic performance of the catalyst through defect engineering, morphology engineering and heterojunction engineering, which provides a promising approach to facilitate the selective photocatalytic reduction of CO2 to methanol.

Morphology-dependent support effect of Ru/MnOx catalysts on CO2 methanation

Catalytic reduction of CO2 to methane constitutes an important reaction for mitigating the climate change and reducing the dependence on fossil energy resources. In this study, morphology effect of MnOx support on Ru catalysts was investigated for CO2 methanation. Significantly higher methanation rates and methane selectivities were obtained over Ru loaded on Mn3O4 hexagonal nanoplates compared to Ru supported on Mn3O4 octahedron catalysts. HR-TEM measurements revealed that the reduced RuHNS and RuONS catalyst consisted of MnO crystal phase with exposing (200) & (111) and (111) crystal facet, respectively. The CH4 yield of RuHNS was almost twice as high as RuONS, and the TOFs (Turnover frequency) calculated for these were 4.00 and 2.08 10−2S−1, respectively Moreover, as revealed by various physicochemical characterization techniques such as Raman, temperature-programmed reduction with hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS) and temperature-programmed surface reaction with carbon dioxide (CO2-TPSR), which are responsible for the observed catalytic behavior, allowing reactants to adsorb more easily and lowering the energy barrier for both H2 and CO2. The present work highlights the importance of support morphology of Ru loaded on reducible support on CO2 methanation.

Effects of Protonation State on Electrocatalytic CO2 Reduction by a Cobalt Aminopyridine Macrocyclic Complex.

A critical component in the reduction of CO2 to CO and H2O is the delivery of 2 equiv of protons and electrons to the CO2 molecule. The timing and sequencing of these proton and electron transfer steps are essential factors in directing the activity and selectivity for catalytic CO2 reduction. In previous studies, we have reported a series of macrocyclic aminopyridine cobalt complexes capable of reducing CO2 to CO with high faradaic efficiencies. Kinetic investigations reveal a relationship between the observed rate constant (kobs) and the number of pendant amine hydrogen bond donors minus one, suggesting the presence of a deprotonated active catalytic state. Herein, we investigate the feasibility of these proposed deprotonated complexes toward CO2 reduction. Two deprotonated derivatives, Co(L4-) and Co(L2-), of the tetraamino macrocycle Co(L) were independently synthesized and structurally characterized revealing extensive delocalization of the negative charge upon deprotonation. 1H nuclear magnetic resonance spectroscopy and ultraviolet-visible titration studies confirm that under catalytic conditions, the active form of the catalyst gradually becomes deprotonated, supporting thus the ndonor - 1 relationship with kobs. Electrochemical studies of Co(L4-) reveal that this deprotonated analogue is competent for electrocatalysis upon addition of an exogenous weak acid source, such as 2,2,2-trifluoroethanol, resulting in faradaic efficiencies for CO2-to-CO conversion identical to those observed with the fully protonated derivative (>98%).

Stepping Stones in CO2 Utilization: Optimizing the Formate to Oxalate Coupling Reaction Using Response Surface Modeling.

One of the crucial steps for the conversion of CO2 into polymers is the catalytic formate to oxalate coupling reaction (FOCR). Formate can be obtained from the (electro)catalytic reduction of CO2, while oxalate can be further processed toward building blocks for modern plastics. In its 175 year history, multiple parameters for the FOCR have been suggested to be of importance. Yet, no comprehensive understanding considering all those parameters is available. Hence, we aim to assess the relative impact of all those parameters and deduce the optimal reaction conditions for the FOCR. We follow a systematic two-stage approach in which we first evaluate the most suitable categorical variables of catalyst, potential poisons, and reaction atmospheres. In the second stage, we evaluate the impact of the continuous variables temperature, reaction time, catalyst loading, and active gas removal within previously proposed ranges, using a response surface modeling methodology. We found KOH to be the most suitable catalyst, and it allows yields of up to 93%. Water was found to be the strongest poison, and its efficient removal increased oxalate yields by 35%. The most promising reaction atmosphere is hydrogen, with the added benefit of being equal to the gas produced in the reaction. The temperature has the highest impact on the reaction, followed by reaction time and purge rates. We found no significant impact of catalyst loading on the reaction within the ranges reported previously. This research provides a clear and concise multiparameter optimization of the FOCR and provides insight into the reaction cascade involving the formation and decomposition of oxalates from formate.

Non-peripheral octamethyl-substituted cobalt phthalocyanine nanorods supported on N-doped reduced graphene oxide achieve efficient electrocatalytic CO2 reduction to CO

Developing electrocatalysts that exhibit highly-efficient CO2reduction is crucial for a healthier environment. This report demonstrates that the eight methyl groups on cobalt phthalocyanine significantly improved its catalytic CO2 reduction performance. Theoretical computations confirmed that the non-peripheral octamethyl-substituted cobalt(II) phthalocyanine (N-CoMe2Pc) catalyst showed enhanced CO2 adsorption and activation on the Co surface at low overpotentials relative to pristine cobalt(II) phthalocyanine (CoPc). The N-CoMe2Pc nanorods and nitrogen-doped reduced graphene oxide (NRGO) nanocomposites were successfully prepared by a facile, non-covalent immobilization strategy and their electrocatalytic CO2 reduction activity was explored in both H-type and flow cell configurations. It was thus verified that immobilizing N-CoMe2Pc nanorods onto NRGO surfaces can lead to enhanced electroactivity and selectivity in terms of reducing CO2 to CO. Among the various tested nanocomposites, N-CoMe2Pc/NRGO with a catalyst: NRGO ratio of 6:10 showed superior CO faradaic efficiency/selectivity (90.0 %) and a total current density reaching 9.7 mA cm−2 at –0.8 V vs. RHE in an H-type cell containing a neutral electrolyte. A CO faradaic efficiency of 90.4% and a current density of 14.8 mA cm−2 were achieved at the same overpotential using a flow cell. The selectivity of this system was further improved to 94.1%, with an accompanying CO current density of 56.4 mA cm−2 and an impressive turnover frequency of 6.2 s−1 at lower potential (–0.6 V vs. RHE) in alkaline solution. This work provides new insights relevant for developing low-cost, effective, phthalocyanine-based catalysts for electrochemical CO2 reduction.

Quantum Dot-Sensitized Photoreduction of CO2 in Water with Turnover Number > 80,000.

Climate change and global energy demands motivate the search for sustainable transformations of carbon dioxide (CO2) to storable liquid fuels. Photocatalysis is a pathway for direct conversion of CO2 to CO, one step within light-powered reaction networks that could, if efficient enough, transform the solar energy conversion landscape. To date, the best performing photocatalytic CO2 reduction systems operate in nonaqueous solvents, but technologically viable solar fuels networks will likely operate in water. Here we demonstrate catalytic photoreduction of CO2 to CO in pure water at pH 6-7 with an unprecedented combination of performance parameters: turnover number (TON(CO)) = 72,484-84,101, quantum yield (QY) = 0.96-3.39%, and selectivity (SCO) > 99%, using CuInS2 colloidal quantum dots (QDs) as photosensitizers and a Co-porphyrin catalyst. At higher catalyst concentration, the system reaches QY = 3.53-5.23%. The performance of the QD-driven system greatly exceeds that of the benchmark aqueous system (926 turnovers with a quantum yield of 0.81% and selectivity of 82%), due primarily to (i) electrostatic attraction of the QD to the catalyst, which promotes fast multielectron delivery and colocalization of protons, CO2, and catalyst at the source of photoelectrons, and (ii) termination of the QD's ligand shell with free amines, which capture CO2 as carbamic acid that serves as a reservoir for CO2, effectively increasing its solubility in water, and lowers the onset potential for catalytic CO2 reduction by the Co-porphyrin. The breakthrough efficiency achieved in this work represents a nonincremental step in the realization of reaction networks for direct solar-to-fuel conversion.

Coordination engineering of the hybrid Co-C and Co-N active sites for efficient catalyzing CO2 electroreduction

Single-atom catalysts (SACs) with well-defined active sites provide an efficient route for catalyzing CO2 reduction reaction (CO2RR). Although enormous attention has been focused on metal-Nx moieties, understanding the effect of metal-C coordination and engineering of the hybrid metal-N/C sites have rarely been reported. Herein, we fabricated Co SACs with tunable isolated Co-N5-xCx (x = 1, 2, 3) sites supported on porous carbon frameworks. Benefiting from the difference in electronegativity of the coordinated N and C atoms, the CO Faradaic efficiency (FECO) enhanced considerably from 54% to 76% and 92% at −0.8 V vs. RHE for Co-N4C1, Co-N3C2, and Co-N2C3, respectively. Further density functional theory (DFT) calculations uncover that the increased ratio of Co-C coordination induced electron enrichment of Co atoms and upper-shift the d-band center to near Fermi level, and thus favorably promotes the electron-donating ability of Co centers and strengthens the adsorption of *COOH.

Plasmon Assisted Highly Efficient Visible Light Catalytic CO2 Reduction Over the Noble Metal Decorated Sr-Incorporated g-C3N4

HighlightsNoble metals (Pt, Au) decorated Sr-incorporated g-C3N4 photocatalysts are fabricated via facile calcination and photo-deposition methods.The optical absorption and charge separation properties of the photocatalysts are remarkably improved and the Pt/0.15Sr-CN photocatalyst exhibited excellent activity for CO2 conversion.A quantum efficiency of 2.92% is predicted for CO2 reduction over the Pt/0.15Sr-CN photocatalyst at 420 nm wavelength, which is accredited to the improved optical absorption and enhanced charge separation via Sr-incorporation and the surface plasmon resonance effect of noble metal nanoparticles.

Revealing the Surface Chemistry for CO2 Hydrogenation on Cu/CeO2–x Using Near-Ambient-Pressure X-ray Photoelectron Spectroscopy

Catalytic reduction of CO2 to valuable products is an attractive route for CO2 recycling. CeO2-supported Cu catalysts have shown high activity and selectivity for the hydrogenation of CO2 to CO. To...

Machine Learning in Screening High Performance Electrocatalysts for CO2 Reduction.

Converting CO2 into carbon-based fuels is promising for relieving the greenhouse gas effect and the energy crisis. However, the selectivity and efficiency of current electrocatalysts for CO2 reductions are still not satisfactory. In this paper, the development of machine learning methods in screening CO2 reduction electrocatalysts over the recent years is reviewed. Through high-throughput calculation of some key descriptors such as adsorption energies, d-band center, and coordination number by well-constructed machine learning models, the catalytic activity, optimal composition, active sites, and CO2 reduction reaction pathway over various possible materials can be predicted and understood. Machine learning is now realized as a fast and low-cost method to effectively explore high performance electrocatalysts for CO2 reduction.

The emerging applications of metal phosphides in carbon dioxide reduction reaction

The development of low-cost and high-efficiency catalysts is very important to promote carbon dioxide reduction reaction (CO2RR). Metal phosphides (MPs) are promising catalysts for CO2 reduction because of their excellent electrical conductivity, good stability, high activity and selectivity. In this review, we summarize the latest progress of MPs in CO2RR from chemocatalysis, electrocatalysis and photocatalysis, and discuss in detail their advantages and catalytic mechanism. In the end, we provide some potential challenges and inspiring outlooks to serve as guidance for future research and practical applications of MPs in catalytic CO2 reduction.

Photocatalytic reduction of CO2 into solar fuels using M-BTC metal organic frameworks for environmental protection and energy applications

The photo catalytic reduction of CO2 into solar fuels and value-added chemicals is very interesting in the view point of green chemistry. It offers a clean and energy saving solution for the major environmental challenges of global warming and climate change. Recently, the use of transition metal-based MOFs photocatalyst has become more popular in this process due to their porous structure, abundance of metal site and organic functionalities. Herein, we derived divalent transition metal-basedMOFs (Zn2+, Cu2+ , Mn2+) as photocatalyst materials. The obtained photo catalyst materials were characterized by XRD, XPS, SEM and TEM technique to know the structural, optical, photocatalytic and morphological properties. They were subsequently tested for photo catalytic reduction of CO2 and results shows that all the heterostructure M-BTC possess significant ability of photo catalytic reduction of CO2. Moreover, among the three catalyst, Zn-BTC MOFs showed the outstanding performance towards of photo catalytic reduction of CO2. Gas chromatographic analysis confirms the formation of value-added products such as CH3OH, Methane and Carbon Monoxide. The possible photo catalytic mechanism discussed and supported its outstanding performance.

In Situ Constructed P–N Junction on Cu2O Nanocubes through Reticular Chemistry for Simultaneously Boosting CO2 Reduction Depth and Ameliorating Photocorrosion

Photocatalytic CO2 conversion into value‐added chemicals is the one‐stone–two‐birds approach to help meet the carbon neutral goal of near future, and lies on the development of competent photocatalysts that efficiently generate and separate the electron‐hole pairs. Herein, through reticular chemistry a p–n heterojunction is constructed on Cu2O nanocubes by in situ transforming the surface to metal–porphyrin coordination polymer. The resulted Cu2O@Cu‐TCPP core–shell heterostructure, when used for catalyzing CO2 reduction, exhibits not only improved activity, but also enhanced reduction depth. This boosted reducing power is attributed to the improved charge separation efficiency and thus populated charge carriers, as a result of the built‐in electron field of the p–n heterojunction. In addition, the Cu‐TCPP coating serves as a protecting sheath to mitigate the self‐corrosion of Cu2O. Consequently, this study opens a new avenue of photocatalyst design and fabrication for simultaneously promoting multielectron products and ameliorating photocorrosion issues.

Hierarchically Porous Metal–Organic Framework/MoS2 Interface for Selective Photocatalytic Conversion of CO2 with H2O into CH3COOH

AbstractMetal–organic frameworks (MOFs) provide a platform to design new heterogeneous catalysts for catalytic CO2 reduction, but selective formation of C2 valuable liquid fuel products remains a challenge. Herein, we propose a strategy to synthesize composites by integrating MoS2 nanosheets into hierarchically porous defective UiO‐66 (d‐UiO‐66) to form Mo‐O‐Zr bimetallic sites on the interfaces between UiO‐66 and MoS2. The active interfaces are favorable for the efficient transfer of photo‐generated charge carriers and for promoting the activity, whereas, the synergy of the components at the interfaces achieves selectivity for C2 production. The d‐UiO‐66/MoS2 composite facilitates the photo‐catalytic conversion of gas phase CO2 and H2O to CH3COOH under visible light irradiation without any other adducts. The evolution rate and selectivity of CH3COOH reached 39.0 μmol g−1 h−1 and 94 %, respectively, without any C1 products, suggesting a new approach for the design of highly efficient photocatalysts of CO2 for C2 production. Theoretical calculations demonstrate the charge‐polarized Zr‐O‐Mo aided the C−C coupling process with the largely reduced energy barrier.