Catalytic CO Research Articles

Spray technique inspired fabrication of metal-organic framework/aerogel composite for catalytic CO2 cycloaddition

Growing metal–organic framework (MOF) on the appropriate porous matrix can effectively circumvent its poor processability and recyclability owing to its powder state by providing more exposed area and enhanced stability. A feasible and efficient spray technique was applied to prepare five kinds of MOF/aerogel composites by spraying the MOF precursor droplet sequentially onto the aerogel, including carboxylate-based MOF/aerogel composites and azolate-based MOF/aerogel composites. The sprayed precursor droplets render MOF growth concentrated on the aerogel walls with resulting continuous and homogeneous MOF film, and avoid the waste of precursor solution, which is scalable with industrial potential. MOF/aerogel composites integrates the porous nature of aerogels with excellent mass transfer property and MOF film grown on aerogel walls with more active sites, which exhibit excellent catalytic activity and stability in CO2 cycloaddition.

Photothermal-boosted S-scheme heterojunction of α-Fe2O3@NiOx for high-selective reduction of CO2 to CO

Self-heating photothermal catalysis, combining light promotion and thermal activation, offers unique advantages for CO2 conversion. The meticulous design of active sites and light-absorbing materials is crucial for high-performance photothermal catalysts. Herein, a S-Scheme heterostructure composed of NiOx subunits with abundant oxygen vacancies (Vo) bonded with α-Fe2O3 nanoplatelets has been fabricated for solar-driven photothermal catalytic CO2 reduction. Under continuous full-spectrum light irradiation (0.3 W·cm−2), the α-Fe2O3@NiOx hybrids exhibited a CO yield rate of 199.3 μmol∙g−1·h−1 in a gas–solid reaction models with near-unity selectivity. Additionally, the apparent quantum yield for CO production at 420 nm reaches 1.56 %. The prominent activity is attributed to three key factors: (1) The Vo-rich NiOx facilitates the accumulation of photogenerated electrons and activation of chemisorbed CO2. (2) The implemented S-Scheme heterostructures boost interfacial charge-transfer and provide spatially separated catalytic sites for efficient overall CO2 reduction. (3) The substantial photothermal effect of NiOx, which arises from nonradiative exciton recombination, induces local heating of the catalyst, thereby enhancing reaction kinetics. This work provides valuable insights into the utilization of a photothermal-photocatalytic S-Scheme heterojunction system for the photothermal catalytic CO2 reduction.

Lewis Acid-Tethered (cAAC)-Copper Complexes: Reactivity for Hydride Transfer and Catalytic CO2 Hydrogenation.

We present a series of borane-tethered cyclic (alkyl)(amino)carbene (cAAC)-copper complexes, including a borane-capped Cu(I) hydride. This hydride is unusually hydridic and reacts rapidly with both CO2 and 2,6-dimethylphenol at room temperature. Its reactivity is distinct from variants without a tethered borane, and the underlying principles governing the enhanced hydricity were evaluated experimentally and theoretically. These stoichiometric results were extended to catalytic CO2 hydrogenation, and the borane-tethered (intramolecular) system exhibits ~3-fold enhancement relative to an intermolecular system.

Electrocatalytic Properties of meso‐ Perfluorinated Metallo Corroles for the Reduction of CO2

Corrole, a contracted tetrapyrrolic macrocycle has been also used to design molecular for the CO2 reduction. The electrochemical activity towards CO2 reduction can rival those of their porphyrin analogues. However, the catalytic activity of the metallocorrole is initiated at the corresponding MII/I couple. Accordingly, a catalytic current in presence of CO2 with cobalt corrole appears when the CoI species is generated. We have designed an electron deficient A2B corrole holding two ‐CF3 groups and a benzonitrile in the meso positions and its cobalt complex (1). We reasoned that these groups could shuffle the redox potentials to reach the M(I) oxidation states at more positive values thereby lowering the overpotential for the catalytic CO2 reduction. Our results clearly show that catalyst 1 when adsorbed on a carbon electrode, shows the most favourable catalytic performance for CO production, achieving an efficiency of 85% with a current density of ‐1.5 mA cm‐2 at ‐1.0 V vs NHE. The current densities of controlled potential electrolysis with increasing amount of KHCO3, were found to increase more than one order of magnitude with the formation of MeOH.

Ultra-pure hydrogen from chemical looping preferential oxidation of CO over a Cu–O–Ce based dual function material

Hydrogen from hydrocarbon reforming contains small amounts of CO, necessitating further purification for its use in fuel cell applications. In this work, a novel chemical looping preferential oxidation (CL-PROX) process is proposed for efficient hydrogen purification. Enabled by a Cu–O–Ce based dual function material (DFM), the process uniquely combines both catalytic CO preferential oxidation and in-situ immobilization. This results in near-complete CO conversion and < 20 ppm COx concentration with hydrogen recovery of 97 % in the purification step. Experimental characterizations indicate that CO is converted into formate and carbonate on the DFM, which can easily decompose to CO2 during the regeneration step. The interaction between copper and ceria species increased the reducibility of the DFM, as well as the CO activation and immobilization. Facile and reversible transformations between Cu2+/Ce4+ and Cu+/Ce3+ were observed throughout the reduction and re-oxidation stages. This work suggests an intensification strategy for selective hydrogen purification, and provides insights into the redox chemistry of Cu–O–Ce DFMs.

Enhanced ethanol synthesis from CO2 hydrogenation over Fe and Na co-modified Rh/CeO2 catalysts

Rh catalyst is investigated as a strong candidate for CO2 hydrogenation to ethanol, but it is still challenging because of the poor conversion efficiency. Here, by screening the promotors systematically and varying the amounts of components simultaneously, the optimized catalyst of 2Rh0.5Fe0.5Na/CeO2 was found to highly efficient catalytic CO2 hydrogenation to ethanol, giving a high ethanol selectivity of 29.8 % with a superior CO2 conversion of 13.0 % at 250 °C, 3 MPa, and the ethanol productivity reached 116.7 mmol·gRh−1·h−1. Characterization results revealed that the modification of Fe and Na, can promote the dispersion of Rh and the formation of Rh+ species, enhancing the capacities of CO2 adsorption and dissociation. In situ DRIFT experiment illuminated that the Rh active sites synergized with Fe and Na can stabilize the adsorbed species of m-CO32− and CO3H−, and promote the generation of HCOO* and CO* intermediates, which can be provided to couple with the CHx species, resulting in the high efficacy for ethanol synthesis from CO2 hydrogenation.

Z-scheme heterojunctions of NF@ZnO/0.5CeO2 monolithic catalyst for photothermal catalytic CO2 reduction under concentrated solar irradiation

Z-scheme heterojunctions of NF@ZnO/0.5CeO2 monolithic catalyst for photothermal catalytic CO2 reduction under concentrated solar irradiation

Breaking the intrinsic activity barriers of bilayer metal oxides for catalytic CO2 reduction

The photocatalytic CO2 reduction reaction is severely limited by sluggish charge kinetics. To address this issue, a strategy utilizing non-metal-doped layered double hydroxide (LDH) has been developed to control the electronic structure of spindle-shaped nanoflowers, resulting in efficient photocatalytic CO2 reduction. The results demonstrate that the designed catalyst yields 263.16 μmol g−1 h−1 for the photoreduction of CO2 to CO. Furthermore, the in situ Fourier transform infrared spectrum (FT-IR) analysis demonstrate that the specific S-ligand (S-bridge) facilitates CO2 activation, ensuring the continuous production of *COOH. The hydrothermal-assisted ionic liquid method proposed in this study offers guidance for modifying catalysts.

Unraveling active sites regulation and temperature-dependent thermodynamic mechanism in photothermocatalytic CO2 conversion with H2O

In the photothermal synergistic catalytic conversion of CO2 and H2O, the catalyst harnesses solar energy to accumulate heat, thereby elevating the reaction system’s temperature. The influence of this temperature effect on surface chemical reactions remains an underexplored area. Here the impact of temperature on the surface-level thermodynamic reactions and conversion of CO2 with H2O on oxide semiconductors at the atomic scale was investigated using first-principle calculations. 13 different metal oxides and 5 transition metal clusters were used to introduce surface functional sites on the TiO2 supporting catalyst. The potential metal oxide cocatalysts that could be most beneficial to the following conversion of CO2 by H2O were initially screened by calculating the degrees of promotion of CO2 adsorption and activation of surface H to provide protons. The proton donation and hydrogen evolution difficulty from H2O were further analyzed, identifying transition metal cocatalysts that promote direct CO2 hydrogenation. Upon introducing bifunctional sites to facilitate adsorption and reduction, the production of CH3OH and CH4 could be further enhanced through the facilitation of the proton donation process of H2O. The results of Gibbs free-energy calculations revealed that increasing temperature enhances the reaction thermodynamics for each C1 product formation at different surface sites to varying degrees. These findings offer valuable theoretical insights for designing and regulating active sites on oxide semiconductor surfaces for efficient photothermal catalytic CO2 reduction by H2O.

Photoelectrochemical catalytic CO2 reduction enhanced by In-doped GaN and combined with vibration energy harvester driving CO2 reduction

Photoelectrochemical (PEC) technology seamlessly integrates and optimizes the merits of photocatalysis and electrocatalysis, facilitating charge separation and enhancing solar conversion efficiency. It stands out as a promising approach for CO2 treatment. GaN as III-Ⅴ semiconductor, has garnered substantial attention in the realm of PEC CO2 reduction reactions (RR). In this study, GaN and In/GaN micro-rods were prepared via straightforward hydrothermal synthesis. Attaining a current density of approximately 10 mA/cm2 and CO Faradaic Efficiency (FE) of ∼45 % at −0.75 VRHE (Reversible Hydrogen Electrode, RHE), In/GaN exhibited exceptional stability over a 2 h PEC CO2 RR. The introduction of In into GaN significantly augmented CO2 adsorption capacity and light harvesting. Additionally, Density Functional Theory (DFT) calculations elucidated that In-doped GaN can diminish the adsorption of intermediate CO, favoring subsequent CO desorption. Furthermore, the N-vacancy increased with In doping, resulting in a rise in the number of unpaired electrons, facilitating carrier transport. Herein, vibration energy harvester was introduced to drive CO2 RR, marking a significant advancement in development of PEC CO2 RR for future green energy applications.

Ru/CeO2 catalyst derived from Ce-based MOF for highly efficient catalytic CO2 methanation integrated with renewable hydrogen

A series of highly ordered microporous Ce-based metal-organic frameworks (MOFs) were synthesized as the precursors for catalyst construction. The corresponding Ru catalysts were prepared by Ru impregnation on the derived CeO2 by pyrolysis of Ce-MOF, and investigated for the CH4 synthesis via CO2 hydrogenation. Among the catalysts, Ru catalyst supported on the CeO2-B derived from Ce-BDC exhibited a highly competitive efficiency for CO2 methanation, giving a CH4 selectivity of 100% with a CO2 conversion of 62% at 275 °C and 0.1 MPa, and the CH4 productivity reached 0.49 mol/(molRu·h). Characterization results revealed that more oxygen vacancies and corresponding surface oxygen species formed on the surface of CeO2-B derived from Ce-BDC caused to the stronger interaction between Ru and CeO2-B, which promoted the CO2 adsorption and hydrogenation capacity of the catalyst, resulting in its better catalytic property. In situ diffuse reflectance infrared Fourier transform (DRIFT) studies further revealed that the route of HCOO* into CH4 is a more competitive way of CO2 hydrogenation to CH4.

Exploring the CO2 Electrocatalysis Potential of 2D Metal-Organic Transition Metal-Hexahydroxytriquinoline Frameworks: A DFT Investigation.

Metal-organic frameworks have demonstrated great capacity in catalytic CO2 reduction due to their versatile pore structures, diverse active sites, and functionalization capabilities. In this study, a novel electrocatalytic framework for CO2 reduction was designed and implemented using 2D coordination network-type transition metal-hexahydroxytricyclic quinazoline (TM-HHTQ) materials. Density functional theory calculations were carried out to examine the binding energies between the HHTQ substrate and 10 single TM atoms, ranging from Sc to Zn, which revealed a stable distribution of metal atoms on the HHTQ substrate. The majority of the catalysts exhibited high selectivity for CO2 reduction, except for the Mn-HHTQ catalysts, which only exhibited selectivity at pH values above 4.183. Specifically, Ti and Cr primarily produced HCOOH, with corresponding 0.606 V and 0.236 V overpotentials. Vanadium produced CH4 as the main product with an overpotential of 0.675 V, while Fe formed HCHO with an overpotential of 0.342 V. Therefore, V, Cr, Fe, and Ti exhibit promising potential as electrocatalysts for carbon dioxide reduction due to their favorable product selectivity and low overpotential. Cu mainly produces CH3OH as the primary product, with an overpotential of 0.96 V. Zn primarily produces CO with a relatively high overpotential of 1.046 V. In contrast, catalysts such as Sc, Mn, Ni, and Co, among others, produce multiple products simultaneously at the same rate-limiting step and potential threshold.

MgO/Ni nanocomposite and its PVP-modified derivative for catalytic CO2 methanation and photocatalytic hydrogen production

In this study, we show that MgO/Ni nanocomposite (NC) synthesized using Laurus nobilis leaf extract display high catalytic activity toward CO2 methanation and photocatalytic hydrogen production. The polyvinylpyrrolidone (PVP)-modified NC displayed improved dispersion and charge separation, hence enhanced performance. The physicochemical characterization of the NCs revealed thermally stable (<0.5 wt% loss up to 400 °C) single nanocrystals, which may aggregate depending on the preparation technique. Fourier transform infrared spectroscopy coupled with thermogravimetry confirmed the incorporation of 0.45 g PVP per 1 g MgO/Ni. Catalytic performance evaluation showed peak CO2 conversion of 94.56 % and 98.74 % for MgO/Ni and MgO/Ni@PVP, respectively, at 390 °C, with higher selectivity towards CH4 observed for MgO/Ni@PVP across all temperatures. Similarly, MgO/Ni@PVP exhibited higher hydrogen production reaching 1.68 mmol/g.h compared with 1.30 mmol/g.h for MgO/Ni. These results underscore the potential of MgO/Ni@PVP NC as an effective catalyst for renewable energy production and carbon utilization.

Enhanced CO2 absorption in amine-based carbon capture aided by coconut shell-derived nitrogen-doped biochar

The sluggish CO2 absorption kinetics and constrained CO2 absorption capacity diminish the practicality of using amine-based absorption for CO2 capture, impeding progress toward carbon neutrality goals. This study aims to develop a catalytic CO2 absorption process to promote CO2 absorption by introducing a solid base catalyst, namely, coconut shell-derived nitrogen-doped biochar (NBC), into an amine-based solution. The coconut shells were modified with urea and activated with KOH to prepare an NBC catalyst with improved basic characteristics. The findings showed that compared to non-catalytic absorption, the NBC catalyst increased the CO2 absorption amount, CO2 absorption rate, and absorption efficiency of the monoethanolamine (MEA) solution by 16.9 %, 43.4 %, and 13.1 %, respectively. The basic sites on the NBC surface provided extra electrons to motivate the formation of MEACOO- and HCO3-. NBC’s large surface area and porous structure also advanced the gas–liquid mass transfer, accelerating the CO2 absorption rate. Furthermore, the NBC exhibited excellent cyclic stability and facilitated the subsequent CO2 desorption process. This work develops a promising and practical approach to significantly improve the amine-based absorption and reuse of waste biomass resources for efficient CO2 capture.

Sub-millisecond pulsed laser engineering of CuOx-decorated Pd nanoparticles for enhanced catalytic CO2 hydrogenation

Catalytic CO2 hydrogenation to fuels and chemicals presents a promising avenue for addressing global warming and advancing toward a net-zero economy. Surface atomic rearrangement of catalysts has attracted growing interest as a means to manipulate catalyst activity and selectivity. Herein, we designed a ternary nanocatalyst comprising CuOx species decorated Pd nanoparticles (NPs) supported on Co oxide (denoted as CPCu) for catalytic CO2 hydrogenation. Sub-millisecond laser treatment (1 mJ per pulse) was used to manipulate the surface atomic arrangements of CPCu the catalyst. The CPCu nanocatalyst showed a significant enhancement in both CH4 production and CO production at 300 °C compared to the Pd/Co catalyst. Notably, the CH4 production using the laser-treated nanocatalyst (denoted as CPCu-L) was 66.6 % higher than the untreated one (CPCu) at 300 °C. Comprehensive catalyst characterizations revealed that CuOx species promoted CO2 activation, while neighboring Pd domains effectively dissociated H2 molecules, leading to enhanced CH4 production. This study demonstrates the potential of sub-millisecond laser treatment for tailoring catalyst surfaces, offering a promising strategy to design more active and selective catalysts for CO2 hydrogenation.

Catalytic behavior of aluminum-modified SAPO-34 catalysts for reducing the energy penalty of CO2-rich amine solutions regeneration

The goal of this research is to develop a potential strategy to significantly decrease the heat duty for the amine-based CO2 capture process. Here, a variety of Al2O3-modified SAPO-34 composite catalysts with varying Al2O3 contents are synthesized and utilized to catalytically facilitate the CO2 desorption process. The catalytic CO2 desorption characteristics of various catalysts, Al-SAPO-34, SAPO-34, and γ-Al2O3 are investigated in a CO2-loaded 5 M monoethanolamine (MEA) solution. The results indicate that all catalysts accelerate CO2 desorption, while the Al-SAPO-34 catalysts work better than the parent Al2O3 and SAPO-34 catalysts. Especially, the 15 % Al-SAPO-34 increases the CO2 desorption rate by 78.4 % and reduces the relative energy requirement by 37 % at a desorption time of 1440 s. The catalysts are characterized by different methods and their structure–activity relationship is analyzed. The increased acid sites and mesoporous surface area of the Al-SAPO-34 catalyst may be responsible for its greater catalytic activity. The intermediates of the catalytic CO2 desorption process are identified by FT-IR and NMR, and then a possible catalytic regeneration mechanism is put forward. Additionally, the cyclic stability of the Al-SAPO-34 catalyst for cyclic CO2 absorption–desorption is evaluated. This work demonstrates that the Al-SAPO-34 exhibits greater catalytic CO2 desorption performance, and outstanding stability, and has the opportunity to become an attractive industrial catalyst for the amine-based CO2 capture process.

Insights into catalytic oxidation mechanism of toluene by lanthanum mangan-based perovskite in wet environment based on in-situ DRIFTS

This paper investigated that the catalytic activity and CO2 selectivity of LaMnO3, La0.9Ca0.1MnO3 and 3-La0.9Ca0.1MnO3 catalysts with different oxygen vacancy concentrations were compared under wet and dry conditions. The 3-La0.9Ca0.1MnO3 catalysts had excellent water resistance. The presence of H2O had less effect on toluene conversion than on CO2 selectivity. In wet environment, the 3-La0.9Ca0.1MnO3 catalyst achieved 90 % toluene conversion at 173 °C, but less than 20 % selectivity for CO2 at this time, and reached 90 % selectivity for CO2 at 220 °C. The effect of H2O on the catalytic oxidation mechanism of toluene was analyzed by in-situ DRIFTS analysis. The presence of H2O could promote the decomposition of toluene into intermediates of benzyl alcohol, benzoic acid, benzaldehyde and maleic anhydride at low temperature (50 °C), but the intermediates were difficult to decompose into CO2 and H2O. It was suggested that surface hydroxyl group could promote the transformation of toluene to intermediate at low temperature, and suitable oxygen vacancies and surface hydroxyl group could jointly promote the transformation of toluene to ideal product. This work provided a theoretical basis for the design of water-resistant catalysts in industry.

Recent Advances Hydrogenation of Carbon Dioxide to Light Olefins over Iron-Based Catalysts via the Fischer-Tropsch Synthesis.

The massive burning of fossil fuels has been important for economic and social development, but the increase in the CO2 concentration has seriously affected environmental sustainability. In industrial and agricultural production, light olefins are one of the most important feedstocks. Therefore, the preparation of light olefins by CO2 hydrogenation has been intensively studied, especially for the development of efficient catalysts and for the application in industrial production. Fe-based catalysts are widely used in Fischer-Tropsch synthesis due to their high stability and activity, and they also exhibit excellent catalytic CO2 hydrogenation to light olefins. This paper systematically summarizes and analyzes the reaction mechanism of Fe-based catalysts, alkali and transition metal modifications, interactions between active sites and carriers, the synthesis process, and the effect of the byproduct H2O on catalyst performance. Meanwhile, the challenges to the development of CO2 hydrogenation for light olefin synthesis are presented, and future development opportunities are envisioned.

Unveiling the mechanism of CO oxidation catalyzed by sulfur-doped fullerenes with the DFT calculations

As an important intermediate for dual carbon targets, catalytic CO oxidation under mild conditions has received sufficient attention, as the reaction mechanism is directly related to the type of employed catalyst. High performance computing is performed with density functional theory to elucidate the mechanism of CO oxidation catalyzed by sulfur doped fullerene (C60-xSx (x = 1 ∼ 3)). The total activation energy for the first CO oxidation on C59S, C58S2, and C57S3 increases gradually, as implies that the CO oxidation on C59S should be easier than those on the other two dopants. Distinct electrons (0.852 e and 1.479 e) are transferred to oxygen atoms (O2) from C59S with the adsorption of O2 and CO. There is no synergistic effect for the doping S atoms. All elementary reactions on C59S are exothermic processes. This means that C59S is a potential material for addressing environmental protection issues and H2 purification for fuel cell applications.

Concentrated solar CO2 reduction in H2O vapour with >1% energy conversion efficiency

H2O dissociation plays a crucial role in solar-driven catalytic CO2 methanation, demanding high temperature even for solar-to-chemical conversion efficiencies <1% with modest product selectivity. Herein, we report an oxygen-vacancy (Vo) rich CeO2 catalyst with single-atom Ni anchored around its surface Vo sites by replacing Ce atoms to promote H2O dissociation and achieve effective photothermal CO2 reduction under concentrated light irradiation. The high photon flux reduces the apparent activation energy for CH4 production and prevents Vo from depletion. The defects coordinated with single-atom Ni, significantly promote the capture of charges and local phonons at the Ni d-impurity orbitals, thereby inducing more effective H2O activation. The catalyst presents a CH4 yield of 192.75 µmol/cm2/h, with a solar-to-chemical efficiency of 1.14% and a selectivity ~100%. The mechanistic insights uncovered in this study should help further the development of H2O-activating catalysts for CO2 reduction and thereby expedite the practical utilization of solar-to-chemical technologies.