CO Hydrogenation Activity Research Articles

Integrated Photothermal Nanoreactors for Efficient Hydrogenation of CO2

To alleviate the energy crisis and global warming, photothermal catalysis is an attractive way to efficiently convert CO2 and renewable H2 into value-added fuels and chemicals. However, the catalytic performance is usually restricted by the trade-off between the dispersity and light absorption property of metal catalysts. Here we demonstrate a simple SiO2-protected metal–organic framework pyrolysis strategy to fabricate a new type of integrated photothermal nanoreactor with a comparatively high metal loading, dispersity, and stability. The core-satellite structured Co@SiO2 exhibits strong sunlight-absorptive ability and excellent catalytic activity in CO2 hydrogenation, which is ascribed to the functional separation of different sizes of Co nanoparticles. Large-sized plasmonic Co nanoparticles are mainly responsible for the light absorption and conversion to heat (nanoheaters), whereas small-sized Co nanoparticles with high intrinsic activities are responsible for the catalysis (nanoreactors). This study provides a new concept for designing efficient photothermal catalytic materials.

Dependency of CO2 methanation on the strong metal-support interaction for supported Ni/CeO2 catalysts

The strong metal-support interaction (SMSI) for supported Ni/CeO2 catalysts with different CeO2 nanomorphologies was systematically explored. The degree of encapsulation of Ni particles originating from the SMSI effect was found to follow the trend of Ni/CeO2-(111) > Ni/CeO2-(100) > Ni/CeO2-(110 + 100), which parallels the CO2 hydrogenation activity. Quasi in situ XPS reveals the presence of Ce3+ sites in accordance with the formation of an amorphous surface CeOx layer encapsulating the Ni nanoparticles. In situ DRIFTS indicates the reaction pathway and rate-determining step are dependent on the degree of the SMSI effect, leading to distinct selectivities towards CH4, especially at a high weight hourly space velocity (WHSV). These findings present a fundamental strategy about tailoring catalytic performance through support facet dependent susceptibility of SMSI phenomena.

Inside Cover: Mapping Active Site Geometry to Activity in Immobilized Frustrated Lewis Pair Catalysts (Angew. Chem. Int. Ed. 32/2022)

Frustration under control: In their Communication (DOI: 10.1002/anie.202202727), Clémence Corminboeuf and co-workers developed a general approach to map the active site geometry of immobilized frustrated Lewis pair catalysts to their activity for CO2 hydrogenation and demonstrated that a manyfold increase in their performance is attainable through judicious spatial control of the acid and base components.

Syngas conversion into light hydrocarbons over bifunctional catalyst: Effect of the density of contact between Cu-ZnO-Al2O3 and SAPO-34

A series of hybrid catalysts with different catalytic bed dispositions (layer bed and simple random mixture) of Cu-ZnO-Al2O3 and SAPO-34 have been adopted and evaluated in syngas conversion into light C2-C4 hydrocarbons. An effect of the proximity between the two solids on the CO hydrogenation activity was demonstrated. A sphere contact quantification model was developed to estimate the concentration of contact between them for any simple random mixture. Comparing the evolution of gain of CO conversion (or hydrocarbon yield) with the theoretical results, it was shown that the density of contact was identified as the key factor for the catalytic performances (contact-activity relationship). Finally, the knowledge of the contact morphology, determined by FEG-SEM, allowed proposing the NH3-TPD as method characterizing the concentration of contact.

CO Hydrogenation to Methanol over Cu/MgO Catalysts and Their Synthesis from Amorphous Magnesian Georgeite Precursors

AbstractThe synthesis of Mg‐substituted copper hydroxycarbonates by constant‐pH co‐precipitation with subsequent ageing of the precipitate has been studied in detail. This allowed the retrieval of crystalline magnesian malachite samples, which showed a “radical‐sign‐shaped” pH drop and the blue/green color change during ageing that is well‐known from the analogous Cu/Zn system. The crystallization of Cu‐rich samples has been studied elaborately by means of powder diffraction, pair distribution function (PDF), and infrared spectroscopy, thus elucidating the ageing chemistry of Cu,Mg hydroxycarbonates in general. It was found that up to 17 % Mg can be incorporated into the crystalline malachite using a synthesis route comparable to that established for Cu/ZnO catalysts, but with drastically elongated precipitate ageing times. For higher Mg contents, a step‐like pH drop was observed instead, and an amorphous variant of the hydroxycarbonate, referred to as “magnesian georgeite”, could be isolated. From such a Mg‐rich sample (Cu/Mg 70 : 30 at. %), a Cu/MgO catalyst has been prepared that shows high activity and good stability in CO hydrogenation to methanol over 800 hrs. time on stream.

The Strong Interaction Between CuOx and CeO2 Nanorods Enhanced Methanol Synthesis Activity for CO2 Hydrogenation

The Strong Interaction Between CuOx and CeO2 Nanorods Enhanced Methanol Synthesis Activity for CO2 Hydrogenation

Tuning activity and selectivity of CO2 hydrogenation via metal-oxide interfaces over ZnO-supported metal catalysts

Metal-oxide interface is generally regarded as the active sites in CO2 hydrogenation while their structure–property relationships are hardly identified. Herein, ZnO-supported Ru (Ru/ZnO) and Ni (Ni/ZnO) catalysts were used for CO2 hydrogenation. Their interfacial structures were finely tuned by altering the nature of supported metal particles and the support morphology, which significantly affect the catalytic activity and product selectivity. Direct evidences indicate that the weak basic sites are responsible for catalytic activity. The catalytic reaction proceeds through the dissociation mechanism involving the key intermediate of adsorbed CO species, whose strength determines product selectivity. A weak CO adsorption capacity on Ni species leads to high CO selectivity on Ni/ZnO catalysts, while CH4 could be produced on Ru/ZnO catalysts with strong CO binding capacity on low-coordination Ru species. Consequently, more low-coordination Ru species presented on Ru/p-ZnO (nanoplates) induced by stronger metal-support interactions contribute to a higher CH4 selectivity. These results deepen the understanding of metal-oxide interface in CO2 hydrogenation and broaden the concept of morphology-dependent catalysis of oxide-based catalysts.

Screening and design of active metals on dendritic mesoporous Ce0.3Zr0.7O2 for efficient CO2 hydrogenation to methanol

Different active metals (PdCu, PdZn, CuZn, CuGa, and CuNi) over novel dendritic Ce0.3Zr0.7O2 (CZ) support were optimized to investigate their metal alloy interactions and further utilize their surface properties of the spherical morphology and the open pores of the dendritic support. The nature of the dendritic support offers a distinctive property in which it can increases the distribution of active sites. This variety of bimetallic phases withhold a distinctive interaction characteristic with the support that could promote CO2 hydrogenation to methanol by improving the oxygen vacancies and modifying the catalyst's reduction property. The addition of ZnO species into PdZn/CZ catalyst and the higher dispersion degrees of active metals could generate more oxygen vacancies that can improve and stabilize the methoxy species and promote the formate routes, thus, improve the activity of CO2 hydrogenation to methanol reaction. PdZn/CZ catalyst displayed the highest CO2 conversions (25.7 %), methanol yield (6.9 %), and superior 100 h long-term stability than those of other bimetallic catalysts. The best CO2 hydrogenation activity of the PdZn/CZ catalyst can be ascribed to the CO2 adsorption capabilities of CZ support that generated added oxygen vacancies and hydrogen dissociation performance of the Pd-ZnO active site.

Interface-dependent activity and selectivity for CO2 hydrogenation on Ni/CeO2 and Ni/Ce0.9Sn0.1Ox

To study the importance of interface microstructure on reactivity for CO2 hydrogenation, Ni/CeO2, Ni/Ce0.9Sn0.1Ox and Ni/0.1SnO2-0.9CeO2 catalysts were prepared, whose support is pristine CeO2, Sn-doped CeO2-based solid solution, and the mixture of SnO2 and CeO2 in sequence with a Sn/Ce molar ratio of 1:9 in the latter two supports. The intrinsic activity of the catalysts for CO2 hydrogenation followed the order: Ni/CeO2 > Ni/0.1SnO2-0.9CeO2 > Ni/Ce0.9Sn0.1Ox. Ni/CeO2 and Ni/0.1SnO2-0.9CeO2 showed CH4 selectivity, while Ni/Ce0.9Sn0.1Ox CO selectivity. The strong interaction between Sn cations and Ni species in Ni/Ce0.9Sn0.1Ox resulted in the immigration of Sn cations to Ni species to form the Ni-O-Sn-O-Ce interface, distinctly differing from the Ni-O-Ce interface in Ni/CeO2 and the Ni-O-Ce plus Ni-O-Sn interfaces in Ni/0.1SnO2-0.9CeO2. The enrichment of Sn cations as acidic sites on the Ni/Ce0.9Sn0.1Ox surface decreased evidently the chemisorption of CO2 and inhibited the generation of HCO3*, thus inhibiting the formate path for CH4. Conversely, the presence of Sn cations in the interface favored the generation of carbonates, thus promoting CO yield. This work shows the activity and selectivity for CO2 hydrogenation are highly dependent on microstructure of an interface in oxide-supported Ni catalysts.

CO2 hydrogenation to methanol promoted by Cu and metastable tetragonal CexZryOz interface

Designing effective catalyst to improve the activity of CO2 hydrogenation to methanol is a potential avenue to realize the utilization of CO2 resources. Herein we construct three kinds of Cu/CexZryOz (CCZ) catalysts with different crystal phases of CexZryOz solid solutions, which demonstrate distinct activity and methanol selectivity in the order of metastable tetragonal-CCZ (CCZ-t″, parts of oxygen in CexZryOz were replaced by tetragonal phase from cubic fluorite phase) > tetragonal-CCZ (CCZ-t) > cubic-CCZ (CCZ-c) for CO2 hydrogenation to methanol. Structural analysis reveals that oxygen vacancies, surface hydroxyls and unsaturated Cu species of CCZ all follow the same sequence as that of activity and methanol selectivity, indicating that the above features are beneficial to improve the catalytic reaction performance. Temperature programmed experiments and mechanism studies show that the interface between Cu and tetragonal (t and t″) CexZryOz can promote CO2 adsorption, and the adsorbed CO2 is more reactive and can generate active bidentate carbonate species, which can be hydrogenated to form active monodentate and bidentate formate species under CO2 and H2 atmosphere. These intermediates should be crucial to the formation of methanol product. CCZ-t″ has stronger H2 activation ability than CCZ-t, which makes the former catalyst have more intermediates and higher methanol selectivity. In contrast, CO2 mainly adsorbs on cubic CexZryOz support of CCZ-c, but its H2 spillover ability is low, which hinders the reaction process. In addition, the strong adsorption of surface intermediates on CCZ-c is also not conducive to methanol formation. Results here demonstrate that constructing active Cu-support interfaces may be an important approach to design effective catalyst for CO2 hydrogenation.

Understanding the geometric and basicity effects of organic polymer modifiers on Ru/TiO2 catalysts for CO2 hydrogenation to hydrocarbons

Modifying inorganic catalysts with basic organic moieties effectively enhances their CO2 hydrogenation activity through CO2 activation, but the effect on C–C coupling rates and selectivity is not as straightforward.

Catalytic Activity for Direct Co2 Hydrogenation to Dimethyl Ether with Different Proximity of Bifunctional Cu-Zno-Al2o3 and Ferrierite

Catalytic Activity for Direct Co2 Hydrogenation to Dimethyl Ether with Different Proximity of Bifunctional Cu-Zno-Al2o3 and Ferrierite

Oxygen Vacancies in Cu/Tio2 Boost Strong Metal–Support Interaction and Improve the Catalyst's Activity, Selectivity, and Stability in Co2 Hydrogenation to Methanol

Oxygen Vacancies in Cu/Tio2 Boost Strong Metal–Support Interaction and Improve the Catalyst's Activity, Selectivity, and Stability in Co2 Hydrogenation to Methanol

Tuning Activity and Selectivity of Co2 Hydrogenation by Using Different Interlayer Anions Over Mechanochemically Pretreated Gibbsite-Based, Nickel-Poor Layered Double Hydroxides

Tuning Activity and Selectivity of Co2 Hydrogenation by Using Different Interlayer Anions Over Mechanochemically Pretreated Gibbsite-Based, Nickel-Poor Layered Double Hydroxides

Role of Zro2 and Ceo2 Support on the In2o3 Catalyst Activity for Co2 Hydrogenation

Role of Zro2 and Ceo2 Support on the In2o3 Catalyst Activity for Co2 Hydrogenation

Rational Design of Main Group Metal-Embedded Nitrogen-Doped Carbon Materials as Frustrated Lewis Pair Catalysts for CO2 Hydrogenation to Formic Acid.

Developing efficient and inexpensive main group catalysts for CO2 conversion and utilization has attracted increasing attention, as the conversion process would be both economical and environmentally benign. Here, based on the main group element Al, we designed several heterogeneous frustrated Lewis acid/base pair (FLP) catalysts and performed extensive first-principles calculations for the hydrogenation of CO2. These catalysts, including Al@N-Gr-1, Al@N-Gr-2, and Al@C2N, are composed of a single Al atom and two-dimensional (2D) N-doped carbon-based materials to form frustrated Al/C or Al/N Lewis acid/base pairs, which are all predicted to have high reactivity to absorb and activate hydrogen (H2). Compared with Al@N-Gr-1, both Al@N-Gr-2 and Al@C2N, especially Al@N-Gr-2, containing Al/N Lewis pairs exhibit better catalytic activity for CO2 hydrogenation with lower activation energies. CO2 hydrogenation on the three catalysts prefers to go through a three-step mechanism, i.e., the heterolytic dissociation of H2, followed by the transfer of the hydride near Al to CO2, and finally the activation of a second H2 molecule. Other IIIA group element (B and Ga)-embedded N-Gr-2 materials (B@N-Gr-2 and Ga@N-Gr-2) were also explored and compared. Both Al@N-Gr-2 and Ga@N-Gr-2 show higher catalytic activity for CO2 hydrogenation to HCOOH than B@N-Gr-2. However, the CO2 hydrogenation path on Ga@N-Gr-2 tends to follow a two-step mechanism, including H2 dissociation and subsequent hydrogen transfer. The present study provides a potential solution for CO2 hydrogenation by designing novel and effective FLP catalysts based on main group elements.

CO2 Conversion to formates catalyzed by iridium(III) catalysts precursors with proton responsive OH and NH electron-rich tetrazole ligands

Recent efforts in addressing the environmental problems have involved using CO2 as a cheap and nontoxic C1 source. Iridium catalysts with bidentate ligands are excellent catalysts for CO2, especially if these complexes possess proton-responsive OH or NH groups. Here-in we report the synthesis of novel Ir half-sandwich complexes with N^N bidentate tetrazolyl ligands. Serendipitous deprotection of methoxy groups resulted in N^N bidentate ligands bearing OH groups. The complexes were evaluated for CO2 hydrogenation, for which the roles of steric bulk or the presence of electronic effects influence their catalytic activity in CO2 hydrogenation. The complexes are highly active for CO2 hydrogenations with around 4.3 mmol of formate produced. The presence of proton responsive groups on the catalysts was found to steer the mechanistic cycle away from using a bridged Ir-H-Ir intermediate before forming catalytically active species. In addition, these catalysts were found to hydrogenate CO2 in the presence of bicarbonate ions selectively.

The Mitigation of CO Present in the Water–Gas Shift Reformate Gas over IR-TiO2 and IR-ZrO2 Catalysts

CO hydrogenation and oxidation were conducted over Ir supported on TiO2 and ZrO2 catalysts using a feed mimicking the water–gas shift reformate stream. The influence of the support interaction with Ir and the catalysts’ redox and CO chemisorption properties on activity and selectivity were evaluated. Both catalysts oxidised CO to CO2 in the absence of H2, and a conversion of 70% was obtained at 200 °C. For the CO oxidation in the presence of H2 over these catalysts, the oxidation of H2 was favoured over CO due to H2 spillover occurring at the active metal and support interface, resulting in the formation of interstitials catalysed by Ir. However, both catalysts showed promising activity for CO hydrogenation. Ir-ZrO2 was more active, giving 99.9% CO conversions from 350 to 370 °C, with high selectivity towards CH4 using minimal H2 from the feed. Furthermore, results for the Ir-ZrO2 catalyst showed that the superior activity compared to the Ir-TiO2 catalyst was mainly due to the reducibility of the support and its interaction with the active metal. Controlling the isoelectric point during the synthesis allowed for a stronger interaction between Ir and the ZrO2 support, which resulted in higher catalytic activity due to better metal dispersions, and higher CO chemisorption capacities than obtained for the Ir-TiO2 catalyst.

Recent strategies for enhancing the catalytic activity of CO2 hydrogenation to formate/formic acid over Pd-based catalyst

The “greenhouse effect” caused by presence of the large amounts of carbon dioxide (CO2) is becoming extremely serious for the environment. Therefore, it is crucial to advance the progress of practical technologies to minimize the CO2 emissions. The catalytic CO2 hydrogenation with hydrogen (H2) to form formic acid/formate over Pd-based catalysts has been considered as an effective technology to deal with environment and CO2 emission issues. In the past decades, increasing efforts have been contributed to these fields and significant achievements have been obtained. In this review, the state-of-the-art of Pd-based heterogenous catalysts for catalytic conversion of CO2 to formate/formic acid is systematically summarized. First, the key factors associated with catalytic performance are discussed including Pd metal dispersion, electron density of Pd metal and acidity of supports. Second, major achievements on the design of efficient Pd nanometal supported on various materials, mainly metal-organic frameworks (MOFs), carbon materials, silica, zeolites and other porous material, are summarized. Third, the successful strategies applied to maximize catalytic activity of CO2 conversion by reducing the particle size of Pd, alloying foreign metal with Pd to change the electron density of Pd, as well as anchoring of functional groups were also highlighted. Special attention has been given to the mechanism of the catalytic reaction. Finally, a brief perspective to the challenges and new directions in the development of innovative catalytic materials to achieve high catalytic activity in CO2 conversion is also proposed, which would be of great interest in realizing carbon-neutrality in near future.

CO2 hydrogenation on CeO2@Cu catalyst synthesized via a solution auto-combustion method

Cu-based catalysts had been widely used in CO2 hydrogenation process for their excellent performance and high selectivity. Micron-sized Cu powder obtained by ball milling exhibited poor CO2 activity for its large particle size and small specific surface area, limited its catalytic application. In this work, micron Cu powder was modified with CeO2 species synthesized from different cerium precursor salts via a solution auto-combustion method to investigate CO2 hydrogenation activity. This work revealed that CeO2 species formed from cerium acetate precursor salt achieved excellent CO2 performance (1.64 mol/gcat.h at 400 °C), which was 3.8 times and 6000 times higher than that from cerium nitrate salt or cerium chloride salt, respectively. Interestingly, a thick dense CeO2 shell would be formed on micron Cu generated from cerium(III) chloride precursor salt, which inhibited CuOx reduction and had the opposite effect for RWGS reaction. In addition, the CuOx species in CeO2@Cu synthesized from cerium chloride salt resulted in the CH4 selectivity. The enhancement performance of the CeO2@Cu prepared from cerium acetate salt and cerium nitrate salt could be attributed to the oxygen defects formed around the Cu-Ox-Ce interface area and metallic Cu in the RWGS reaction. Cerium precursor salts enhanced the structural integrity of CeO2@Cu and played a vital role in RWGS reaction. These results will support a new direction for exploring micron Cu powder in Cu-based catalysts for CO2 utilization.