CO Hydrogenation Research Articles

Enhanced CO2-to-CH4 conversion via grain boundary oxidation effect in CuAg systems

The authentic active sites of oxide-derived copper (OD-Cu), namely grain boundaries (GBs) and oxidized Cuδ+ species, is still debatable, and their role in governing CH4 conversion remains unclear. Herein, this study answers these questions using bimetallic catalysts by novel electro-shock strategy with controllable GBs for the oxidization of Cuδ+ species by modulating Ag loading. The Ag enrichment at the GBs facilitates the bonding of oxygen with the uncoordinated Cu atoms, resulting in GB oxidation effect. The obtained CH4 selectivity is twice that of GBs or nanoalloy effect. The enhanced performance is attributed to the stable Cuδ+ species and unique electron transfer mechanism from GB oxidation structure. Operando attenuated-total-reflection Fourier-transform-infrared-spectroscopy unveils the reaction pathway of CO2-to-CH4 and the sluggish reversible quenching processes of intermediates. Theoretical calculations indicate that the weak *CO adsorption on GB oxidation structure facilitates *CO hydrogenation, promoting CO2-to-CH4 conversion.

Lithium iodide promoted CO2 hydrogenation towards ethanol via biphasic lewis-acid-base pairs synergistic catalysis

Lithium iodide promoted CO2 hydrogenation towards ethanol via biphasic lewis-acid-base pairs synergistic catalysis

Highly active and stable mixed-phase In2O3-supported Ni catalyst for CO2 hydrogenation to methanol

Ni/In2O3 catalysts perform well for CO2 hydrogenation to methanol. However, there is still room for improvement in terms of methanol selectivity. In this study, Ni/In2O3 catalysts with distinct crystalline phases of indium oxide, namely cubic In2O3 (c-In2O3) and a mixed phase of cubic and hexagonal In2O3 (h + c-In2O3), were synthesized. The results showed that the Ni/h + c-In2O3 catalyst demonstrated the greatest catalytic performance, with a methanol selectivity of 96.7 % and a space time yield of methanol of 15.79 mmol·g−1·h−1 at 2 MPa, 300°C, and 24.0 L·g−1·h−1. Based on the characterization results, we concluded that the improvement of the methanol synthesis performance on the Ni/h + c-In2O3 catalyst was mainly due to improved hydrogen dissociation ability and the increased surface oxygen vacancies. The energy barrier (Ea) of the rate-limiting steps for the CH3OH and CO productions was calculated. The decreased Ea(CH3OH) and increased Ea(CO) indicate the favorable improvement of catalytic activity and selectivity for CH3OH production by Ni/In2O3, especially for Ni/h-In2O3(104).

Understanding and Tuning the Effects of H2O on Catalytic CO and CO2 Hydrogenation.

Catalytic COx (CO and CO2) hydrogenation to valued chemicals is one of the promising approaches to address challenges in energy, environment, and climate change. H2O is an inevitable side product in these reactions, where its existence and effect are often ignored. In fact, H2O significantly influences the catalytic active centers, reaction mechanism, and catalytic performance, preventing us from a definitive and deep understanding on the structure-performance relationship of the authentic catalysts. It is necessary, although challenging, to clarify its effect and provide practical strategies to tune the concentration and distribution of H2O to optimize its influence. In this review, we focus on how H2O in COx hydrogenation induces the structural evolution of catalysts and assists in the catalytic processes, as well as efforts to understand the underlying mechanism. We summarize and discuss some representative tuning strategies for realizing the rapid removal or local enrichment of H2O around the catalysts, along with brief techno-economic analysis and life cycle assessment. These fundamental understandings and strategies are further extended to the reactions of CO and CO2 reduction under an external field (light, electricity, and plasma). We also present suggestions and prospects for deciphering and controlling the effect of H2O in practical applications.

Tuning CO2 Hydrogenation to Light Olefin Selectivity via Cu/Zn/Zr Supported on Modified SAPO‐34

AbstractTo alleviate CO2 emissions and reduce reliance on fossil fuels, a groundbreaking bifunctional catalyst system was introduced, which ingeniously merged CZZ with modified SAPO‐34 zeolite, to convert CO2 into light olefins. Different metals were impregnated into SAPO‐34 to form MeSAPO‐34 (Me = Zn, Zr, Mn) and the metal Zr content was altered. Furthermore, CZZ and MeSAPO‐34 was combined into CZZ/MeSAPO‐34 composite catalysts, which was used for CO2 hydrogenation. The MeSAPO‐34 and xZrSAPO‐34 catalysts were rigorously characterized by various techniques, revealing key physicochemical attributes. This innovative approach harnessed the synergistic effects between the metallic CZZ component and the modified zeolite to facilitate a series of reactions, effectively generating C2‐C4‐rich hydrocarbons. Benefiting from weak acid, higher oxygen vacancy concentration and interactions between components, the CZZ/ZrSAPO‐34 catalyst system has shown remarkable efficiency in enhancing the light olefin selectivity. The key aspects of this system are its ability to modulate surface acidity and oxygen vacancy concentration, thus creating favorable conditions for light olefin production via enhanced tandem reaction based on CO2 hydrogenation. This work enriches our insight into designing novel composite catalysts for promoting CO2 conversion and hence mitigating CO2 emissions.

Catalytic Activity of Tandem Catalysts Based on ZnGa2O4 and MFI Zeolite in CO2 Hydrogenation

Catalytic Activity of Tandem Catalysts Based on ZnGa2O4 and MFI Zeolite in CO2 Hydrogenation

Catalytic N‐Formylation of CO2 by Atomically Precise Au8Pd1(DPPF)42+ Clusters into a Two‐Dimensional Metal–Organic Framework

AbstractBy highly efficient ligand‐exchange strategy, atomically precise Au8Pd1(PPh3)82+ (PPh3=triphenylphosphine) cluster can be transformed into a Au8Pd1(DPPF)42+ (DPPF=1,1′‐bis(diphenylphosphino)ferrocene) cluster that can maintain the atomic‐packing structure but overcome the lability of Au8Pd1(PPh3)82+. Catalytic evaluation for the CO2 hydrogenation coupled with o‐phenylenediamine demonstrates that the Au8Pd1(DPPF)42+ catalyst can remarkably enhance both activity and stability compared to the Au8Pd1(PPh3)82+ catalyst. More notably, the direct construction of a two‐dimensional metal–organic framework (2D MOF) can be elaborately accomplished in the formylation process of o‐phenylenediamine, CO2 and H2 with zinc nitrate enabled by the Au8Pd1(DPPF)42+ catalyst. The 2D MOF further enables the capture and transformation of CO2 to combine in the organic synthesis with epoxides under mild conditions. This work provides opportunities for creating highly active cluster sites for the chemical recycling of CO2.

Catalytic N-Formylation of CO2 by Atomically Precise Au8Pd1(DPPF)4 2+ Clusters into a Two-Dimensional Metal-Organic Framework.

By highly efficient ligand-exchange strategy, atomically precise Au8Pd1(PPh3)8 2+ (PPh3=triphenylphosphine) cluster can be transformed into a Au8Pd1(DPPF)4 2+ (DPPF=1,1'-bis(diphenylphosphino)ferrocene) cluster that can maintain the atomic-packing structure but overcome the lability of Au8Pd1(PPh3)8 2+. Catalytic evaluation for the CO2 hydrogenation coupled with o-phenylenediamine demonstrates that the Au8Pd1(DPPF)4 2+ catalyst can remarkably enhance both activity and stability compared to the Au8Pd1(PPh3)8 2+ catalyst. More notably, the direct construction of a two-dimensional metal-organic framework (2D MOF) can be elaborately accomplished in the formylation process of o-phenylenediamine, CO2 and H2 with zinc nitrate enabled by the Au8Pd1(DPPF)4 2+ catalyst. The 2D MOF further enables the capture and transformation of CO2 to combine in the organic synthesis with epoxides under mild conditions. This work provides opportunities for creating highly active cluster sites for the chemical recycling of CO2.

Strong Metal‐Support Interaction between Pt and TiO2 over High‐temperature CO2 Hydrogenation

The catalytic activities and stability of oxide‐supported metal catalysts are significantly affected by metal‐support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal‐support interaction (SMSI) and electronic metal‐support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile‐supported Pt nanoparticles (NP) over high‐temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2−x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high‐temperature reverse water‐gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM‐1×h‐1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time‐on‐stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Strong Metal-Support Interaction between Pt and TiO2 over High-temperature CO2 Hydrogenation.

The catalytic activities and stability of oxide-supported metal catalysts are significantly affected by metal-support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal-support interaction (SMSI) and electronic metal-support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile-supported Pt nanoparticles (NP) over high-temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2-x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high-temperature reverse water-gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM-1×h-1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time-on-stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Modification of the Fe/MgAl2O4 Catalyst of CO Hydrogenation with Indium

Modification of the Fe/MgAl2O4 Catalyst of CO Hydrogenation with Indium

Photothermal CO2 Hydrogenation to Methanol over Ni-In2O3/g-C3N4 Heterojunction Catalysts

Selective CO2 hydrogenation faces significant technical challenges, although many efforts have been made in this regard. Herein, a Ni-doped In2O3 catalyst supported by g-C3N4 was prepared using the co-precipitation method, and its composition, morphology, specific surface area, and band gap were characterized using TEM, XPS, BET, XRD, CO2-TPD, H2-TPR, UV-Vis, etc. The catalytic hydrogenation reduction of CO2 to produce methanol was tested. Under low-photothermal conditions (1.0 MPa), the hydrogenation of carbon dioxide to methanol is stable, effective, and highly selective, with a spatiotemporal yield of 86.0 gMeOHh−1 kgcat−1, which is 30.9% higher than that of Ni-In2O3 without g-C3N4 loading under the same conditions.

Pt‐Mo₂N Catalyst Formed by Inverse Sintering for the Reverse Water‐Gas Shift Reaction

AbstractThe reverse water‐gas shift (RWGS) reaction is significant for the resource utilization of CO2. However, this reaction requires high temperatures and metal catalysts are prone to agglomeration, leading to loss of activity. In this work, a Pt catalyst supported on Mo₂N formed via phase transition and metal reverse sintering under a high‐temperature NH₃ atmosphere is developed. This catalyst exhibits excellent RWGS activity, achieving a CO production rate of 294.8 mmolgcat−1 h−1 at 623 K, with CO selectivity maintained at 93%. Moreover, under continuous testing conditions for 100 h, the catalyst's activity shows no significant decline. Notably, further investigation reveals that the surface reaction mechanism at 623 K differs from the previously reported associative mechanism, instead following a redox mechanism in the presence of H₂. This research not only provides a deeper theoretical understanding of the mechanism of CO2 hydrogenation but also offers valuable insights for developing novel and efficient metal catalyst regeneration technologies.

Catalytic methanol cracking to hydrogen and formaldehyde over heterogeneous catalysts by radiolysis: Sectoral industrial symbiosis by waste radiation utilisation

In order to create a sustainable, carbon-neutral society, it is of utmost importance to link the energy sector with the chemical industry. Radiation from nuclear power plants proves to be useful for H2 production from water or carriers such as methanol. In our study, we investigated the potential for the production of hydrogen and formaldehyde by endothermic radiolytic cracking of 50 mol% aqueous methanol, which can be produced by direct CO2 hydrogenation without distillation. We developed an elegant experimental setup and performed irradiation tests in the TRIGA reactor with system analysis by GC-MS (gas chromatography with mass spectroscopy), SEM-EDS (scanning electron microscopy with energy dispersive spectroscopy), XRD (X-ray powder diffraction) and Monte Carlo simulations of radiation absorption. Among the different routes tested, a semiconductor-based photocatalytic material (TiO2) increased the H2 yield by 24%. In the critical evaluation of radiation utilisation, spent fuel radiation sources were found to be promising as they require low heat exchange and could produce 3600 kg H2/day in a single spent fuel pool. The advantage of radiolytic methanol cracking lies in its ability to produce formaldehyde and hydrogen (∼53% methanol value increase), whereas conventional partial oxidation of methanol with O2 for formaldehyde production (only ∼31% methanol value increase) inevitably produces water, which reduces the overall energy efficiency.

Direct cleavage of C=O double bond in CO2 by the subnano MoOx surface on Mo2N

Compared to H2-assisted activation mode, the direct dissociation of CO2 into carbonyl (*CO) with a simplified reaction route is advantageous for CO2-related synthetic processes and catalyst upgrading, while the stable C = O double bond makes it very challenging. Herein, we construct a subnano MoO3 layer on the surface of Mo2N, which provides a dynamically changing surface of MoO3↔MoOx (x < 3) for catalyzing CO2 hydrogenation. Rich oxygen vacancies on the subnano MoOx surface with a high electron donating capacity served as a scissor to directly shear the C = O double bond of CO2 to form CO at a high rate. The O atoms leached in CO2 dissociation are removed timely by H2 to regenerate active oxygen vacancies. Owing to the greatly enhanced dissociative activation of CO2, this MoOx/Mo2N catalyst without any supported active metals shows excellent performance for catalyzing CO2 hydrogenation to CO. The construction of highly disordered defective surface on heterostructures paves a new pathway for molecule activation.

A Comprehensive Review of CO2 Hydrogenation into Formate/Formic Acid Catalyzed by Whole Cell Bacteria.

The increasing levels of carbon dioxide (CO2) in the atmosphere, primarily due to the use of fossil fuels, pose a significant threat to the environment and necessitate urgent action to mitigate climate change. Carbon capture and utilization technologies that can convert CO2 into economically valuable compounds have gained attention as potential solutions. Among these technologies, biocatalytic CO2 hydrogenation using bacterial whole cells shows promise for the efficient conversion of CO2 into formate, a valuable chemical compound. Although it was discovered nearly a century ago, comprehensive reviews focusing on the utilization of whole-cell bacteria as the biocatalyst in this area remain relatively limited. Therefore, this review provides an analysis of the progress, strategies, and key findings in this field. It covers the use of living cells, resting cells, or genetically modified bacteria as biocatalysts to convert CO2 into formate, either naturally or with the integration of electrochemical and protochemical techniques as sources of protons and electrons. By consolidating the current knowledge in this field, this review article aims to serve as a valuable resource for researchers and practitioners interested in understanding the recent progress, challenges, and potential applications of bacterial whole cell catalyzed CO2 hydrogenation into formate.

Cation rearrangement at tetrahedral sites in the Cu/ZnAl2O4 spinel enhancing CO2 hydrogenation to methanol

Cu/ZnAl2O4 spinel is a promising catalyst for CO2-to-methanol due to its dual-site H2 activation. However, controlling surface properties and metal-support interactions (MSI) through the coordination environment of spinel cations remains underexplored. Herein, the occupancy of Zn2+ and Al3+ cations in Cu/ZnAl2O4 spinel is fine-tuned by manipulating the calcination atmosphere. More disordered structures (AlO4 and ZnO6) observed on the CZA-Ar catalyst benefit the creation of oxygen vacancies and surface hydroxyl groups, which facilitate the formation of highly dispersed small-sized Cu species. This enhances MSI and hydrogen spillover effects, thereby boosting CO2 conversion and the space-time yield (STY) of methanol. High-pressure in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results reveal that the crucial formate intermediates form at tetrahedral sites in ZnAl2O4 spinel, with more Al-HCOO- species observed on the CZA-Ar catalyst due to the formation of AlO4. This work advances the understanding of spinel catalysts in CO2 hydrogenation to methanol.

Theoretical predictions of CO2, H2 and H2O adsorption mechanisms on M2C-MXene: Selectivity and potential application insights

M2C-MXenes, owing to their abundant adsorption sites, exhibit significant potential in CO2 capture, utilization, and storage (CCUS) and hydrogen energy applications, contributing to hydrogen utilization and global carbon reduction, and thus solving intractable energy and environmental problems. However, the extensive variety of M2C compounds poses challenges to the systematic evaluation of their applications in these fields. The exploration of the adsorption properties of M2Cs is a key fundamental aspect of these studies, and therefore, this study employs calculations across 456 adsorption systems to elucidate the adsorption mechanisms of 19 M2C compounds for small molecules (CO2, H2 and H2O). The results indicate that these M2C materials possess structural stability and metallic characteristics, with periodic variations in the d-band center aligning with trends in CO2 adsorption energy. Notably, molecular orientation impacts adsorption energy more significantly than adsorption sites, particularly for CO2, while M2C compounds primarily exhibit physical adsorption towards H2. Specifically, Sc2C preferentially adsorbs CO2 in atmospheric conditions, and shows chemical adsorption towards H2O, but exhibits negligible adsorption for H2; conversely, Cr2C demonstrates higher adsorption potential for H2. Both materials exhibit favorable thermodynamic stability, suggesting Sc2C is suitable for CCUS applications, while Cr2C holds promising prospects for hydrogen storage.

Constructing efficient Pd/Al2O3 catalyst for reverse water-gas shift via alkali-modification

The intrinsic nature of irreducible oxides (e.g. Al2O3) makes it hard to tune the charge state of supported late-transition metals, then difficult to adjust the selectivity of catalysts in CO2 hydrogenation. Herein, we find that modifying the Pd/Al2O3 catalyst with alkali metals (especially potassium) is efficient to boost the CO formation in CO2 hydrogenation. In comparison to Pd/Al2O3, approximately twenty-fold promotion in reverse water–gas shift (RWGS) rate was achieved on K-modified catalysts with proper K/Pd proportions. Combined structural characterizations demonstrate that the enhanced Pd-O interactions through K mediation stabilize the ca. 2 nm sized Pd particles as well as the electron-deficient state of Pd, which are robust enough during long-termed evaluation with undamped performance. In situ spectroscopy unveils a bi-dentate *HCOO associated reaction mechanism taking effect on alkali-modified catalysts, which contributes to ∼ 100 % of CO selectivity and 3318.1 mmol∙gPd-1∙h−1 of CO formation rate at 340°C.

Abundant interfacial and intrinsic oxygen vacancies enabling small nickel/ceria nanocrystal efficient CO2 methanation

Smaller nano-sizes typically result in supported catalysts with abundant interfacial and intrinsic oxygen vacancies for better adsorption and activation of small molecules, including CO2, leading to improved efficiency of CO2 methanation. Here, Ni/CeO2-S with the smaller nano-size of around 4.2 nm is used to catalyze CO2 methanation, which exhibits significantly enhanced activity compared to larger nano-sized Ni/CeO2-L catalyst, even surpassing the most majority of previously reported catalysts using CeO2 as the support or Ni as the active metal. The coexistence of interfacial defects and intrinsic oxygen vacancies allows for enhanced adsorption and activation of CO2 molecules as well as H spillover, resulting in such improved CO2 methanation. In-situ DRIFTS demonstrate a nearly sole Formate pathway on Ni/CeO2-S for efficient CO2 hydrogenation. This research provides valuable insights into the reaction mechanism over a small nanosize supported catalyst.