Integrated CO2 Capture Research Articles

In-Situ CO2 Release from Captured Solution and Subsequent Electrolysis: Advancements in Integrated CO2 Capture and Conversion Systems

The electrochemical reduction of carbon dioxide (CO2ER) offers a compelling strategy for sustainable energy and carbon management by transforming CO2 into valuable chemicals and fuels. This approach is particularly attractive when powered by surplus renewable energy, aiding in the closure of the carbon cycle. However, the significant energy requirements for CO2 isolation, pressurization, and purification from capture media pose challenges for industrial-scale implementation. To overcome these obstacles, recently innovative electrolyzers have developed that directly convert reactive carbon solutions, such as bicarbonate-rich effluents from carbon capture units, into higher-value products. This electrolyzers produces CO2 in situ by reacting (bi)carbonate with acid generated within the electrolyzer, facilitating efficient CO2ER at the cathode surface and eliminating the need for costly CO2 recovery and compression steps. This study details recent efforts in advancing this type of electrolyzer, focusing on CO2 sources for capturing step, technical aspect consideration of integrated systems, electrolyzer design consideration and membrane designs for integrated systems. Herein, we emphasize the need for a permeable cathode that allows efficient (bi)carbonate ion transport while maintaining a high catalytic surface area. Additionally, we discuss the critical role of electrolytes, including the impact of (bi)carbonate concentration, their effect on CO2 utilizations and CO2ER selectivity. We also demonstrate the state-of-the-art performance metrics for electrolyzers that utilize CO2-captured solutions, such as Faradaic efficiency, experimental validation of CO2 sources, current density, and CO2 utilization efficiency, a guideline for future studies. Collectively, we believe that this analysis will contribute to the development of industrial-scale electrochemical reactors for CO2 conversion, advancing towards a sustainable and closed-loop carbon cycle.

Very low Ru loadings boosting performance of Ni-based dual-function materials during the integrated CO2 capture and methanation process

Herein, the effect of the Ru:Ni bimetallic composition in dual-function materials (DFMs) for the integrated CO2 capture and methanation process (ICCU-Methanation) is systematically evaluated and combined with a thorough material characterization, as well as a mechanistic (in-situ diffuse reflectance infrared fourier-transform spectroscopy (in-situ DRIFTS)) and computational (computational fluid dynamics (CFD) modelling) investigation, in order to improve the performance of Ni-based DFMs. The bimetallic DFMs are comprised of a main Ni active metallic phase (20 wt%) and are modified with low Ru loadings in the 0.1–1 wt% range (to keep the material cost low), supported on Na2O/Al2O3. It is shown that the addition of even a very low Ru loading (0.1–0.2 wt%) can drastically improve the material reducibility, exposing a significantly higher amount of surface-active metallic sites, with Ru being highly dispersed over the support and the Ni phase, while also forming some small Ru particles. This manifests in a significant enhancement in the CH4 yield and the CH4 production kinetics during ICCU–Methanation (which mainly proceeds via formate intermediates), with 0.2 wt% Ru addition leading to the best results. This bimetallic DFM also shows high stability and a relatively good performance under an oxidizing CO2 capture atmosphere. The formation rate of CH4 during hydrogenation is then further validated via CFD modelling and the developed model is subsequently applied in the prediction of the effect of other parameters, including the H2 inlet concentration, inlet flow rate, dual-function material weight, and reactor internal diameter.

Recent advancements in integrating CO2 capture from flue gas and ambient air with thermal catalytic conversion for efficient CO2 utilization

Recent advancements in integrating CO2 capture from flue gas and ambient air with thermal catalytic conversion for efficient CO2 utilization

Integrated CO2 capture and conversion to form syngas

Integrated CO2 capture and conversion to form syngas

Environmental tradeoff on integrated carbon capture and in-situ methanation technology

Compared to conventional CO2 removal methods, carbon capture and in-situ conversion using dual function materials avoid compression and transportation of CO2, which is regarded as a promising technology. Although it brings additional economic benefits, the environmental impacts of CO2 capture and conversion remain unclear. A life cycle assessment of an integrated CO2 capture and methanation system using dual function materials is conducted to investigate its feasibility to reduce global warming. Life cycle inventory is obtained through construction, operation, and disposal process of the integrated system. A dynamic model of CO2 capture and methanation is developed to obtain the operating parameters. Results show that the optimal global warming potential is 0.706 kg CO2,eq per kilogram captured CO2, which indicates the advantages of using dual function materials for carbon mitigation. Global warming potential is a minor factor among the overall normalized environmental impacts, only accounting for 0.5 % of the total normalized impact, while the main factor marine aquatic ecotoxicity accounts for around 73 %, and fresh water aquatic ecotoxicity accounts for around 23 %. Global warming potential is the most affected by green hydrogen input, followed by dual function material input. Results reveal that the integrated CO2 capture and conversion using dual function materials is conducive to carbon mitigation but has significant other environmental impacts, such as marine aquatic ecotoxicity, and the main contributors to the environmental impacts are wind electricity, green hydrogen, refrigerator, and dual function material.

Investigating proton shuttling and electrochemical mechanisms of amines in integrated CO2 capture and utilization

Carbon capture and utilization (CCU) technologies present a promising solution for converting CO2 emissions into valuable products. Here we show how amines, such as monoethanolamine (MEA) and 2-amino-2-methyl-1-propanol (AMP), influence the electrochemical CO2 reduction process in an integrated CCU system. Using in situ spectroscopic techniques, we identify the key roles of carbamate bond strength, proton shuttling, and amine structure in dictating reaction pathways on copper (Cu) and lead (Pb) electrodes. Our findings demonstrate that on Cu electrodes, surface blockage by ammonium species impedes CO₂ reduction, whereas on Pb electrodes, proton shuttling enhances the production of hydrocarbon products. This study provides additional insights into optimizing CCU systems by tailoring the choice of amines and electrode materials, advancing the selective conversion of CO₂ into valuable chemicals.

Microwave-powered integrated carbon capture and utilisation (ICCU) for methane production with rapid temperature response from minimal thermal inertia

Integrated CO2 capture and utilisation (ICCU), emerging as an effective approach for achieving global carbon neutrality goals, demonstrates its potential through the transformation of captured CO2 into valuable methane and the concurrent hydrogen storage via methanation reaction. However, traditional ICCU strategies are heavily reliant on conventional thermal conduction heating, and the in-situ methanation process is constrained by reaction thermodynamics, posing significant challenges. In this study, we introduce for the first time a novel microwave-powered system, employing a clean and efficient energy source that offers rapid heating and on-demand operation and acts as an external field enhancement method in the ICCU-methanation procedure. The designed blend of Ni-loaded CaO and carbon nanotubes (CNTs) integrates the functions of CO2 adsorption, hydrogenation catalysis, and microwave absorbing ability. This novel approach achieved a CO2 capture capacity of 3.31 mmol gDFM-1 with CO2 conversion and CH4 selectivity reaching 71.01 % and 98.17 %, respectively, at a nickel loading of 20 wt%. We also propose a possible rate enhancement mechanism for the microwave-powered ICCU-methanation cyclic process compared to conventional methods. The microwave-powered system can substantially enhance overall efficiency by swiftly responding to temperature swings, thus reducing processing time in ICCU-methanation cycles.

Promoting proximity to enhance Fe-Ca interaction for efficient integrated CO2 capture and hydrogenation

Integrated CO2 capture and utilization (ICCU) using “capture-conversion” dual functional materials (DFMs) paves a cost-effective path for restricting CO2 emissions by eliminating the energy-intensive intermediate processes. The interactions between catalysts and absorbents are believed pivotal in ICCU; however, there is a lack of environment-friendly strategy to fabricate the interaction for industrial applications. Here, we propose a solvent-free mechanochemical approach to promote the interaction by improving the proximity between natural calcium and iron sources. The interaction was systemically investigated and confirmed using XRD, XPS, TEM, TPR, etc. As a result, the mechanochemical approach derived DFM achieved 5.5 mmol/g CO2 capacity, 87 % CO2 conversion, and 100 % CO selectivity at 650 °C, significantly outperforming the CaO-alone benchmark (CO2 capacity < 4.5mmol/g, CO2 conversion < 73 %). Further incorporating MgO would alleviate the sintering and promote the CO2 capture stability (< 15 % decrease after 20 cycles) by acting as a thermal-stable barrier. Based on in situ XRD, it is further confirmed that Fe-Ca interaction exhibits a dynamic looping mechanism in ICCU. The techno-economic analysis strongly supports the superiority of ICCU catalyzed by naturally sourced DFMs on eliminating the energy and H2 consumption for CO2 capture and upgradation. As a result, producing CO via ICCU using mechanochemical derived DFMs exhibits 20 % and 10 % cost decrease compared to the conventional CCU and ICCU using CaO alone scenarios, pointing out the potential of ICCU technology in industrial applications.

Impact of CO2 as an oxidant on the decarburization and chromium retention and an approach for CO2 recycling

This study explores the unique role of CO2 as an oxidant in stainless steel smelting, focusing on its effectiveness in decarbonization and chromium retention. The research begins by theoretically demonstrating that although the introduction of CO2 increases the CO partial pressure in the reaction system, the decarburization and chromium (Cr) retention capabilities of CO2 can still be stably maintained through the rational adjustment of the molten steel composition, temperature, and inert gas proportions. Further experimental findings indicate that chromium does not exhibit significant oxidation losses when the carbon (C) content exceeds 1.0% (mass). Finally, a novel CO2 recovery and utilization approach is proposed, integrating CO2 capture from smelting flue gas and recycling it for smelting, reducing O2 consumption and energy costs. This innovative process, compatible with existing smelting plants, presents a promising pathway towards carbon neutrality in the iron and steel industry, bridging theoretical insights with practical applications.

Efficient sorbent/catalyst composites for CO2-mediated oxidative dehydrogenation of ethane via isothermal integrated CO2 capture and utilization

The isothermal integrated CO2 capture and utilization to produce ethylene (ICCU-ODHE) performances of dual functional materials (DFM) were improved by doping five transition metal elements (Fe, Co, Ni, Cu, Zn). The results show that the DFM doped with Zn exhibits excellent ICCU-ODHE performance with an ethylene yield of 35.1 %. The results based on in-situ XPS and DFT calculation show that the doping transition metal elements can reduce the energy barriers for activating ethane and CO2. It is mainly because doping transition metal elements with strong electronegativity can increase the coordinative unsaturated Cr3+ ions to adsorb more ethane molecules, meanwhile, the doping also reduces the charge density of Cr3+ and generates additional unfilled electron orbitals facilitating charge transfer to improve the CO2 and ethane activation. However, the decrease in charge density can increase the difficulty of ethylene desorption and reduce the ethylene selectivity. In addition, the cyclic regeneration experiment shows that the ICCU-ODHE performance of DFM can decrease with the increase of cycles, however, significant performance restoration is achievable after regeneration in the air at 650 °C, attributed to the limited graphitization of coke deposition on the DFM.

Taking dual function materials (DFM) from the laboratory to industrial applications: A review of DFM operation under realistic integrated CO2 capture and utilization conditions

Taking dual function materials (DFM) from the laboratory to industrial applications: A review of DFM operation under realistic integrated CO2 capture and utilization conditions

Engineering nanoparticle structure at synergistic Ru-Na interface for integrated CO2 capture and hydrogenation

The development of dual functional material for cyclic CO2 capture and hydrogenation is of great significance for converting diluted CO2 into valuable fuels, but suffers from kinetic limitation and deactivation of adsorbent and catalyst. Herein, we engineered a series of RuNa/γ-Al2O3 materials, varying the size of ruthenium from single atoms to clusters/nanoparticles. The coordination environment and structure sensitivity of ruthenium were quantitatively investigated at atomic scale. Our findings reveal that the reduced Ru nanoparticles, approximately 7.1 nm in diameter with a Ru-Ru coordination number of 5.9, exhibit high methane formation activity and selectivity at 340 °C. The Ru-Na interfacial sites facilitate CO2 migration through a deoxygenation pathway, involving carbonate dissociation, carbonyl formation, and hydrogenation. In-situ experiments and theoretical calculations show that stable carbonyl intermediates on metallic Ru nanoparticles facilitate heterolytic C–O scission and C–H bonding, significantly lowering the energy barrier for activating stored CO2.

Oxygen vacancy modulation for enhanced hydrogen production via chemical looping water-gas shift

Chemical looping water gas shift (CL-WGS)is prospective to generate high-purity hydrogen with integrated CO2 capture. However, this technology is impeded by the lack of active oxygen carriers at mid-temperatures. Here, we synthesized several Ni-doped CoFe2O4-δ to modulate oxygen vacancies and investigate its effect on promoting hydrogen production reaction via chemical looping water gas shift at 650 °C. The findings delineate that doping Ni considerably lowers the energy barriers associated with the oxygen vacancies formation, thereby augmenting their concentration. The underlying mechanism elucidates that within the CL-WGS process, the transfer of lattice oxygen acts as the rate-limiting step. NixCo1-xFe2O4 lowers the formation energy of oxygen vacancies and facilitates the bulk lattice oxygen diffusion through the bulk. Hence, Ni0.5Co0.5Fe2O4 demonstrates the most reduction depth and reversibility via redox reactions, resulting in an elevated hydrogen yield (∼15.5 mmol g−1) at 650 °C, which surpasses the yield from undoped CoFe2O4 by 1.4 times. This performance remains consistently high with only a minimal decline over 100 cycles. The findings introduce a promising approach to promote the reactivity of oxygen carriers, particularly for mid-temperature applications.

Integrated CO2 capture and dynamic catalysis for CO2 recycling in a microbrewery

In this study, we used fermentation off-gases from a brewery for integrated CO2 capture and utilisation in order to produce CH4 with a dual-function material (DFM) containing NiRu as catalyst and dispersed CaO as adsorbent. CH4 was produced from captured CO2 via 2 pathways (fast and slow), proceeding through formyl intermediates according to the operando DRIFTS-MS results. The NiRuCa DFM showed a stable CH4 capacity over 8 cycles (105 μmol/gDFM) with fermentation off-gases being used as a CO2 capture feed. H2O and O2, which were present in small amounts in the emissions feed, resulted in the passivation of Ni in the form of a NiO layer and hence, the DFM did not undergo excessive oxidation and deactivation. This work constitutes a first in terms of validating the use of DFMs with real industrial emissions, and it directly correlates the DFM activity performance with its reaction mechanism and intermediate species.

Study on the arrangement of CO2 sorbent and catalyst for integrated CO2 capture and methanation

Integrated CO2 capture and utilization (ICCU) is an emerging technology to reduce CO2 emissions by greatly simplifying the processes of conventional CO2 capture and utilization. In particular, ICCU-methanation could directly convert the low-concentration CO2 into CH4 using hydrogen from new energy electricity, representing an efficient Power-to-Gas route. CO2 adsorption/catalytic materials play a crucial role for the operation of ICCU-methanation, and it is more feasible to scale up material production and avoid components interference by directly combining the sorbent and catalyst. However, it is necessary to reveal the effect of different arrangements of sorbent and catalyst on reaction characteristics of ICCU-methanation. In the work, the matching of K2CO3-doped Li4SiO4 sorbent with various supported Ni-based catalyst was tested and four arrangements of sorbent and catalyst particles in a fixed-bed were investigated to understand the influences on ICCU-methanation. Results show that the presence of catalyst accelerates CO2 supply by sorbent and achieves quicker methanation, and the promotion effect becomes more obvious with a closer contact between the sorbent and catalyst. Under optimized conditions, ICCU-methanation of uniformly mixed K-Li4SiO4 and Ni/Al2O3 shows an excellent performance with very stable CO2 conversion of 95.58% and CH4 selectivity of 93.29% during cyclic reactions.

Cu promoted Ni-Ca dual functional materials for integrated CO2 capture and utilization in O2-containing flue gas: Eliminating the delay in the utilization stage

Integrating CO2 capture and utilization by dry reforming methane (ICCU-DRM) technology is promising in concentrating and utilizing diluted CO2 from flue gas, which depends on developing Dual Functional Materials (DFMs) with adsorption and catalytic sites. Ni-Ca materials are widely applied in ICCU-DRM due to their excellent catalytic and CO2 adsorption properties. Nevertheless, the challenge remains that oxygen in the actual flue gas would oxidize the active Ni, leading to a delay in the DRM stage. In this work, Cu-promoted, ZrO2-stabilized Ni-Ca based DFMs were developed, which suppressed the delay and enhanced the performance of the DRM reaction. Attribute to the excellent reducing properties, Cu could be rapidly reduced in the CH4 atmosphere and further promote the reduction of NiO to the catalytically active Ni monomers by activating methane to generate reactive hydrogen (H*). What’s more, attributed to the disappearance of delay times, it is accompanied by a satisfying yield distribution with a 0.11 decrease in H2/CO ratio and an improvement in conversion, especially CH4 conversion with an increase of more than 10%. In addition, the bifunctional material also exhibits favorable cycling stability due to the stabilizers.

Developing an integrated CO2 capture and mineralization process with lower energy consumption

Developing an integrated CO2 capture and mineralization process with lower energy consumption

Calcium looping-enhanced biomass gasification for methanol production: Integrating methane dry reforming and carbon utilization

Developing integrated CO2 capture and utilization (ICCU) is an attractive strategy that aims to reduce CO2 emissions while realizing the potential benefits of CO2. This paper investigates the techno-environmental-economic performance of biomass gasification to methanol (BtM) based on calcium looping (CaL) coupled with dry reforming of methane (DRM) and CaL coupled with reverse Boudouard reaction (RB). The results indicate that BtM systems based on CaL-DRM (BtM:CaL-DRM) and CaL-RB (BtM:CaL-RB) achieve CO2 capture and utilization, and enable efficient methanol synthesis. Compared to BtM:CaL-DRM, BtM:CaL-RB demonstrates higher exergy efficiency and lower global warming potential (GWP). The exergy efficiency of BtM:CaL-RB reaches 71.60 %. In terms of economic viability, BtM:CaL-DRM demonstrates more promising economic feasibility. The BtM systems reaches breakeven when the methanol selling price ranges from 440.8 $/ton to 529 $/ton. This study provides valuable insights into exploring novel ICCU systems.

Structure–activity relationship of a dual-function amine-based electrolyte for integrated CO2 capture and electrochemical conversion

Integrated carbon dioxide (CO2) capture and electrocatalytic reduction processes through dual-function amine-based electrolytes and their integration into a single reactor can lead to significant energy savings, simplified process flow, and reduced transportation risks. This work investigates the structure–activity relationship of dual-functional amine-based electrolytes for CO2 capture and electrocatalytic reduction and develops an efficient dual-functional amine-based electrolyte system. We investigated 10 different amine-based solutions for their CO2 capture and reduction performances. The substituents on the nitrogen atom of the intermediate carbamate and the positions of the hydroxyl and branched groups affect the capture and electrochemical reduction. The 1,3-propanediamine system demonstrated enhanced CO2 solubility uptake (58.1 %), Faradaic efficiency (10.6 %), and current density (52.1 %) compared with the monoethanolamine system, indicating its potential as a dual-function amine-based electrolyte. Furthermore, density functional theory calculations indicated that the charge distribution of carbamate and the dissociation of C–N bonds directly influence the adsorption of carbamates on the electrode surface and the Faradaic efficiency of the reduced products. In addition, reaction path analysis based on the zwitterionic mechanism indicated that intermediates (carbamate R1R2NCOO-) with higher electronegativity are more conducive to adsorb onto the electrode surface and inhibit hydrogen generation from protonated amines (R1R2NHH+). The results suggest that the selection or design of dual-functional amine-based electrolytes should prioritize amines with straight alkanol chains rather than branched ones, which do not form intramolecular hydrogen bonds or heterocyclic structures. This work provides directions and guidance for designing and developing dual-functional electrolytes for integrated carbon capture and electrocatalytic conversion technologies.

Morphology effects of CeO2 on the performance of CaO-Cu/ CeO2 for integrated CO2 capture and conversion to CO

CeO2 support inhibits CaO sintering, and oxygen vacancy influences CO2 hydrogenation performance, making CeO2 widely applied in Integrated CO2 capture and in-situ conversion technology for reverse water–gas shift (ICCC-RWGS). Oxygen vacancy concentration was dependent on the morphology of CeO2, which would affect metal dispersion and CO2 hydrogenation conversion. However, Very little is known about the morphology effect of CeO2 on the carbon capture and in-situ hydrogenation performance of DFMs. Here, Cu/CeO2 with different CeO2 morphologies was synthesized, and high Cu dispersion was achieved on Cu/CeO2-R, exhibiting the best CO2 hydrogenation performance. Integrated Cu/CeO2 with CaO by physical mixing method, CaO-Cu/CeO2 was used to investigate the morphology effects of CeO2 on the performance of CaO-Cu/CeO2 for integrated CO2 capture and conversion to CO. CaO-Cu/CeO2-R exhibited the best capture-hydrogenation performance (CO2 conversion rate of 75 %, CO production rate of 9.72 mmol/g). The CeO2-R provided more surface oxygen vacancies, enhancing carbonate hydrogenation. The larger specific surface area and {110} crystal plane of CeO2-rod enhanced Cu dispersion, and the smaller particle size of CeO2-R enhanced its interaction with CaO, improving the cyclic stability of CaO-Cu/CeO2-R. The hydrogenation performance of CaO-Cu/CeO2 was dependent on the morphology of CeO2, providing insights into the design of high-activity metal catalytic components in ICCC-RWGS.