Dual-functional Materials Research Articles

Study on K-modified Ca-based dual-functional materials for carbon capture and in-situ methane dry reforming

Integrated carbon capture and in-situ methane dry reforming (ICCU-DRM) is a promising technology for chemical looping transformation, this process involves the sequential switching of feedstocks within a single reactor, allowing CO2 capture to occur before methane dry reforming without direct CO2-CH4 contact. However, a significant challenge in the ICCU-DRM process is the disparity between the optimal temperatures required for carbon capture and dry reforming, with the latter necessitating considerably higher temperatures. This could lead to substantial CO2 losses when the reaction temperature is elevated to the optimal level for dry reforming. To address this issue and improve CO2 conversion efficiency, this study explores K doping in synthesizing a dual-functional material, NiCa1.6K0.4@Al2O3, through extrusion-spheronization. The synthesized material exhibits a stable pore structure and a large internal surface area, crucial for enhancing CO2 capture. The optimum temperature for DRM is around 800 °C. Notably, the formation of 1K2Ca(CO3)2 during the calcination of NiCa1.6K0.4@Al2O3, with a thermal decomposition temperature of approximately 800°C, plays a crucial role in minimizing CO2 release during the heating process, thereby significantly improving the CO2 conversion. To evaluate the impact of K doping on the material, the samples were subjected to carbon capture at 650 °C and dry reforming of methane at 750 °C. The results showed that the CO2 conversion rate of NiCa1.6K0.4@Al2O3 reached 52.8%, compared to only 18.9% for NiCa2@Al2O3 under the same conditions. Moreover, this study also investigates the impact of carbon capture temperature, dry reforming temperature, and catalytic metal loading on the performance of the ICCU-DRM process.

Carbon dots-doped melamine–formaldehyde microsphere as a dual functional material for sensing and adsorption of oxytetracycline

The abuse of oxytetracycline (OTC) leaves serious environmental residues and triggers accumulation in organisms, constituting a threat to human health. Constructing an effective platform based on dual-functional materials for monitoring and removing OTC residues is a preferable solution. Herein, we proposed a novel composite material by doping carbon dots (CDs) into melamine–formaldehyde microsphere (MFM) through a one-pot method and named CDs@MFM, which inherited the fluorescence property of CDs and porous structure of MFM simultaneously. CDs@MFM demonstrated dual functions for the detection and removal of OTC concurrently within a few minutes, with its performance compared in detail with bare CDs and MFM as controls. By virtue of the pre-enrichment effect attributed to its porous structure, CDs@MFM exhibited a lower detection limit for OTC than bare CDs (0.027 mg/L vs 0.067 mg/L) and a higher adsorption capacity than MFM (73.01 mg/g vs 68.76 mg/g) resulting from more affiliated functional groups available for OTC provided by the CDs. Overall, CDs@MFM has proven to be an efficient and convenient candidate capable of monitoring and removing OTC synchronously, and this work offers an avenue for the design of dual-functional materials in the field of environmental science.

Dual-capable spinel cobalt oxide nanoparticles for electrocatalytic oxygen evolution and water contaminant removal.

This study investigates the synthesis and electrocatalytic performance of cobalt oxide (Co3O4) nanoparticles for the oxygen evolution reaction (OER) and their role in water treatment as contaminant removal agents. Cobalt oxide nanoparticles are recognized as promising materials in electrocatalysis due to their tunable properties and nanoscale engineering potential. Here, fine cobalt oxide nanoparticles are synthesized using the sol-gel method followed by various sintering temperatures to achieve precise control over surface morphology, size, and shape. Characterization via high-resolution scanning electron microscopy (HRSEM) and high-resolution transmission electron microscopy (HRTEM) elucidates the impact of sintering temperature on nanoparticle properties. Thin film electrodes of cobalt oxide are fabricated using the doctor blade method and evaluated using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Among the tested sintering temperatures, cobalt oxide electrodes sintered at 600°C exhibit superior catalytic activity, demonstrating an overpotential of 258mV (vs RHE) at 10mAcm-2 current density and a Tafel slope of 17.33mV dec-1. Furthermore, these electrodes demonstrate excellent stability, maintaining OER performance for 10h in 1M NaOH electrolyte. Additionally, the role of cobalt oxide nanoparticles in water treatment is explored using inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental results reveal that lower sintering temperatures enhance the electrocatalytic properties of cobalt oxide nanoparticles, highlighting their potential contribution to sustainable energy and water treatment technologies. This work underscores the significance of cobalt oxide nanoparticles as dual-functional materials for advancing electrocatalysis and water purification applications, thus paving the way for the development of efficient and environmentally friendly technologies.

Cu@Zn@800 bimetallic-based carbon nanomaterials for dark-catalyzed degradation and 4-NP-catalyzed reduction of azo dyes

Metal-organic frameworks (MOFs) were adaptable templates that might be used to create multifunctional materials containing carbon nanostructures. In this work, we had prepared a novel Cu-MOF using fumaric acid (H2FA) and N,N′-bis(pyridin-3-yl)isophthalamide (3-bpia) as the mixed ligands. Then, the Cu-MOF was served as a template to derive bimetallic-based carbon nanomaterials by introducing a second metal through doped ZnO by both re-calcined and directly calcined methods (Cu@Zn@800) and single-metal-based carbon nanomaterials (Cu@800). Cu@Zn@800 was able to catalyze the degradation of azo dyes at a rate higher than 99.40 % because of its capacity to create h+ and ·OH active substances and the uniformity of its metal active sites. Additionally, Cu@Zn@800 might use NaBH4 to decrease 4-NP in 30 s with the rate of decline was over 100 %. Cu@Zn@800 was a special and efficient dual-functional material that might be used in a variety of ways to remove contaminants from water.

Effect of Li-Na sorbent phase in Ru/Al2O3 dual function materials for the Integrated CO2 capture and methanation

The design of highly performing dual functional materials (DFMs) is the key to the successful deployment of Integrated Carbon Capture and Methanation (ICCM) process that combines both steps into a single unit operation with high energy efficiency. Intending to enhance the CO2 working capacity while preserving high catalytic methanation activity, herein we set out to investigate the effect of combining Li and Na as the CO2 sorbent phase in Ru/Al2O3 DFMs. ICCM tests in a fixed bed reactor operated with alternate feeds indicated that combining Na with Li (or partially substituting it for Li) effectively increases the CO2 capture capacity and methane production of the DFM. However, this generally requires higher temperatures to properly activate the catalytic methanation and to regenerate the DFM compared to a pure Li-based formulation. Transient operando DRIFTS and catalytic kinetic experiments provided mechanistic insights into the activation/inhibition of different reaction paths on those DFMs containing only Li and/or Na.

Utilizing Limestone Alone for Integrated CO2 Capture and Reverse Water-Gas Reaction in a Fixed Bed Reactor: Employing Mass and Gas Signal Analysis

The integrated CO2 capture and utilization coupled with the reverse water-gas shift reaction (ICCU-RWGS) presents an alternative pathway for converting captured CO2 into CO in situ. This study investigates the effectiveness of three calcium-based materials (natural limestone, sol-gel CaCO3, and commercial CaCO3) as dual-functional materials (DFMs) for the ICCU-RWGS process at intermediate temperatures (650–750 °C). Our approach involves a fixed-bed reactor coupled with mass spectrometry and in situ Fourier transform infrared (FTIR) measurements to examine cyclic CO2 capture behavior, detailed physical and chemical properties, and morphology. The in situ FTIR results revealed the dominance of the RWGS route and exhibited self-catalytic activity across all calcium-based materials. Particularly, the natural limestone demonstrated a CO yield of 12.7 mmol g−1 with 100% CO selectivity and 81% CO2 conversion. Over the 20th cycle, a decrease in CO2 capture capacity was observed: sol-gel CaCO3, natural limestone, and commercial CaCO3 showed reductions of 44%, 61%, and 59%, respectively. This suggests inevitable deactivation during cyclic reactions in the ICCU-RWGS process, while the skeleton structure effectively prevents agglomeration in Ca-based materials, particularly in sol-gel CaCO3. These insights, coupled with the cost-effectiveness of CaO-alone DFMs, offer promising avenues for efficient and economically viable ICCU-RWGS processes.

Integrated CO2 Capture and Dry Reforming of CH4 to Syngas: A Review.

Integrating carbon capture with dry reforming of methane offers a promising approach to addressing greenhouse gas emissions while producing valuable syngas. This review examines the complexities and progress made in this integrated process, wherein catalysts play a critical role in adsorbing carbon dioxide and facilitating the conversion of methane to syngas. The chemical process entails the concurrent capture of CO2 emissions and their usage in dry reforming, a reaction in which CH4 interacts with CO2 to generate syngas, an essential precursor for various industrial applications. The dual-functional materials can adsorb carbon dioxide and actively reform to an end-use application. The much-studied Ca-based sorbents exhibit a theoretical carbon capture capacity of 17.8 mmol g-1. However, during practical exploration of these materials as a dual-functional catalyst for integrated carbon capture and the dry reforming of methane, the uptake reduces to ∼13 mmol g-1 carbon capacity with 96.5 and 96% conversions of CO2 and CH4, respectively. Therefore, a thorough analysis of the complex relationship between CO2 capture and CH4 reforming catalysis is attempted herein based on various reported materials. Design concepts, structural optimization, and performance evaluation analysis of the dual-functional materials reveal their importance in carbon capture and reformation technology. Additionally, this review covers the field difficulties, future perspectives, and attractive commercial implementation predictions. This scrutiny illustrates the significance of dual-functional materials for sustainable energy production and environmental protection.

In Situ Capture and Conversion of CO2 to CO Using CaZrO3 Promoted Fe–CaO Dual-Functional Material

In Situ Capture and Conversion of CO₂ to CO Using CaZrO₃ Promoted Fe–CaO Dual-Functional Material

Continuous CO2 capture and reduction to CO by circulating transition-metal-free dual-function material in fluidized-bed reactors

To mitigate global warming and achieve a sustainable society, innovative technologies for efficient CO2 utilization are required. Integrated CO2 capture and reduction (CCR) using dual-function materials (DFMs) is favorable owing to its potentially low energy consumption, capital investment, and processing costs. Although numerous studies have focused on catalytic science, continuous and steady-state CCR operations have not been sufficiently addressed from an engineering perspective. In this study, a circulating fluidized bed (CFB) system is investigated for continuous CCR to syngas (CO + H2). In the CFB system, transition-metal-free DFM (Na/Al2O3) particles are circulated between two bubbling fluidized-bed reactors. The DFM captures CO2 in one reactor (CO2 capture reactor) and reduces the captured CO2 to CO by the reaction with H2 in the other reactor (H2 reactor). The effluent gas concentrations from both reactors reach steady state and are maintained for over 8 h. For the product gas from the H2 reactor, the CO2 conversion and CO selectivity exceed 80 % and 99 %, respectively. However, the H2 conversion is <20 %, indicating a potential challenge for the CFB system for integrated CCR. Furthermore, this study confirms that the H2/CO ratio for syngas can be controlled by adjusting the experimental conditions (particularly, the H2 flow rate). Consequently, the CFB system can be modified to facilitate the interaction between H2 gas and the DFM particles.

Social Self-Sorting of Quasi-Racemates: A Unique Approach for Dual-Pore Molecular Crystals.

Despite recent advances in porous organic molecular crystals, the engineering of dual-pore systems within the intermolecular voids remains a significant challenge. In this study, we have achieved the crystallization-induced social self-sorting of "quasi-racemic" dialdehydes into a macrocyclic imine. X-ray crystallographic analysis unambiguously characterizes the resulting structure as incorporating two quasi-racemate pairs with four diamine molecules. Notably, different alkyl substituents on the quasi-racemates afford two types of one-dimensional pores within the macrocyclic imine crystal. The different adsorption properties of these pores were substantiated through adsorption experiments. An intriguing helical arrangement of guest molecules was observed within one of the pores. This study provides pioneering evidence that the social self-sorting of quasi-racemates offers a new methodology for creating dual-functional supramolecular materials.

Copper complex@Paclitaxel: A new dual-functional fluorescent-responsive composite material and treatment on esophageal cancer cells

Esophageal cancer (EC) is a common and fatal malignant tumor of the digestive tract, characterized by high morbidity and mortality. Despite advances in surgery, radiotherapy, and anti-cancer drugs, the five-year survival rate remains low. Therefore, exploring effective therapeutic agents to inhibit the proliferation and invasion of EC is crucial. In this study, a novel coordination polymer CP1 was synthesized by reacting the bifunctional ligand 2,5-bis(1H-1,2,4-triazol-1-yl)terephthalic acid (H2dttpa) containing carboxylic acid and triazolyl groups with Cu(NO3)2·3H2O in a mixed solvent of water and N,N-dimethylformamide. Structural analysis revealed that CP1 adopts a two-dimensional layered network with a trinodal (3,4,4)-connected topology. Furthermore, CP1 exhibits excellent fluorescent properties due to charge transfer from the ligand to the metal, making it suitable for selective and sensitive fluorescence sensing of Fe3+ with a quenching efficiency of up to 90.5 %. This indicates the potential application of CP1 as a fluorescent sensor for Fe3+ detection. Moreover, paclitaxel was selected as a model drug to form a prodrug (CP1@Paclitaxel) with hydrogen bonding enhancing the interaction between the prodrug and CP1. The photothermal properties of CP1@Paclitaxel were investigated, showing an increase of 13 °C and 25 °C, respectively, in a concentration-dependent manner. The therapeutic activity of the newly synthesized system against EC cancer was evaluated, and its specific mechanism of action was investigated. This design provides a novel approach to address drug delivery issues in EC and offers a flexible strategy for expanding the biomedical applications of metal–organic frameworks (MOFs).

Modulating multiple interfaces, defects, and dual-scale interlinked frameworks of cotton-derived spiral CF@Ni@CNT fibers for boosted thermal conduction and microwave absorption

Developing dual-functional materials with excellent thermal conduction and microwave absorption has emerged as a critical strategy for addressing increasingly serious electromagnetic pollution and heat dissipation difficulties. While the advancements in these materials are constrained by their high loading and incompatible performance. To develop a thermally conductive and microwave-absorbing material with a low load, this work fabricates a series of cotton-derived spiral fibers, i.e., carbon fibers (CFs), carbon fiber/Ni (CF@Ni) fibers, and carbon fiber/Ni/carbon nanotube (CF@Ni@CNT) fibers, via a freeze-drying calcination method. By controlling the amount of nickel acetate (n) and methylbenzene volume (V), we finely modulated the multiple heterostructure interfaces, dual-scale interconnected network, defects, and magnetic/dielectric-loss of the spiral CF@Ni@CNT fibers. Results show that the comprehensive properties of spiral CF@Ni and CF@Ni@CNT fibers, obtained by combining spiral CFs with magnetic Ni nanoparticles and/or CNTs, are significantly improved. The spiral CF@Ni fibers formed at n = 8.4 mmol exhibit a lower thermal conductivity (TC = 3.64 W/m⋅K) but a wider absorption bandwidth (EAB = 6.4 GHz; 10 wt% load) than CFs. Besides, the spiral CF@Ni@CNT fibers formed at n = 4.2 mmol and V = 2 mL bear a higher TC (4.27 W/m⋅K) and a larger EAB (7.52 GHz/mm) at the same load (10 wt%). The low load could be ascribed to the low percolation threshold of a dual-scale interconnected framework consisting of CFs, CNTs, and Ni0. Additionally, the simultaneous improvement in thermal conduction and microwave absorption of the spiral CF@Ni@CNT fibers is associated with their magnetic-dielectric dual loss, electron-phonon co-transmission, and dual-scale interconnected framework.

Dual‐Functional NiMg2−xCaxAl‐Hydrotalcite for Integrated CO2 Capture and In Situ Methanation

Integrated carbon capture and conversion (ICCC) is a promising technology to achieve cost‐effective carbon capture, usage, and storage. The development of efficient dual‐functional materials (DFMs) is crucial for advancing ICCC in industrial applications. Herein, a series of NiMg2−x Ca x Al‐hydrotalcite (x = 0, 0.5, 1, 1.5, 2) DFMs are prepared and applied to integrated CO2 capture and methanation. Characterization results illustrate that magnesium stabilizes the porous structure of hydrotalcite, and calcium significantly modulates surface basicity. Codoping of Mg and Ca yields merits of both functions and leads to increased methanation efficiency. By optimizing the catalyst and operating conditions, NiMg0.5Ca1.5Al‐hydrotalcite exhibits an excellent CO2 adsorption capacity of 313 μmol g−1 DFM and methane yield of 225 μmol g−1 DFM with almost full selectivity toward methane at 320 °C. NiMg0.5Ca1.5Al‐hydrotalcite also exhibits good cyclability at 320 °C under ambient pressure. Overall, Mg and Ca codoped hydrotalcite offers a promising approach to construct bifunctional materials for efficient integrated CO2 capture and in situ methanation.

A study on novel dual-functional photothermal material for high-efficient solar energy harvesting and storage

The solar-heat storage efficiency of devices based on phase change materials (PCMs) is limited due to the light absorption and internal heat transfer within the PCMs, unclear thermal conductivity-enhancement mechanism within nanocomposite PCMs, and uncontrollable photothermal-interface modulation. Therefore, a novel controllable strategy was proposed in this study to fabricate dual-functional photothermal storage three-dimensional (3D) phase change blocks (PCBs) with higher thermal conductivity (27.98 W/m·K) and spectral absorption (98.03 %) compared to those of most previously reported PCM-based devices. The as-synthesized PCBs contained millimeter-sized graphite plates with horizontal Van der Waals bonds and oriented micro/nanoscale graphite nanosheets. The structural properties of thin PCM layers between the PCB sheets have synergistically reduced the internal interfacial thermal resistance of the PCBs. Laser-controllable induction was used to fabricate integrated biomimetic-forest 3D optical absorbers on the high thermal conductivity interface of the PCBs, which significantly reduced the thermal resistance of the optical-thermal interface. The resulting 3D-PCBs, integrated with thermoelectric generators, powered portable electronic devices, expanding the applications of traditional PCM heat-storage devices. Therefore, this study will guide the future design of high-performance solar-thermal storage PCMs with a wide range of practical applications.

The role of reverse Boudouard reaction during integrated CO2 capture and utilisation via dry reforming of methane

Integrated carbon capture and utilisation (ICCU) is an emerging technology for simultaneous CO2 adsorption and conversion into value-added products. This provides a more sustainable approach compared to carbon capture and storage. Dual-functional materials (DFMs) that couple CO2 sorbents (e.g. CaO) and catalysts (e.g. Ni) enable direct utilisation of sorbed CO2 for reactions like dry reforming of methane (DRM). However, the potential interactions between sorbent and catalyst components within DFMs may induce distinct mechanisms compared to individual materials. Elucidating these synergies and interfacial phenomena is vital for guiding the rational design of DFMs. This article investigates the respective roles of Ni/SiO2 catalyst and sol–gel synthesised CaO sorbent in integrated CO2 capture and utilisation via dry reforming of methane (ICCU-DRM) using a decoupling approach. Through decoupled reactor experiments, it is found that Ni/SiO2 activates CO2 to react with carbon deposits from CH4 decomposition, achieving maximal CO and H2 yields of 43.41 mmol g−1 and 46.78 mmol g−1 as well as 87.2 % CO2 conversion at 650 °C. Characterisation shows that coke would encapsulate Ni nanoparticles and be active for CO2 conversion via Boudouard reaction, indicating sufficient catalyst-sorbent contact is necessary for CO2 spillover. In-situ DRIFTS reveals that no obvious CH4-CaCO3 reaction occurs, CO2 chemisorption on Ni/SiO2 enables the reverse Boudouard reaction, which is further verified by DFT calculations. The findings elucidate the dependent and synergistic roles of Ni/SiO2 and CaO/CaCO3 in ICCU-DRM, and highlight the importance of catalyst-adsorbent interactions in optimising dual-functional materials.

High-performance triboelectric-electromagnetic hybrid nanogenerator using dual-functional flexible neodymium iron boron/ethyl cellulose (NdFeB/EC) composite films for wind energy scavenging

Triboelectric-electromagnetic hybrid nanogenerator (HNG) with high output performance provides a very promising solution for realizing self-powered microelectronic devices. However, the complex structures and large mass of traditional HNGs make them difficult to prepare and carry. In this study, a rotating HNG based on flexible neodymium iron boron/ethyl cellulose (NdFeB/EC) composite films was designed for wind energy scavenging. A lightweight composite film with triboelectric and ferromagnetic properties, which can significantly reduce the weight of the rotor, was prepared to replace the magnet. Operated at a wind speed of 15.5 m/s, the triboelectric nanogenerator (TENG) unit of the optimized HNG with an interdigitated electrode gap of 2 mm can generate an open-circuit voltage (Voc) and a short-circuit current (Isc) of 55 V and 5.4 μA, respectively. The maximum power of TENG is 99.2 μW under the condition of an external load resistance of 10 MΩ. The corresponding electromagnetic generator (EMG) unit can produce Voc and Isc of approximately 0.16 V and 59.3 μA, delivering an output power of 2.5 μW at a matched loading resistance of 2.3 kΩ. Compared to the individual TENG or EMG units, the HNG exhibited better charging performance. A 470 μF capacitor can charge to 3.4 V within 600 s, and the stored energy can successfully power a commercial soil temperature–humidity meter to work continuously for 75 s and light 30 blue LEDs in parallel. This research is of great scientific significance for developing triboelectric–ferromagnetic dual-functional materials and designing highly integrated and lightweight HNGs.

Optimizing alkali metal Salt-Induced structural assembly of Ni-MgO dual function materials for enhanced CO2 capture and methanation performance

Alkali metal salts (AMS) promoted Ni-MgO dual function materials (DFMs) show exhibit potential in integrated CO2 capture and methanation. However, the CO2 adsorption and methanation efficiency of these materials is contingent upon their adsorptive and catalytic sites, which are significantly susceptible to the incorporated AMS. Herein, we investigate the effect of assemble configuration of AMS and Ni on the structural properties and integrated CO2 capture and methanation performance of the AMS-promoted Ni-MgO DFMs. By preferentially incorporating AMS to form the Ni-AMS-MgO configuration, AMS is allocated throughout both the internal core and external layer of MgO particles. Given AMS's preferential occupation of specific pore structures, Ni is evenly distributed as smaller particles on the MgO surface, minimally influenced by the carbonate formed during adsorption. The Ni-AMS-MgO configuration demonstrates superior integrated CO2 capture and methanation performance, featuring high CO2 uptake (1.86 mmol/g) and CH4 yield (1.37 mmol/g).

Photothermally-activated piezo-pyroelectric multifunctional hybrid energy harvester for motion sensing and thermal therapy

Herein a piezoelectric-pyroelectric hybrid energy harvester (PPEH) is developed for the simultaneous conversion of mechanical and thermal energy into electrical power. In this work, poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) is selected as the polymer matrix due to its flexibility, light weight, easy processing, and biocompatibility, while nanoparticles of a photothermal poly(2-ethylaniline) (PEAn) are added as a dopant to enhance the piezoelectric output and simultaneously endow the composite material with pyroelectric properties. As a result, the output voltage under solar irradiation is enhanced by up to 3.26 times relative to that of an energy harvester based on the piezoelectric property alone. Moreover, the application of this dual-functional material is demonstrated in a wearable electronic device that is capable of detecting motion in diverse joint regions and providing thermal therapy, suggesting the potential to function as both a sensor and a therapeutic tool, thereby demonstrating its viability as a multifunctional wearable device.

Integrated CO2 capture and conversion by Cu/CaO dual function materials: Effect of in-situ conversion on the sintering of CaO and its CO2 capture performance

The integrated carbon capture and utilization (ICCU) technology has been considered a prospective strategy for mitigating carbon emissions issues. Compared to conventional CO2 capture and utilization, the ICCU process reduces transporting, product purification, construction, and operation costs. However, few works focus on investigating the effect of in-situ CO2 conversion on the sintering of CaO at high temperatures. In this work, Cu/CaO dual functional materials (DFMs) were synthesized and used in the Calcium Looping-Reverse Water-Gas Shift (CaL-RWGS) process at 650 °C. The results showed that it is thermodynamically feasible to couple the CaL with the RWGS reaction. In the cyclic CO2 capture test, Ca1Cu0.1 DFMs showed desirable CO2 capture performance (11.34 mmol/gDFMs) and self-activated phenomenon in the first 15 cycles. Moreover, Cu nanoparticle catalysts in the DFMs effectively inhibited the sintering of CaO by accelerating the desorption of CO2 from the CaO surface and converting it to CO during the conversion stage. In-situ DRIFTS of Ca1Cu0.1 DFMs revealed that formates might be the RWGS intermediates in CaL-RWGS.

CO2 capture and methanation using Ru/Na2O/Al2O3 dual-function materials: Effect of support synthesis method and Ru load

Ru/Na2O/Al2O3 dual-function materials were prepared by varying the support synthesis method and Ru load. Different sol-gel-type and precipitation/ hydrothermal preparation methods were employed in order to synthesize materials with variable nanostructure, surface chemistry and textural properties, thereby effectively tuning the material activity for the methanation of pre-adsorbed CO2. The materials were thoroughly characterized and evaluated during the integrated CO2 capture and methanation process. It was found that the Pechini sol-gel synthesis method led to the structure with the highest porosity, basic site population and high dispersion of methanation and adsorption active Ru0 and Al-O--Na+ sites. The corresponding material displayed the highest CH4 yield (0.47 mmol/g) and fastest CH4 production kinetics, while stable performance was achieved under successive adsorption-hydrogenation cycles and under the co-presence of O2 and H2O during CO2 adsorption. Lastly, the increase in Ru load (0.25 wt% - 4 wt% range) could incrementally improve the CH4 production kinetics during hydrogenation.