One-step CO2 Research Articles

One-Step laser induced molybdenum carbide/graphene hybrid electrode for supercapacitor

Transition metal carbides (TMCs) have garnered significant attention in various energy applications owing to their outstanding conductive and electrochemical properties. Despite these advantages, challenges persist in terms of non-toxicity and efficient fabrication methods. In this study, a Mo3C2/laser-induced graphene (LIG) heterostructure was synthesized via one-step CO2 laser induced conversion process. The specific area capacitance of the Mo3C2/LIG hybrid electrode reached 23.5 mF cm−2, which is 2.5 times higher than that of pure Mo3C2 and 9 times greater than pure LIG electrodes. Moreover, the hybrid electrode exhibited robust cycling stability, maintaining 98.4 % of its initial capacitance after 10,000 charge–discharge cycles. Theoretical simulation also revealed superior hydrogen adsorption and high electrical conductivity of the Mo3C2/LIG hybrid electrode. This work presents a promising approach for developing advanced molybdenum carbide-based composites and offers an alternative strategy for enhancing the electrochemical performance of capacitive electrodes.

Sorption enhanced DME synthesis by one-step CO2 hydrogenation

DME synthesis by direct CO2 hydrogenation was studied on physical mixture of commercial CuZnO/Al2O3 (CZA) and in-house synthesized PTA (phosphotungstic acid)/γ-Al2O3 catalysts. Effects of PTA loading (0–50 % by mass) and relative amounts of the catalysts on CO2 conversion and DME yield were investigated. The process was intensified through integration of in-situ steam separation by Zeolite 3A (Z3A) adsorbent mixed with the catalysts. Experiments were run at 498 K, 30 bar, H2:CO2=3:1 and GHSV=1750 h−1 (based on CZA catalyst). Optimum PTA loading and CZA:PTA/γ-Al2O3 mass ratio were 30 % and 1:2, respectively, that gave ∼21 % CO2 conversion and 6.3 % DME yield. These values remained below the respective thermodynamic limits (28.5 % and 21 %), which were exceeded upon adsorbent integration. Catalytic performance depended strongly on adsorbent quantity studied at the catalyst (CZA+PTA/γ-Al2O3):adsorbent mass ratio range of 1:0.33–4. Catalysts and the adsorbent remained stable during the pressure swing driven adsorption-regeneration cycles. Sorption assistance at catalyst:adsorbent ratio=1:4 increased catalyst productivity from 5.5×10−3 to 2×10−2 kgDME h−1 kgcat−1. The latter value was comparable to those of the sorption enhanced CO2+CO hydrogenation systems due to the PTA-based dehydration catalyst with strong acidic features and was promising when the strong thermodynamic limitations of CO2-DME conversion was considered.

Chitosan Oligosaccharide Laser Lithograph: A Facile Route to Porous Graphene Electrodes for Flexible On-Chip Microsupercapacitors.

In this study, a convenient chitosan oligosaccharide laser lithograph (COSLL) technology was developed to fabricate laser-induced graphene (LIG) electrodes and flexible on-chip microsupercapacitors (MSCs). With a simple one-step CO2 laser, the pyrolysis of a chitosan oligosaccharide (COS) and in situ welding of the generated LIGs to engineering plastic substrates are achieved simultaneously. The resulting LIG products display a hierarchical porous architecture, excellent electrical conductivity (6.3 Ω sq-1), and superhydrophilic properties, making them ideal electrode materials for MSCs. The pyrolysis-welding coupled mechanism is deeply discussed through cross-sectional analyses and finite element simulations. The MSCs prepared by COSLL exhibit considerable areal capacitance of over 4 mF cm-2, which is comparable to that of the polyimide-LIG-based counterpart. COSLL is also compatible with complementary metal-oxide-semiconductor (CMOS) and micro-electro-mechanical system (MEMS) processes, enabling the fabrication of LIG/Au MSCs with comparable areal capacitance and lower internal resistance. Furthermore, the as-prepared MSCs demonstrate excellent mechanical robustness, long-cycle capability, and ease of series-parallel integration, benefiting their practical application in various scenarios. With the use of eco-friendly biomass carbon source and convenient process flowchart, the COSLL emerges as an attractive method for the fabrication of flexible LIG on-chip MSCs and various other advanced LIG devices.

Ultrastructure, CO2 Assimilation and Chlorophyll Fluorescence Kinetics in Photosynthesizing Glycine max Callus and Leaf Mesophyll Tissues

The ultrastructural and functional features of photosynthesizing callus cells are poorly known. Electron microscopy studies on green, compact Glycine max calluses have shown that they are composed of photosynthesizing cells characterized by clear ultrastructural signs of senescence. Studies on chlorophyll fluorescence and CO2 assimilation kinetics have shown that such cells were still able to maintain photosynthesis but could not compensate for the respiratory CO2 uptake. Having a one-step CO2 assimilation kinetics, photosynthesis in calluses differed from photosynthesis in leaves, which had a two-step CO2 assimilation kinetics. In contrast to leaves, the fluorescence induction curves in G. max calluses strongly differed in shape depending on the color of actinic light (red or blue). Red (in contrast to blue) light excitation did not lead to CO2 assimilation in the calluses, thus suggesting anoxygenic photosynthesis in this case. In particular, the data obtained indicate that the actinic light spectrum should be considered when cultivating calluses for micropropagation of plants and for callus tissue research.

Experimental investigation of a packed bed membrane reactor for the direct conversion of CO2 to dimethyl ether

In this study, the performance of a packed bed membrane reactor (PBMR) based on carbon molecular sieve membranes for the one-step CO2 conversion to dimethyl ether (DME) is experimentally compared to that of a conventional packed bed reactor (PBR) using a CuO-ZnO-Al2O3/HZSM-5 bifunctional catalyst. The PBMR outperforms the PBR in most of the experimental conditions. The benefits were greater at lower GHSV (i.e., conditions that approach thermodynamic equilibrium and water formation is more severe), with both XCO2 and YDME improvements of +35–40 % and +16–27 %, respectively. Larger sweep gas-to-feed (SW) ratios increase the extent of water removal (ca. 80 % at SW=5), and thus the performance of the PBMR. Nevertheless, alongside the removal of water, a considerably amount of all products are removed as well, leading to a greater improvement in the CO yield (+122 %) than the DME yield (+66 %). Higher temperatures selectively improve the rWGS reaction, leading to a lower YDME with respect to the PBR at 260 °C, due to the significant loss of methanol. Furthermore, larger transmembrane pressures (∆P) were not beneficial for the performance of the PBMR due to the excess reactant loss (i.e., 98–99 % at ∆P = 3 bar). Finally, the reactor models developed in our previous studies accurately describe the performance of both the PBR and PBMR in the range of tested conditions. This result is of high relevance, since the reactor models could be used for further optimization studies and to simulate conditions which were not explored experimentally.

Laser-Induced Graphene Formation on Chitosan Derivatives toward Ecofriendly Electronics

Laser-induced graphene (LIG) has aroused a wide range of research interests ranging from micro-nano energy devices to the Internet of Things (IoT). Nevertheless, the non-degradability of most-used synthetic polymer carbon sources poses a serious threat to the environment. In this work, ecofriendly chitosan-based derivatives, including carboxymethyl chitosan (CMCS), chitosan oligosaccharide, and chitosan hydrochloride, are successfully converted into LIGs for the first time via a convenient one-step CO2 laser engraving at ambient air. The obtained LIGs are characterized by a three-dimensional hierarchical porous structure and exhibit good sheet conductivity. The consecutive carbonization and graphitization mechanism of target precursors induced by laser heat accumulation is also deeply discussed. Besides, based on a mechanically reliable LIG/CMCS composite film and tribo-negative acrylic/polyimide anti-layers, two contact-separation mode triboelectric nanogenerators are built and their power densities range from 1.44 to 2.48 mW cm–2. These devices with long cycle life can be used for low-frequency mechanical energy harvesting and commercial capacitance charging, which could be potentially applied in the wireless sensor network nodes. Such a family of chitosan derivatives paves a new route for LIG synthesis and provides new ideas for ecofriendly LIG electronics.

Techno-economic assessment of the one-step CO2 conversion to dimethyl ether in a membrane-assisted process

This study investigates the impact of the membrane reactor (MR) technology with in-situ removal of water to boost the performance of the one-step DME synthesis via CO2 hydrogenation at process scale. Given the higher efficiency in converting the feedstock, the membrane reactor allows for a remarkable decrease in the main cost drivers of the process, i.e., the catalyst mass and the H2 feed flow, by ca. 39% and 64%, respectively. Furthermore, the MR-assisted process requires 46% less utilities than the conventional process, especially in terms of cooling water and refrigerant, with a corresponding decrease in environmental impact (i.e., 25% less CO2 emissions). Both the conventional and MR-assisted plants were found effective for the mitigation of the CO2 emissions, avoiding ca. 1.4–1.6 tonCO2/tonDME. However, given the higher reactor and process efficiency, the membrane technology contributes to a significant reduction (i.e., 25%) in the operating costs, which is a remarkable improvement in this OPEX intensive process. Nevertheless, the calculated minimum DME selling price (i.e., 1739 €/ton and 1960 €/ton for the MR-assisted and the conventional process, respectively) is over 3 times greater than the current DME market price. Yet, with the predicted decrease of renewable H2 price and a zero-to-negative cost for the CO2 feedstock, the MR-assisted system could become competitive with the benchmark between 2025 and 2050.

Perspective on CO2 Hydrogenation for Dimethyl Ether Economy

The CO2 hydrogenation to dimethyl ether (DME) is a potentially promising process for efficiently utilizing CO2 as a renewable and cheap carbon resource. Currently, the one-step heterogeneous catalytic conversion of CO2 to value-added chemicals exhibits higher efficiency than photocatalytic or electrocatalytic routes. However, typical catalysts for the one-step CO2 hydrogenation to DME still suffer from the deficient space–time yield and stability in industrial demonstrations/applications. In this perspective, the recent development of the one-step CO2 hydrogenation to DME is focused on different catalytic systems by examining the reported experimental results and the reaction mechanism including the catalytic nature of active sites, activation modes and of CO2 molecules under relevant conditions; surface intermediates are comparatively analyzed and discussed. In addition to the more traditional Cu-based, Pd-based, and oxide-derived bifunctional catalysts, a further emphasis is given to the characteristics of the recently emerged In2O3-based bifunctional catalysts for the one-step conversion of CO2 to DME. Moreover, GaN itself, as a bifunctional catalyst, shows over 90% DME selectivity and a reasonably high activity for one-step CO2 hydrogenation, and the direct hydrogenation of CO2 via the unique non-methanol intermediate mechanism is highlighted as an important illustration for exploring new catalytic systems. With these analyses and current understandings, the research directions in the aspects of catalysis and DME economy are suggested for the further development of one-step DME synthesis from CO2 hydrogenation.

Synthesis of highly effective [Emim]IM applied in one-step CO2 conversion to dimethyl carbonate

Ionic liquid 1-ethyl-3-methylimidazolium ([Emim]IM) with high thermal stability and strong basicity was successfully synthesized. Using [Emim]IM as catalyst, dimethyl carbonate (DMC) was directly synthesized from epoxy propane (PO), CO2, and methanol under mild reaction conditions. A continuous two-stage DMC synthesis process was developed. The cycloaddition of CO2 and PO was first conducted to produce propylene carbonate (PC), and then methanol was introduced into the system to synthesize DMC. During the cycloaddition process, 97.40% PO conversion and 97.40% PC yield were achieved with TON of 99.49. In the subsequent transesterification stage, DMC yield attained 83.63% with selectivity higher than 99% and TON of 70.15. [Emim]IM was reused for seven times without obvious deactivation, exhibiting good stability. The effects of reaction temperature, reaction time, the initial pressure of CO2, and catalyst weight on cycloaddition and transesterification reactions were systematically investigated. The kinetic study showed that the activation energies (Ea) of cycloaddition and transesterification reactions were 28.02 and 38.53 KJ·mol−1, respectively, much lower than those of catalysts reported in the literatures. In addition, [Emim]IM displayed superior catalytic activity for the cycloaddition of CO2 with various epoxy compounds.

Hermetic Welding of an Optical Fiber Fabry-Pérot Cavity for a Diaphragm-Based Pressure Sensor Using CO2 Laser.

A diaphragm-based hermetic optical fiber Fabry–Pérot (FP) cavity is proposed and demonstrated for pressure sensing. The FP cavity is hermetically sealed using one-step CO2 laser welding with a cavity length from 30 to 100 μm. A thin diaphragm is formed by polishing the hermetic FP cavity for pressure sensing. The fabricated FP cavity has a fringe contrast larger than 15 dB. The experimental results show that the fabricated device has a linear response to the change in pressure, with a sensitivity of −2.02 nm/MPa in the range of 0 to 4 MPa. The results demonstrate that the proposed fabrication technique can be used for fabricating optical fiber microcavities for sensing applications.

Techno-Economic Assessment of the One-Step Co2 Conversion to Dimethyl Ether in a Membrane-Assisted Process

Techno-Economic Assessment of the One-Step Co2 Conversion to Dimethyl Ether in a Membrane-Assisted Process

Techno-Economic Assessment of the One-Step Co2 Conversion to Dimethyl Ether in a Membrane-Assisted Process

Techno-Economic Assessment of the One-Step Co2 Conversion to Dimethyl Ether in a Membrane-Assisted Process

1,1'-Carbonyldiimidazole-copper nanoflower enhanced collapsible laser scribed graphene engraved microgap capacitive aptasensor for the detection of milk allergen

The bovine milk allergenic protein, ‘β-lactoglobulin’ is one of the leading causes of milk allergic reaction. In this research, a novel label-free non-faradaic capacitive aptasensor was designed to detect β-lactoglobulin using a Laser Scribed Graphene (LSG) electrode. The graphene was directly engraved into a microgapped (~ 95 µm) capacitor-electrode pattern on a flexible polyimide (PI) film via a simple one-step CO2 laser irradiation. The novel hybrid nanoflower (NF) was synthesized using 1,1′-carbonyldiimidazole (CDI) as the organic molecule and copper (Cu) as the inorganic molecule via one-pot biomineralization by tuning the reaction time and concentration. NF was fixed on the pre-modified PI film at the triangular junction of the LSG microgap specifically for bio-capturing β-lactoglobulin. The fine-tuned CDI-Cu NF revealed the flower-like structures was viewed through field emission scanning electron microscopy. Fourier-transform infrared spectroscopy showed the interactions with PI film, CDI-Cu NF, oligoaptamer and β-lactoglobulin. The non-faradaic sensing of milk allergen β-lactoglobulin corresponds to a higher loading of oligoaptamer on 3D-structured CDI-Cu NF, with a linear range detection from 1 ag/ml to 100 fg/ml and attomolar (1 ag/ml) detection limit (S/N = 3:1). This novel CDI-Cu NF/LSG microgap aptasensor has a great potential for the detection of milk allergen with high-specificity and sensitivity.

Comparative Life Cycle Assessment of CO2 Electrosynthesis to Fuels and Feedstocks

Development of electrochemical pathways to convert CO2 into fuels and feedstock is rapidly progressing over the past decade. Here we present a comparative cradle-to-gate life cycle assessment (LCA) of one and two-step electrochemical conversion of CO2 to eight major value-added products; wherein we consider CO2 capture, conversion and product separation in our process model. We measure the carbon intensity (i.e., global warming impact) of one and two-step electrochemical routes with its counterparts – thermochemical CO2 utilization and fossil-fuel based incumbent synthesis routes for those products. Due to inevitable carbonate formation or CO2 crossover in one-step CO2 electrolysis using neutral pH membrane electrode assembly, the two-step electrosynthesis pathways (CO2 to CO in solid oxide electrolysis cell followed by CO electroreduction in alkaline flow cell) would be distinctively compelling through the lens of climate benefits. This analysis further reveals that the carbon intensity of electrosynthesis products is due to significant energy requirement for conversion (75–85% of total energy consumption for gas products) and product separation (30–85% of total energy consumption for liquid products) phases. Electrochemical route is highly sensitive to the electricity emission intensity and is compelling only when coupled with low emission intensity (<0.25 kg CO2e per kWh). As the technology advances, we identify near-term compelling products that would provide climate benefits over incumbent routes, including syngas, ethylene and n-propanol. We further identify technological goals required for electrochemical route to be competitive, notably achieving liquid product concentration >20 wt%. It is our hope that this analysis will guide the CO2 electrosynthesis community to target achieving these technological goals, such that when coupled with low-carbon electricity, electrochemical route would bring climate benefits in near future.

Ex-LDH-Based Catalysts for CO2 Conversion to Methanol and Dimethyl Ether

CO2-derived methanol and dimethyl ether can play a very important role as fuels, energy carriers, and bulk chemicals. Methanol production from CO2 and renewable hydrogen is considered to be one of the most promising pathways to alleviate global warming. In turn, methanol could be subsequently dehydrated into DME; alternatively, one-step CO2 conversion to DME can be obtained by hydrogenation on bifunctional catalysts. In this light, four oxide catalysts with the same Cu and Zn content (Cu/Zn molar ratio = 2) were synthesized by calcining the corresponding CuZnAl LDH systems modified with Zr and/or Ce. The fresh ex-LDH catalysts were characterized in terms of composition, texture, structure, surface acidity and basicity, and reducibility. Structural and acid–base properties were also studied on H2-treated samples, on which specific metal surface area and dispersion of metallic Cu were determined as well. After in situ H2 treatment, the ex-LDH systems were tested as catalysts for the hydrogenation of CO2 to methanol at 250 °C and 3.0 MPa. In the same experimental conditions, CO2 conversion into dimethyl ether was studied on bifunctional catalysts obtained by physically mixing the ex-LDH hydrogenation catalysts with acid ferrierite or ZSM-5 zeolites. For both processes, the effect of the Al/Zr/Ce ratio on the products distribution was investigated.

Demonstration of a ceria membrane solar reactor promoted by dual perovskite coatings for continuous and isothermal redox splitting of CO2 and H2O

The direct one-step CO2 and H2O splitting using an oxygen-transport membrane (OTM) reactor was investigated as a potentially ideal way to generate renewable fuels from concentrated solar energy. The solar-driven thermolysis of CO2 (or H2O) was promoted by in-situ oxygen removal across nonstoichiometric ceria-based membranes. A new solar membrane reactor integrating a tubular densified membrane made of either pure ceria or perovskite-coated ceria was designed and operated under high-flux concentrated solar radiation. A continuous flow of inert gas on the permeate side was used to create the required oxygen partial pressure gradient (driving force) and ensure continuous oxygen permeation via oxygen ion diffusion across the densified ceria membrane. The continuous OTM solar operation at high temperature was demonstrated through testing under various operating conditions. The CO and O2 production rates were sharply enhanced by increasing the operating temperature (up to 1550 °C). The increase of CO2 concentration or oxidant gas flow rate also enhanced the process performance. Unprecedented fuel production rates (>0.07 μmol s−1 cm−2 at 1550 °C) were achieved with a pure CO2 stream on the feed side and flowing Ar on the sweep side of the reactive ceria membrane. An original composite membrane integrating two different perovskite coatings on each side of the ceria membrane, with a sandwich-like structure, was designed and tested under concentrated sunlight. Thin layers of La0.5Sr0.5Mn0.9Mg0.1O3 on the inner side and Ca0.5Sr0.5MnO3 on the outer side were added to enhance oxygen ion transfer. With such a membrane configuration, a remarkable production of CO (>0.13 μmol s−1 cm−2) and oxygen (with CO:O2 ratio of 2) was obtained simultaneously, respectively on the inner and outer sides of the OTM. These results outperform the production rates achieved with the uncoated ceria membranes, and demonstrate the benefits of using composite membranes composed of a densified core material coated with (or sandwiched in between) redox active perovskite materials.

Exploring non-adiabaticity to CO reduction reaction through ab initio molecular dynamics simulation

Non-adiabatic chemical reaction refers to the electronic excitation during reactions. This effect cannot be modeled by the ground-state Born–Oppenheimer molecular dynamics (BO-MD), where the electronic structure is at the ground state for every step of ions’ movement. Although the non-adiabatic effect has been explored extensively in gas phase reactions, its role in electrochemical reactions, such as water splitting and CO2 reduction, in electrolyte has been rarely explored. On the other hand, electrochemical reactions usually involve electron transport; thus, a non-adiabatic process can naturally play a significant role. In this work, using one-step CO2 reduction as an example, we investigated the role of the non-adiabatic effect in the reaction. The reaction barriers were computed by adiabatic BO-MD and non-adiabatic real-time time dependent density functional theory (rt-TDDFT). We found that by including the non-adiabatic effect, rt-TDDFT could increase the reaction barrier up to 6% compared to the BO-MD calculated barrier when the solvent model is used to represent water. Simulations were carried out using explicit water molecules around the reaction site under different overpotentials, and similar non-adiabatic effects were found.

Preparation of micro-mesoporous carbon from seawater-impregnated sawdust by low temperature one-step CO2 activation for adsorption of oxytetracycline

Porous carbons (PCs) were prepared from seawater (SW)-impregnated sawdust (SD) by CO2 activation at 700 °C. The preparation process was investigated on-line by thermogravimetric analyzer coupled with FTIR (TG-FTIR). PCs were characterized by N2-adsorption/desorption and Fourier transform infrared spectroscopy. The adsorption abilities of PCs for oxytetracycline (OTC) were compared and the adsorption isotherms of OTC on the optimum sample were studied. Results showed that SW impregnation led to the release of more CO from SD at 700 °C, indicating a higher degree of CO2 activation, thus a 81% higher BET surface area (SBET) can be achieved under the same activation condition. Mesopore volume of PC increased from 0.089 to 0.301 cm3 g−1 with the activation time increasing from 5 to 60 min. PC obtained after 60-min activation with a SBET of 490 m2 g−1 and an average pore diameter of 3.78 nm had the highest adsorption ability for OTC. Its adsorption equilibrium data for OTC followed Langmuir model with a maximum monolayer adsorption capacity up to 100 mg g−1.

Tannin-derived micro-mesoporous carbons prepared by one-step activation with potassium oxalate and CO2

Micro-mesoporous carbons (MMCs) were successfully prepared using natural polyphenolic compounds, condensed tannins, and glyoxal, a nontoxic aldehyde, in lieu of synthetic phenolic compounds like formaldehyde and resorcinol as carbon precursors. Such MMCs were fabricated by a soft-templating strategy under mild conditions. Porosity development was achieved by varying the amount of potassium oxalate as an in-situ activator coupled with one-step CO2 activation at 700 °C. This strategy allowed for the enhancement of microporosity as well as retention of the uniform mesoporous structure of the carbons. The CO2 uptakes of 5.2 mmol/g at 0 °C and 3.6 mmol/g at 25 °C were achieved at 1 bar pressure for the tannin-derived activated MMC sample with a surface area of 1192 m2/g, a volume of fine micropores (sizes below 1 nm) of 0.33 cm3/g, and a mesopore volume of 0.49 cm3/g. This study opens new opportunities for a facile and green synthesis of MMCs from less toxic precursors with tailored porosity by synergistic effects of chemical and physical activation. The resulting MMCs exhibit the potential applicability not only as CO2 sorbents but also in other environmental applications such as adsorption of organic volatile compounds and dye molecules, which require slightly larger pores.

Interaction effects between CuO-ZnO-ZrO2 methanol phase and zeolite surface affecting stability of hybrid systems during one-step CO2 hydrogenation to DME

Abstract A significant boost to the catalytic technology of CO2-to-DME hydrogenation in a single step was recently given by the design of novel hybrid multimetallic/zeolite systems. However, a significant drop of catalyst activity after few hours of operation time pushes now the research interest towards the development of more stable multifunctional systems, suitable to ensure activity, selectivity and lifetime under typical industrial conditions. In this work, the influence of different home-made zeolite samples (i.e., Sil-1, MFI, Y, FER, BEA, MOR), integrated in a weight ratio of 1:1 with a CuO-ZnO-ZrO2 metal-oxide(s) phase, was investigated under long-term stability tests in a fixed bed reactor during CO2 hydrogenation reaction to assess the activity-selectivity pattern of the hybrid catalyst as well as their deactivation trend during operation time. The individuation of key structure-activity relationships helped to explain how the extent of interaction between the metal-oxides phase with the zeolite surface as well as the strength of the acid sites significantly control the catalyst stability.