Carbon Yield Research Articles

Basic-Functionalized Ionic Porous Organic Polymers: Triple Roles in One for Highly Efficient and Recyclable Carboxylative Cyclization of CO2 under Mild Conditions.

The transformation of carbon dioxide (CO2) into high-value chemicals is a significant step towards achieving the goal of "carbon neutrality". α-methylene cyclic carbonate, as an intermediate for the synthesis of many important organic compounds, is widely employed in industrial productions. In this work, a series of ionic porous organic polymers (IPOPs) with different basic-functionalized anions were successfully synthesized and adjusted to have certain BET surface areas and high contents of ion sites by post-modification. These basic-functionalized IPOPs could exhibit excellent catalytic performance for carboxylative cyclization of CO2 at 30 °C and 1 bar in presence of silver salts, eliminating the use of the extra organic bases. In the whole catalytic reaction, the basic-functionalized anions could play triple roles: enriching CO2 for further transformation, activating the hydroxyl groups of substrates to improve the catalytic performance, while coordinating with Ag atom to stabilize and regenerate catalyst. Notably, the catalytic system of DCX-4-Tet/Ag2O exhibited excellent recyclability, and the yield of α-alkylidene cyclic carbonate was well maintained at 99 % after 5 cycles. To the best of our knowledge, the catalytic system was the first example of basic-functionalized IPOPs that played multiple roles for highly efficient CO2 cyclization under mild conditions without any extra organic bases.

Revalorisation of Vine Pruning Waste Through the Production of Zero CO2 Emission Charcoal

This research studies the production of charcoal from a by-product of viticulture such as the vine pruning remains of vine (vine shoots). During this study, several carbonisation tests were carried out in an electric muffle furnace where vine shoot samples were tested at different temperature ranges (150–450 °C) and with test durations of 2 h and 3 h. From these tests, the mass yields and carbon yields were studied, as well as the characterisation of the chemical composition of the resulting charcoals, obtaining the maximum results of the fixed carbon content of up to 80.4%. Subsequently, the tests’ energy consumptions were also recorded in order to optimise the amount of grammes of carbon per kWh of energy used. The average value obtained in the trials was 18.55 g of carbon per kWh of energy used in the carbonisation process. Finally, special emphasis was placed on studying the sustainability of this charcoal through the net balance of CO2 eq emissions. To this end, the CO2 eq emissions associated with the energy consumption of the trials and how, through the use of this waste to produce 10–12 g of charcoal, the negative net emission values of up to −522.74 g of CO2 eq were achieved were evaluated. This demonstrates the possibility of charcoal production with a zero-carbon footprint. This acts as evidence of the possibility of zero carbon footprint charcoal production, a key innovative aspect that helps to achieve greater sustainability in industrial sectors with a high impact on the region.

A Statistical Study Comparing Experimental and Theoretical Yields of Activated Carbon Prepared from Pomegranate (Punica granatum) Peels via Chemical Treatment

Due to the great importance that activated carbon has gained through its use in combating pollution, removing dyes components, and other uses, it has been prepared in different ways. In this research, a statistical study was conducted to compare the practical and theoretical values of activated carbon yield prepared from pomegranate peels with some additives (Novolak resin and Beji asphalt) in order to improve its specifications. Since the preparation of activated carbon is controlled by a group of variables, a number of matters were tested for the possibility of finding a linear relationship based on the effect of the amount of the iodine number, density, ash content, and humidity on the yield of all prepared types of activated carbon, and considering the possibility of achieving the relationship through additional additives that can be obtained through it on carbon with a homogeneous surface and specifications. Also, finding a general mathematical relationship that brings together all the types prepared from pomegranate peels after adding new variables representing the percentages of adding asphalt to them and novolak resin used in preparation and activation. This equation makes it possible to control the proportions of the resulting yield before trying to measure, test and evaluate any of the practically calculated values such as the iodine number, density, ash content and humidity using the mathematical equation and calculating them for unknown values if the other characteristics are known. This achieves a shortening of the time period. The success of this method is evidenced by the high experimental R2 values, the low SE, and the logical variation of the variable coefficients.

Waste wood tar based porous carbon electrodes for supercapacitors with excellent performances through condensation cross-linking modification

Wood tar is an unavoidable by-product during a slow-pyrolysis process of biomass, which is usually discarded as a waste and results in environment pollution. Recently, wood tar has been used as a starting material for carbon electrodes because of its thermoplasticity and high carbon content. However, wood tar is mainly composed of various light phenolic molecules, which usually leads to a low carbonization yield after carbonization and an inferior electrochemical performance after activation. In this work, in order to improve the carbonization rate and electrochemical performance of these materials, wood tar was first condensed and crosslinked with formaldehyde and urea via a condensation reaction to produce condensed macromolecular resins, which were then carbonized at 550°C and activated with KOH at 800°C to prepare high-performance nitrogen-doped carbon electrodes for supercapacitors. The samples possess high carbonization yield, large specific surface area (3515.1 m2g-1) and moderate nitrogen content (1.11%). The high-performance carbon electrodes fabricated by this method achieves a high capacitance of 437.8Fg-1 (6M KOH electrolyte) at 1A/g-1. The assembled supercapacitor has an energy density of 13.41Whkg-1 at a power density of 124.93Wkg-1. And the capacitance retention was essentially 100% after 10000 cycles at 5Ag-1. The study presents an innovative strategy for the production of porous carbon for supercapacitors using wood tar and improves carbonization yield via condensation cross-linking modification.

Ether chain-modified Alkanolguanidine for CO2 capture and subsequent conversion

Capturing CO2 and converting it into valuable chemicals has attracted considerable attention in recent years. Herein, a kind of ether chain-modified alkanolguanidines (ECMAs) was designed and synthesized as a dual functional reagent for carbon dioxide capture and conversion. Due to the presence of basic sites and CO2-philic ether chains, these ECMAs demonstrated almost equimolar CO2 capture at room temperature and atmospheric pressure through the synergy of physical and chemical absorption. Even for diluted CO2 (15 % CO2), 0.7 mol CO2 per mole capture reagent can still be achieved, showing their potential application in post-combustion capture. The synthesized ECMAs can also serve as catalyst in the cycloaddition reaction of CO2 with various epoxides, affording 75–99 % yield of corresponding cyclic carbonates under 3 MPa CO2 with tetrabutylammonium iodide (TBAI) as co-catalyst. Moreover, these ECMAs can be applied to the integrated CO2 capture and conversion, in which the ECMAs can react with CO2, forming the alkyl carbonate zwitterion as active CO2 species in the capture step. And in the subsequent cycloaddition reaction with propylene oxide, 52 % yield of propylene carbonate was obtained.

One-step condensation synthesis of di-tertiary ammonium salt protic ionic liquid for efficiently catalytic CO2 cycloaddition reaction under cocatalyst- and solvent-free conditions

A novel protic ionic liquid di-tertiary ammonium bromide ionic liquid (DTAB-IL) was synthesized by one-step condensation at 0 ℃ with 85 % yield. DTAB-IL also exhibited effective catalytic activity for CO2 cycloaddition without cocatalyst and solvent. The catalytic reaction conditions were optimized to 90 ℃, 4 h, 1 MPa, and the yield of propylene carbonate was obtained 96 % with high selectivity 99 %. Under the optimal conditions, DTAB-IL catalyst exhibited good recyclability and universality to various epoxides. Furthermore, temperature influence and kinetic investigation for propylene carbonate synthesis were studied. The activation energy for DTAB-IL catalyzing CO2 cycloaddition reaction was 43.93 kJ/mol, and the reaction was found to follow first-order for propylene oxide. Efficient cycloaddition reaction of CO2 and epoxide was attributed to the activation of epoxide and CO2 by di-tertiary ammonium and epoxide ring-opening by bromide anion in DTAB-IL.

Transesterification of glycerol with dimethyl carbonate for the synthesis of glycerol carbonate and glycidol by Iron (III) salen complex

The transesterification of glycerol and dimethyl carbonate (DMC) was investigated in the presence of μ-oxo-Fe(salen)2 under the optimal reaction condition. Several transition metal(salen) were tested, and only Fe (salen) shows an excellent results towards transesterification of glycerol. Therefore, Fe (salen) was characterized by IR, elemental analysis, MS, XPS and Surface Basicity test, and it can be confirmed that the as-synthesized Fe(salen) was existed in the form of μ-oxo-Fe(salen)2. It was proposed that the μ-oxo-Fe(salen)2 can provide two different reaction pathway based on its molecular structures and the electronic configuration of iron itself. μ-oxo-Fe(salen)2 was reacted with the mixture of glycerol and DMC under microwave-heating in 60 min at 100°C and at the molar ratio of glycerol:DMC:μ-oxo-Fe(salen)2 of 1:2:0.01 and obtaining the highest glycerol carbonate yield of 93.8 %.

Multi-amino functionalized triazine-based polymers as the catalyst for cycloaddition of CO2 to epoxides

Designing efficient catalysts for CO2 cycloaddition to reduce CO2 emission is one of crucial for environmental issues technology. Herein, the multiple-amino functionalized triazine-based polymer (MAFTP) was prepared through the nucleophilic reaction of cyanuric chloride with melamine and ethylenediamine by a conventional heating method, which are favorable for CO2 adsorption due to their nitrogen-rich structure. MAFTP was characterized entirely, the CO2 adsorption capacity of MAFTP showed the CO2 uptake performance with the values of 5.73 cm3g−1 at 273 K and 1 bar. MAFTP/KI catalyst exhibited efficient catalytic activity for CO2 fixation to epoxides. 99 % propylene carbonate yield and 99 % selectivity were obtained under 120 °C, 2.0 MPa for 2.0 h without organic solvent. Additionally, the catalysts could be recycled easily from the products after reaction by centrifugation and then reused 5 times efficiently. Meanwhile, the catalytic activity of MAFTP/KI to other substituted epoxides was discussed. Moreover, DFT calculation was adopted to analyze the possible cycloaddition reaction mechanism. The MAFTP/KI system is a promising candidate for CO2 chemical fixation attributing to the low cost, abundant availability, easy separation and high catalytic activity for CO2 chemical fixation.

One-pot construction of highly active defective g-C3N4 via hydrogen bond of the biomass for the improvement of CO2 conversion

Graphitic carbon nitride (g-C3N4) containing conjugated tri-s-triazine units has a high abundance of amine and guanidine groups, which are ideal for the application of CO2 conversion. However, absolute g-C3N4 is inherently scarce in Lewis base sites, which leads to low catalytic activities. In this study, we present a simple and green method to in situ construct chrysanthemum stalk-derived porous carbon/ highly active defective g-C3N4 (PC/g-C3N4) through hydrogen bond, increasing the surface area and a high density of Lewis base sites. The chrysanthemum stalk contains cellulose, hemicellulose and lignin, which possess a significant number of hydroxyl functional groups and drain channels, thereby providing more hydrogen bonding for highly active defective g-C3N4. The XPS spectra revealed that, in comparison to PC/g-C3N4–1 and PC/ g-C3N4–2.5, PC/g-C3N4–2 exhibited a higher C-NH2 content at the edge of the nitrogen element. PC/g-C3N4–2 had a high specific surface area to expose more active sites for absorbing CO2. The quantification of the base sites is determined by the peak area of the thermal programmed desorption of CO2 and is 229.6 μmol/g for PC/g-C3N4–2. PC/g-C3N4–2 demonstrated excellent catalytic activity in the cycloaddition with hierarchical pores. The yield of cyclic carbonate was up to 99% with a selectivity of 99% under mild solvent-free conditions. The mechanistic studies indicate that PC/g-C3N4–2 not only captured CO2, but also provided hydrogen bonds to activate the oxygen atom of epichlorohydrin (ECH). It is our contention that the multifunctional organic-inorganic hybrid materials have considerable potential for the production of cyclic carbonate.

Pyrolysis characterization and mechanism studies of different structural plastics: A comparative study at optimal temperatures

Thermal conversion technology is an effective means to transform waste plastics into high-value-added products. This study explored the thermal decomposition characteristics and cracking mechanism of four different types of plastics (polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET)) for thermal conversion technology. The findings revealed that PP exhibited the highest hydrogen yield, reaching 3.56 mmol/g at 510°C. PET's gas production was predominantly comprised of carbon monoxide and carbon dioxide. PVC gas products contained a significant amount of HCl, followed by hydrogen and methane. For solid products, the carbon yield followed the order PET > PVC > PS > PP, with the carbon content of PET accounting for 35.63% of the total products. PP and PS demonstrated higher oil yields for liquid products than PET and PVC. The oil yield of PP was 94.38%. Further analysis of the cracking mechanism found that during the thermal decomposition process, plastics underwent random fragmentation, leading to reactions such as β-scission, intramolecular and intermolecular hydrogen transfer, rearrangement, cyclization, etc., due to structural variations. This work provided foundational data for the thermal decomposition studies of different types of plastics.

Construction of carbon nanotube-multifunctional porous ionic polymer core–shell nanocomposite for efficient conversion of carbon dioxide under co-catalyst free conditions

Metalated porous ionic polymers featuring multiple active sites show significant potential for carbon dioxide (CO2) fixation. However, general and efficient strategies to enhance their catalytic efficiency still remain to be developed. Herein, carbon nanotube-multifunctional ionic polymer core–shell composite (CNT@P(TBr-Py)-ZnBr2) was easily prepared by a solvothermal radical copolymerization strategy, followed by metallization with ZnBr2. Characterization revealed that the synthesized composite exhibited a distinct core–shell tubular nanostructure, with CNT serving as the core, and multifunctional polymer containing Lewis acid (Zn), nucleophilic Br¯ and CO2-philic triazine groups as the shell. Furthermore, the composite displayed broad pore size distribution and large average pore size. Impressively, CNT@P(TBr-Py)-ZnBr2 delivered an outstanding catalytic efficiency in the cycloaddition of CO2 to epichlorohydrin, surpassing the control catalysts poly(triazine-based vinyl ionic liquid) (PTBr), bipyridine-functionalized porous ionic polymer (P(TBr-Py), and ZnBr2 metalated P(TBr-Py) (P(TBr-Py)-ZnBr2) by factors of 5.4, 5.8, and 1.3, respectively. At 140 °C, a high turnover frequency (TOF) of 11174 h−1 and a 93.4 % yield of target cyclic carbonate were achieved in the absence of any additional co-catalyst. This exceptional catalytic performance of CNT@P(TBr-Py)-ZnBr2 can be mainly attributed to its unique core–shell structure, along with the synergistic catalytic effect of its multifunctional active sites. Also, the reaction can proceed smoothly under near-ambient conditions (30 °C, 1 bar CO2), though a longer reaction time was required. Additionally, CNT@P(TBr-Py)-ZnBr2 demonstrated a wide range of substrate compatibility and excellent recycling stability. This work therefore presents a viable approach for designing efficient and multifunctional ionic polymer-based catalysts for CO2 fixation.

Effects of iron oxide minerals on the pyrolysis of polyvinyl chloride: Catalytic dechlorination, chlorine capture, and carbon sequestration

To reduce the risk of organochlorine contamination during the pyrolysis of chlorine-containing plastics, catalytic pyrolytic dechlorination of polyvinyl chloride (PVC) by iron oxides is a promising strategy. However, differences in the structural properties of various iron oxides mineral phases may lead to different catalysis activity. In this study, various characterization methods and theoretical calculations were integrated to reveal the effects of ferrihydrite (Fhy) and hematite (Hem) on the pyrolysis characteristics of PVC at 400–800 °C. Both Fhy and Hem lower the dechlorination temperature of PVC, consequently retarding the degradation of dechlorination intermediates and mitigating the emission of volatile compounds. Fhy and Hem reduced the release of chlorinated hydrocarbons and immobilized chlorine as Rokuhnite. Specifically, the yield of HCl at 400 °C decreased from 88.8% for pure PVC to 29.9%/55.8% with the additions of 30% Fhy/Hem. The surface catalytic activity of Hem is stronger than that of Fhy, resulting in better catalytic dechlorination; while Fhy has a larger specific surface area (more adsorption sites), which leads to better chlorine fixation. Fhy and Hem also facilitated the dehydroaromatisation reaction of dechlorinated PVC, increasing the residual carbon yield at 400 °C from 45.5% to 65.4% and to 75.8%, respectively. Preferably from the perspective of pollutant emission, Fhy with large specific surface area and weak crystallinity can adsorb more HCl and catalyze dechlorination as well, so the addition of Fhy (>30%) to PVC pyrolysis process can be beneficial to the control of pollutant emission and carbon sequestration.

Application of CeO2 catalyst derived from alkaline-etched MOF-808 (Ce) for DMC synthesis from CO2

To achieve higher yields of dimethyl carbonate (DMC), it is crucial to have precise control of reaction conditions and to develop advanced catalysts with synergistic interactions at active sites. In this work, we synthesized a series of alkali-modified MOF-808 (Ce) catalysts by varying NaOH concentrations (0–1.0 M), followed by carbonation to yield the advanced catalysts—M-CeO₂-CX. Our evaluations of catalytic performance revealed that a 0.5 M NaOH alkaline environment (M-CeO₂-C0.5) was the most effective in breaking the non-covalent interactions within Ce-BTC ligands. Comprehensive characterization further confirmed that M-CeO₂-C0.5 exhibited markedly increased oxygen vacancies and higher densities of basic sites. Both of them are pivotal for enhancing CO₂ activation, leading to superior catalytic performance. Particularly, it was also applied, for the first time, in the direct synthesis of DMC from methanol and CO₂ without a dehydrating agent. Using Plackett-Burman (PB) and Box–Behnken Design (BBD) experimental techniques, we demonstrated that thermodynamic forces significantly outweighed kinetic effects in driving the reaction. Additionally, predictive yield models were developed and rigorously validated, identifying optimal conditions that resulted in a DMC yield of 24.61 mmol/g cat•h. Remarkably, the catalyst retained 97.88 % of its initial activity after 12 cycles, underscoring its exceptional stability and promising industrial scalability.

Accounting for the impact of genotype and environment on variation in leaf respiration of wheat in Mexico and Australia.

An approach to improving radiation use efficiency (RUE) in wheat is to screen for variability in rates of leaf respiration in darkness (Rdark). We used a high-throughput system to quantify variation in Rdark among a diverse range of spring wheat genotypes (301 lines) grown in two countries (Mexico and Australia) and two seasons (2017 and 2018), and in doing so quantify the relative importance of genotype (G) and environment (E) in influencing variations in leaf Rdark. Through careful design, residual (unexplained) variation represented less than 10% of the total observed. Up to a third of the variation in Rdark (and related traits) was under genetic control. This suggests opportunities for breeders to use Rdark as a novel selection tool. In addition, E accounted for more than half of the total variation in area-based rates of Rdark. Here, the day of measurement was crucial, suggesting that day-to-day variations in the environment influence rates of Rdark measured at a common temperature. Overall, this study provides new insights into the role G and E play in determining variation in rates of leaf Rdark of one of the most important cereal crops, with implications for future improvements in carbon use efficiency and yield.

Co‐feeding CO2 for Methylfuran Aromatization over Bifunctional Zeolite‐supported ZnMoO4

Aromatization of biofuran offers promising approaches for sustainable biochemical production. However, this process is often hampered by low yields and severe coking on traditional zeolite catalysts. Herein, we report co‐feeding CO2 for 2‐methylfuran (MF) aromatization (CCMA) over bifunctional ZSM‐5 supported ZnMoO4. This bifunctional catalyst can achieve both MF and CO2 conversions of >97%, generating >85% carbon yield of target arenes and CO with negligible alkenes (0.05%). Meanwhile, coke formation is remarkably suppressed from 22.3% to 8.6%. ZnMoO4/ZSM‐5 is capable of selectively manipulating the reaction intermediates and pathways of the CCMA reactions, favoring the cyclopentenones‐ and alkenes‐based dehydro‐aromatization rather than the benzofurans‐based pathway. This finding challenges the prevailing understanding that MF aromatization follows a hydrocarbon pool mechanism. Moreover, the abundant surface oxygen vacancies of ZnMoO4 facilitate the adsorption of CO2 and its subsequent reaction with coke. These insights into reaction mechanism and catalyst design for co‐conversion of CO2 and biofuran can offer guidelines for process intensification in biomass utilization with a carbon‐negative manner.

Co-Feeding CO2 for Methylfuran Aromatization over Bifunctional Zeolite-Supported ZnMoO4.

Aromatization of biofuran offers promising approaches for sustainable biochemical production. However, this process is often hampered by low yields and severe coking on traditional zeolite catalysts. Herein, we report co-feeding CO2 for 2-methylfuran (MF) aromatization (CCMA) over bifunctional ZSM-5 supported ZnMoO4. This bifunctional catalyst can achieve both MF and CO2 conversions of >97 %, generating >85 % carbon yield of target arenes and CO with negligible alkenes (0.05 %). Meanwhile, coke formation is remarkably suppressed from 22.3 % to 8.6 %. ZnMoO4/ZSM-5 is capable of selectively manipulating the reaction intermediates and pathways of the CCMA reactions, favoring the cyclopentenones- and alkenes-based dehydro-aromatization rather than the benzofurans-based pathway. This finding challenges the prevailing understanding that MF aromatization follows a hydrocarbon pool mechanism. Moreover, the abundant surface oxygen vacancies of ZnMoO4 facilitate the adsorption of CO2 and its subsequent reaction with coke. These insights into reaction mechanism and catalyst design for co-conversion of CO2 and biofuran can offer guidelines for process intensification in biomass utilization with a carbon-negative manner.

Development and Large-Scale Production of High-Oleic Acid Oil by Fermentation of Microalgae

Our classical strain improvement began with an isolate showing 28% palmitic and 60% oleic acids. UV and chemical mutagenesis enhanced our strain’s productivity, carbon yield, and oleic acid content. The iterative methodology we used involved the creation of mutant libraries followed by clonal isolation, assessments of feedstock utilization and growth, oil titer, and the validation of oil composition. Screening these libraries facilitated the identification of isolates with the ability to produce elevated levels of oleic acid, aligning with the targets for high-oleic acid substitutes. Utilizing a classical strain improvement approach, we successfully isolated a high-oleic acid strain wherein the level of oleic acid was increased from 60 to >86% of total FA. The performance of the classically improved high oleic acid-producing strain was assessed at fermentation scales ranging from 1 L to 4000 L, demonstrating the utility of our strain and process at an industrial scale. These oils offer promise in various applications across both the food and industrial sectors, with the added potential of furthering sustainability and health-conscious initiatives.

CO2-free production of hydrogen via pyrolysis of natural gas: influence of non-methane hydrocarbons on product composition, methane conversion, hydrogen yield, and carbon capture

Methane pyrolysis represents a CO2-free hydrogen production route that enables simultaneous carbon capture. While the majority of previous studies in the field focus on pure CH4 as feed gas stream, commercial processes will typically rely on natural gas as feedstock that contains also non-methane hydrocarbons such as ethane, propane, and n-butane. Therefore, the present study evaluates how CH4 conversion, H2 selectivity, product composition, and solid carbon yield evolve when using either pure CH4 or synthetic natural gas (SNG) as feed gas stream for a thermal pyrolysis process in a lab-scale high-temperature reactor. For this, industrially viable conditions are applied, namely temperatures between 1000 °C and 1600 °C, residence times between 1 s and 7 s, and molar H2 dilution ratios between 1:1 and 4:1. Although the use of SNG results in slightly lower hydrocarbon conversions because the additional components in SNG result in a higher effective H2 dilution ratio compared to a CH4-only feed, the non-methane hydrocarbons in the SNG have a positive effect on both H2 selectivity and solid carbon yield. Taking existing mechanistic understanding into account, these positive effects are attributed to radicals formed from the non-methane hydrocarbons, which facilitate dehydrogenation steps from ethane to ethylene and hereby increase the relative amount of H2 originating from CH4. The introduction of a carbonaceous fixed bed further benefits the performance of the pyrolysis process and ultimately enables to capture more than 98% of carbon in its solid form under industrially viable process conditions.

A kinetic study of nonthermal plasma pyrolysis of methane: Insights into hydrogen and carbon material production

Nonthermal plasma-assisted methane pyrolysis has emerged as a promising approach for hydrogen production under mild conditions while simultaneously yielding valuable carbon materials. Herein, we develop a plasma chemical kinetic model to elucidate the underlying reaction mechanisms involved in methane pyrolysis to hydrogen and solid carbon within a gliding arc (GA) reactor. A zero-dimensional (0D) chemical kinetics model was developed to simulate the plasma chemistry during the GA-based methane pyrolysis process, incorporating reactions involving electrons, excited species, ions, and heavy species. The model accurately predicted methane conversion and product selectivity in agreement with the experimental data. A strong correlation between hydrogen production and methane conversion was observed, primarily driven by the reaction CH4 + H → CH3 + H2, contributing 44.2% to hydrogen formation and 37.7% to methane depletion. Electron impact collisions with hydrocarbons play a secondary role, accounting for 31.1% of H2 formation. This work provides a detailed investigation into the mechanism of solid carbon formation in GA-assisted methane pyrolysis. Most of the solid carbon originates from the electron impact dissociation of C2H2 through reactions e + C2H2 → e + C2 + H2/2H and subsequent C2 condensation. C2 radicals are highlighted as the major contributors to solid carbon formation, accounting for 95.0% of the total carbon yield, which might be due to the relatively low C–H dissociation energy in C2H2. This kinetic study offers a comprehensive understanding of the mechanisms behind H2 and solid carbon formation during GA-assisted methane pyrolysis.

Direct reduction of CO2 to carbon material on liquid cathode in molten salts

This study presents a novel method for the direct reduction of CO2 to produce carbon materials on a liquid cathode in high-temperature molten salts. CO2 gases were introduced into a Sn-Li liquid alloy, and they were subsequently reduced to solid carbons by the Li in the alloy. Unreacted CO2 gases were absorbed as carbonate ions (CO32−) in molten salts containing oxide ions (O2−). Subsequently, these carbonate ions were electrochemically reduced to solid carbons on the liquid cathode surface. Consequently, the current density was five times higher than that achieved using the conventional method without bubbling CO2 into the liquid cathode. The enhanced current density can be attributed to the combined thermochemical reduction of CO2 by Li and the electrochemical reduction of CO32−. This combination was realized for the first time at a relatively positive potential range, where pure Li or Ca cannot be deposited, leading to the carbon yield of over 90 % relative to CO2 feed reached. The resulting carbons contained a trace amount of Sn, which could be removed by washing after milling. These results show the potential for efficient and sustainable carbon capture and conversion technologies using liquid cathodes in high-temperature molten salts for CO2 reduction.