Molten Carbonate Electrolysis Research Articles

Recycling of Waste Secondary Battery Materials to Recovery of Lithium Carbonate By Using Eco-Friendly Pyro-Metallurgical Electrolysis Process

Recently, many types of vehicles that has been used fossil fuels energy are being replaced with EVs (Electric Vehicles) uses electrical energy. Since secondary batteries that use as the main power device of electric vehicles have a constant lifespan of 7 to 8 years, accordingly, many operating countries are constructing various plans and policies to handle with this issue. Various valuable rare metals such as nickel, cobalt, lithium, and manganese that all has limited resource, are contained in the wasted cathode material, and it could be used as a useful high-quality source if those materials can be recovered in recycle process. Thus, in this study, recover existing resources from waste cathode materials through the eco-friendly Molten Carbonate Electrolysis (MCE) process was performed. Through the process, the lithium, the main recovery target element could be recovered in the form of a compound as lithium carbonate while valuable metals such as nickel and manganese were separated and precipitated. Even though this process does not require any of acidic or organic solvent, it showed high recovery results with more environmentally friendly than the commercial hydrometallurgical recovery method while the sequence was also relatively simple. Various analysis was performed in Xray diffraction, X-ray fluorescence and FE-SEM to confirming characteristics status in recovered lithium carbonate and other precipitated powder, and thermodynamical calculation was accompanied by HSC chemistry to estimate the proper process conditions and electrode materials. In addition, through electrochemical analysis such as chronoamperometry (CA) and cyclic-voltammetry (CV), the correlation between electrode reaction tendency and lithium compound recovery rate was identified.

Buckypaper made with carbon nanotubes derived from CO2.

Unusual buckypapers, sheets of graphene nanocarbons (GNCs) such as carbon nanotubes, were formed with GNCs directly derived from CO2 via molten carbonate electrolysis. Examples are presented for buckypapers made from CO2 using either crushed or chemically washed GNCs, epoxy-infused CNTs, or GNCs pressed directly using a hot electrolyte to remove excess electrolyte.

Structure and dynamics of Li1.24K0.76CO3 molten carbonate electrolyte from molecular simulations with explicit polarization.

Molten carbonate electrolysis cells represent a key technology for harnessing surplus energy from renewable sources and converting it into gaseous energy carriers. To optimize their efficiency, a comprehensive understanding of each step in the operational process is essential. Here, we focus on the electrolyte of choice in molten carbonate cells: the Li1.24K0.76CO3 melt. Utilizing molecular dynamics with explicit polarization, we demonstrate that the structure of this molten mixture is characterized by a dense network of lithium-carbonate complexes, with K+ ions loosely embedded within this network. This structural insight enables us to rationalize from an atomistic perspective the conductivity trends observed experimentally in molten carbonates. Moreover, our work highlights the importance of including polarization for the simulations of dense liquid carbonates. It also acts as a foundational step towards more advanced theoretical studies for elucidating the role of the electrolyte in these devices.

Dynamic exploration of a 1 MW molten carbonate electrolyzer: A modeling study approach

The reversible use of a commercially available molten carbonate fuel cell (MCFC) as a molten carbonate electrolysis cell (MCEC) is an appealing prospect for both storing surplus renewable energy and converting CO2 into valuable syngas (H2 and CO). This work aims to explore the dynamic aspects of this type of electrolyzer. The study investigates the dynamic behavior of the MCEC, involving dynamic model development, degradation analysis, and cold start-up evaluation. The findings revealed that cell degradation results in a 0.8 % decrease in H2 and a 1.5 % decrease in CO at a 1 % degradation rate, rising to 7.9 % H2 and 14.3 % CO decrease at a 10 % degradation rate, necessitating an increase in the current to maintain the same production. Additionally, the study identifies the most energy-efficient cold start-up heating process for the MCEC. These insights emphasize the importance of addressing degradation issues and optimizing start-up procedures for real-world applications.

Enhancing performance of molten carbonate electrolysis cell via deposition of gold nanoparticles on anode

The power-to-gas method utilizing electrolysis has attracted attention for ecofriendly and efficient energy storage. The use of a molten carbonate electrolysis cell (MCEC) allows the production of a large amount of hydrogen using carbonate electrolytes. However, compared with conventional fossil-fuel-based production methods, the use of MCECs involves higher costs and a lower efficiency, necessitating the exploration of strategies to improve MCECs performance. To this end, herein, an AuNP-deposited anode is proposed for improving the performance of MCECs. Au nanoparticles (AuNPs) can enhance the oxygen evolution reaction (OER) activity, increase the reaction surface area, and increase the electrical conductivity of the anode. Additionally, because of their oxygen molecule desorption properties, AuNPs are suitable anode catalyst materials for MCECs. By depositing AuNPs on the anode, the conductivity was increased, reducing the Ohmic resistance, and the charge transfer resistance and mass transfer resistance due to the characteristics of the OER and oxygen gas desorption were significantly reduced.

Conversion of CO2‐Derived Amorphous Carbon into Flash Graphene Additives

AbstractCO2 emissions have become a significant environmental problem over the last few decades, often stemming from combustion of fossil fuels. Production and disposal of waste plastic also contribute greatly to greenhouse gas emissions, due to combustion of fossil fuels during manufacture and incineration or pyrolysis of the waste materials. Hence, researchers have begun developing technologies geared toward the capture, sequestration, and utilization of CO2. Several methods are shown to be useful for conversion of gaseous CO2 into solid carbon feedstocks, such as molten carbonate electrolysis. At the same time, flash Joule heating can rapidly and inexpensively convert carbon‐rich feedstocks into flash graphene (FG). Here, amorphous carbon derived from molten carbonate electrolysis of carbon dioxide is converted into FG, sometimes in combination with waste plastic, and demonstrated for use as a reinforcing additive in composite applications. FG can be used in epoxy and vinyl ester resins with a maximum increase in Young's modulus and hardness of 73% and 73%, respectively. Life cycle assessment also shows that adding 5 wt% 25:75 amorphous carbon‐derived FG to the epoxy results in 7.7%, 5%, and 2.7% decreases in CO2 emissions, water consumption, and energy consumption, respectively.

Effect of temperature on the electrode overpotential of molten carbonate electrolysis and fuel cells with inert-gas step addition method

This study explores molten carbonate electrolysis and fuel cell behaviour across temperatures from 823 to 973 K using steady-state polarization (SSP), electrochemical impedance spectroscopy (EIS), and inert-gas step addition (ISA) techniques. The findings reveal that total voltage loss decreases with rising temperature in fuel cell (FC) and electrolysis (EC) modes. The ohmic loss similarly declines as temperature increases. The ISA method determines the gas-phase mass transfer-induced overpotential, which increases as temperature increases in both modes at the hydrogen electrode (HE). This indicates that pore diffusion resistance strongly affects the HE in both modes. The liquid-phase mass transfer-induced overpotential at the oxygen electrode (OE) exhibits a much smaller value in EC mode than in FC mode at all temperatures. The increased O2 and CO2 partial pressures and decomposition of sufficient amounts of carbonate electrolytes to generate O2 in EC mode would reduce the liquid-phase resistance and its induced overpotential at the OE in the temperature range.

CO2-Rich Gas Conversion to Carbon Nanotube via Molten Salt Electrolysis

The CO2 capture via electrolysis process is a potentially promising and attractive pathway for greenhouse gas removal and global warming reduction by converting CO2 into value-added materials. In this study, the conversion of CO2 from CO2-rich gas into value-added carbon nanomaterial was successfully achieved via molten Li2CO3 electrolysis with a NiCr anode and a stainless steel cathode. The characterization by FESEM and TEM analyses showed that the obtained carbon product was a carbon nanotube with a bamboo-like structure and an outer average diameter of 36 nm. The EDS and XRD characterization indicated the growth of carbon nanotube in electrolysis was achieved through metal nucleation points on the electrolysis cathode. In addition, the Raman analysis showed that the carbon product exhibited high quality and crystallinity. The results from the present study revealed that the molten carbonate electrolysis offered a viable approach for direct transformation of CO2 from industrial flue gas into valuable carbon product, providing an alternative solution to reduce CO2 emissions.

Electrolyte engineering for efficient molten-carbonate electrolysis of CO2

Molten carbonate electrolysis cells (MCEC) are a promising electrochemical CO2 capture and conversion process. However, the CO2 absorption and energy efficiencies are limited by the sluggish CO2 absorption kinetics and high electrode overpotentials. Herein, we propose an electrolyte engineering strategy to improve the CO2 absorption rate and reduce overpotentials at both the anode and the cathode. When BO33− was added into molten Li2CO3-Na2CO3-K2CO3, the CO2 adsorption efficiency was improved from 3.3% to 60%, the overpotential was reduced by ∼ 567 mV at the cathode and by ∼ 238 mV at the anode under 200 mA cm−2. Accordingly, the energy efficiency reached 76.2 % at 650 °C. The improved CO2 absorption and energy efficiencies are thanks to the BO33− that changes the thermodynamic properties of the molten carbonate, i.e., the BO33−–CO32− complex reduces the energy barrier for the reduction of CO32− at the cathode and for the liberation of O2− that can be oxidized at a lower potential than CO32− at the anode. Therefore, the electrolyte engineering is an effective strategy for designing high-temperature CO2 electrolyzers with high CO2 absorption and energy efficiency.

Liquid Metal–CO2 Battery Bridged Intermittent Energy Conversion and O2 Production in the Martian Atmosphere

Oxygen and fuels are requisites for outer space exploration. Herein, we use a liquid Na–Sn cathode and a Ni-based inert anode to convert CO2 into Na–Sn and oxygen in molten Na2CO3–NaCl by electrolysis, aiming to produce oxygen and store solar energy in liquid Na–Sn when the sun shines. In the same Na2CO3–NaCl electrolyte, the liquid Na–Sn serves as a negative electrode coupled with a porous FeNi positive electrode that allows the reduction of CO2 to CO in a primary cell, converting chemical energy stored in Na–Sn into electricity and CO that is a valuable fuel when the sun does not shine. This system has an overall energy efficiency of 51.0% at 100 mA cm–2. Therefore, the molten carbonate electrolysis device equipped with a liquid metal electrode could be applied for producing O2 and storing solar energy in energetic chemicals (e.g., Na–Sn, CO), which could be applied for outer space exploration such as Mars.

Improving bio aviation fuel yield from biogenic carbon sources through electrolysis assisted chemical looping gasification

The second-generation bio aviation fuel production via Chemical Looping Gasification (CLG) of biomass combined with downstream Fischer-Tropsch synthesis is a possible way to decarbonize the aviation sector. Although CLG has a higher syngas yield and conversion efficiency compared to the conventional gasification processes, the fraction of biogenic carbon which is converted to biofuel is still low (around 28%). To increase carbon utilization and biofuel yield, incorporation of two types of electrolyzers, Polymer Electrolyte Membrane (PEM) and Molten Carbonate Electrolysis Cell (MCEC), for syngas conditioning has been investigated. Full chain process models have been developed using an experimentally validated CLG model in Aspen Plus for Iron sand as an oxygen carrier. Techno-economic parameters were calculated and compared for different cases. The results show that syngas conditioning with sustainable hydrogen from PEM and MCEC electrolyzers results in up to 11.5% higher conversion efficiency and up to 8.1 % higher biogenic carbon efficiencies in comparison to the syngas conditioning with water gas shift reactor. The study shows that the lowest carbon capture rates are found in the configurations with the highest biogenic carbon efficiency which means up to 14% more carbon ends up in FT crude compared to the case with conventional WGS conditioning. Techno-economic analysis indicates that syngas conditioning using PEM and MCEC electrolyzers would result in an increase of the annual profit by a factor of 1.4 and 1.7, respectively, when compared to using only WGS reactors.

Production of synthetic gas by the co-electrolysis of H2O and CO2 in the molten carbonate electrolyzer

The reversible operation of a commercialized molten carbonate fuel cell as an electrolyzer is attractive to store the surplus of renewable energy and convert CO2 into valuable fuel, like syngas (H2 and CO). This work aims to assess this capability by developing a model for the co-electrolysis of CO2 and H2O in the molten carbonate electrolysis cell (MCEC). Furthermore, a 1 MW power-to-gas system is simulated and optimized to maximize the process efficiency via a profound sensitivity analysis and a pinch heat integration analysis. The study's results reveal that when CO2 electrolysis occurs, there is a risk of reaching the limiting current density at lower values, thus affecting the cell's performance. As for the simulation, the process yields an efficiency of 68.87% with an electrolyzer's power density of 0.082 W/cm2 per cell, producing 1.3 tons/day of methane gas ready for injection into the natural gas network.

Unraveling the role of substrate materials in governing the carbon/carbide growth of molten carbonate electrolysis of CO2.

The interface interaction between deposited carbon and metallic electrode substrates in tuning the growth of CO2-derived products (e.g., amorphous carbon, graphite, carbide) is mostly unexplored for the high-temperature molten-salt electrolysis of CO2. Herein, the carbon deposition on different transition-metal cathodes was performed to reveal the role of substrate materials in the growth of cathodic products. At the initial stage of electrolysis, transition metals (e.g., Cr, Fe, Ni, and Co) that exhibit appropriate carbon-binding ability (in range of -30 to 60 kJ mol-1) allow carbon diffusing into and then dissociating from metal to form graphite, as the carbon-binding ability can be determined by the Gibbs free energy of formation of metallic carbides. The catalytic cathodes showing super strong (e.g., Ti, V, Mo, and W) or weak (e.g., Cu) carbon-binding ability produce stable carbides or amorphous carbon, respectively. However, the subsequent deposited carbon is immune to the catalysis of the substrate, forming amorphous carbon nanoparticles and nanofibers on the surface of carbides and graphite, respectively. This paper not only highlights the role of the catalytic cathodes for carbon deposition, but also offers a material selection principle for the controllable growth of CO2-derived products in molten salts.

CO2 Capture and Purification for Use in the Molten Carbonate Electrolysis Cell

CO2 Capture and Purification for Use in the Molten Carbonate Electrolysis Cell

Regulating electrolyte basicity via CaCO3 additives for enhanced corrosion resistance of Ni anodes in low-temperature molten carbonate

Electrochemical reduction of CO2 in molten carbonate at low temperatures (< 500 °C) is restricted by the instability of Ni anodes. Herein, we revealed that the corrosion of Ni anodes in low-temperature molten carbonates was induced by the decrease in local basicity of anode/electrolyte interface during electrolysis. Thus, CaCO3 was used as an additive to increase electrolyte basicity and modulate the anode/electrolyte interface. The addition of CaCO3 significantly reduced the solubility of NiO scale in molten carbonate and enhanced the corrosion resistance of Ni at 475 °C, thereby making Ni as a suitable inert anode for low-temperature molten carbonate electrolysis.

Electrolysis Assisted Biomass Gasification for Liquid Fuels Production

Gasification is a promising pathway for converting biomass residues into renewable transportation fuels and chemicals needed to comply with the ambitious Swedish environmental targets. The paper investigates the integration of a molten carbonate electrolysis cell (MCEC) in biofuel production pathway from sawmill byproducts, to improve the performance of gas cleaning and conditioning steps prior to the final conversion of syngas into liquid biofuels. The energy, material, and economic performance of process configurations with different gasification technologies are simulated and compared. The results provide relevant information to develop the engineering of gas-to-liquid transportation fuels utilizing renewable electricity. The MCEC replaces the water-gas shift step of a conventional syngas conditioning process and enables increased product throughput by as much as 15%–31%. Depending on the process configuration and steam-methane reforming technology, biofuels can be produced to the cost range 140–155 €/MWh in the short-term.

Local Basicity Dependent Gas-Liquid Interfacial Corrosion of Nickel Anode and Its Protection in Molten Li2CO3-Na2CO3-K2CO3

Revealing the gas-liquid interfacial corrosion mechanism of metals under anodic polarization in molten salts is crucial for the development of metallic anodes for molten carbonate electrolysis. Herein, the effects of operating temperature, gas atmosphere, applied current density and electrolysis time on the gas-liquid interfacial corrosion behaviors of nickel anodes in molten Li2CO3-Na2CO3-K2CO3 were systematically investigated. It was found that the gas-liquid interfacial corrosion of nickel anodes was accelerated with decreasing temperature and increasing CO2 content of gas atmosphere. Three distinct corrosion regions of nickel anodes can be identified: (I) the thin salt film region, (II) the meniscus region, and (III) the full immersion region. It was revealed that the formation of negative basicity gradient in the meniscus induced the dissolution/re-precipitation of NiO scale, thereby accelerating the gas-liquid interfacial corrosion of nickel anodes. Furthermore, an Al2O3 sheath was applied to shield the gas-liquid part of nickel electrodes to prevent gas-liquid interfacial corrosion, thus making Ni a stable oxygen-evolution inert anode.

Investigation of molten carbonate electrolysis cells performance for H2 production and CO2 capture

Molten carbonate electrolysis cells have recently gained interest for the sustainable production of H2 or syngas to substitute fossil fuels. However, they can be also used for CO2 sequestration, as they pump it from one electrode inlet to the opposite electrode outlet. Thus, they can easily be applied to segregation of CO2 from H2 based fuels while also increasing the fuel heat of combustion for example after a steam reforming reactor.To explore the use of molten carbonate electrolysis cell for this application, in this work the authors investigate the performance of the cell under different operating conditions in term of both operating temperature and fuel electrode gas composition. Polarization curves, gas crossover and electrochemical impedance spectroscopy are used to evaluate specific issues (high electrolyte losses due to water and temperature) or benefits (excess of H2O in regard to CO2 that allows for higher CO2 capture rate). After, a series of long-term tests at −150 mA cm−2 and 650 °C are performed to demonstrate long term stability. In particular, before electrolyte loss made the performance unstable, different cells are operated for about 1000 h with an average voltage of about 1.14 V demonstrating also the repeatability of such tests.

Controlled Growth of Unusual Nanocarbon Allotropes by Molten Electrolysis of CO2

This study describes a world of new carbon “fullerene” allotropes that may be synthesized by molten carbonate electrolysis using greenhouse CO2 as the reactant. Beyond the world of conventional diamond, graphite and buckyballs, a vast array of unique nanocarbon structures exist. Until recently, CO2 was thought to be unreactive. Here, we show that CO2 can be transformed into distinct nano-bamboo, nano-pearl, nano-dragon, solid and hollow nano-onion, nano-tree, nano-rod, nano-belt and nano-flower morphologies of carbon. The capability to produce these allotropes at high purity by a straightforward electrolysis, analogous to aluminum production splitting of aluminum oxide, but instead nanocarbon production by splitting CO2, opens an array of inexpensive unique materials with exciting new high strength, electrical and thermal conductivity, flexibility, charge storage, lubricant and robustness properties. Commercial production technology of nanocarbons had been chemical vapor deposition, which is ten-fold more expensive, generally requires metallo-organics reactants and has a highly carbon-positive rather than carbon-negative footprint. Different nanocarbon structures were prepared electrochemically by variation of anode and cathode composition and architecture, electrolyte composition, pre-electrolysis processing and current ramping and current density. Individual allotrope structures and initial growth mechanisms are explored by SEM, TEM, HAADF EDX, XRD and Raman spectroscopy.

Oxidation behavior of H2 and CO produced by H2O and/or CO2 reduction in molten carbonates: Effect of gas environment and hydroxides

Co-electrolysis of water and carbon dioxide in molten carbonates is nowadays a key issue in MCEC (molten carbonate electrolysis cell) and, reversely, for a better understanding of MCFC (molten carbonate fuel cell). The products of water and carbon dioxide reduction are the fuels that might be used in MCFC or other energy devices. The present study is dedicated to a thorough electrochemical investigation by voltammetric techniques (Cyclic Voltammetry CV or Linear Sweep Voltammetry LSV) at a Pt electrode of such fuels in Li2CO3-K2CO3 eutectic, under varied atmosphere conditions, including partial pressures of H2O, CO2, H2 and Ar at 650°C. The conditions of formation of soluble and/or adsorbed H2 and CO are established together with qualitative thermodynamics information on the redox systems involved. C is only detected in very specific conditions. Knowing that hydroxides, produced in the conditions of MCEC and MCFC, have a significant role on the operation of such devices, an electrochemical analysis (CV and impedance measurements) of the effect of added amounts of hydroxides is developed for the first time, showing the enhancement of oxidation currents and the progressive increase in electrolyte conductivity.