Direct Carbon Fuel Cell Research Articles

Numerical Modeling of Electrolyte-Supported Button Solid Oxide Direct Carbon Fuel Cell Based on Boudouard Reaction

Numerical Modeling of Electrolyte-Supported Button Solid Oxide Direct Carbon Fuel Cell Based on Boudouard Reaction

Modeling of Fluidized Bed Molten Carbonate Direct Carbon Fuel Cell: Effect of Reverse Boudouard Reaction

Direct carbon fuel cells (DCFCs) are an alternative technology to coal-fired power plants for converting the chemical energy of abundant carbon-rich fuel into electrical energy. DCFCs have higher electrical efficiency and lower greenhouse emissions, which are easier to separate and capture. In the transition to renewable sources of energy, efficient and low-emission technologies need to be explored. Since DCFC technologies are in their early stages of development, modeling and simulation studies are needed to reduce costs and aid in experimental design. In this study, an electrochemical and transport model for a fluidized bed molten carbonate DCFC (FBMCDCFC) is developed. The performance of the fuel cell is evaluated through the polarization losses. This study expounds on recent developments in DCFCs by considering the effect of the reverse Boudouard reaction and the 2-electron oxidation of CO alongside the 4-electron oxidation of carbon at higher temperatures. The electrolyte used is a 62 : 38 mol % Li2CO3/K2CO3 eutectic mixture, while the fuel is activated carbon impregnated by HNO3. The results show that the greatest polarization losses for the FBMCDCFC are from anode activation overpotential and ohmic overpotential. The cathode activation and concentration overpotentials are relatively small. Increasing the reaction temperature results in a greater decrease in anode activation overpotential than ohmic overpotential, despite the increase in CO formation from the reverse Boudouard reaction. The peak power density of the FBMCDCFC is 434.437 W m-2 when operated at 923 K and a gas flow rate of 30 mL min-1. The peak power density of the FBMCDCFC is greater with higher temperatures, where the peak increases to 584.802 W m-2 when operated at 1023 K. The peak power density is greater with lower gas flow rates, where the peak increases to 458.175 W m-2 at a gas flow rate of 25 mL min-1. The mathematical model can aid in optimizing the performance of FBMCDCFCs, such as how increasing the operating temperature favorably increases anode reaction kinetics and reduces ohmic resistances in the cell. Future work will focus on improving the model correlations to close the gap between the results of modeling and actual experiments.Figure 1. a) Power curves at different temperatures, 823 K to 1323 K (30 mL min-1 flow rate, 1 atm total pressure); b) Power curves at different gas (O2 and CO2) flow rates (923 K, 1 atm total pressure) Figure 1

Thermodynamic performance evaluation and optimization of a hybrid system integrating vacuum graphene-anode thermionic converters with direct carbon fuel cells

An efficient hybrid system integrating a direct carbon fuel cell (DCFC) with a vacuum graphene-anode thermionic converter (VGTC) is proposed for cogeneration. The VGTC efficiently recycles waste heat released from the DCFC and generate additional electricity, significantly improving energy utilization efficiency and economic performance. A comprehensive mathematical model is developed to quantitatively assess the thermodynamic performance of the hybrid system, taking into account the overpotential losses of the DCFC and the irreversible energy losses occurring within the system. The results show that at an operating temperature of 923 K, the hybrid system can achieve a maximum power density of 466 W/m2, which is approximately 1.34 times that of a single DCFC, indicating a significant improvement in output performance. Besides, the optimal operating region and parameter selection criteria for the hybrid system are determined using finite-time thermodynamic optimization theory. Furthermore, the effects of essential parameters on the output performance of the hybrid system, such as the operating temperature of the DCFC, the heat transfer coefficient, the Fermi level of graphene, the work function of the cathode, the thermal emissivity, and the reflectivity of the back mirror, are investigated. Finally, the comparative study shows that the proposed hybrid system outperforms other previously reported hybrid systems regarding output electric power and conversion efficiency due to the efficient high-grade waste heat recovery and energy conversion by the VGTC.

Artificial Intelligence for Electrochemical Prediction and Optimization of Direct Carbon Fuel Cells Fueled with Biochar

At present, direct carbon fuel cells constitute an emerging energy technology that electrochemically converts solid carbon to electricity with high efficiency. The recent trend of DCFCs fueled with biochar from biomass carbonization as green fuel has reinforced the environmental benefits of DCFCs as a clean and sustainable technology. However, there remain new challenges related to some complex unknown kinetic parameters, X=(αa,αc,σg,i0,a,i0,c,ilO2,ilCO2,c,ilCO2,a,ilCO), of the electrochemical conversion of biochar in DCFCs and there is a need for intelligent techniques for prediction and optimization, refering to the available experimental data. The differential evolution (DE) algorithm, which ranked as one of the top performers in optimization competitions with competitive accuracy and convergence speed, was used here for providing the optimized values of these parameters by minimizing the root mean squared errors (RMSE). The proposed technique was then applied to DCFCs fueled by activated pure carbon (APC) using CO2 and CO/CO2 electrochemical models with RMSE around 10−2 and 10−3, respectively. Then, the CO/CO2 model was applied to a DCFC fueled with almond shell biochar (ASB), which displayed a slight increase in RMSE (of the order of 10−2) due to the complex porous structure of ASB and the content of additional chemical elements that affect the electrochemistry of the DCFC and are not considered in the model.

Performance Improvement of a Direct Carbon Fuel Cell through an Irreversible Vacuum Thermionic Generator

A novel hybrid system consisting of a direct carbon fuel cell (DCFC), a thermionic generator (TIG), and a regenerator is developed to recover the exhaust heat from the fuel cell. Expressions for the power output and efficiency of subsystems and the hybrid system are derived. Based on the energy balance equation, the area matching problem between the DCFC and the TIG is discussed and solved. By considering the main irreversibilities, the influences of the DCFC’s current density and the TIG’s voltage on the performance of the hybrid system are revealed. The maximum power output density and the corresponding efficiency of the hybrid system are, respectively, equal to 379 W/m2 and 36%. To enhance the maximum power density of the single DCFC, the optimal regions of the main parameters are determined.

Utilization of Organic Waste in a Direct Carbon Fuel Cell for Sustainable Electricity Generation

There is much organic waste that comes from by-products of agriculture and product processing, solid waste from livestock, and municipal waste. Conventional methods that are widely used for the treatment and management of organic fractions of waste are landfilling, composting, anaerobic digestion, incineration, gasification, and pyrolysis. Among the above methods, pyrolysis is a relatively simple, robust, and scalable technology for transforming diverse organic waste feedstock into renewable energy products. Recently, the electrochemical conversion of biochar into electricity in direct carbon fuel cells (DCFC) has also been investigated and shown to be feasible and highly efficient. This paper focuses on the utilization of organic waste as a fuel and the investigation of their characteristics during electrochemical reactions in molten hydroxide direct carbon fuel cells (MH-DCFCs). Organic waste of different origins (the food-processing industry, urban and suburban areas, municipal solid organic waste, sewage sludge) with diversified characteristics was used as the main feedstock. The lowest power density was determined for sewage sludge (5.1 mW cm−2), and the best results were obtained for peanut shells (53.14 mW cm−2). This study concludes that higher elemental carbon, lower ash content and the presence of reactive surface oxygen functional groups in biochar obtained from organic waste might contribute to better cell performance. Moreover, the research establishes the potential of carbonized organic waste as a prospective alternative fuel source for power generation in an MH-DCFC.

A novel integration of plasma gasification melting process with direct carbon fuel cell

As municipal solid waste (MSW) is a low-cost, available, and basically renewable source, energy recovery from MSW is a beneficial technique for reducing fossil fuel usage while also lowering MSW disposal challenges. The current study proposes a novel scheme consisting of plasma gasification melting (PGM) process and direct carbon fuel cell (DCFC) system for converting MSW into high-quality syngas and power. Plasma air and high-temperature steam are employed in the process as gasification agents. The DCFC runs on the pyrolysis char, which is a carbon-rich source and is extracted during the PGM process and sent to the DCFC. The process is simulated in Aspen Plus, and a computational model for estimating the DCFC's output voltage and power is developed in MATLAB. Effects of main operating parameters, including equivalence ratio, steam to biomass ratio, plasma energy ratio, char separation fraction, and fuel cell operating temperature on the system's performance indicators, namely syngas composition, syngas lower heating value, syngas yield, gasification temperature, overall efficiency, and DCFC power output were investigated. By increasing the char separation fraction, more pyrolysis char was extracted and forwarded to the DCFC, which leads to less amount of char entering the gasification section and higher power output through the DCFC. Keeping other parameters constant, at a fuel cell operating temperature of 923 K, the optimal value for char extraction fraction was 0.15, resulting in a 79.5% overall efficiency.

Investigation of the Abnormal I-V Curve Shape of Hybrid Direct Carbon Fuel Cell Using Lanthanum Strontium Calcium Titanate-Based Anode

Solid oxide direct carbon fuel cell are being developed for use with waste derived materials. To avoid problems of the state-of-art Ni/YSZ anode, perovskite-based anode materials are being investigated. We have fabricated solid oxide fuel cells with La0.2Sr0.25Ca0.45MxTi1-xO3- δ (M=Ni, Fe, or Co) anodes, YSZ electrolyte, and LSM cathode. Electrochemical performance of these cells have been evaluated with both hydrogen and solid carbon as the fuel and promising results have been recorded. For example, fuel cells with La0.2Sr0.25Ca0.45Ni0.05Ti0.95O3- δ anode tested in hybrid direct carbon fuel cell mode reached a maxmium power density of 82.3 mW/cm2 measured in N2 purging gas at 850 °C. During hybrid direct carbon fuel cell testing with solid carbon fuel and nitrogen purging gas, I-V curves obtained showed an abnormal shape between 0.6V to 0.7 V. To investigate the origin of this line shape, we have used methods such as electrochemical impedance spectroscopy, potentiostatic study, analyzing of off gases from fuel cell using gas choromotography, SEM imaging, EDS analysis and Raman mapping of the tested fuel cell. These results can not only help explain the observed shape of I-V curve, but also provide insight into the mechanism of hybrid direct carbon fuel cells, thus benefiting further development of fuel cells for solid waste to energy applications.

Exhaust Gas Composition of Lignin Reactions in Molten Carbonate Salt of Direct Carbon Fuel Cell Using FactSage

Abstract The most studied molten carbonate-direct lignin fuel cell (MC-LFC) or molten carbonate-direct carbon fuel cell (MC-DCFC) prototypes are those which are fed by fossil fuel. Substituting these fossilized fuels in the MC-DCFC operation with lignin, which is a bio-based carbon, may make this system more efficient, clean, and sustainable. The manipulation module (Mixture) and the computational module (Equilib) of the FactSage package were used to simulate two systems that can represent the anodic compartment of a direct carbon fuel cell based on MC-DCFC. The first system includes lignin and a mixture of molten carbonate (Li2CO3-Na2CO3-Cs2CO3). The second system uses also lignin and a mixture of molten carbonate (Li2CO3-Na2CO3-Cs2CO3) and CO2 gas was also added. The results show the formation of mixed gases in the anodic compartment which are composed of H2, CO, CO2, CH4, and H2O. The relative concentration of each of the species of this mixed gas has an impact on the efficiency of the MC-DCFC. How the relative concentration of these gases in this electrolyte can impact the performance parameters of the MC-DCFC is systematically analyzed. If the operating conditions of the fuel cell are optimized to get a gas composition of mainly CO2 with low amounts of H2, CO, CH4, and H2O in the anode compartment of the MC-DCFC, this will help to improve the conversion efficiency of lignin fuel in the MC-DCFC.

Investigation of the Abnormal I-V Curve Shape of Hybrid Direct Carbon Fuel Cell Using Lanthanum Strontium Calcium Titanate-Based Anode

Solid oxide direct carbon fuel cells are being developed for use with waste derived materials. We have fabricated solid oxide fuel cells with La0.2Sr0.25Ca0.45MxTi1-xO3-δ (M=Ni, Fe, or Co) anodes, YSZ electrolyte, and LSM cathode. Electrochemical performance of these cells has been evaluated with solid carbon as the fuel and promising results have been recorded. For example, fuel cells with La0.2Sr0.25Ca0.45Ni0.05Ti0.95O3-δ anode tested in hybrid direct carbon fuel cell mode reached a maximum power density of 82.3 mW/cm2 measured in N2 purging gas at 850 °C. During hybrid direct carbon fuel cell testing with solid carbon fuel and nitrogen purging gas, I-V curves obtained showed an abnormal shape between 0.6V and 0.7 V. To investigate the origin of this line shape, we have used methods such as electrochemical impedance spectroscopy, potentiostatic study, and analysis of off gases from fuel cell using gas chromatography.

Valorization of Exhausted Olive Pomace for the Production of a Fuel for Direct Carbon Fuel Cell

In this study, exhausted olive pomace (EOP) biochar prepared by carbonization at 400 °C is investigated as a fuel in a direct carbon fuel cell (DCFC) with an electrolyte-supported configuration. The feasibility of using the EOP biochar in the DCFC is confirmed, showing a maximum power density of 10 mW·cm−2 at 700 °C. This limited DCFC performance is compared with other biochars prepared under similar conditions and interrelated with various biochar physico-chemical characteristics, as well as their impact on the DCFC’s chemical and electrochemical reaction mechanisms. A high ash content (21.55%) and a low volatile matter (40.62%) content of the EOP biochar are among the main causes of the DCFC’s limited output. Silica is the major impurity in the EOP biochar ash, which explains the limited cell performance as it causes low reactivity and limited electrical conductivity because of its non-crystal structure. The relatively poor DCFC performance when fueled by the EOP biochar can be overcome by further pre- and post-treatment of this renewable fuel.

Modification of carbon black fuel to improve the performance of a direct carbon fuel cell

Developers of direct carbon fuel cell (DCFC) technology seek to convert carbon to a pure or highly concentrated carbon dioxide stream that could ultimately be transported and sequestered. Carbon black produced by natural gas cracking processes is very pure and is therefore a candidate for use in DCFCs. In this study the performance of As received and Treated carbon blacks are compared in a planar cell configuration. At a more viable operating temperature of 750 °C, the As received carbon was found to produce a peak power density of 51 mW/cm2 at a current density of 104 mA/cm2. The performance then increased to 105 mW/cm2 at a current density of 145 mA/cm2 at 850 °C. Acid treatment of the carbon was found to improve performance of the DCFC at 750 °C by 35% (69 mW/cm2 at 160 mA/cm2) and only by 5% at 850 °C (111 mW/cm2 at 201 mA/cm2).

Effect of Ionic Mass Transport on the Performance of a Novel Tubular Direct Carbon Fuel Cell for the Maximal Use of a Carbon-Filled Porous Anode.

Despite a large number of existing studies about direct carbon fuel cells (DCFCs), sufficient power generation has remained a major technical challenge for the commercialization of DCFCs. This study was designed to implement the benefits of a carbon-filled porous anode developed in our recent studies in a unit cell. First, we developed a new tubular cell assembly comprising an anode, a thin matrix, and a tubular cathode with a certain number of holes in its surface. By employing a reference electrode, we measured the resistance and I–V–P characteristics of the anode, a cathode with a single hole, and the entire cell. As a result, we found that the cathode performance was degraded by resistance to ionic mass transfer, while the anode resistance was invariant (∼0.4 Ω cm2). By developing a semi-empirical current–potential model including an ion mass transport effect, we proved that the number of holes in the cathode surface is the key to the maximal utilization of the present anode. This eventually led to notable gains in the maximum power density to 205 mW cm–2 at 700 °C in experiments. Lastly, a durability test was conducted to reconfirm the effect of ionic mass transfer on the power generation over time.

Strong Metal-Support Interactions of Ni-CeO2 Effectively Improve the Performance of a Molten Hydroxide Direct Carbon Fuel Cell.

A strong metal–support interaction (SMSI) type catalyst has been synthesized and applied to a molten hydroxide direct carbon fuel cell (MHDCFC) to enhance the reaction activity of the anode carbon fuel through the interaction between the metal Ni and the support CeO2. Two catalysts have been prepared by a direct precipitation method (denoted NiO@CeO2) and a hydrothermal method (denoted NiO-CeO2), which are reduced by H2 to obtain Ni@CeO2 and Ni-CeO2, respectively. X-ray photoelectron spectroscopy (XPS), Raman, and temperature-programmed hydrogen reduction (H2-TPR) analysis results show that there are obvious oxygen vacancies and a Ni-O-Ce interface structure in NiO-CeO2 and Ni-CeO2, which is induced by the interaction between Ni and CeO2. The calculation results of current density and power density show that the performance of the MHDCFC is significantly improved in the presence of Ni-CeO2. The function fitting curves of the logarithm of the reaction rate constant (ln k) and the reciprocal of the temperature (1/T) show that the slope of the curve is decreased significantly after the addition of Ni-CeO2. In combination with density functional theory (DFT), the anode carbon reaction path is simulated in the MHDCFC, and the calculation results show that the reaction energy for the anodic carbon to generate carbon dioxide is decreased by 1.03 eV in the presence of Ni-CeO2.

Application of Black Liquor Derived Carbonaceous Compound as Fuel in Direct Carbon Fuel Cell

Direct carbon fuel cell (DCFC) with higher power efficiency and lesser emissions is being viewed as a potential clean energy source. The application of renewable biochar as fuel for DCFC is found to be feasible to replace coal or carbon black for power generation. Black liquor from the paper production might be a suitable fuel source for DCFC due to its high lignin or carbon content. In this study, the feasibility of using compound extracted from black liquor as fuel source for DCFC was investigated in the aspect of physico-chemical and electrochemical properties. Suitable pyrolysis temperature in producing biochar from black liquor compound was first investigated. Results have shown that fixed carbon and ash content increased slightly with increasing pyrolysis temperature. The ash content is made up of majority of silica as depicted in FESEM-EDX results. Oxygen containing functional group was decomposed under high pyrolysis temperature of 700°C and 800°C. Besides, biochar obtained at 500°C of pyrolysis temperature has given the highest power density of 1.22 mW cm-2 whereas 1.44 mW cm-2 was obtained from coal which was used as the control. Future work on ash removal from the black liquor prior to pyrolysis might improve the potential of black liquor derived compound as a fuel source for DCFC.

Effect of Manganese Catalysts on the Performance of Anodes in Direct Carbon Fuel Cells

Effect of Manganese Catalysts on the Performance of Anodes in Direct Carbon Fuel Cells

Biochar and Other Carbonaceous Materials Used in Steelmaking: Possibilities and Synergies for Power Generation by Direct Carbon Fuel Cell

Biochar and Other Carbonaceous Materials Used in Steelmaking: Possibilities and Synergies for Power Generation by Direct Carbon Fuel Cell

Molten salt gasification characteristics of various organic waste fuels for HF-DCFC

With fossil fuel prices soaring due to the Ukraine crisis, countries must not only achieve energy self-sufficiency in the future, but also curb CO2 emissions to prevent global warming. In order to achieve both of these goals, our laboratory has been developing a High Functional Direct Carbon Fuel Cell (HF-DCFC) composed of a molten salt gasification and a Tubular Molten Carbonate Fuel Cell. HF-DCFC can generate electricity directly using various organic wastes as fuel, but the previous study was elucidated that its cell performance is greatly affected by the fuel type. In this study, the gasification characteristics of polyethylene (PE), wood pellets (WP), and onion peels (ONION) were investigated for the installation of HF-DCFCs in each community as a waste treatment generator. As a result, the highest CO and H2 production as fuel for HF-DCFC occurred with WP under 70(25CO2/75N2)/30H2O atmosphere. PE produced hardly CO and H2 productions, but high sulfide emissions. ONION gasification produces CO and H2 second only to WP with little CH4 production, but gasification characteristics were greatly enhanced when ONION was wrapped in PE and fed. Moreover, in all fuels, the addition of air inhibits the formation of fuel gas through partial oxidation reactions and reduces gasification efficiency but increases energy efficiency because the oxidation reactions raise the temperature of the molten salt.

X-ray Micro-imaging of Direct Carbon Fuel Cell around the Anode

X-ray Micro-imaging of Direct Carbon Fuel Cell around the Anode

Utilization of Birch Biochar with Natural Oxidation Catalysts as the Fuel of a Direct Carbon Fuel Cell

Utilization of Birch Biochar with Natural Oxidation Catalysts as the Fuel of a Direct Carbon Fuel Cell