Direct Carbon Solid Oxide Fuel Cells Research Articles

The Utilisation of Solid Fuels Derived from Waste Pistachio Shells in Direct Carbon Solid Oxide Fuel Cells.

The comprehensive results regarding the physicochemical properties of carbonaceous materials that are obtained from pistachio shells support their usage as solid fuels to supply direct carbon solid oxide fuel cells (DC-SOFCs). The influence of preparation conditions on variations in the chemical composition, morphology of the biochar powders, and degree of graphitization of carbonaceous materials were investigated. Based on structural investigations (X-ray diffraction analysis and Raman spectroscopy), it was observed that disordered carbon particles developed during the application of thermal treatments. The use of X-ray fluorescence enabled a comparative analysis of the chemical composition of the inorganic matter in biocarbon-based samples. Additionally, the gasification of carbonaceous-based samples vs. time at a temperature of 850 °C was investigated in a H2O or CO2 gas atmosphere. The analysis demonstrated the conversion rate of biochar obtained from pistachio shells to H2, CH4 and CO during steam gasification. The electrochemical investigations of the DC-SOFCs that were supplied with biochars obtained from pistachio shells were characterized by satisfactory values for the current and power densities at a temperature range of 700–850 °C. However, a higher power output of the DC-SOFCs was observed when CO2 was introduced to the anode chamber. Therefore, the impact of the Boudouard reaction on the performance of DC-SOFCs was confirmed. The chars that were prepared from pistachio shells were adequate for solid fuels for utilization in DC–SOFCs.

Highly efficient utilization of industrial barium slag for carbon gasification in direct carbon solid oxide fuel cells

Direct carbon solid oxide fuel cells (DC-SOFCs) are recognized as an efficient energy conversion device. With regard to their operation mechanism, the reverse Boudouard reaction rate is the crucial factor influencing cell performance. In this work, a new-type catalyst derived from industrial barium slag (BS) was first developed to enhance the reverse Boudouard reaction and DC-SOFC performance. The chemical composition and micro-morphologies of BS and barium slag-derived catalyst (BSC) were characterized in detail. The superiorities of BS and BSC were reflected in the enhanced DC-SOFC performance and high fuel utilization. The single cell fueled by BSC-loaded carbon yielded the best output of 249 mW cm−2 at 850 °C. This result was comparable to the 266 mW cm−2 output of a hydrogen-fueled SOFC due to the superior catalytic activity of metallic catalysts toward carbon gasification. The advantage of the BSC was also observed in the durable operation of the corresponding DC-SOFCs, which lasted for 36.2 h at 50 mA with the fuel utilization of 29.0%. This work provides a new channel for green and efficient utilization of BS and other industrial residues, and a novel option to the development of energy conversion technology.

A Comparative Study on the Performance of Direct Carbon Solid Oxide Fuel Cells Powered with Different Rank Coals

Assessing the effect of coal characteristics on the performance of direct carbon solid oxide fuel cells (DC-SOFCs) is a prerequisite for developing DC-SOFCs powered with coal. In this study, three ...

Highly efficient utilization of walnut shell biochar through a facile designed portable direct carbon solid oxide fuel cell stack

The direct carbon solid oxide fuel cell (DC-SOFC) is a green and efficient energy conversion device with all-solid-state structure, which can convert carbon fuel into electricity directly. Recently, using biomasses as fuels for DC-SOFC has become fascinating due to their abundance and renewable property. However, it usually provides inferior performance compared to that with gas fuel feeding (hydrogen). Here, we report a promising and high-performing tubular segmented-in-series YSZ electrolyte-supported DC-SOFC stack. Thereinto, the YSZ electrolyte supports are fabricated by dip-coating and both pure walnut shell biochar and Fe-loaded biochar are used as fuels. The single cell can achieve a maximum power density of 147 mW cm−2 at 800 °C and it is improved to 205 mW cm−2 as FenOm catalyst is loaded on the biochar fuel. Furthermore, a two-cell-stack of DC-SOFC operated with Fe-loaded walnut shell char is assembled and tested. It delivers an outstanding performance, with an OCV of 1.98 V, an output power of 1.11 W and a maximum volumetric power density of 505 mW cm−3 at 800 °C, indicating high potentials for developing into a high performance battery for portable or distributed applications.

In-situ catalytic gasification of kelp-derived biochar as a fuel for direct carbon solid oxide fuel cells

Direct carbon solid oxide fuel cell (DC-SOFC) is a larruping type of fuel cell due to its all-solid-state structure, which can generate electricity from converting the chemical energy contained in solid carbon fuels directly into electrical energy. As the most abundant carbon storage base on earth, besides commercial carbon, coal or the common biomass carbon fuels, the exploitation of marine biomass as an alternative fuel for DC-SOFC is a very intriguing topic. In order to make efficient utilization of biomass carbon obtained from the ocean, a high performing direct carbon solid oxide fuel cell fuelled by kelp biochar is demonstrated. As comparison, the performances of DC-SOFCs with activated carbon and catalyst-loaded activated carbon fuels are also investigated. Thereinto, the best performance of 285 mW cm−2 at 850 °C is achieved in a DC-SOFC using kelp biochar fuel with Ag-Gd0.1Ce0.9O2-δ /YSZ/ Ag-Gd0.1Ce0.9O2-δ configuration. This study will provide promising utilization of alternative biomass in DC-SOFCs and broaden their available carbon scope.

A hybrid system using a looped multi-stage thermoacoustically-driven cryocooler to harvest the waste heat from a direct carbon solid oxide fuel cell

A novel hybrid system model is established to assess the feasibilities of using a looped multi-stage thermoacoustically-driven cryocooler (LMSTDC) to harvest the waste heat from a direct carbon solid oxide fuel cell (DC-SOFC). Mathematical expressions for the equivalent power output and equivalent efficiency of the proposed hybrid system are given and the performance characteristics are investigated under different operating conditions. The results demonstrate that the LMSTDC can effectively harvest the possible waste heat released in the DC-SOFC, especially under a large working current density. The peak equivalent power density and efficiency of the hybrid system can be, respectively, up to 6500.0 W m−2 and 51.8% at 1173.0 K and 30,000.0 A m−2. Comprehensive numerical calculations are carried out to examine the impacts of the working temperature, the working current density, the distance between the anode and carbon layer, and the engine stage number in the LMSTDC on the hybrid system performance.

Modeling the concentration profiles of CO and CO2 in a direct carbon solid oxide fuel cell—effect of cathode and electrolyte design parameters

A mathematical model is developed to study the concentration profile of gases, namely carbon dioxide and carbon monoxide, across the anode of a direct carbon solid oxide fuel cell (DC-SOFC) under anode-supported configuration. The concentration profiles are evaluated as a function of cathode and electrolyte design parameters, namely cathode porosity, cathode tortuosity, cathode composition, cathode pressure, electrolyte thickness, and length of the triple-phase boundary (TPB). The effect of operating potential on these concentration profiles is modeled. The effects of electrolyte thickness and TPB length are found to be major factors in determining the performance of the DC-SOFC. Model results are compared with experimental data and found to compare well.

Sulfur-tolerant Fe-doped La0·3Sr0·7TiO3 perovskite as anode of direct carbon solid oxide fuel cells

Fe-doped La0·3Sr0·7TiO3 (LSFT) is synthesized and systematically characterized towards application as an anode material for direct carbon solid oxide fuel cells (DC-SOFCs). The structural, electrical and electrochemical properties of LSFT under the operation conditions of DC-SOFCs have been evaluated. High structural stability, improved ionic conductivity, electrocatalytic activity, and electrochemical performance are demonstrated. Electrolyte-supported DC-SOFC with LSFT anode provides a maximum power density of 292 mW cm−2 at 850 °C, which is comparable to those state-of-the-art Ni-YSZ anode for DC-SOFC. In addition, it shows excellent long-term operational stability (over 110 h) in H2S-containing CO atmosphere. It thus promises as a novel anode candidate for DC-SOFCs with whole-solid-state configuration.

High-performance gas–electricity cogeneration using a direct carbon solid oxide fuel cell fueled by biochar derived from camellia oleifera shells

Direct carbon solid oxide fuel cells (DC-SOFCs) are promising for generating electricity cleanly and efficiently from solid carbon fuel. Biochar from Camellia oleifera shells is used in a tubular electrolyte-supported 2-cell DC-SOFC stack with a yttrium-stabilized zirconia (YSZ) electrolyte and silver–gadolinium-doped ceria (Ag-GDC) as symmetrical electrodes. The DC-SOFC exhibits comparable electrical performance to the same cell operated on hydrogen fuel and can cogenerate CO and electricity when fueled by biochar. The gas–electricity cogeneration performance of the DC-SOFC is tested under constant-current discharge in terms of electrical power output, CO output rate and purity, electrical conversion efficiency, and gas–electrical cogeneration conversion efficiency. The purity of the output CO can reach more than 80%. Considering the chemical energy of CO a part of the output power, the energy conversion efficiency of >70% is attained. Furthermore, the gas–electricity cogeneration performance is relatively stable before the biochar fuel is exhausted.

Performance improvement of a direct carbon solid oxide fuel cell via strontium-catalyzed carbon gasification

As a new way of power generation, direct carbon solid oxide fuel cells (DC-SOFCs) exhibit great potential in solution of energy crisis and environmental pollution. According to the working principle, the cell operation is a kinetically controlled process, and the reverse Boudouard reaction is the rate-determining step of the whole system. In this study, a Sr-based catalyst is successfully introduced to accelerate carbon gasification and thus enhance cell performance of DC-SOFCs. The electrochemical performance of DC-SOFCs operated on coconut active charcoal with various Sr loading contents (3 wt%–10 wt%), are studied and compared with that of DC-SOFCs with traditional Fe-catalyzed carbon fuel. Experimental results demonstrate that the best output of 316 mW cm−2 is achieved from the single cell powered with 5 wt% Sr-loaded coconut active charcoal at 850 °C, higher than those of DC-SOFCs fueled by pure and 5 wt% Fe-loaded active charcoal. The superiority of the Sr-based catalyst is also demonstrated by the operation stability of the corresponding DC-SOFC, which displays a relatively long operation time of 22.68 h at 0.25 A cm−2 with the fuel utilization of 18.3%. The SEM/EDX results indicate that the Sr-based catalyst exhibits good stability without agglomeration during cell operation at high temperature. In addition, the carbon gasification mechanism catalyzed by Sr-based catalyst is also proposed on the basis of these properties. This study indicates that the designed Sr-loaded coconut active charcoal is expected to be an alternative carbon fuel for DC-SOFCs.

Ni-doped A-site-deficient La0.7Sr0.3Cr0.5Mn0.5O3-δ perovskite as anode of direct carbon solid oxide fuel cells

A Ni-doped A-site-deficient La0.7Sr0.3Cr0.5Mn0.5O3-δ perovskite (N-LSCM) was synthesized and systematically characterized towards the application as the anode electrode for direct carbon solid oxide fuel cells (DC-SOFCs). The microstructure and electrochemical properties of N-LSCM under the operation conditions of DC-SOFCs have been evaluated. An in-situ exsolution of Ni nanoparticles on the N-LSCM perovskite matrix is found, revealing a maximum power density of 153 mW cm−2 for the corresponding DC-SOFC at 850 °C, compared to 114 mW cm−2 of the cell with stoichiometric LSCM. The introduction of Ni nanoparticles exsolution and A-site deficient is believed to boost the formation of highly mobile oxygen vacancies and electrochemical catalytic activity, and further improves the output performance of the DC-SOFC. It thus promises as a suitable anode candidate for DC-SOFCs with whole-solid-state configuration.

Enhancing the Catalytic Activity of Y0.08Sr0.92TiO3−δ Anodes through in Situ Cu Exsolution for Direct Carbon Solid Oxide Fuel Cells

In recent years, many researchers have been interested in studying direct carbon-solid oxide fuel cells (DC-SOFCs) because of their simple structure and the highly efficient method for converting t...

Efficient use of waste carton for power generation, tar and fertilizer through direct carbon solid oxide fuel cell

Abstract The rapid development of express logistics industry has yielded more carton wastes, how to utilize them as resources has become an important issue in recent years. In this paper, effective and multifunctional applications of waste carton are explored to obtain products of solid carbon fuel and tar via pyrolysis process. Solid carbon derived from waste carton is utilized as fuel for direct carbon solid oxide fuel cells (DC-SOFCs) with the symmetric perovskite La0.3Sr0.7Fe0.7Ti0.3O3-δ electrodes and scandium stabilized zirconia electrolyte for power generation. The maximum output performance of this DC-SOFC is up to 307.8 mW cm-2 at 850 °C. The cell fueled by 0.2 g carbonated waste carton is operated at constant resistance discharging mode of 20 Ω, and 5.8 h discharging with a capacity of 658 C is represented. Ash of the carton fuel is collected after operation. Infrared spectrum and surface-enhanced Raman spectrum are employed to characterize tar from pyrolysis, and they show that tar contains many organic matters with a potential to be used as chemical raw materials. Energy dispersive spectroscopy and X-ray diffraction results show various inorganic salts and oxides in the ash, it means that the ash may be a promising candidate for fertilizer.

Thermal effects in H2O and CO2 assisted direct carbon solid oxide fuel cells

Thermal effects in a H2O and CO2 assisted tubular direct carbon solid oxide fuel cell (DC-SOFC) are numerically investigated. Parametric simulations are further conducted to study the effects of operating potential, the distance between carbon and anode, inlet gas temperature, and anode inlet gas flow rate on the thermal behaviors of the fuel cell. It is found that the fuel cell with H2O as gasification agent performs considerably better than the cell with CO2 as gasification agent in all cases. It is also found that the temperature field of the fuel cell is highly uneven. The breakdown of the heat sources in the fuel cell shows that the H2O assisted DC-SOFC has much higher heat generation and consumption than the CO2 assisted cell. Interestingly, a thermal neutral voltage is observed, at which no heating or cooling of the cell is needed. In addition, the distance between the anode and the carbon layer is required to be as small as possible, which improves the temperature uniformity of the fuel cell. The results of this study demonstrates the importance of thermal effects in DC-SOFCs and form a solid foundation for DC-SOFC thermal management.

A Microtubular Direct Carbon Solid Oxide Fuel Cell Operated on the Biochar Derived from Pepper Straw

Direct carbon solid oxide fuel cell (DC‐SOFC) is a promising energy conversion system, which can directly convert the chemical energy of biomass into electrical energy with high efficiency and low pollution. Herein, a microtubular DC‐SOFC fueled with the biochar derived from pepper straw for electrical power generation is reported. The DC‐SOFC operated on pepper straw char gives a maximum power density of 217 mW cm−2, comparable with 252 mW cm−2 for that with hydrogen fuel at 850 °C. Moreover, the lifetime of the DC‐SOFC reaches 21 h at a discharge current of 100 mA with the fuel utilization of 44.4%. The pepper straw char is characterized physically by scanning electron microscopy, energy‐dispersive spectrometer, X‐ray diffraction, Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The results demonstrate that the pepper straw char contains natural catalysts in itself and their contribution on the electrochemical performance of the microtubular DC‐SOFC is analyzed in detail.

A steel slag–derived Boudouard reaction catalyst for improved performance of direct carbon solid oxide fuel cells

Solid oxide fuel cells (SOFCs) can directly utilize solid carbon as fuel by integrating with the reverse Boudouard reaction in the anode chamber. Efficiency of the Boudouard gasification of solid carbon fuel is one of the crucial factors influencing the performance of direct carbon SOFCs (DC-SOFCs). In this paper, a novel Boudouard reaction catalyst derived from steel slag was first introduced into DC-SOFCs for improving the electrochemical performance. The catalytic activity of the steel slag was activated using the molten alkali method to decompose the inert mineral phases of the raw material. The steel slag–derived catalyst was loaded on the activated charcoal by a wet ball milling method. This kind of catalyst can match up to the readily available solid carbon fuels in cost. Promoted by this highly active Boudouard reaction catalyst, the initial Boudouard gasification temperature of the carbon fuel decreased by 99°C, and the producing rate of carbon monoxide doubled. Furthermore, the power outputs of the fuel cells increased from 91 to 159 mW cm, and the fuel utilization increased from 17.10% to 46.43% at 825°C. This study demonstrates that the steel slag–derived catalyst is a promising material for the performance improvement of DC-SOFCs and may make a valuable contribution to their commercial application.

Hot corrosion of yttria-stabilized zirconia by liquid antimony and antimony oxide

Direct carbon solid oxide fuel cells (DC-SOFCs) with a liquid Sb anode have many advantages over other types of SOFCs; however, their electrolyte faces corrosion by liquid Sb and Sb2O3. To evaluate the tolerance of the electrolyte to the liquid Sb and Sb2O3, 8 mol.% Y2O3–ZrO2 electrolyte (YSZ) discs are prepared and evaluated at 750 °C for up to 100 h in both chemical and electrochemical modes, simulating DC-SOFC operating conditions. In the chemical mode, the corrosion by liquid Sb causes Y dissolution from YSZ into the liquid Sb, while the YSZ experiences a phase transformation from cubic to tetragonal structure and grain boundary crack on the surface. Liquid Sb2O3 is more corrosive than liquid Sb, penetrating additionally the grain boundaries into a depth around 15 μm. In the electrochemical mode, liquid Sb is separated from YSZ by a layer (~150 μm) of liquid Sb2O3 formed during cell operation. The liquid Sb2O3 layer so formed corrodes YSZ in the same way as in the chemical mode, but the corrosion is intensified with the presence of a current, resulting in a top porous layer (~15 μm) on YSZ surface with a grain boundary penetration layer (~100 μm) underneath.

A hybrid system using Brayton cycle to harvest the waste heat from a direct carbon solid oxide fuel cell

A new hybrid system model is developed to evaluate the potentials of a Brayton cycle heat engine for waste heat recovery from a direct carbon solid oxide fuel cell (DC-SOFC). The maximum power density of the proposed system is up to 0.8675 W cm−2, which is approximately 1.8 times as large as that of the single DC-SOFC. Numerical calculations also indicate that the proposed hybrid system is an efficient approach to boost the fuel utilization, and the maximum power density of the proposed system is markedly better than that of the DC-SOFC/thermophotovoltaic cell, DC-SOFC/thermionic generator, and DC-SOFC/Otto heat engine hybrid systems except for the DC-SOFC/Stirling engine hybrid system. The optimum regions for power density, efficiency and operating current density of the proposed system are determined. The higher operating temperature and lower gap between the anode and carbon layer increase the power density and efficiency of the proposed system. Moreover, the higher heat transfer coefficient boosts the power density and efficiency at high current density. The compression efficiency, expansion efficiency and recuperator coefficient significantly affect the power density and efficiency.

A high performance direct carbon solid oxide fuel cell – A green pathway for brown coal utilization

Direct carbon solid oxide fuel cells (DC-SOFCs) are promising, all-solid-state, highly efficient and environment-friendly power generating devices fueled by solid carbons. In addition, utilization of real-world coal as fuel for DC-SOFC is an attractive topic, however, they still yield poor performance due to negative effect of impurities in coal. In order to utilize brown coal to generate electricity efficiently and environmentally, here we report a high-performance direct carbon solid oxide fuel cell that enables a green pathway for brown coal utilization. The cell consists of nano Al2O3 doped yttria-stabilized zirconia (YSZ) electrolyte supports and Ag-Gd0.1Ce0.9O2-δ as symmetrical composite catalyst electrodes. Fueled with raw brown coal and brown coal char at 850 °C separately, the cells can achieve maximum power densities of 211.4 and 221 mW cm−2, respectively. Furthermore, a stable discharging voltage and platform with the fuel utilization of 61.5% are demonstrated when brown coal char fueled DC-SOFC is operated under a constant current of 0.1 A.

Enhancing the Power Output of Direct Carbon Solid Oxide Fuel Cell Using Ba‐Loaded Activated Carbon Fuel

The performance of direct carbon solid oxide fuel cells (DC‐SOFCs) is limited by the slow carbon gasification kinetics at operating temperatures. To address this limitation, a carbon fuel loaded with Ba catalyst is developed for DC‐SOFCs to improve the electrochemical performance in this study. Ba is loaded on activated carbon in the form of BaCO3 by the wet agglomeration technique. The effect of the Ba catalyst with various contents on the electrochemical performance in single cells and fuel utilization of DC‐SOFCs are examined. Experimental results show that the optimized Ba content is 5 wt% and the DC‐SOFC with this Ba‐loaded activated carbon fuel gives the best output with a maximum power density of 328.4 mW cm−2 at 850 °C. Furthermore, the DC‐SOFC fueled by 5 wt% Ba‐loaded activated carbon operates steadily for 28.76 h with the fuel utilization of 16.0%, which is also superior to many other cells. The enhancement of cell performance suggests that Ba is an effective catalyst to the Boudouard reaction, and the catalytic mechanism is also discussed in detail.