Direct carbon conversion in a SOFC-system with a non-porous anode

Nürnberger, S.; Bussar, R.; Desclaux, P.; Franke, Björn; Rzepka, M.; Stimming, Ulrich

doi:10.1039/b916995d

Cited by 87 publications

(69 citation statements)

References 12 publications

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“…[106][107][108][109]. While the literature on electrochemical oxidation of carbon in molten-salt systems is vast, it is beyond the scope of this paper.…”

Section: Carbon Electrochemical Oxidationmentioning

confidence: 99%

Fundamentals of electro- and thermochemistry in the anode of solid-oxide fuel cells with hydrocarbon and syngas fuels

Hanna

Lee

Shi

et al. 2014

Progress in Energy and Combustion Science

180

110

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“…[106][107][108][109]. While the literature on electrochemical oxidation of carbon in molten-salt systems is vast, it is beyond the scope of this paper.…”

Section: Carbon Electrochemical Oxidationmentioning

confidence: 99%

Fundamentals of electro- and thermochemistry in the anode of solid-oxide fuel cells with hydrocarbon and syngas fuels

Hanna

Lee

Shi

et al. 2014

Progress in Energy and Combustion Science

180

110

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“…14-16 M. Rzeka and U. Stimming et al 17 correlated activation barriers of graphite (256 kJ mol −1 ) and amorphous carbon (95-140 kJ mol −1 ) to reverse Boudouard reaction with DCFC performance. Low cell performance shown in graphitic carbon is attributed to scission of carbon bonds, which is thought of the most important reaction step for electrooxidation of carbon.…”

mentioning

confidence: 99%

Performance of Direct Carbon Fuel Cells Operated on Coal and Effect of Operation Mode

Chien

Arenillas

Jiang

et al. 2014

J. Electrochem. Soc.

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Previous experimental results have shown that a system with molten carbonate and solid oxide electrolyte is feasible for Direct Carbon Fuel Cell (DCFC). A study is presented to investigate cell performance with a range of solid carbon (i.e. coals, biochars, graphite) and operation mode in this hybrid electrolyte system. The results show that less crystalline coal with high fixed carbon, low sulfur, medium volatile material and moisture is best suited to this system. Using high rank of fuel such as anthracite coal, good cell performance can be obtained only by elevating temperature and with adequate pretreatment to remove impurities. Discussion of cell operation indicates that cell degradation and operation failure were due to coal agglomeration, ash buildup, and limited fuel supply in potentiostatic mode. Instead, galvanostatic operation gave stable cell performance over 60 hours. This result allows better understanding of anode reaction mechanism on the hybrid electrolyte system. Thus, long-term operation is promised when suitable solid fuel and optimized operation parameters are applied. Direct Carbon Fuel Cell (DCFC) is a promising technology to use solid carbon for energy production. This technology allows direct conversion of chemical energy to electricity, thus giving a high thermodynamic efficiency, i.e. 100%, when carbon is oxidized to carbon dioxide. The concept of DCFC is simple. Solid carbon is fed to a fuel cell and electrochemically oxidized at the anode to produce electricity.1-3 Pure product, carbon dioxide (CO 2 ), is obtained in complete oxidation and is easy for carbon sequestration. Furthermore, application of DCFC benefits from sufficient fuel supply with abundant coal and biomass in the world. These advantages as well as established infrastructure of transportation, storage, and processing for solid carbon make a DCFC feasible and very attractive.One of design challenges to develop a DCFC is choice of fuel. 4Despite large reserves of solid carbon available, different sources of carbon have varying activity and indeed affect DCFC performance. In the past, many attempts have been made to evaluate effect of solid carbon on DCFC for electric power generation. Cooper et al. 5 reported cell polarization on nine particulate carbon derived from fuel oil, coal, biochar, petroleum coke, etc. The highest discharge rate, 100-125 mA cm −2 at 0.8 V and 800• C, was obtained with biochar-derived carbon. They found that properties of carbon fuel which control discharging rates are (i) crystallographic disorder, (ii) electrical conductivity, (iii) active surface sites, and (iv) sulfur and ash impurities. Less graphitized and high disordered carbon such as chars is more reactive to oxidation; however, this property counterbalances electrical conductivity since chars are poor conductors. By contrast, neither particle size, surface area, nor morphology was found to have much impact on the electrochemical discharge rate. Moreover, Zhu et al 6 investigated factors that determine performance of carbon fuel in the D...

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“…A variable OCV is observed in cells operating on molten Pb 14 and molten Ag 13 but not with molten Sb. 10,19 Second, the large difference in densities between Sb (6.7 g/cm 3 ) and Sb 2 O 3 (5.2 g/cm 3 ) implies that natural convection will be important in this system. Figure 5 shows the flow patterns that are expected for natural convection with horizontal and inclined heated plates.…”

Section: Resultsmentioning

confidence: 99%

“…2 The transfer of oxide ions from the electrolyte to the solid fuel is often found to be the limiting step for SOFCs operating on solid fuels. 3 Among various approaches to facilitate this transfer, [4][5][6][7] one of the most promising routes is to use of molten-metal electrodes. [8][9][10] In this scheme, the anode reaction occurs in two steps:…”

mentioning

confidence: 99%

Zirconia-Based Electrolyte Stability in Direct-Carbon Fuel Cells with Molten Sb Anodes

Zhou

Vohs

et al. 2015

J. Electrochem. Soc.

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Direct carbon fuel cells (DCFC) that use zirconia-based electrolytes and molten Sb anodes have much promise for the efficient conversion of carbonaceous solid fuels into electricity. However, etching of the electrolyte, and ultimately cell failure, has been observed during operation. In this study, we have investigated this etching phenomenon as a function of the electrolyte composition and cell operating conditions and demonstrated that it is not electrochemical in nature, but rather results from reaction between the electrolyte and Sb 2 O 3 that is produced during cell operation. Etching was also observed when a yttria-stabilized zirconia ( Electrical power generation in a solid oxide fuel cell (SOFC) directly utilizing solid, carbonaceous fuels (e.g. coal and biomass) would provide significant benefits including high energy conversion efficiency. CO 2 sequestration, if needed, is easy since the exhaust gas from the anode is highly concentrated.1 Direct utilization of solid carbonaceous fuels would eliminate the need for gasification and steam reforming steps leading to great simplification of the overall system. The transfer of oxide ions from the electrolyte to the solid fuel is often found to be the limiting step for SOFCs operating on solid fuels.3 Among various approaches to facilitate this transfer, 4-7 one of the most promising routes is to use of molten-metal electrodes. [8][9][10] In this scheme, the anode reaction occurs in two steps:The first step (Equation 1) is the electrochemical oxidation of some portion of the metal in the anode at the electrolyte-anode interface. The oxidized metal is then transported (via diffusion, natural convection or mechanical mixing) to access solid fuel where the carbon is oxidized while reducing metal oxide back to metal (Equation 2). Sn previously attracted much attention as the molten metal phase for this process. 8,9Unfortunately, there is evidence that a solid SnO 2 layer forms at the electrolyte-anode interface during fuel cell operation, inhibiting further facile transfer of the oxygen from the electrolyte, resulting in high electrode losses. 11,12 While this can be avoided by using a molten metal with high oxygen solubility that does not form a stable bulk oxide phase at SOFC operating temperatures (such as Ag), electrode impedances can still be high due to slow diffusion of oxide ions within the molten metal. 13In our opinion, the metal that has provided the most intriguing results as an anode for this type of direct carbon fuel cell (DCFC) is Sb.14-16 Both Sb (melting point 903 K) and Sb 2 O 3 (melting point 929 K) become liquid at SOFC operation temperature ranging from 973 to 1073 K. This precludes the formation of a solid metal-oxide film at the electrolyte-anode interface as in the case of Sn. Furthermore, reduction of Sb 2 O 3 by carbon is facile and has been practiced industrially for more than 100 years.17 Although the Open-Circuit Voltage (OCV) for Sb oxidation is only 0.75 V at 973 K, the energy losses associated with this low potential are largely c...

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Direct carbon conversion in a SOFC-system with a non-porous anode

Cited by 87 publications

References 12 publications

Fundamentals of electro- and thermochemistry in the anode of solid-oxide fuel cells with hydrocarbon and syngas fuels

Fundamentals of electro- and thermochemistry in the anode of solid-oxide fuel cells with hydrocarbon and syngas fuels

Performance of Direct Carbon Fuel Cells Operated on Coal and Effect of Operation Mode

Zirconia-Based Electrolyte Stability in Direct-Carbon Fuel Cells with Molten Sb Anodes

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