Carbon fuel cell

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The direct carbon fuel cell ( engl. Direct Carbon Fuel Cell DCFC) is a fuel cell , according to the principle of conversion of carbon and oxygen in carbon dioxide (CO 2 ) under direct release electrical energy works ( "cold combustion"). The arrangement allows chemical energy to be converted into electrical energy while avoiding high-loss conversion stages, as is the case in conventional coal-fired power plants .

Carbon fuel cells have been known in principle since 1894 at the latest, but are still at an early stage of research and development. In contrast to all other known fuel cell types that use liquid or gaseous fuels such as methanol or hydrogen , the DCFC uses a solid as an energy supplier, namely carbon, which, due to its extraordinarily high melting point, cannot be supplied to the cell in liquid or gaseous form.

principle

Scheme of a carbon fuel cell. The carbon C is supplied to the negative pole side (anode) shown on the left and oxidized to carbon dioxide CO 2 . At the electrode shown here on the right, the cathode (positive pole), oxygen O 2 is reduced to the oxide ion O 2− . Between the electrodes is the electrolyte, which conducts oxygen ions so that they can get from the cathode to the anode.

The electrochemical processes on the electrodes and the overall reaction are:

  • Anode: C + 2 O 2− → CO 2 + 4 e -
  • Cathode: O 2 + 4 e - → 2 O 2−
  • Cell: C + O 2 → CO 2

Also the Boudouard equilibrium

  • CO 2 + C ⇌ 2 CO

plays a role, since it reduces the efficiency of the cell (especially at temperatures above 850 ° C) if CO 2 is produced instead of CO 2 .

The potential difference between anode and cathode is approx. 0.8 volts (theoretically 1.02 volts under standard conditions). The electrical efficiency is relatively high, around 80% (compare hydrogen fuel cell up to approx. 70%, coal thermal power plant approx. 40%). In practice, however, lower efficiencies are to be expected. Because of the higher state of charge of the carbon atom in contrast to the hydrogen molecule , the expected current density at the anode approximately be double.

It is possible to operate carbon fuel cells with coal or coke. In the long term, however, the accumulating ash can poison the catalysts at the anode. Therefore, coal should be cleaned by washing out interfering inorganic constituents before being used in fuel cells.

Depending on the electrolyte used, carbon fuel cells are either solid oxide fuel cells (SOFC) or molten carbonate fuel cells ( MCFC) or both at the same time if both liquid carbonates and solid electrolytes are used in one cell. It is also possible to use molten hydroxide as an electrolyte.

Current research

One of the current research topics in the field of carbon fuel cells is the production of carbon it from renewable resources by from these plants coal is produced. For example, the carbon for SOFCs can be obtained from wheat straw, reeds, walnut or grapefruit shells, sawdust, olive wood or corn cobs.

At present, some basic research is still necessary in this area in order to be able to use the principle. An outlook on the actual technical use cannot be given at the moment.

Historical

According to Wilhelm Ostwald , a first attempt was made with a "carbon element", i.e. H. a carbon fuel cell, carried out by Pawel Jablotschkow (Paul Jablochkoff). It used molten saltpetre as an electrolyte and delivered very low currents. In 1894, Wilhelm Ostwald put forward the vision of a technical revolution through the carbon fuel cell: “We have a galvanic element which directly supplies electrical energy from coal and oxygen in the air, in an amount that is somewhat in relation to the theoretical values then we are facing a technical upheaval, against which the one with the invention of the steam engine must disappear. [...] No smoke, no soot, no steam boiler, no steam engine ”. As a result, the idea of ​​electricity directly from coal received international attention, and several inventors tried to implement Ostwald's concept. This also includes the US inventor William W. Jacques , who received a US patent in 1896 for the direct conversion of energy from carbon into electrical energy (“the potential energy of the carbon may be converted directly into electrical energy instead of into heat "). In 1897 he received a corresponding Canadian patent on his apparatus. Jacques reported on his fuel cell in a magazine article; he speculated that it would also be suitable for driving railroad trains or transatlantic ships. He emphasized the advantage that his conversion of coal could run cleaner without combustion, and envisioned smoke-free power plants. He reported measurements that a test set-up operated with his carbon cell had an output of around 2 hp and had an efficiency of 32%, which was forty times more efficient than the conventional way of combustion, steam generation and a generator. Allegedly, from 100 cells connected in series, it received a voltage of 90 volts and currents of up to 16 amperes . A few years later, the first attempts at carbon fuel cells were seen as failures. In 1907 it was stated in summary:

"Unfortunately, there has been no practical success so far, because as much effort has been put into solving this problem, the first preliminary attempts have not yet been made."

In 1909 and 1910 Emil Baur (1873–1944) demonstrated a carbon-oxygen fuel cell in his lecture in Braunschweig. He used hot (200–250 ° C) concentrated sulfuric acid as the electrolyte. A platinum sheet surrounded by oxygen served as an electrode on the positive pole side; In addition, he used a mixture of vanadium salts ( vanadium pentoxide and vanadyl sulfate ) as a catalyst on this electrode . Voltages of 0.6 to 0.7 volts were measured and currents of up to 0.2 amperes were obtained. In 1919 and 1920 Emil Baur and his student William Treadwell received patents on solid electrolyte fuel cells , where they also suggested coal and coke as fuel. In 1937, Baur published the first scientific publication on solid electrolyte fuel cells, using coke grains in addition to fuel gases such as hydrogen. In the early 1950s, Eduard Justi achieved open-circuit voltages of 0.99 to 1.0 volts at 650 ° C in his improved solid electrolyte fuel cell.

Web links

Individual evidence

  1. ↑ a b c d Friedrich Wilhelm Ostwald: The scientific electrochemistry of the present and the technical of the future . Lecture given to the 2nd annual meeting of the Association of German Electrical Engineers on June 8, 1894 in Leipzig. In: Wilhelm Ostwald and J. H. van't Hoff (ed.): Journal for physical chemistry, stoichiometry and kinship theory . tape 15 , no. 4 . Wilhelm Engelmann, Leipzig 1894, p. 409-421 ( online at Internet Archive ).
  2. ↑ a b Sukhvinder PS Badwal, Hyungkuk Ju, Sarb Giddey, Aniruddha Kulkarni: Direct Carbon Fuel Cells . In: Encyclopedia of Sustainable Technologies . Elsevier, 2017, ISBN 978-0-12-804792-7 , pp. 317-329 , doi : 10.1016 / b978-0-12-409548-9.10119-8 .
  3. ↑ a b Patent DE899212 : Process for the direct conversion of the chemical energy of carbon or combustible gases into electrical energy by electrochemical means. Registered on 1951 , published on October 29, 1953 , inventor: Eduard Justi, Herbert Spengler (Fe 3 O 4 was used as the catalyst on the oxygen side . Alkali and alkaline earth carbonates with magnesium oxide as a carrier are proposed as the solid electrolyte.). ‌
  4. ^ A b c John F. Cooper, Robert Selman: Electrochemical Oxidation of Carbon for Electric Power Generation: A Review . In: ECS Transactions . ECS, San Francisco, CA 2009, pp. 15-25 , doi : 10.1149 / 1.3220176 .
  5. ^ A b S. Nürnberger, R. Bußar, B. Franke, Ulrich Stimming: Efficient and environmentally friendly use of carbon for electricity generation (presented by U. Stimming). In: Working Group Energy (AKE) archive. Energy working group AKE of the German Physical Society DPG, 2009, accessed on April 7, 2019 .
  6. ↑ a b Wenting An, Xiaojie Sun, Yong Jiao, Paulo Sérgio Barros Julião, Wei Wang: A solid oxide carbon fuel cell operating on pomelo peel char with high power output . In: International Journal of Energy Research . tape 43 , no. 7 , June 10, 2019, ISSN  0363-907X , p. 2514-2526 , doi : 10.1002 / er.4097 .
  7. ↑ a b c d Hyung Kuk Ju, Jiyoung Eom, Jae Kwang Lee, Hokyung Choi, Tak-Hyoung Lim: Durable power performance of a direct ash-free coal fuel cell . In: Electrochimica Acta . tape 115 . Elsevier, January 2014, p. 511-517 , doi : 10.1016 / j.electacta.2013.10.124 .
  8. ^ A b Xiang Li, Zhonghua Zhu, Roland De Marco, John Bradley, Andrew Dicks: Evaluation of raw coals as fuels for direct carbon fuel cells . In: Journal of Power Sources . tape 195 , no. 13 . Elsevier, July 2010, p. 4051-4058 , doi : 10.1016 / j.jpowsour.2010.01.048 .
  9. ↑ Yong-min Xie, Jiang-lin Li, Jin-xing Hou, Pei-jia Wu, Jiang Liu: Direct use of coke in a solid oxide fuel cell . In: Journal of Fuel Chemistry and Technology . tape 46 , no. 10 , October 2018, p. 1168-1174 , doi : 10.1016 / S1872-5813 (18) 30048-3 .
  10. ↑ a b Jinshuai Yu, Yicheng Zhao, Yongdan Li: Utilization of corn cob biochar in a direct carbon fuel cell . In: Journal of Power Sources . tape 270 , December 2014, p. 312-317 , doi : 10.1016 / j.jpowsour.2014.07.125 .
  11. ↑ a b c Patent DE325783 : fuel element . Registered on September 20, 2016 , published on September 17, 1920 , inventor: Emil Baur, William Dupré Treadwell ("To burn coal with an electric motor [...] the fuel electrode-forming coal (coke, hard coal, etc.)"). ‌
  12. ^ A b Emil Baur, Hans Price: About fuel chains with fixed ladders . In: Journal of Electrochemistry and Applied Physical Chemistry . Reports of the Bunsen Society for Physical Chemistry. tape 43 , no. September 9 , 1937, ISSN  0005-9021 , pp. 727-732 , doi : 10.1002 / bbpc.19370430903 .
  13. ↑ S. Zecevic, EM Patton, P. Parhami: Direct Carbon Fuel Cell With Hydroxide Electrolyte: Cell Performance During Initial Stage of a Long Term Operation . In: 3rd International Conference on Fuel Cell Science, Engineering and Technology . ASMEDC, Ypsilanti, Michigan, USA 2005, ISBN 978-0-7918-3764-1 , pp. 507-514 , doi : 10.1115 / FUELCELL2005-74169 ( asme.org [accessed October 18, 2019]).
  14. ↑ Andrzej Kacprzak: Hydroxide electrolyte direct carbon fuel cells Technology review . In: International Journal of Energy Research . tape 43 , no. 1 . John Wiley & Sons, January 2019, ISSN  0363-907X , p. 65-85 , doi : 10.1002 / er.4197 .
  15. ↑ N. Jafri, WY Wong, V. Doshi, LW Yoon, KH Cheah: A review on production and characterization of biochars for application in direct carbon fuel cells . In: Process Safety and Environmental Protection . tape 118 , August 2018, p. 152–166 , doi : 10.1016 / j.psep.2018.06.036 .
  16. ↑ a b Michalis Konsolakis, Nikolaos Kaklidis, George E. Marnellos, Dimitra Zaharaki, Kostas Komnitsas: Assessment of biochar as feedstock in a direct carbon solid oxide fuel cell . In: RSC Advances . tape 5 , no. 90 , 2015, ISSN  2046-2069 , p. 73399-73409 , doi : 10.1039 / C5RA13409A .
  17. ↑ Kai Xu, Jizhou Dong, Xian Li, Junquan Wang, Zhenzhong Hu: Evaluation of biomass and its thermal decomposition products as fuels for direct carbon fuel cells . In: Biomass and Bioenergy . tape 130 , November 2019, p. 105359 , doi : 10.1016 / j.biombioe.2019.105359 .
  18. ↑ Weizi Cai, Jiang Liu, Peipei Liu, Zhijun Liu, Haoran Xu: A direct carbon solid oxide fuel cell fueled with char from wheat straw . In: International Journal of Energy Research . tape 43 , no. 7 , June 10, 2019, ISSN  0363-907X , p. 2468-2477 , doi : 10.1002 / er.3968 .
  19. ↑ Jun Wang, Lijun Fan, Tongtong Yao, Juanjuan Gan, Xiaojing Zhi: A High-Performance Direct Carbon Fuel Cell with Reed Rod Biochar as Fuel . In: Journal of The Electrochemical Society . tape 166 , no. 4 , 2019, ISSN  0013-4651 , p. F175-F179 , doi : 10.1149 / 2.0321904jes .
  20. ↑ Magdalena Dudek, Bartosz Adamczyk, Maciej Sitarz, Michał Śliwa, Radosław Lach: The usefulness of walnut shells as waste biomass fuels in direct carbon solid oxide fuel cells . In: Biomass and Bioenergy . tape 119 , December 2018, p. 144–154 , doi : 10.1016 / j.biombioe.2018.09.026 .
  21. ↑ Shuangbin Li, Cairong Jiang, Juan Liu, Haoliang Tao, Xie Meng: Mechanism of enhanced performance on a hybrid direct carbon fuel cell using sawdust biofuels . In: Journal of Power Sources . tape 383 , April 2018, p. 10–16 , doi : 10.1016 / j.jpowsour.2018.02.040 .
  22. ↑ Amal Elleuch, Kamel Halouani, Yongdan Li: Investigation of chemical and electrochemical reactions mechanisms in a direct carbon fuel cell using olive wood charcoal as sustainable fuel . In: Journal of Power Sources . tape 281 , May 2015, p. 350–361 , doi : 10.1016 / j.jpowsour.2015.01.171 .
  23. ↑ Qianyuan Qiu, Mingyang Zhou, Weizi Cai, Qian Zhou, Yapeng Zhang: A comparative investigation on direct carbon solid oxide fuel cells operated with fuels of biochar derived from wheat straw, corncob, and bagasse . In: Biomass and Bioenergy . tape 121 . Elsevier, February 2019, p. 56-63 , doi : 10.1016 / j.biombioe.2018.12.016 .
  24. ^ Jeff Sheets: Electricity Direct from Coal - Fuel Cell Technology - Electricity Direct from Coal. In: Free Energy Planet. Retrieved June 29, 2019 .
  25. ^ Alfred H. Bucherer: Electricity directly from coal . In: Journal of the Franklin Institute . tape 139 , no. 5 , May 1895, p. 378-384 , doi : 10.1016 / 0016-0032 (95) 90083-7 .
  26. ↑ Electricity directly from coal: Some papers from the literature of the last decades . In: Walther Nernst, Wilhelm Borchers (Hrsg.): Journal for electrical engineering and electrochemistry . tape 4 , no. 5 . Wilhelm Knapp, September 5, 1897, ISSN  0372-8323 , p. 129-136 , doi : 10.1002 / bbpc.18970040502 .
  27. ^ Electricity straight from coal: Some papers from the literature of the last decades . In: Walther Nernst, Wilhelm Borchers (Hrsg.): Journal for electrical engineering and electrochemistry . tape 4 , no. 6 . Wilhelm Knapp, September 20, 1897, ISSN  0372-8323 , p. 165-171 , doi : 10.1002 / bbpc.18970040604 .
  28. ↑ Etienne de Fodor (István Fodor 1856–1929): Electricity directly from coal . Hartleben's Verlag, 1897, OCLC 248542156 , element oxygen-coal ( limited preview in Google book search).
  29. ↑ a b Matthew Brown, Matthew Cohen, Keith Gary: Fuel Cell Origins. William Jacques' carbon battery apparatus, 1896. In: Fuel Cells. Smithsonian Institution, 2001, accessed on May 20, 2018 (English): "The result was an efficiency of only 8 percent."
  30. ↑ Christina Rubin: Mr. Edison and the Talking Doll. Antique Toy Collectors of America, 2012, accessed on June 2, 2018 (English): "Jacques with his partner, Lowell Briggs co-founded the Edison Phonograph Toy Manufacturing Company in 1887"
  31. ↑ Patent US555511 : Method of converting potential energy from carbon into electrical energy. Published March 3, 1896 , inventor: William W. Jacques. ‌
  32. ↑ Patent CA55129 : Electric Power Converter. Published March 1, 1897 , inventor: William W. Jacques. ‌
  33. ^ A b c William W. Jacques: Electricity Direct From Coal. In: Harper's New Monthly Magazine . tape 94 , no. 559 . Harper & Brothers Publishers, December 1896, pp. 144–150 (English, archive.org [accessed on May 16, 2018]): “fourty times greater than plants of corresponding size […] Think of a smokeless London!”
  34. ↑ Robert Lüpke, Emil Bose: Fundamentals of electrochemistry on an experimental basis . 5th edition. Springer Berlin Heidelberg, Berlin, Heidelberg 1907, ISBN 978-3-662-23587-4 , III. Section. The osmotic theory of galvanic power generation, Chapter 4. The chains of reduction and oxidation, § 4. Obtaining electrical energy directly from coal, p. 172–173 , doi : 10.1007 / 978-3-662-25666-4 ( online in the Internet Archive).
  35. ↑ a b c d Emil Baur: Topics of physical chemistry . Lectures given at the instigation of the Association of German Engineers at the Technical University of Braunschweig. Akademische Verlagsgesellschaft mb H., Leipzig 1910, second lecture. Volta chains, S. 19–22 ( online on Internet Archive, University of California book [accessed July 20, 2019]).
  36. ↑ Patent GB126766 : Improvements in Electric Cells or Batteries. Applied on March 16, 1918 , published on May 16, 1919 , inventors: Emil Baur, William Dupré Treadwell (coke electrode, iron oxide catalyst for oxygen reduction). ‌