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Microbial electrolysis cell (MEC): Strengths, weaknesses and research needs from electrochemical engineering standpoint

Rousseau, Raphaël and Etcheverry, Luc and Roubaud, Emma and Basséguy, Régine and Délia, Marie-Line and Bergel, Alain Microbial electrolysis cell (MEC): Strengths, weaknesses and research needs from electrochemical engineering standpoint. (2020) Applied Energy, 257. 113938. ISSN 0306-2619

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Official URL: https://doi.org/10.1016/j.apenergy.2019.113938

Abstract

Microbial electrolysis cells (MECs) produce hydrogen at the cathode associated with the oxidation of organic matter at the anode. This technology can produce hydrogen by consuming less electrical energy than water electrolysis does. However, it has been very difficult so far to scale up efficient MECs beyond the size of small laboratory cells. This article firstly revisits the fundamentals of MECs to assert their theoretical advantages. The low formal equilibrium cell voltage of 0.123 V and electrical and thermal energy yields as high as 10 and 12, respectively, are major assets. Other theoretical strengths are discussed, including the possibility to produce methane, and some safety advantages. The experimental achievements at pilot scale (several litres volume) are analysed through the prism of electrochemical engineering. This analysis leads to recommendations to modify some research efforts, notably by giving priority to increasing current density rather than working with volumetric parameters, using Faradaic yields to detect dysfunctions, and systematizing control experiments at open circuit. The critical analysis successively addresses electrolytes, electrode kinetics, temperature, substrate concentration, reactor architecture, and control procedures. It brings to light intrinsic weaknesses of the MEC concept and identifies improvements that can be made using current technology, for instance, by the catalysis of hydrogen evolution at neutral pH. The problem of the low electrolyte conductivity is pointed out and, in return, how increasing it can be detrimental to the key issue of anode acidification. Finally, research lines are proposed with the objective of moving ahead towards MEC development.

Item Type:Article
HAL Id:hal-02351495
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
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Agence Nationale de la Recherche (ANR)
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Deposited On:06 Nov 2019 13:14

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