Résumé
Here we present the development of
a non-conventional fuel cell with a liquid redox cathode.
The originality of the project comes from the regeneration of a redox mediator in an additional tank outside of the cell. Instead of oxygen classically used at the cathode, a liquid catalyst is reduced and a fuel (H
2
) is oxidized at the anode. This system is called a chemically regenerative redox flow cell (CRRFC). This technology allows to answer both issues i.e. price (Platinum free cathode) and chemical stability (absence of ROS at the interface electrode/membrane).
Few examples of chemically regenerative redox fuel cell have been described in the literature[1] with different redox couples (NO
3-
/NO
2-
,[2] polyoxometalate[3]). The best performances have been obtained with polyoxometalate derivatives developed and commercialized recently by the ACAL-energy company.[4] The Flowcath® technology is based on a polyoxometalate (POM) solution as catholyte. Their technology has been able to provide energy during more than 10,000 hours. The major issues arising from their technology are the crossover of the polyoxometalate and the efficiency during regeneration process.
In this study, we first synthesize and characterize molecules as redox mediator to carry electron between the regenerator and the electrode. The redox molecule belongs to the family of polyoxometalate containing vanadium moiety. These molecules are a key element of the device and needs to answer some criteria such as a fast electron transfer, a redox potential below 1.23 V vs. ESH and a fast chemical oxidation by dioxygen.
A specific cell stand has been developed with an additional tank to oxidize the redox mediator. All the challenge comes from the regenerator chamber in order to not be limited by mass transport of the oxidised species. Polarization curves have been recorded to give access to the cell performances.
[1] Tolmachev, Y. V.; Vorotyntsev, M. A.
Russ. J. Electrochem.
2014
,
50
, 403–411, doi:10.1134/S1023193514020050.
[2] Han, S. B.; Kwak, D. H.; Park, H. S.; Choi, I. A.; Park, J. Y.; Kim, S. J.; Kim, M. C.; Hong, S.; Park, K. W.
Angew. Chemie - Int. Ed.
2017
,
56
, 2893–2897, doi:10.1002/anie.201610738.
[3] (a) Ward, D. B.; Gunn, N. L. O.; Uwigena, N.; Davies, T. J.
J. Power Sources
2018
,
375
, 68–76, doi:10.1016/j.jpowsour.2017.11.035. (b) Ward, D. B.; Davies, T. J.
Johnson Matthey Technol. Rev.
2018
,
62
, 189–203, doi:10.1595/205651318X696800.
[4] Creeth, A. Pt-free PEM cathode technology with fundamental durability benefits: FlowCath®.
Fuel Cells Bull.
2011
,
2011
, 12–15, doi:10.1016/S1464-2859(11)70126-2.