Low voltage water electrolysis: Decoupling hydrogen production using bioelectrochemical system Pierre Belleville a,b , Francois Guillet a,c , Alessia Pons c , Jonathan Deseure a,* , G  erard Merlin a,b , Florence Druart a , Julien Ramousse b , Elisa Grindler c a Univ. Grenoble Alpes, CNRS, Grenoble INP, Institute of Engineering Univ. Grenoble Alpes, LEPMI, 38000 Grenoble, France b Laboratoire D'Optimisation et Conception D'Ing enierie Environnementale (LOCIE), UMR CNRS 5271 Universit e de Savoie Mont-Blanc, Le Bourget Du Lac, France c ERGOSUP, 145 Chemin de La Roche Du Guide, RN7 Espace Combeli ere Sud, 26780 Malataverne, France article info Article history: Received 12 February 2018 Accepted 12 June 2018 Available online xxx Keywords: Bioelectrochemical system Microbial fuel cell Hydrogen production Decoupling water electrolysis Wastewater valorization abstract Decoupling water electrolysis using mediator is an interesting way to produce pure hydrogen. The present work validates the proof of concept of decoupled electrolyser associated with a bioelectrochemical system (MFC-DES) through a redox flow mediator (potassium hexacyanoferrate (KHCF)). Low voltage (1 V) hydrogen production was achieved with a current density up to 25 mA cm 2 . Regeneration of the mediator was performed by glucose fed microbial fuel cells. The oxidation rate of KHCF in the electrolyser is, at least, an order of magnitude higher than the reduction rate in MFC cascade fed system. MFC-DES is thus a promising set up as it desynchronizes limited microbial rate and hydrogen pro- duction, generate value from wastewater and reduce energetic cost of water electrolysis. © 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction The growing need for energy by the human society and depletion of conventional energy sources demands renew- able, safe, low-cost and omnipresent energy sources. Bio- electrochemical system (BES) have gained interest over the last decade to convert biomass wastes into bioelectricity and chemicals [1]. Indeed, it's possible to take advantage of interactions between bacteria and electrodes to run electro- chemical reaction [2]. In conjunction with this strategy, power-to-gas and in particular power-to-hydrogen shall be part of our future (renewable) energy mix [3]. At present, most H 2 produced has a fossil origin and mankind strives to develop renewable H 2 production, e.g. by water electrolysis (J. Mergel, 2014) based on the electrochemical reaction of water splitting: H 2 O ð1Þ /H 2ðgÞ þ 1=2O 2ðgÞ (1) List of acronyms: BES, Bioelectrochemical systeml; COD, chemical oxygen demand; DES, decoupling electrolysis system; ECPB, elec- tron-coupled proton buffer; HCF, hexacyanoferrate; KHCF, potassium hexacyanoferrate; MEC, microbial electrolysis cell; MES, microbial electrosynthesis; MFC, microbial fuel cell; OER, oxygen evolution reaction; RFB, redox flow battery; RHE, reversible hydrogen electrode. * Corresponding author. E-mail address: jonathan.deseure@lepmi.grenoble-inp.fr (J. Deseure). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2018) 1 e9 https://doi.org/10.1016/j.ijhydene.2018.06.080 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Belleville P, et al., Low voltage water electrolysis: Decoupling hydrogen production using bio- electrochemical system, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.06.080