• Energy Research

Abstract A Bioelectrochemical System (BES) is used for charging an electrochemical fuel to be used in a Redox Flow Cell (RFC), demonstrating the first proof of concept of a microbially-charged electrochemical fuel. Geobacter sulfurreducens, electroactive bacteria, was used to charge anthraquinone-2,6-disulfonate (2,6-AQDS) producing current densities of ca. 200–500 mA m−2 and maximum power densities of ca. 33 mW m−2. The microbially-charged electrochemical fuel and potassium ferricyanide, K3[Fe(CN)6] were introduced in a RFC producing a potential difference of 0.62 V, with a ca. 80% energy conversion efficiency. The use of a BES for charging the posilyte of a RFC is now envisioned. The bio-conversion of waste biomass energy into electrochemical fuels (microbially-charged electrochemical fuel for negalyte and posilyte) for later use in a RFC to produce electricity is a promising approach of converting biomass into storable and easy to use energy.

M.S.S. Santos is grateful to Portuguese Foundation for Science and Technology (FCT) for her PhD fellow (reference: SFRH/BD/104087/ 2014). Kashif Mushtaq is grateful to MIT Portugal Program for his doctoral grant (PD/BD/128041/2016) under the scope of the FCT. The authors would like to acknowledge to the FCT under the scope of the strategic funding of UID/BIO/04469 unit and COMPETE 2020 (POCI 01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145- FEDER-000004) funded by the European Regional Development Fund (ERDF), under the scope of Norte2020 - Programa Operacional Regional do Norte. The authors also acknowledge the Projects: i) POCI-01-0145- FEDER-006939 (LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy – UID/EQU/00511/2013), funded by the ERDF, through COMPETE2020 – Programa Operacional Competitividade e Internacionalizacao (POCI) and by nationals funds through FCT, ii) by the Project SunStorage - Harvesting and storage of solar energy”, with reference POCI-01-0145-FEDER-016387, funded by ERDF, through COMPETE 2020 –POCI), and by national funds, through FCT; (iii) Project PTDC/EQU-EQU/30510/2017 - POCI-01-0145- FEDER-030510 – Sunflow “Solar energy storage into redox flow batteries” funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) and by national funds (PIDDAC) through FCT/MCTES and iV) NORTE-01-0145- FEDER-000005 – LEPABE-2-ECO-INNOVATION, supported by North Portugal Regional Operational Programme (Norte 2020), under the Portugal 2020 Partnership Agreement, through the ERDF. The authors are indebted with all the colleagues who assisted in the laboratory work.