Ferric iron enhances electricity generation by Shewanella oneidensis MR-1 in MFCs

► Fe(III) accelerated the growth of Shewanella oneidensis MR-1 biofilm. ► The addition of Fe(III) exhibited a higher power output and a shorter start-up period. ► A maximum power density by the supplement of Fe(III) was increased to two times. ► The addition of Fe(III) enhanced the total amount of flavins secreted by strain MR-1.