Acetate production from inorganic carbon (HCO3-) in photo-assisted biocathode microbial electrosynthesis systems using WO3/MoO3/g-C3N4 heterojunctions and Serratia marcescens species.

• WO 3 /MoO 3 /g-C 3 N 4 and Serratia marcescens catalyze the production of acetate in photo-assisted MES. • Appreciable high production of acetate and coulombic efficiency are achieved. • WO 3 /MoO 3 and g-C 3 N 4 interact in a Z-scheme mechanism to enhanced electrons-holes separation. • Photo-induced electrons on the conduction band of semiconductor enhance H 2 production. • Photo-generated holes favor higher current and thus higher acetate production. The efficient production of acetate from HCO 3 − is demonstrated in a photo-assisted microbial electrosynthesis system (MES) incorporating a WO 3 /MoO 3 /g-C 3 N 4 heterojunction photo-assisted biocathode supporting Serratia marcescens Q1 electrotroph. The WO 3 /MoO 3 /g-C 3 N 4 structured electrode consisting of a layer of g-C 3 N 4 coated on graphite felt decorated with W/Mo oxides nanoparticles exhibited stable photocurrents, 4.8 times higher than the g-C 3 N 4 electrode and acetate production of 3.12 ± 0.20 mM/d with a CE acetate of 73 ± 4 % and current of 2.5 ± 0.3 A/m2. Photo-induced electrons on the conduction bands of WO 3 /MoO 3 /g-C 3 N 4 favoured hydrogen evolution, which was metabolized by S. marcescens with HCO 3 − to acetate, while the holes were refilled by the electrons travelling from the anode. Such mechanism reduced the interfacial resistances creating a supplementary driving force leading to higher acetate production. The biocompatible components of WO 3 /MoO 3 /g-C 3 N 4 synergistically couple light-harvesting and further catalyze S. marcescens to acetate from HCO 3 −, providing a feasible strategy for achieving sustainable high rates of acetate production. [ABSTRACT FROM AUTHOR]