A light-management film layer induces dramatically enhanced acetate production in photo-assisted microbial electrosynthesis systems

A light-management system consisting of a Al-doped ZnO (AZO) film layer was combined for the first time with different bio-photocathodes (Serratia marcescens Q1 electrotroph immobilized on g-C3N4, MnFe₂O₄ or MnFe₂O₄/g-C3N4) to significantly enhance acetate production from bicarbonate in photo-assisted microbial electrosynthesis systems (MES). The AZO light-management system exhibiting optical properties independent of the light incident angle mitigated the shielding effect of light by electrotrophs, increasing light trapping and decreasing light reflection, ultimately allowing higher rates of photon absorption and redistributions of photons over the photo-active layers. As a result, more reducing equivalents as H2 produced up to 242% (g-C3N4/AZO-filter) and 543% (g-C3N4/AZO) increase in acetate production at coulombic efficiencies of 70% (g-C3N4/AZO-filter) and 81% (g-C3N4/AZO). The record high solar-to-acetate efficiency obtained with the MnFe₂O₄/g-C3N4/AZO biocathode was 3.20%. The light-management system proposed in this study opens a new promising way to construct efficient bio-photocathodes for inorganic carbon reduction in photo-assisted MES.