Enhancement of acetate production in hydrogen-mediated microbial electrosynthesis reactors by addition of silica nanoparticles

Microbial electrosynthesis (MES) is a promising technology for CO₂ fixation and electrical energy storage. Currently, the low current density of MES limits its practical application. The H₂-mediated and non-biofilm-driven MES could work under higher current density, but it is difficult to achieve high coulombic efficiency (CE) due to low H₂ solubility and poor mass transfer. Here, we proposed to enhance the hydrogen mass transfer by adding silica nanoparticles to the reactor. At pH 7, 35 ℃ and 39 A·m^− 2 current density, with the addition of 0.3wt% silica nanoparticles, the volumetric mass transfer coefficient (k_La) of H₂ in the reactor increased by 32.4% (from 0.37 h^− 1 to 0.49 h^− 1), thereby increasing the acetate production rate and CE of the reactor by 69.8% and 69.2%, respectively. The titer of acetate in the reactor with silica nanoparticles (18.5 g·L^− 1) was 56.9% higher than that of the reactor without silica nanoparticles (11.8 g·L^− 1). Moreover, the average acetate production rate of the reactor with silica nanoparticles was up to 2.14 g·L^− 1·d^− 1 in the stable increment phase, which was much higher than the other reported reactors. These results demonstrated that the addition of silica nanoparticles is an effective approach to enhancing the performance of H₂-mediated MES reactors. Graphical Abstract: [Figure not available: see fulltext.]