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

## TL;DR

Adding silica nanoparticles to a reactor improves hydrogen transfer and boosts acetate production in a CO2 fixation process.

## Contribution

Silica nanoparticles significantly enhance hydrogen mass transfer and acetate production in hydrogen-mediated microbial electrosynthesis.

## Key findings

- Silica nanoparticles increased hydrogen mass transfer by 32.4% and acetate production rate by 69.8%.
- Acetate titer increased by 56.9% with silica nanoparticles.
- The reactor achieved a high acetate production rate of 2.14 g·L−1·d−1.

## Abstract

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 (kLa) 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.

The online version contains supplementary material available at 10.1186/s40643-023-00627-6.