Strengthening H2 gas-liquid mass transfer using superaerophobic cathodes for enhanced methane production from CO2 in H2-mediated microbial electrosynthesis system.

H2-mediated microbial electrosynthesis (MES) could run under a high current density, but the low solubility of H2 limited its performance. Reducing the H2 bubble size facilitates H2 gas-liquid mass transfer and it has been reported to be realized on superaerophobic electrodes. Therefore, we adopted a CoP nanowire-modified nickel foam (CoP-NiF) as the superaerophobic cathode in a H2-mediated MES reactor to enhance the methane production from CO2. The CoP nanowire modification reduced the average diameter of H2 bubbles from ∼ 300 μm to ∼ 100 μm, thereby exhibiting a 129 % enhancement of the H2 mass transfer coefficient (KLa = 0.32 min-1). The maximum CH4 production rate with CoP-NiF cathode exhibited a 27 % improvement (2.31 L/L/d) at a high current density of 166.67 A/m2. More importantly, a coulombic efficiency higher than 80 % was achieved in the reactor. These results demonstrated that using superaerophobic cathodes is an efficient way to enhance the performance of H2-mediated MES reactors.