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 (K_La = 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.