Bajracharya Suman, Vanbroekhoven Karolien, Buisman Cees J N, Pant Deepak, Strik David P B T B
Separation and Conversion Technologies, Flemish Institute for Technological Research (VITO), Mol, Belgium.
Sub-department of Environmental Technology, Wageningen University, Wageningen, The Netherlands.
Environ Sci Pollut Res Int. 2016 Nov;23(22):22292-22308. doi: 10.1007/s11356-016-7196-x. Epub 2016 Jul 20.
Microbial catalysis of carbon dioxide (CO) reduction to multi-carbon compounds at the cathode is a highly attractive application of microbial electrosynthesis (MES). The microbes reduce CO by either taking the electrons or reducing the equivalents produced at the cathode. While using gaseous CO as the carbon source, the biological reduction process depends on the dissolution and mass transfer of CO in the electrolyte. In order to deal with this issue, a gas diffusion electrode (GDE) was investigated by feeding CO through the GDE into the MES reactor for its reduction at the biocathode. A combination of the catalyst layer (porous activated carbon and Teflon binder) and the hydrophobic gas diffusion layer (GDL) creates a three-phase interface at the electrode. So, CO and reducing equivalents will be available to the biocatalyst on the cathode surface. An enriched inoculum consisting of acetogenic bacteria, prepared from an anaerobic sludge, was used as a biocatalyst. The cathode potential was maintained at -1.1 V vs Ag/AgCl to facilitate direct and/or hydrogen-mediated CO reduction. Bioelectrochemical CO reduction mainly produced acetate but also extended the products to ethanol and butyrate. Average acetate production rates of 32 and 61 mg/L/day, respectively, with 20 and 80 % CO gas mixture feed were achieved with 10 cm of GDE. The maximum acetate production rate remained 238 mg/L/day for 20 % CO gas mixture. In conclusion, a gas diffusion biocathode supported bioelectrochemical CO reduction with enhanced mass transfer rate at continuous supply of gaseous CO. Graphical abstract ᅟ.
微生物在阴极将二氧化碳（CO₂）还原为多碳化合物是微生物电合成（MES）极具吸引力的应用。微生物通过获取电子或还原在阴极产生的当量来还原CO₂。在使用气态CO₂作为碳源时，生物还原过程取决于CO₂在电解质中的溶解和传质。为了解决这个问题，研究了一种气体扩散电极（GDE），通过将CO₂通过GDE进料到MES反应器中，以便在生物阴极进行还原。催化剂层（多孔活性炭和聚四氟乙烯粘合剂）和疏水气体扩散层（GDL）的组合在电极处形成三相界面。因此，CO₂和还原当量将可用于阴极表面的生物催化剂。由厌氧污泥制备的富含产乙酸细菌的接种物用作生物催化剂。阴极电位相对于Ag/AgCl保持在-1.1 V，以促进直接和/或氢介导的CO₂还原。生物电化学CO₂还原主要产生乙酸，但也将产物扩展到乙醇和丁酸。使用10 cm的GDE，分别以20%和80%的CO₂气体混合物进料，平均乙酸生产率分别为32和61 mg/L/天。对于20%的CO₂气体混合物，最大乙酸生产率保持在238 mg/L/天。总之，气体扩散生物阴极支持生物电化学CO₂还原，在连续供应气态CO₂时传质速率得到提高。图形摘要ᅟ。
