微生物光电还原CO2合成乙酸对外电压的响应机制

以TiO₂光阳极结合自养型生物阴极，构建双室微生物光电合成（MPES）系统，以光能作为主要的能量来源，探究MPES还原CO₂合成乙酸的性能及其限制因素.结果表明，光阳极取代纯电化学阳极显著降低了MPES生物阴极对外电压的需求.MPES能持续稳定运行，平均产乙酸速率为（1.18 ±0.11） mmol/（L·d），法拉第效率为45.75%±3.97%.光阳极驱动阴极产生氢气，推测阴极微生物倾向于利用氢转移的方式来进行电子传递.外加电压通过影响光阳极的给电子能力从而对MPES的性能产生显著的影响，当外电压从0.4V升高至0.6V时，MPES的电流，乙酸产量和法拉第效率都显著提高，系统的性能主要受限于阳极.当外电压高于0.6V，系统电流，乙酸产量的增速减缓，法拉第效率在外加电压0.8V时达到最大值，随后下降，表明生物阴极的得电子能力已经达到饱和，此时MPES的性能主要受限于阴极.作为电子传递中间体，H₂的不完全利用是法拉第效率没有随着外电压的增加进一步提升的原因.

Microbial photoelectric reduction of CO2 to acetate and its response mechanism to external applied voltage

For evaluating the performance of microbial photoelectric synthesis (MPES) to reduce CO₂ to synthesize acetic acid and its limiting factors, this study tried to construct a novel double-chamber microbial photo-electrosynthesis system (MPES)by coupling TiO₂ photoanode with biocathode and using solar energy as main energy. The replacement of pure electrochemical anodes by photoanodes significantly reduced the external voltage requirements of MPES biocathodes, and MPES could continue to operate stably, with an average acetic acid production rate of (1.18 ±0.11) mmol/(L·d) and a Faraday efficiency of 45.75% ±3.97%. The photoanode drives the cathode to produce hydrogen, suggesting that the cathodic microorganisms tend to use H₂-mediated electron transfer. The external voltage influenced the performance of the MPES significantly by affecting the electron donating ability of the photoanode. When the external voltage was increased from 0.4~0.6V, the MPES current, acetate production and Faraday efficiency were significantly improved, and the performance of the MPES was mainly limited by the photoanode. When the external voltage was higher than 0.6V, the system current and the output of acetic acid increased mildly, and Faraday efficiency reached the maximum value at 0.8V, and then declined, indicating that the electron-acceptting ability of biocathode was saturated at 0.8V and the performance of the MPES was mainly limited by the biocathode. As an electron intermiate, H₂ was incompletely utilized during the operation of MPES, explaining why the Faraday efficiency was not further improved with an increase in external voltage.