Department of Civil and Environmental Engineering , The Pennsylvania State University , 231Q Sackett Building , University Park , Pennsylvania 16802 , United States.
Biological and Environmental Sciences and Engineering Division, Water Desalination and Reuse Research Center , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Saudi Arabia.
Environ Sci Technol. 2018 Aug 7;52(15):8977-8985. doi: 10.1021/acs.est.8b02055. Epub 2018 Jul 17.
Low solution conductivity is known to adversely impact power generation in microbial fuel cells (MFCs), but its impact on measured electrode potentials has often been neglected in the reporting of electrode potentials. While errors in the working electrode (typically the anode) are usually small, larger errors can result in reported counter electrode potentials (typically the cathode) due to large distances between the reference and working electrodes or the use of whole cell voltages to calculate counter electrode potentials. As shown here, inaccurate electrode potentials impact conclusions concerning factors limiting power production in MFCs at higher current densities. To demonstrate how the electrochemical measurements should be adjusted using the solution conductivity, electrode potentials were estimated in MFCs with brush anodes placed close to the cathode (1 cm) or with flat felt anodes placed further from the cathode (3 cm) to avoid oxygen crossover to the anodes. The errors in the cathode potential for MFCs with brush anodes reached 94 mV using acetate in a 50 mM phosphate buffer solution. With a felt anode and acetate, cathode potential errors increased to 394 mV. While brush anode MFCs produced much higher power densities than flat anode MFCs under these conditions, this better performance was shown primarily to result from electrode spacing following correction of electrode potentials. Brush anode potentials corrected for solution conductivity were the same for brushes set 1 or 3 cm from the cathode, although the range of current produced was different due to ohmic losses with the larger distance. These results demonstrate the critical importance of using corrected electrode potentials to understand factors limiting power production in MFCs.
低溶液电导率已知会对微生物燃料电池 (MFC) 的发电产生不利影响，但在报告电极电位时，其对测量电极电位的影响经常被忽视。虽然工作电极（通常为阳极）的误差通常较小，但由于参考电极和工作电极之间的距离较大或使用全电池电压来计算对电极电位，可能会导致报告的对电极电位（通常为阴极）出现较大误差。如这里所示，不准确的电极电位会影响在更高电流密度下限制 MFC 发电的因素的结论。为了展示如何根据溶液电导率调整电化学测量，使用靠近阴极（1 厘米）的电刷阳极或远离阴极（3 厘米）的毛毡阳极的 MFC 估算了电极电位，以避免氧气交叉到阳极。在 50mM 磷酸盐缓冲溶液中使用醋酸盐时，电刷阳极 MFC 的阴极电位误差达到 94mV。使用毛毡阳极和醋酸盐时，阴极电位误差增加到 394mV。虽然在这些条件下，电刷阳极 MFC 的功率密度比毛毡阳极 MFC 高得多，但这种更好的性能主要是由于电极间距在纠正电极电位后得到了改善。经溶液电导率校正的电刷阳极电位对于距离阴极 1 或 3 厘米的电刷相同，尽管由于较大距离的欧姆损耗，产生的电流范围不同。这些结果表明，使用校正后的电极电位来理解限制 MFC 发电的因素非常重要。
