Abstract:

The liquid level difference between the cathode and the anode increased obviously with increase of operation cycles in the dual chamber microbial fuel cell (DCMFC). To analyze this phenomenon, the transport behavior of proton and water was investigated from evaporation, osmotic pressure, metabolism and electric field. The relationship between water production and the fuel's performance was studied. The results showed that within 360 h, the liquid change due to evaporation and osmotic pressure was less than 0.50 ml (liquid level declined near 0.5 mm). Within 312 h of circuit breakage, the anodic metabolism gas led to the proton exchange membrane (PEM) deformation convex to the cathode. The anodic liquid decreased 6.20 ml (liquid level reduced near 6.5 mm), the cathodic liquid increased 10.75 ml (liquid level rose near 11.2 mm) and the liquid level difference reached 17.7 mm. Under the circuit connection, except the PEM deformation, the protons were dragged by electro-osmotic to the cathode and reduced to water. Within 312 h, the anodic liquid decreased 10.70 ml (liquid level reduced about 11.1 mm), the cathodic liquid increased 17.00 ml (liquid level rose about 17.7 mm), and then formed a 28.8 mm liquid level difference. Moreover, the water transmission increased with the increase of output voltage. The results implied that the biological metabolism and electro-osmotic had an important influence on DCMFC liquid difference. It was possible to calculate proton transfer rate based on its water production. The proton transfer rate in the system was over 54%. This study provided a simple and intuitive basis for judging the electricity production efficiency.

Key words: fuel cells, liquid volume change, electro-osmosis drag, proton transfer, bio-catalysis, anaerobic

摘要：

随着DCMFC产电周期的增加，阴阳极间的液位差明显增加。为解析此现象，从蒸发、渗透压、生物代谢及电场角度考察了质子和水的传递行为，研究了产水与电池性能的关系。结果表明：360 h内蒸发、渗透压引起的液量变化少于0.50 ml（液面降低0.5 mm）；断路312 h，阳极代谢气体使PEM形变凸向阴极，阳极液减少6.20 ml（下降6.5 mm），阴极液增加10.75 ml（上升11.2 mm），两腔液位差达17.7 mm；通路下，除膜的形变，水合质子被电渗透到阴极并还原成水，312 h内阳极液减少10.70 ml（下降11.1 mm），阴极液增加17.00 ml（上升17.7 mm），两腔液位差达28.8 mm，且产水量随电压的增大而增加。研究表明，生物代谢及电渗透对两腔液量影响较大，产水量可表征质子传递率。经计算该系统质子传递率大于54%，为评判产电效率提供了简便依据。

关键词: 燃料电池, 液量变化, 电渗透, 质子传递, 生物催化, 厌氧