Ni-Coated Carbon Fiber as an Alternative Cathode Electrode Material to Improve Cost Efficiency of Microbial Fuel Cells

- Ni-coated carbon fiber exhibits stronger affinity with AC than carbon cloth.
- The higher AC loading on Ni-CF results in lower charge transfer resistance.
- Ni-CF coated with AC leads to more power production in the MFC test.
- Initial AC loading of 4 g is identified as the optimal catalyst loading rate.
- The highest cost efficiency of 299.0 mW $−1 is obtained with Ni-CF coated with AC.

Electrode material is a key component in microbial fuel cells (MFCs), and exploring cost-effective electrode materials will greatly help with MFC development, especially the scaling up. In this study, a commercially available material - nickel-coated carbon fiber (Ni-CF) has been investigated as an alternative cathode electrode material to carbon cloth (CC). Both three-electrode cell and MFC tests are carried to examine electrochemical performance and actual electricity generation of the prepared cathode electrodes. It is found that Ni-CF exhibited higher current generation in linear sweep voltammetry (LSV) and lower resistance in electrochemical impedance spectroscopy (EIS) tests than those of CC and CF. When being coated with AC, Ni-CF has the highest actual loading amount among the tested materials. As a result, AC/Ni-CF leads to lower charge transfer resistance (95.1 Ω) and higher current density (8.07 mA m−2) than AC/CC (115.3 Ω and 3.40 mA m−2). In the MFC test, the cathode using AC/Ni-CF results in the maximum power density of 6.50 W m−3, higher than AC/CC at 4.29 W m−3. This high power output gives cost efficiency of AC/Ni-CF at 299.0 mW $−1, nearly twice that of AC/CC (151.7 mW $−1). The initial AC coating amount of 4 g is found to be the optimal amount to achieve optimally actual AC loading amount on the cathode electrode with balanced catalytic ability and (possible) oxygen transfer. Those results encourage further investigation of Ni-CF for MFC applications towards improved performance and cost efficiency.