Power generation of microbial fuel cells (MFCs) with low cathodic platinum loading

This study aims at investigating the effects of platinum (Pt) loadings on the cathodic reactions in Single Chamber Microbial Fuel Cells (SCMFCs) and developing cost-effective MFC operational protocols. The power generation of SCMFCs was examined with different Pt loadings (0.005–1 mgPt/cm2) on cathodes. The results showed that the power generation of the SCMFCs with 0.5–1 mgPt/cm2 were the highest in the tests, decreased 10–15% at 0.01–0.25 mgPt/cm2, and decreased further 10–15% at 0.005 mgPt/cm2. The SCMFCs with Pt-free cathode (graphite) had the lowest power generation. In addition, the power generation of SCMFCs with different Pt loadings were compared in raw wastewater (Chemical oxygen demand (COD): 0.36 g/L) and wastewater enriched with sodium acetate (COD: 2.95 g/L). The solution conductivity in SCMFCs decreased with the degradation of organic substrates. Daily polarization curves (V–I) showed a decrease in current generation and an increase in ohmic losses over the operational period (8 days). The SCMFCs (with 0.5–1 mgPt/cm2 at cathode) fed with wastewater and sodium acetate (NaOAc) reached the highest power generation (786 mW/m2), while the SCMFCs (with 0.5–1 mgPt/cm2 at cathode) fed only with wastewater obtained the lower power generation (81 mW/m2). The study demonstrated that lowering the Pt loadings in two magnitude orders (1 to 0.01, 0.5 to 0.005 mgPt/cm2) only reduced the power generation of 15–30%, and this reduction of the power generation become less substantial with the decrease in the solution conductivity of SCMFCs.

► Lowering Pt loadings by 2 magnitudes only reduced the power generation of 20–30%.
► Pt-free cathodes could still have stable power generation due to the biofilms growing on cathodes.
► The differences in power generation of cathodes with different Pt loadings became smaller at lower solution conductivity.