Effect of NaOH concentration as activator on calcined eggshell and its application for yeast microbial fuel cell

Eggshells may be utilized as an advanced material. Yeast microbial fuel cells may benefit with calcined eggshell at carbon felt anodes. Stability issues and poor power density prohibit its wider usage. We determined the eggshell-to-NaOH ratio for calcined eggshell anode material. Calcined eggshell with a 1:4 eggshell-NaOH ratio had a high maximum power density (31 mW.m−2) and voltage stability of 45 mV after 30 days incubation. The addition of NaOH activator may also increase crystal size and crystallinity to 145 nm and 43.92 %, respectively, which may accelerate electron transport as evidenced by a decrease in the energy band gap from 5.6 to 5.2 eV, as determined by DFT analysis. The addition of NaOH activator during incubation increased the surface area to 181.2 m2.g−1, improving the anode's potential to host yeast biofilms. Calcined eggshell with a 1:4 eggshell-NaOH ratio is a good anode for yeast microbial fuel cells. [Display omitted] •Eggshell is activated using NaOH before calcined.•The main crystalline phase of calcined eggshell is calcite.•The largest signal at 1421–1439 cm−1 indicates all samples contain carbonate ions.•Calcined eggshell used as anode for MFC.•MFC which use 1:4 calcined eggshell as anode results higher MPD of 31 mW/m2.