Dye decolorization and energy recovery of photocatalytic fuel cell subjected to optimization of supporting electrolyte concentration and external resistance

The concentrations of supporting electrolyte and external resistance (Rext) played crucial roles to improve photocatalytic fuel cell (PFC) efficiency. Herein, the significant influence of Na2SO4 concentration (0.05-0.20 M) and the Rext (100, 280, 500, 1000 and 10,000 ω) on the power production and dye decolorization in PFC were addressed. Analysis of variance (ANOVA) revealed that the further increment of 0.10 M of Na2SO4 concentration only enhanced maximum power density (Pmax) but had no significant effect on the dye decolorization (P > 0.05). Conversely, the result showed distinct differences in PFC performances under different Rext (P < 0.05). The PFC operated with Rext of 280 ω from the maximum power point (RMPP) yielded the highest Pmax of 11.85 ± 0.45 μW cm-2 and decolorization rate of 0.51 h-1 with a total chemical oxygen demand (COD) removal of 88.82 ± 3.70%. Interestingly, it was discovered that the Pmax was significantly enhanced by the impedance-matching of Rext with RMPP while the decolorization rate was inversely proportional to RMPP. Besides, the dynamic behavior of PFC was associated with the polarization study which the main internal losses contributor was examined. Additionally, the present study provided insight into the toxicity reduction of the treated dye solution through simple phytotoxicity test by using lettuce seed bioassays.