Enhancing conversion from glucose to electricity by ferric chloride in a redox flow fuel cell

Fuel cells that directly convert biomass to CO2 can obtain maximum electrons from biomass and avoid the disposal of residuals. In this study, a redox flow fuel cell catalyzed by phosphomolybdic acid (PMO12) and FeCl3 is studied aiming to complete utilization of glucose. At room temperature, the highest power density of 6.5 mW cm−2 is obtained when the cell is catalyzed by 0.10 mol L−1 PMo12 alone. However, the power density reaches 5.8 mW cm−2 when it is catalyzed by 0.5 mol L−1 FeCl3 and 0.05 mol L−1 PMo12 together, and hence the cell can save 50% of PMo12 usage. Furthermore, the mixed catalysts has better capability to degrade glucose than PMO12 or FeCl3 alone. After 108 h of continuous reaction at 80 °C, 84.3% of total organic carbon (TOC) in glucose is converted to CO2 with the help of 1.0 mol L−1 FeCl3 and 0.1 mol L−1 PMo12, which is higher than the ratio of 69.5% obtained by 0.2 mol L−1 PMO12 alone. In the cell, FeCl3 with Lewis acidity contributes to glucose degradation, enhances the kinetics of cell reaction, and simultaneously acts as an electron shuttle to promote the discharging reaction. These allow the cell achieve better performance with less use of PMo12.