Direct Conversion of Wheat Straw into Electricity with a Biomass Flow Fuel Cell Mediated by Two Redox Ion Pairs

In this paper, a biomass flow fuel cell to directly convert wheat straw to electricity at low temperature (80-90 °C) and atmospheric pressure is presented. Two redox ion pairs, Fe³⁺ /Fe²⁺ and VO₂⁺ /VO²⁺ , acting as redox catalysts and charge carriers, were used in the anode and cathode flow tanks, respectively. The wheat straw was first oxidized by Fe³⁺ in the anode tank at approximately 100 °C. The reduced Fe²⁺ in the anode was used to construct a fuel cell with VO₂⁺ in the cathode. The VO₂⁺ ions were reduced to VO²⁺ and regenerated to VO₂⁺ by oxygen oxidation. The wheat straw flow fuel cell showed a power output of 100 mW cm^-2 . Mediated with liquid Fe³⁺ carriers, the solid powder of wheat straw could be gradually degraded into low-molecular-weight organic molecules and even oxidized to CO₂ at the anode without using noble-metal catalysts. The overpotential for the electrodes of the flow fuel cell was examined and the energy cost was estimated.