Ferric-ferrous redox couple mediated low temperature symmetric flow fuel cell for direct conversion of biomass residues into electricity

Abstract

As one of promising candidates for high-efficient energy conversion device, biomass flow fuel cells (BFFCs) can directly convert biomass into electricity at low temperature without noble metal catalyst. Most BFFCs utilize polyoxometalates which are high molecular weight inorganic clusters with low molar solubility in water and relative high cost. Here we report a new, cheap and environmentally benign symmetric biomass flow fuel cell (BFFC) mediated by simple Fe3+/Fe2+ redox couple on both sides, which can directly and efficiently convert various biomass residues into electricity at low temperature. Fe3+ in anode can efficiently oxidize biomass residues into high value chemicals, such as 5-hydroxymethylfurfural, furfural, etc., and simultaneously being reduced to Fe2+. The low electric potential Fe2+ in anode and the high electric potential Fe3+ in cathode are assembled into a fuel cell. The consumed Fe3+ in cathode can be regenerated immediately under the strong synergism of O2 and HNO3. The designed cell yields a power density 54.5 mW cm−2 and can discharge continuously more than 7 h at a constant current density 200 mA cm−2. The BFFC can successfully light 43 LED bubbles. This approach is highly desirable for the development of low cost, high-performance and environment-friendly biomass flow fuel cells.