Asymmetric acidic-alkaline design achieves high power density for a direct ascorbate liquid fuel cell without using noble metal catalysts

In order to efficiently convert ascorbic acid/ascorbate to electricity, a direct liquid fuel cell (DLFC) was developed with graphite as electrodes and VO2+/VO2+ as the cathode electron carrier under the activation of HNO3 for promoting electron transfer to the final accepter, oxygen. Alkaline anolyte was used for ascorbate oxidation, while acidic catholyte was used for oxygen reduction. Effects of various operation factors and cell structural features on the discharging performance were studied. Under the optimal operation conditions, the maximal output power density (Pmax) of 449.4 mW cm−2 was obtained at 90 ℃ with a short circuit current density of 987 mA cm−2. The cell showed 98.7% anode efficiency, 98.6% discharging efficiency and 99.9% cathode efficiency, with 97.2% total efficiency of electron transfer. The DLFC developed in this work also can well convert various biomass-derived organic fuels including fruit juice, sugars and sodium lignosulphonate to electricity with Pmax of 48–213 mW cm−2, which are at the highest level of the reported results. Therefore, this work provides a novel asymmetry acidic-alkaline design of DLFC with efficient electron transport chain for promoting the kinetics of oxygen reduction thus achieving high efficiency of electricity generation from ascorbate and various biomass-derived fuels without using any noble metal catalysts and expensive oxidants. This novel DLFC thus may provide new routes for efficient biomass-to-electricity conversion. © 2022 Elsevier Ltd