Rechargeable PEM Fuel-Cell Batteries Using Quinones as Hydrogen Carriers

Rechargeable fuel-cell batteries (RFCBs) that employ organic chemical hydrides as hydrogen storage media have potential as next-generation power sources; however, the reversible storage and release of hydrogen remains a significant challenge. In particular, the hydrogenation of organic compounds during cell charge is difficult to achieve with 100% conversion. However, this report demonstrates that quinones, especially anthraquinone (AQ), can function as a hydrogen carrier for RFCBs, where AQ is hydrogenated to anthrahydroquinone (AH 2 Q) during charge and AH 2 Q is dehydrogenated to AQ during discharge. This redox reaction occurred at a more positive potential than that for hydrogen reduction, so that undesired hydrogen production can be avoided by adjusting the charge voltage to 1 V. The resulting RFCB maintained 100% electrical capacity at room temperature, 91% at 50°C, and 63% at 75°C of the respective initial performance with coulombic efficiencies greater than 90% after 300 cycles. Moreover, the RFCB functioned as a secondary battery with energy densities of 0.8–3.4 Wh kg −1 , power densities of 9.5–258.9 W kg −1 , and as a fuel cell with power densities of 0.001–0.26 W cm −3 . Based on the performance and degradation data, the limitations of this RFCB and directions for future research are discussed.