Abstract
Conventional electric double-layer capacitors are energy storage devices with a high specific power and extended cycle life. However, the low energy content of this class of devices acts as a stumbling block to widespread adoption in the energy storage field. To circumvent the low-energy drawback of electric double-layer capacitors, here we report the assembly and testing of a hybrid device called electrocatalytic hydrogen gas capacitor containing a hydrogen gas negative electrode and a carbon-based positive electrode. This device operates using pH-universal aqueous electrolyte solutions (i.e., from 0 to 14) in a wide temperature range (i.e., from - 70 °C to 60 °C). In particular, we report specific energy and power of 45 Wh kg(-1) and 458 W kg(-1) (both values based on the electrodes' active materials mass), respectively, at 1 A g(-1) and 25 °C with 9 M H(3)PO(4) electrolyte solution. The device also enables capacitance retention of 85% (final capacitance of about 114 F g(-1)) after 100,000 cycles at 10 A g(-1) and 25 °C with 1 M phosphate buffer electrolyte solution.