Reversible transient hydrogen storage in a fuel cell–supercapacitor hybrid device

Abstract

A new concept is investigated for hydrogen storage in a supercapacitor based on large-surface-area carbon material (Black Pearls 2000). Protons and electrons of hydrogen are separated on a fuel cell-type electrode and then stored separately in the electrical double layer, the electrons on the carbon and the protons in the aqueous electrolyte of the supercapacitor electrode. The merit of this concept is that it works spontaneously and reversibly near ambient pressure and temperature. This is in pronounced contrast to what has been known as electrochemical hydrogen storage, which does not involve hydrogen gas and where electrical work has to be spent in the loading process. With the present hybrid device, a H(2) storage capacity of 0.13 wt% was obtained, one order of magnitude more than what can be stored by conventional physisorption on large-surface-area carbons at the same pressure and temperature. Raising the pressure from 1.5 to 3.5 bar increased the capacity by less than 20%, indicating saturation. A capacitance of 11 μF cm(-2), comparable with that of a commercial double layer supercapacitor, was found using H(2)SO(4) as electrolyte. The chemical energy of the stored H(2) is almost a factor of 3 larger than the electrical energy stored in the supercapacitor. Further developments of this concept relate to a hydrogen buffer integrated inside a proton exchange membrane fuel cell to be used in case of peak power demand. This serial setup takes advantage of the suggested novel concept of hydrogen storage. It is fundamentally different from previous ways of operating a conventional supercapacitor hooked up in parallel to a fuel cell.

Nitrogen and Phosphorous Co‐Doped Graphene Monolith for Supercapacitors

“…The quasi‐rectangular CV curves and the symmetrical GC profiles of both the N/P‐G samples and un‐G (Figure ) are characteristic of an electrode material in which electric double layer capacitance (EDLC) is the dominant charge‐storage mechanism. However, a pair of humps is observed at around 0.4 V vs. Ag/AgCl in the CV profiles of N/P‐G‐3 and N/P‐G‐10; these features are typically related to the surface oxygen functionalities and contribute pseudo‐capacitance to the charge storage. The GC profiles of the N/P‐G‐3 and N/P‐G‐10 electrodes show a very small IR drop whereas un‐G has a much larger IR drop (around 0.1 V), which demonstrates that the N/P‐G samples have faster charge propagation than un‐G.…”

Effect of electrode thickness variation on operation of capacitive deionization

“…due to acidic or phenolic groups in the carbon particles. If this chemical charge is important, then one expects that desalination performance depends on pH, because pH influences the ionization degree of such surface groups [40,41]. For instance, acidic groups reduce their charge at lower pH (are increasingly protonated, thus neutralized at low pH).…”

Synthesis of P‐Doped and NiCo‐Hybridized Graphene‐Based Fibers for Flexible Asymmetrical Solid‐State Micro‐Energy Storage Device

“…Figure a and Figure S7b (Supporting Information) show the cyclic voltammetry (CV) curves of the four samples at a scan rate of 10 mV s −1 . It can be seen that a pair of reversible redox peaks at ≈−0.6 V versus Hg/HgO appear in both PGO/CF and GO/CF, which is generally attributed to the reversible groups on the carbon surface . In the PGO/CF sample, this peak at ≈−0.6 V versus Hg/HgO is speculated to CO from graphene oxide and PO from phytic acid.…”