Abstract
The inherently variable nature of renewable energy sources makes them storage-dependent when providing a reliable and continuous energy supply. One feasible energy-storage option that could meet this challenge is storing surplus renewable energy in the form of hydrogen. In this context, storage of hydrogen electrochemically in porous carbon-based electrodes is investigated. Measurements of hydrogen storage capacity, proton conductivity, and capacitance due to electrical double layer of several porous activated carbon electrodes are reported. The hydrogen storage capacity of the tested electrodes is found in the range of 0.61−1.05 wt.%, which compares favorably with commercially available metal hydride-based hydrogen storage, lithium polymer batteries, and lithium ion batteries in terms of gravimetric energy density. The highest obtained proton conductivity was 0.0965 S/cm, which is near to that of the commercial polymer-based proton conductor, nafion 117, under fully hydrated conditions. The obtained capacitance due to double-layers of the tested electrodes was in the range of 28.3–189.4 F/g. The relationship between specific surface area, micropore volume and hydrogen storage capacity of the carbon electrodes is discussed. The contribution of capacitance to the equivalent hydrogen storage capacity of carbon electrodes is reported. The implications of the obtained experimental results are discussed.
Highlights
IntroductionThe regular use of fossil-based fuels for various activities (such as transport, electricity generation, etc.)has led to the increased dependency of humankind on fossil fuels with associated serious consequences and, has been causing an issue of global warming [1,2,3]
The regular use of fossil-based fuels for various activitieshas led to the increased dependency of humankind on fossil fuels with associated serious consequences and, has been causing an issue of global warming [1,2,3]
It was observed that proton conductivity of activated carbon (aC) samples increased with the rise in level of porosity because more acid is accessible for proton conduction
Summary
The regular use of fossil-based fuels for various activities (such as transport, electricity generation, etc.)has led to the increased dependency of humankind on fossil fuels with associated serious consequences and, has been causing an issue of global warming [1,2,3]. The increased consumption of fossil fuels has pushed the available reserves on earth towards depletion [4,5] These challenges are rendering it mandatory to switch, over coming decades, to a zero-emission renewable energy-based economy [6]. In this historical shift of technology, technologies to harness, store, and transport renewable energy have a vital role to play [7,8,9]. To address this challenge, hydrogen generation from electrolysis of water and storing it for reuse later in fuel cells to give electricity and water was suggested in the early. As hydrogen in fuel cells can lead to a zero-emission transportation structure [13,14], as well as providing long-term storage of renewable energy on the main electricity grid systems [15]
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