Slurry electrode properties for minimizing power loss of flowable electrochemical hydrogen storage systems

Abstract

Electrochemical hydrogen storage in porous carbon particles in slurry electrodes is a function of particle size, shape, and material. Ideal slurry electrodes have high electrical (both electronic and proton) conductivity to minimise the electric resistance and ohmic power loss, and low viscosity to minimise parasitic pumping power, while utilising porous particles with high surface areas for hydrogen storage. In this paper we show that although carbon black (CB) particles have higher electronic conductivity than activated carbon (aC) particles, their proton conductivity is significantly lower, and they cannot be used for hydrogen storage. We increase the electronic conductivity of aC slurries by adding CB particles. We demonstrate that the addition of a 1:10 ratio by weight of CB to aC particles reduces the electric resistance and ohmic power loss by 50%, while parasitic pumping power increases by only 15% compared to slurries with no CB particles. We conclude that at low Reynolds numbers, for 5 to 20 wt% aC slurries with different particle sizes, slurries containing 20 wt% spherical aC particles smaller than 50 μm mixed with 2 wt% CB particles provide the highest electronic and proton conductivity, while not significantly increasing parasitic pumping power.