Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia

Ammonia has received increasing attention in recent years as a possible energy carrier, in particular, as a carrier of hydrogen for use in fuel cells. The traditional approach of thermal decomposition suffers from high concentrations of residual ammonia, which poison the catalysts in polymer electrolyte membrane fuel cells, whereas newer strategies based on electrochemical decomposition in aqueous solution operate at high overpotentials, implying low efficiency. Our approach integrates a thermal decomposition catalyst (Cs-promoted Ru on carbon nanotubes) with an all-solid-state electrochemical conversion cell (based on the proton-conducting electrolyte, CsH₂PO₄) in a device that is operable at 250°C. The resulting polarization curves indicate high current density at a modest voltage (far beyond what can be attained from alkali electrolyte cells), as well as catalyst utilization efficiency that far exceeds traditional thermal decomposition.