Electrochemical Hydrogenation of a Liquid Organic Hydrogen Carrier Using a Pd Membrane Reactor

Liquid organic hydrogen carriers (LOHCs) store hydrogen in the chemical bonds of organic molecules. Unsaturated molecules, like toluene, can store hydrogen at densities comparable to compressed gas, but have the distinct advantage of being transportable as liquids under ambient conditions. Thermochemical hydrogenation using H2(g) requires high temperatures and pressures, whereas electrochemical hydrogenation can proceed at ambient conditions and without H2(g). However, the electrochemical hydrogenation of toluene is limited by the low solubility of toluene (<6 mM) in water. Here, we demonstrate the hydrogenation of neat liquid toluene electrochemically by using a palladium membrane reactor. We show that this reactor prevents toluene permeation to the anode chamber, which is a persistent issue for other forms of electrochemical hydrogenation. This paper outlines how the membrane reactor also overcomes many other issues associated with electrochemical hydrogenation, thereby enabling the hydrogenation of LOHCs without H2(g).