Hydrogenation without H2 Using a Palladium Membrane Flow Cell

Electrocatalytic palladium membrane reactors (ePMRs) use electricity to hydrogenate organic molecules at ambient temperature and pressure. These benign reaction conditions position ePMRs as a sustainable alternative to thermochemical hydrogenation, which requires high-temperature and high-pressure reaction conditions. However, ePMRs suffer from slow reaction rates and a limited understanding of the factors that govern reaction performance in these devices. In this work, we report the design and validation of an ePMR flow cell. This flow cell increases reaction rates 15-fold and current efficiencies by 30% relative to H-cell reactors. We use this device to reveal that the hydrogen content in the palladium membrane governs the speed and selectivity of hydrogenation reactions, while the amount of hydrogen gas evolved at the palladium surface is deterministic of current efficiency. We contend that this flow cell, which enables hydrogenation without hydrogen gas, is an important step for translating ePMRs into practice.