Anodic Pd membrane H₂ extraction enhances thermochemical dehydrogenation.

Abstract

Dehydrogenation reactions underpin fuel processing¹, chemical synthesis² and hydrogen storage and transport³. Many are endothermic and kinetically inhibited by H₂, leading to low single-pass yields at moderate temperatures⁴. These reactions can be promoted by integrating the catalyst with a hydrogen-selective membrane, which relies on an H₂ partial pressure differential to drive in situ hydrogen removal⁵. However, this approach often results in limited hydrogen flux, reduced mechanical stability and low recovered hydrogen partial pressures⁶. Here we use a hydrogen-selective Pd-based membrane as the anode of a molten-hydroxide electrochemical cell with a hydrogen-evolving cathode. This construct enables electrochemically driven H₂ separation at dehydrogenation temperatures without a pressure differential. We demonstrate that low anode potentials of <0.3 V versus the reversible hydrogen electrode are sufficient to drive diffusion-limited H transport across the membrane. Compared with pressure-driven processes, this approach enables a 4-fold enhancement in the hydrogen separation rate at 300 °C, while enriching H₂ from 0.05 atm (balance Ar) to a pure 1.0 atm H₂ stream. Interfacing the anode with a dehydrogenation catalyst enables the conversion of ammonia and methylcyclohexane at 250 °C up to 91% and 94%, respectively. This work provides a proof-of-concept demonstration for electrochemically assisted hydrogen removal to enhance selected dehydrogenation reactions.