Advances in Electrochemical Hydrogen Compression and Purification

Abstract

These are exciting times to be pioneering Electrochemical Hydrogen Compression (EHC) as the call for linking renewable electrical energy and chemical energy storage is becoming stronger. Hydrogen is ideally suited for electrochemical conversion, thanks to its relative abundance in compounds on earth, extremely fast redox reaction and highest energy content by weight. Although we do not produce hydrogen, we are utilising the fast redox reaction to convert hydrogen gas at the membrane interface to protons, and back to hydrogen gas again. The principles of Electrochemical Hydrogen Compression have been disseminated before and demonstrated the capability to achieve high pressures of 100 MPa single stage (14,503 psi), while simultaneously purifying the hydrogen gas. The company HyET is developing a product that will be suitable for multiple applications, ranging from (home) refuelling hydrogen vehicles to purification and recycling of industrial hydrogen (bio)gas. Here we present the outcome of the project PHAEDRUS and DONQUICHOTE, where EHC technology was developed and validated as compressor for a Hydrogen Refuelling Station, further compressing the hydrogen gas supplied directly from a PEM electrolyser. Both technologies exhibit dynamic operation, fast response and modularity making them well compatible. The most effective system configuration to capture renewable wind and solar energy and deliver high pressure hydrogen has been investigated. In addition, we review the purification ability of the EHC technology, extracting hydrogen selectively from mixed gasses in low and high concentrations. Hydrogen gas is typically produced from compounds (e.g. methane), its value is highly determined by its quality and any residual contaminations. The solid membrane was design to hold back high pressure hydrogen, and therefore shows superior permselectivity limiting passage of larger molecules. As for the active hydrogen extraction process, the membrane selection should be viewed in tandem with the catalyst system, which may be affected by specific contaminations. Technical working principles are elaborated on in this presentation, pointing out key benefits and scientific challenges that were encountered and to some degree resolved, finally discussing the roadmap ahead leading towards very attractive applications. Figure 1