A Versatile High-Temperature Electrochemical Pump for Hydrogen Separations

Abstract

Hydrogen is an excellent energy carrier and can enable zero or near-zero emissions in transportation, stationary or remote power, and portable power applications. Over 95% of hydrogen is derived from reformed natural gas, steam cracking, and other fossil fuel processes that often cause complex mixtures requiring purification. Further, with an increasing demand for hydrogen delivery, there is a current search going on for converting and using natural gas pipelines to carry a blend of natural gas and hydrogen (up to 15% H2). By blending natural gas and H2, the growing demand for hydrogen delivery could be met, but this requires on-site hydrogen purification and compression. Electrochemical hydrogen pumps (ECHP), as a standalone device, could be a better solution for on-site hydrogen purification and compression, making a cost-effective and direct process.Most ECHP research focuses on membrane development and its relation to ECHP performance. Many of these studies use BASF fuel cell electrodes. The role of electrode ionomer binder on ECHP performance has not been investigated with rigor. This talk presents our work on investigating the influence of ionomer binders on ECHP performance at high temperatures. A newly developed PC-PBI membrane (50:50 QPPSf-PBI H3PO4) was used as HT-PEM in our ECHP. The newly developed PC-PBI HT-PEM overcomes the 180 °C temperature limitation of H3PO4 doped PBI by incorporating tethered cationic moieties into the polymer host that anchors the H3PO4 through ion-pair interactions. Further, this talk will reveal the advantage of employing phosphoric acid tethered polymer electrolyte by comparing it against a liquid phosphoric acid imbibed polymer electrolyte in electrode binders. The final part of this talk will present the high-temperature ECHP performance with new phosphonic acid functionalized polymer electrode binders under industrial relevant mixtures (e.g., syngas, cracking, and reformate mixtures). Our work has shown that the higher temperature operation of ECHP minimizes the impact from CO and performance is governed by H2 concentration in the mixtures.