High Purity Hydrogen Separation with HT-PBI Based Electrochemical Pump Operation at 120 °C

Abstract

Electrochemical Hydrogen Pumps (EHP) provide a unique highly efficient means of separating and compressing hydrogen with continuous steady-state operation. In this paper, we demonstrate the performance of a commercially available, polybenzimidazole (PBI) membrane based platform as a benchmark for ultra-high efficiency performance. A primary gas mixture of CO 2 and H 2 with a ratio of 4:1 respectively was selected to demonstrate the performance of EHP s with near theoretical Faradaic efficiency with negligible CO poisoning due to reverse water gas shift reaction (RWGS). It was found that humidification of the feed gas at room temperature improved polarization performance while also improving energy efficiency, thus reducing the need for a tightly controlled relative humidity of feed gas. A new perspective on EHP energy efficiency calculation methodology is also provided by including the cell heating requirement in the calculation. In this manner, an overall improvement to the energy efficiency of nearly 20% was realized by dropping the cell temperature to 120 °C while paying no significant penalty to electrochemical performance. Nearly 99.99% pure H 2 and 99.93% pure CO 2 were produced with a hydrogen yield of 99.34%.