Electrochemical Gas Separations for Green Energy Integration

Abstract

Separation and purification of molecules and compounds is one of the fundamental processes of chemistry and a hugely important factor in industrialization, accounting for as much as 15% of world’s energy consumption. As the world tries to limit and reduce the effects of climate change, simultaneous development of a green chemical economy and carbon sequestration strategies are needed. Both these goals need to effectively and efficiently separate gas phase molecules to make the implementation of these technologies feasible, requiring an even higher demand for economical and green gas phase separation. The current methods of gas phase separation used in industry rely predominantly on inefficient processes, such as cryogenic distillation or temperature or pressure swing absorption. Gas phase separation by electrochemical means can offer theoretically high energy efficiency separation, as the energy supplied can operate exclusively on the molecule of interest, if proper material and design criteria are met, while traditional methods act upon the entire gas mixture. Additionally, electrochemical separations can reduce the number of steps needed as they can simultaneously separate and compress the purified gas, easing the demand for high energy processing required when using mechanical pumps. However, the effectiveness of these technologies depends largely on the operating conditions and materials that make up the electrochemical cell. Thus, a key factor driving improvement in this field relies heavily on material development, such as improved membranes/separators, catalysts, and other cell materials which can in turn give rise to novel techniques and high performance of the electrochemically driven devices. Electrochemical gas phase separations integrated with green energy are critical to reaching climate change targets, but they in turn rely on the development of novel materials at enlarged scales and implementation of these technologies at reduced costs. In this article, we discuss the principles and applications of three electrochemical gas separations: hydrogen (H2) pump, ammonia (NH3)compression, and carbon dioxide (CO2) separation.