(136c) The Impacts of Fixed Chemical Charge Location and Abundance on the Performance and Cost of Capacitive Deionization Systems

Capacitive deionization (CDI) is an electrochemical separation technique that couples salt removal with electrochemical energy storage. CDI has recently received renewed interest as a potentially energy efficient method of desalting brackish groundwater. The charge efficiency (CE) of a CDI cell, defined as the ratio of adsorbed charge to applied charge, is a critical cell performance metric, as it directly relates to salt adsorption capacity (SAC) and thermodynamic energy efficiency. Several strategies have been proposed to improve CE by introducing complementary fixed charge groups to promote counter ion storage within capacitive electrode macro- and micropores. These strategies include placing ion exchange membranes (IEMs) between the electrodes and desalination channel, fixing charge directly onto the carbon surface, and incorporating charged polymers within the electrode macrostructure with binders. In this talk we will present simulated and experimental evidence that reveals how the location and density of fixed charge groups in conjunction with cell cycling behavior can dramatically impact CDI adsorption capacity and energy efficiency. We will also discuss these impacts in the context of capital and operating cost.