Scaling Up the Simultaneous Production of Clean Electricity and Clean Water

Abstract

The desalination fuel cell (DFC) is a nascent technology for co-production of clean electricity and water from a single cell, driven by the hydrogen-oxygen redox couple. Previously, DFCs employed a single cation and anion exchange membrane pair, and demonstrated desalination of feedwaters of 30 g l−1 NaCl while generating up to 8.6 kWh per m3 of desalinated water. Here, we propose and demonstrate a scaling strategy for DFCs, by adding additional alternating anion and cation exchange membrane pairs. Such a strategy is supported by previous measurements showing small potential loss across membranes in DFCs relative to that at the electrodes. We characterize and compare three cell configurations, including single, double or triple membrane pairs. We show that adding membrane pairs maintains the desalination performance of our DFC, while only moderately reducing cell power density. In addition, adding membrane pairs enables increased flexibility in the choice of anolyte and catholyte solutions, as these are no longer the primary brine channels. We show that optimizing the anolyte and catholyte enables a record power density of up to 10 mW cm−2 during desalination. We further develop and implement expressions for quantification of the thermodynamic energy efficiency of a multiple-membrane-pair DFC.