Chloride-Tolerant, Inexpensive Fe/N/C Catalysts for Desalination Fuel Cell Cathodes

Abstract

Clean technologies, which utilize or generate clean energy rather than fossil fuel-based energy, are under intense development to aid in addressing climate change. Current water desalination technologies are a growing user of fossil fuelderived electricity. A recently developed technology, termed the desalination fuel cell (DFC), can address this issue by instead using hydrogen gas to drive both feedwater desalination and green electricity generation simultaneously in a single cell. The main bottleneck is the use of Pt-based catalysts, which leads to high device costs and catalyst surface poisoning due to chloride ions (Cl − ) present in the feedwater. We here propose and demonstrate the first use of non-platinum group metal (non-PGM) catalysts toward DFCs. We synthesized a Fe/N/C based catalyst which demonstrated effective and Cl − tolerant oxygen reduction reaction ex situ and while used as a DFC cathode. The synthesis temperature and the metal concentrations were optimized using rotating disk electrode measurements, with an onset potential of up to 0.84 V vs RHE, on par with that of commercial Pt/C catalysts in a Cl − environment. When using the optimized Fe/N/C catalyst as a cathode in a prototype DFC, open circuit voltage was significantly improved relative to Pt/C, and measured cell voltage and desalination performance versus current density were nearly equivalent. Overall, these results show that non-PGM catalysts maintain or improve cell performance while significantly reducing cell costs, improving greatly the outlook for this nascent technology.

Electrochemical Methods for Water Purification, Ion Separations, and Energy Conversion

“…In particular, the hydrogen–oxygen couple is promising, as it relies on relatively inexpensive gas-phase reactants, and the product of the chemical reaction is simply water (Figure a); cells that use the hydrogen–oxygen chemistry are termed “desalination fuel cells.” , Other chemistries that rely on liquid-phase reactants or that produce a waste product complicate disposal of the brine. , The hydrogen–oxygen chemistry, however, exhibits relatively low thermodynamic efficiency relative to other chemistries, such as zinc–bromine, mainly due to losses at electrodes attributed to (platinum) catalyst poisoning by halide ions in the brine (Figure c). , Therefore, a crucial area of research is the design and development of inexpensive catalyst materials tailored to long-term operation in desalination fuel cells. Asokan et al demonstrated the use of chloride-tolerant, iron-based catalysts for oxygen reduction in a desalination fuel cell, which opens the field of nonplatinum group metal catalysts for these systems …”

“…Asokan et al demonstrated the use of chloride-tolerant, ironbased catalysts for oxygen reduction in a desalination fuel cell, which opens the field of nonplatinum group metal catalysts for these systems. 455…”

Hollow Nickel Nanochains Coated with Nickel-Iron Hydroxide for Oxygen Evolution

“…Fossil fuel usage shows directly proportional relationship to the energy demand and is a major cause of environmental pollution, resulting in global warming and abnormal climate events. , For eco-friendly power generation, renewable energy sources, such as solar, wind, and geothermal power, have garnered considerable interest. However, the technological limitations associated with intermittent power generation using these renewable energy sources have hindered the development of sustainable energy systems .…”

Comparison of Ion Selectivity in Electrodialysis and Capacitive Deionization

“…ED is an established water desalination technology, which leverages an electric current applied normal to the feedwater flow direction and ion-exchange membranes (IEMs) placed along the flow direction to separate the feed stream into a desalinated stream and a brine stream (Figure a). , The applied electric field drives cation migration through cation-exchange membranes (CEMs) and anions through anion-exchange membranes (AEMs) to the brine channel. Recently, several novel ED cell and system architectures have been developed, including electrodeionization, shock-ED, , multistage ED, chemical energy-driven ED, − and bipolar membrane ED . Ion selectivity in ED can be achieved via careful design of the membranes, which can affect the population of certain ions within the membrane or the diffusion of ions through the membrane in a selective manner.…”