Characterization of redox active materials to enable electrochemical separations through faradaic deionization
type: CreativeWork
description: Faradaic deionization (FDI) is an emerging electrochemical separations technique which has received tremendous research interest in the past decade. Established electrochemical separations techniques such as capacitive deionization are limited by low charge storage capacity due to electric double layer charge storage, high energy consumption, and inability to selectively remove specific ions. FDI employs redox active materials with higher charge storage capacity, high selectivity, and offers low energy consumption for the separation process by operating within a moderate potential window. This work is focused on fundamental characterization of materials for FDI to enable a broad range of applications ranging from saltwater desalination, selective ion removal from water streams in agriculture and industry, and carbon dioxide capture from the atmosphere. Nickel hexacyanoferrate (NiHCFe) is chosen as an intercalation host compound for removal of sodium ions from saltwater. To enable high-rate capability, microscopic mechanisms that limit cation intercalation within porous electrodes comprised of NiHCFe nanoparticles, conductive carbon additives and polymer binder are investigated. A combination of experimental characterization, particle-scale transport modeling, and porous electrode theory show that slow electron conduction through nanoparticle agglomerates is linked to rate limitations during galvanostatic cycling, while naïve predictions based on crystal-scale diffusion alone suggest rate 4-5 orders of magnitude higher than in experiment. These insights are used to target improvement in electronic conductivity of porous electrodes of NiHCFe, resulting in significantly improved desalination performance. Investigation of cation intercalation is carried further from Na+ to insertion of Mg2+ and Ca2+ into NiHCFe in aqueous electrolytes. Capacity fades of up to 75% are observed within 200 cycles during intercalation of Mg2+(aq) and Ca2+(aq). A combination of experimental …
abstract: Faradaic deionization (FDI) is an emerging electrochemical separations technique which has received tremendous research interest in the past decade. Established electrochemical separations techniques such as capacitive deionization are limited by low charge storage capacity due to electric double layer charge storage, high energy consumption, and inability to selectively remove specific ions. FDI employs redox active materials with higher charge storage capacity, high selectivity, and offers low energy consumption for the separation process by operating within a moderate potential window. This work is focused on fundamental characterization of materials for FDI to enable a broad range of applications ranging from saltwater desalination, selective ion removal from water streams in agriculture and industry, and carbon dioxide capture from the atmosphere. Nickel hexacyanoferrate (NiHCFe) is chosen as an intercalation host compound for removal of sodium ions from saltwater. To enable high-rate capability, microscopic mechanisms that limit cation intercalation within porous electrodes comprised of NiHCFe nanoparticles, conductive carbon additives and polymer binder are investigated. A combination of experimental characterization, particle-scale transport modeling, and porous electrode theory show that slow electron conduction through nanoparticle agglomerates is linked to rate limitations during galvanostatic cycling, while naïve predictions based on crystal-scale diffusion alone suggest rate 4-5 orders of magnitude higher than in experiment. These insights are used to target improvement in electronic conductivity of porous electrodes of NiHCFe, resulting in significantly improved desalination performance. Investigation of cation intercalation is carried further from Na+ to insertion of Mg2+ and Ca2+ into NiHCFe in aqueous electrolytes. Capacity fades of up to 75% are observed within 200 cycles during intercalation of Mg2+(aq) and Ca2+(aq). A combination of experimental …
author: Shrivastava, Aniruddh
language: en
keywords: Faradaic deionization, electrochemical separations, aqueous batteries, Prussian blue analogues, Nickel hexacyanoferrate, porous electrodes, diffusion, NASICON, Sodium titanium vanadium phosphate, selective capture, CO2 capture
date published: 2021-08
date modified: 2026-07-22T22:24:56Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2142/117884