Routine, non-destructive water-state sensing in ion-exchange membranes under controlled temperature and humidities using terahertz spectroscopy
Lead Research Organisation:
Lancaster University
Department Name: Engineering
Abstract
Ion-exchange membranes (IEMs) are required for a diversity of applications across many fields spanning clean energy, environmental remediation, and healthcare. Examples include: green hydrogen producing electrolysers and low temperature fuel cells; carbon dioxide electrolysis into high value chemicals; salinity gradient power; hydrogen peroxide generation; redox flow batteries; actuators; batteries and supercapacitors; electrodialysis and diffusion dialysis for the recovery, extraction, and separation of inorganics including heavy metals ions and acid and bases; chromatography materials for protein purification; biomaterials for tissue engineering; and fouling resistant membranes for microfiltration.
The Lancaster University team will develop a novel table-top facility using terahertz time-domain spectroscopy (THz-TDS) to routinely and non-destructively quantify the different states of water (bound, bulk, and free) in IEMs in environments with both relative humidity (RH) and temperature control. Previously, water states and contents have only been measured in uncontrolled environments using either pulse field gradient nuclear magnetic resonance experiments or with destructive techniques like differential scanning calorimetry. The developed THz-TDS system will be used to gain a more extensive TRL1-2 level fundamental understanding of how the states of water vary in IEMs with different composition characteristics. These IEMs will be either commercial types (including those provided by a project partner) or those fabricated at the University of Surrey (see below). Underpinning preliminary work at Lancaster University has shown that THz-TDS derived water state information can be collected at different RHs, but this was only possible at ambient temperatures. A more comprehensive development of a system, that can collect such data with both RH and temperature control, is required. Commercial ion-exchange membrane developers and users, including project partners, have indicated that they would like to see this knowledge deficiency rectified, where routinely collected water-state data is available over a wider range of conditions.
Radiation grafting is a useful method for bulk functionalisation of polymers with defined characteristics (films, powders, fibres). The University of Surrey will supply a range of small-scale (10 × 10 cm) samples of radiation-grafted cation- and anion-exchange membranes with a diversity of: (1) ion-exchange capacities; (2) chemistries; (3) thicknesses, and (4) nano-morphologies (distribution and size of crystallites). This will aid the generation of new fundamental scientific knowledge related to how IEM characteristics affect their water contents and states.
In the latter stages, the Surrey team will then conduct TRL3 scale-up work on down-selected radiation-grafted IEMs, an effort that will be supported by the developed Lancaster University-based THz-TDS capability. For initial translation to impact, the scaled-up RG-IEMs will be those that have the right balance of properties for application in peroxide generating cells, an interest of our aerospace partner. It is well known that the in situ performances of IEMs (in numerous electrochemical systems) is as much a function of water contents (and mobility) as they are of ion-conductivity. Hence it will be important to elucidate the homogeneity of the distribution of water states across different areas of scaled-up (30+ × 30+ cm) batches of IEM, as well as the consistency of water states across multiple repeat batches. It is currently unknown if homogeneous ion-exchange capacities actually lead to homogeneous water states.
The Lancaster University team will develop a novel table-top facility using terahertz time-domain spectroscopy (THz-TDS) to routinely and non-destructively quantify the different states of water (bound, bulk, and free) in IEMs in environments with both relative humidity (RH) and temperature control. Previously, water states and contents have only been measured in uncontrolled environments using either pulse field gradient nuclear magnetic resonance experiments or with destructive techniques like differential scanning calorimetry. The developed THz-TDS system will be used to gain a more extensive TRL1-2 level fundamental understanding of how the states of water vary in IEMs with different composition characteristics. These IEMs will be either commercial types (including those provided by a project partner) or those fabricated at the University of Surrey (see below). Underpinning preliminary work at Lancaster University has shown that THz-TDS derived water state information can be collected at different RHs, but this was only possible at ambient temperatures. A more comprehensive development of a system, that can collect such data with both RH and temperature control, is required. Commercial ion-exchange membrane developers and users, including project partners, have indicated that they would like to see this knowledge deficiency rectified, where routinely collected water-state data is available over a wider range of conditions.
Radiation grafting is a useful method for bulk functionalisation of polymers with defined characteristics (films, powders, fibres). The University of Surrey will supply a range of small-scale (10 × 10 cm) samples of radiation-grafted cation- and anion-exchange membranes with a diversity of: (1) ion-exchange capacities; (2) chemistries; (3) thicknesses, and (4) nano-morphologies (distribution and size of crystallites). This will aid the generation of new fundamental scientific knowledge related to how IEM characteristics affect their water contents and states.
In the latter stages, the Surrey team will then conduct TRL3 scale-up work on down-selected radiation-grafted IEMs, an effort that will be supported by the developed Lancaster University-based THz-TDS capability. For initial translation to impact, the scaled-up RG-IEMs will be those that have the right balance of properties for application in peroxide generating cells, an interest of our aerospace partner. It is well known that the in situ performances of IEMs (in numerous electrochemical systems) is as much a function of water contents (and mobility) as they are of ion-conductivity. Hence it will be important to elucidate the homogeneity of the distribution of water states across different areas of scaled-up (30+ × 30+ cm) batches of IEM, as well as the consistency of water states across multiple repeat batches. It is currently unknown if homogeneous ion-exchange capacities actually lead to homogeneous water states.