Ex Situ and In Situ Neutron Imaging of Enzymatic Electrochemical Cells

Neutron imaging provides a route for studying the effect of environmental conditions on enzymatic electrochemical cell (EEC) performance. Here, the application of 2D and 3D neutron imaging is demonstrated as a means to investigate effects of environmental conditions on EEC performance. Changes in aqueous solutions that are vital to the operation of EECs have been directly observed in real time using neutron radiography (NR). These changes include uptake of aqueous solutions in electrode materials and in situ observation of water content during operation. The EEC structure has also been observed using ex situ neutron tomography. Initially samples constructed to simulate EEC geometry were imaged, and aqueous buffer solution uptake behavior was observed in carbon paper cell components. In follow-on studies neutron tomography was used to map regions of enzyme catalyst inks, defining active regions within the EEC electrode. The higher neutron attenuation of polymeric ink components enables this observation. Finally, in situ imaging of a prototype EEC pouch cell was performed using a standard chronoamperometry arrangement while performing real time neutron radiography. Neutron radiographs acquired during operation show a clear variation in transmission behavior, primarily due to drying. Together these studies demonstrate the applicability and attendant challenges of neutron imaging for the study of EEC performance and reliability.