Operando Interfacial Ionics

ongoing

Electrochemistry provides direct control over the electron free energy and thus a path to electrically probe and drive chemical reactions. In strong contrast, no versatile technique exists that controls the free energy of a specific ion directly and in isolation. This has led to poor understanding of interfacial ionics. Take for example water dissociation , which is of key relevance for many energy technologies, such as for producing green H2 in alkaline conditions or bipolar membranes (BPMs) that generate acid and base using (renewable) electricity in electrodialysis. BPMs are unique, because they isolate water dissociation spatially at a junction between two electrically-isolating, but ionically-conducting polymers. However, macroscopic BPMs do not provide x-y-z resolution. These geometric constraints limit our scientific understanding about the fundamental underpinnings of WD. It is not still clearly understood what causes the kinetic barriers of WD at heterogeneous interfaces, let alone the influence of the catalyst’s surface structures or local electrostatics. In Orion, I want to scale down the ion-selective contacts of the BPM and develop “ionomer pipette microscopy”. By forming and controlling a microscopic BPM junction, we will resolve and study WD activity as a function of crystal facets, metal oxide clusters and bias-dependent surface speciation. In general, water dissociation serves us as ionic test reaction to study the impact and link between local electrostatics and local acid-base chemistry, which is fundamentally important for interfacial ionics in general. More broadly, developing a table-top setup to control the free energy of specific ions with microscopic precision could have tremendous impact across the disciplines. Example include interfacial ion transport in solid-state electrochemical systems, (de)hydrogenation in organic chemistry and enzyme function, proton gradients and action potentials in biochemistry.