The focus of Thrust 2 is elucidate the roles of solid-liquid interfacial structure, potential gradient, and confinement on proton dynamics, water clustering and organization at the interface, and their effects on water chemistry and catalytic and electrocatalytic reaction dynamics.
The goal is to develop reactivity-surface chemical and structural property relationships and to control reaction selectivity. Thrust 2 utilizes AMEWS’ ability to design and synthesize atom-precise catalysts to investigate the reactions in complex aqueous media on designer reactive interfaces. Competing, and sometimes conflicting, requirements for optimal interfacial processes lead to well-known volcano plots of reactivity-property relationships. Surmounting these relationships will depend on intentional materials design to introduce selective chemical pathways. Sequential reactions introduced by hierarchical design and extreme confinement enable pathways that would otherwise be impossible to achieve in bulk systems.
Current research activities in Thrust 2 are centered around two Research Questions:
1. What is the explicit role of water in determining the chemical and catalytic properties of interfaces within pores of solid acid/base materials?
Despite the ubiquity of aqueous reactive interfaces, models that capture the full structural and chemical complexity of these interfaces remain largely in their infancy. This is a result of the wide range of pertinent length- and time-scales involved, as well as the underlying molecular and chemical complexity. For example, water can act as a reactant, as a modifier of surface species, as coordinating ligand of ions on the solid surfaces and in solution, as adsorbate on surfaces, and to screen strong electric fields. Thrust 2 will attempt to tease out these factors individually and determine their significance in determining the interfacial properties. AMEWS focuses on cases where water unambiguously participates in the reactivity through hydrogen bonding, protonation/deprotonation, autoionization and electrochemical redox processes of H3O+ or OH-.
2. What is the effect of confinement on molecular electrocatalysis?
Unprecedented control of hierarchical architectures over length scales from Ångstroms to microns will enable new mechanistic investigation of interfacial processes as a function of restricted transport. AMEWS will elucidate the redox electrochemical process at interfaces under controlled electric field, using both in-situ and time-resolved spectroscopic methods, to illuminate mechanistic details of individual steps in chemical reactions and tailor reaction pathways. The experiment effort will be supplemented by first-principles simulations of solid-water interfaces under bias to understand how the electronic states, and hence, the charge transfer across interfaces is affected by the application of a potential.