Nanoscale Organic-Inorganic Construct for Deterministic Surface Property Tuning

Abstract

Coinage metals such as Au are known to display various plasmonic effects. Modified Au surfaces have been used as surface-enhanced Raman spectroscopy (SERS) substrates in many applications, including studying interfacial electrochemical reaction mechanism and the development of microfluidic light-based sensors. Here, we focus on studying proton-coupled electron transfer (PCET) reactions that are found in many renewable energy electrocatalytic conversion processes. We will describe our efforts in constructing a hybrid organic-inorganic coating on Au surfaces to modulate the intrinsic reaction parameters of PCET, in particular for the oxygen reduction reaction (ORR). ORR fundamentally limits the efficiency of fuel-cell-related technologies. Our nanoscale organic-inorganic coating features a hybrid bilayer membrane containing a self-assembled monolayer (SAM), a Cu-based ORR electrocatalyst, a monolayer of lipid, and a membrane additive[1]. These four components control the thermodynamics and kinetics of electron and proton transfer processes that determine the overall ORR selectivity and activity. By optimizing the relative rates of proton and electron transfer using our Au system, the Cu electrocatalyst undergoes predominantly the 4e- pathway to form H2O as the only product without sacrificing the reaction yield or the catalyst efficiency. Collaborations to take advantage of the plasmonic Au substrate by using SERS to probe surface reaction intermediates will be solicited to better understand the electrocatalytic mechanism. Based on the mechanism proposed, new paradigm for electrocatalyst design will be put forward. In summary, our organic-inorganic hybrid coating on plasmonically-active Au surfaces will provide unique insights into the intricate reaction parameters of PCET steps and also offer new opportunities to probe fuel generation and energy storage processes using SERS.