Layer-by-Layer Electrodeposition of Gold and Ruthenium Using Self-Assembly for Oxygen Reduction

Precise control over catalyst composition and structure is essential for optimizing oxygen reduction reaction (ORR) performance in energy conversion devices. In this study, we design ORR catalysts using the layer-by-layer electrodeposition of Au and Ru on glassy carbon electrodes modified with self-assembled monolayers of metal complexes. Two surface modulation architectures are explored. In the first, we electrodeposit layers of metals using successively appended coordination complexes via multiple rounds of amide coupling. In the second, we utilize a templated method to regenerate thiol-metal coordination for successive layer-by-layer electrodeposition. Both methods offer tunable multi-metal and multi-layer architectures. Cyclic voltammetry and CN- poisoning studies confirm metal electrodeposition and catalytic function. Higher order layering of metals significantly enhances ORR performance, and rotating ring-disk electrode measurements show improved selectivity for water over H2O2 with increasing metal layers. The most selective ORR catalyst for water is a five-layer Au electrode that reduces O2 by an average of 3.6 electrons in neutral media despite bulk Au favoring the two-electron pathway under analogous conditions. This work introduces a flexible and generalizable framework for constructing multi-metal catalysts with a high degree of compositional control, which could have applications in ORR cathodes and other electrocatalytic systems.