UC Berkeley

Electrochemical carbon dioxide reduction (CO₂R) has emerged as a promising strategy for transformingrenewable electricity into chemical fuels and value-added carbon products. Among heterogeneous electrocatalysts, Cu uniquely enables the generation of multicarbon products through complex proton-coupled electron transfer and carbon–carbon coupling pathways. A broader range of metals, including Ag, can carry out CO2 conversion to CO. Colloidal nanocatalysts provide a particularly powerful platform for studying these reactions because their size, composition, surface structure, and interfacial chemistry can be systematically tuned. In particular, the Cu nanograin catalyst, which is evolved from these colloidal nanoparticles, has emerged as a key system for probing the relationship between dynamic surface restructuring, interfacial re-organization and intermediate/co-adsorbate stabilization which help to promote selective C2+ formation under low overpotential conditions. Chapter 1 introduces the major mechanistic challenges associated with electrochemical CO2R, highlighting the interconnected roles of catalyst restructuring and the local interfacial environment on directing activity and product manifolds resulting from CO2R. Chapter 2 details the application of vibrational spectroscopy to investigate ligand dynamics on model Ag nanocatalysts, establishing how nanoparticle-ligand interfacial interactions evolve and later impact catalytic turnover and surface reactivity within the nanoparticle ordered ligand interlayer (NOLI). Chapter 3 presents in situ spectroscopic investigations of the evolution of adsorbate populations on Cu nanograins using SERS and SEIRAS. Chapter 4 illustrates the effects of compositional modification through an emergent Cu alloying strategy. Here, Cu-Ga nanoalloys help to examine the effect on C1/C2 reaction selectivity, as well as effective CO2R overpotential/operating potential, while extending mechanistic studies to high current density flow cell and membrane electrode assemblies (MEA). Clearly, this work grapples with the competing structural and interfacial effects that emerge with catalyst evolution under reaction conditions. Rather than treating catalyst surfaces as static active sites, these studies highlight electrochemical interfaces as coupled and continuously reorganizing environments. This dissertation therefore serves as an initial framework for understanding how these intertwined phenomena can inform the design principles governing next generation electrocatalysts for selective carbon conversion. More broadly, these findings underscore the need to consider not only intrinsic catalyst energetics, but also the complex, yet specific interactions that emerge across the catalyst-adsorbate-local interfacial boundary. Here, competing adsorbates, ligand dynamics, proton activity, hydrogen-bonding networks and local interfacial environments cooperatively shape reaction pathways. Though the precise roles of these competing interfacial phenomena cannot yet be generalized entirely, a major limitation remains the difficulty of experimentally resolving these transient electrochemical interfaces across spatial, temporal, and current-density regimes.