(Invited) Tailoring Metal Nanostructures for Energy-Efficient Electroreduction of CO2 and O2

Abstract

Electrocatalysts play a vital role in the development of renewable energy technologies based on electrical-chemical energy conversions, such as fuel cells, electrolyzers, photoelectrochemical solar cells and metal-air batteries. Many metallic nanostructures have emerged as promising candidates for such electrocatalytic applications, but the performances are yet to be improved to meet the technical and cost-effectiveness standards for practical implementations. On the other hand, it traditionally relies on the model-catalyst studies of well-defined extended surfaces for mechanistic understanding of electrocatalysis, but discrepancies in catalytic performance and knowledge gaps are also realized to be present between the extended surfaces and nanomaterials. The latter is probably not only due to the intrinsically different bulk and surface structures of materials at these two extremes of size, but also caused by the challenges in probing the active sites and reaction pathways on nanostructured materials. This presentation aims to discuss two examples of our efforts on tailoring metallic nanostructures for electrocatalytic applications: i) highly dense Cu nanowires for the electroreduction of CO2 and CO, and ii) Co/Pt core/shell nanoparticles as sustainable electrocatalysts for the oxygen reduction reaction (ORR). These nanostructures are characterized by combining electron-based microscopic imaging, diffraction and elemental mapping, while the surface structures are probed by using surface-specific adsorption/desorption of small molecules (e.g., COad and OHad). The gained structural information is correlated to the measured catalytic activity, durability and/or selectivity, based on which computational simulations are further performed to understand the established structure-property relationships, depict the active sites and reveal the catalytic enhancement mechanisms. Our work highlights the great potential of tailoring nanostructured materials to improve the energy conversion and chemical transformation efficiencies of electrochemical systems.