Understanding Mechanisms of Degradation in CuOx Nanoparticles and Electrocatalysts for CO2 Reduction

• Adil Sheikh, Chemistry, University of Delaware

• Rachel Davidson, Chemistry, University of Delaware

Reaching the ambitions goals outlined in the Paris Climate Accord requires both technologies which minimize CO₂ production as well as innovative approaches which result in negative emissions. One solution to decarbonize the atmosphere is the reduction of carbon dioxide to valuable hydrocarbons and oxygenates. Cu and CuO_x is the only single metal catalyst which selectively produces higher valued multi-carbon products with high selectivity in significant concentrations, however under catalytic environments it often undergoes substantial structural transformations which alter catalytic performance over time. We aim to study how Cu-based nanostructured electrocatalysts evolve under electrocatalytic conditions through use of in-situ and correlative measures which allow for particle-by-particle mapping of crystallographic structure, electronic structure, and local catalytic activity.

During the summer, our goal was to add to the library of copper and copper oxide nanocrystals which vary in degree of oxidation and morphology via electrodeposition. This technique has allowed us to control the resulting structure by tuning the solution composition through changing the identity and concentration of the Cu precursor, solvent, and the degree of incorporation of growth directing ligands, as well as the deposition parameters such as potential and current. These parameters alter factors including which crystallographic facets are presented at the crystal surface, the particle surface energy, and the degree to which surface absorbates are present on the particle surface which together determine the activity and selectivity of catalytic sites.

To increase efficiency in our study of copper nanocrystals, the use of statistical analysis, Design of Experiments (DOE) was utilized. DOE allows for the analysis of multi-variable changes which can be used to examine a wider synthetic space. Moreover, DOE can be used to determine variable interactions that could otherwise be missed when utilizing a one-variable method. The characterization of these nanocrystals was performed utilizing transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to look at particle structure and morphology, use energy-dispersive X-ray spectroscopy (EDX) and powder X-ray diffraction (XRD) to get compositional information. Using DOE has allowed for the examination of several copper salt systems yielding distinct morphologies that can be examined for the CO₂-reducing properties.