(Invited) Evolution of Single Atom Catalysts during CO2 Electrocatalytic Reduction

Abstract

The re-utilization of CO2 via its electrocatalytic reduction (CO2RR) into value-added chemicals and fuels is a promising avenue to minimize the impact of existing technologies on the climate change. This requires the development of low cost, efficient, selective and durable electrocatalysts based of their rational understanding. Moreover, it should be considered that even morphologically and chemically well-defined pre-catalysts can be susceptible to drastic modifications under operation, especially when the reaction conditions themselves change dynamically.This talk will address the transformations that Metal-N-C catalysts (M=Cu, Ni, Co, Fe, Sn, Zn) experience during static and pulsed CO2RR using operando quick X-ray absorption spectroscopy (XAS) and Raman spectroscopy. In particular, I will illustrate the astonishing behaviordisplayed by Cu-N-C catalystsduring CO2RR, featuring reversible transformations from single atom sites towards Cu nanoparticles. The switchable nature of these species that can be achieved by applying different potential pulses holds the key for the on-demand control of the distribution of the CO2RR products and thus, a wide-spread adoption of this process.Moreover, I will elucidate the nature of the ligands forming under CO2RR at singly dispersed Ni sites in Ni-N-C catalysts, which are currently drawing great attention for their high performances in the CO formation. This will be achieved by a synergistic combination of conventional XAS, high energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) spectroscopy, and X-ray emission spectroscopy (XES) coupled with unsupervised and supervised machine learning methodologies and density functional theory.Overall, my lecture will feature the importance of operando characterization of electrocatalysts in order to unveil structure/composition-reactivity correlations during CO2RR.