Selectivity Control under Dynamic CO2 Electroreduction Conditions

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Electroreduction of carbon monoxide (CO2RR) on Cu-based electrocatalysts can provide significant yields of multi-carbon (C2+) products and thus opens a promising way for its conversion into valuable feedstock chemicals and fuels. Dynamic (potential pulsed) CO2RR has recently received significant attention, as it allows to periodically generate/restore distinct catalyst states and morphological motifs in situ, offering new possibilities for tuning the product selectivity, and regenerating poisoned catalyst surfaces. However, the active catalyst state and its dynamic evolution are still unclear and the detailed mechanisms of dynamic CO2RR require clarification.We will explore enhancing the CO2RR selectivity towards C2+ products using dynamic reaction conditions. Optimized conditions will be identified from extensive electro¬catalytic studies and studied in-depth by operando time-resolved methods. We aim to identify the influence of the potentiodynamic charac¬teris¬tics (pulse shape, range, and period) on the catalyst selectivity. By varying the anodic potential (to oxidizing and non-oxidizing conditions) and time regime (from ms to hours) different modifications of the electrode’s state are possible, such as changes in the surface charge, adsorbed species, redox state, and surface morphology. We will identify how this can improve the evolution of the C2+ selectivity and overcome catalyst poisoning to ensure stable catalyst activitiy and selectivity.Apart from pure Cu catalysts (Cu2O nanocubes, Cu single crystals) we will also study those decorated with secondary metal nanoparticles (Ag, Au, Zn) for tandem catalysis. Further-more, we will explore the selective promotion/inhibition of mechanistic pathways by chemical species (alkali cations, halide anions). For both, an increase in C2+ selectivity under potentiostatic conditions has been shown and we will extend these studies to the potentiodynamic case. For an improved understanding, the potential-dependent adsorption geometries, surface concentrations of the involved species (intermediates, inhibitors/promotors) and their influence on the Cu structure will be studied.For these studies, the FHI and CAU teams will employ their complementary expertise in operando techniques comprising a variety of spectroscopic (Raman, XAS) and X-ray scattering (powder and surface X-ray diffraction) as well as microscopic (STM/AFM) methods. These will provide comprehensive insights into the catalyst structure, adsorption geometry of important reaction intermediates (CO) and active spectator species as well as the dynamic changes of the catalyst’s properties. These insights will be directly correlated to the catalytic activity and C2+ selectivity. Furthermore, the FHI group will transfer the obtained understanding to electrolyzer-like gas-fed flow cells. Thereby, we will significantly contribute to a fundamental understand on the C2+ formation during CO2RR and especially, under potentiodynamic reaction conditions.