Climate change concerns have spurred a growing interest in developing environmentally friendly technologies for energy generation, including green H₂ production from water splitting. Moreover, concerted attempts are also being made to re-utilize CO₂ by electrocatalytically converting it into value-added chemicals and fuels, offering the possibility to store renewable energy into chemical bonds. Thus, efficient, selective and durable electrocatalysts that can operate under mild reaction conditions (atmospheric pressure and low overpotential) are urgently needed. However, the latter challenging goal can only be achieved when fundamental understanding of the electrocatalyst structure and surface composition under reaction conditions becomes available. It should also be kept in mind that even morphologically and chemically well-defined pre-catalysts are commonly susceptible to drastic modifications under operando conditions, especially when the reaction conditions themselves change dynamically. Here, a synergistic experimental approach taking advantage of a variety of cutting-edge microscopy (EC-AFM, EC-TEM), spectroscopy (NAP-XPS, XAS, Raman Spect., GC/MS) and diffraction (XRD) has been employed to unveil the complexity of energy conversion electrocatalysts.

In particular, I will provide new insights into the electrocatalytic reduction of CO₂ as well as the oxygen evolution reaction using operando characterization methods while targeting model pre-catalyst systems ranging from single crystals to thin films and metal nanoparticles. Some of the aspects that will be discussed include: (i) the design of size- and shape-controlled catalytically active nanoparticle pre-catalysts (Cu, Cu₂O cubes, ZnO@Cu₂O cubic NPs, CoOx NPs), (ii) the understanding of the active state formation and (iii) the correlation between the dynamically evolving structure and composition of these electrocatalysts under operando reaction conditions and their activity, selectivity and durability.

Our results are expected to open up new routes for the reutilization of CO₂ through its direct conversion into industrially valuable chemicals such as ethylene and ethanol and the generation of H₂ through water splitting.

[1] Grosse, P.; Yoon, A.; Rettenmaier, C.; Herzog, A.;. Chee, S.W.; and Roldan Cuenya, B., Nature Comm. 2021, 12, 6736

[2] Timoshenko, J.; Bergmann, A.; Rettenmaier,  C.; Herzog, A.; Aran Ais, R.; Jeon, H.; Haase, F.; Hejral, U.; Grosse, P.; Kühl, S.; Davis, E.; Tian, J.; Magnussen, O.; Roldan Cuenya, B.; Nature Catalysis 2022, 5, 259.

[1] Haase, F.;  Bergmann, A.; Jones, T.; Timoshenko, J.; Herzog, A.; Jeon, H.; Rettenmaier, C.; Roldan Cuenya, B., Nature Energy (2022) 7, 765.