Modelling heterogeneous electrocatalysis is key to gain atomistic insights into the mechanism of various catalytic reactions that are expected to become large-scale industrial processes in the future such as the hydrogen evolution reaction (HER), CO2 electroreduction or biomass electro-oxidation. In particular, grand-canonical density functional theory (GC-DFT) has been developed over the last ten years to a practical tool for investigations of electrocatalytic reactions.1 Still, modelling of electrocatalysis remains challenging: the interfaces need to be of sufficient sizes to account for the liquid nature of the electrolyte and diffusion is slow at the solid/liquid interface. Finally, obtaining kinetic information via the identification of transition states is burdensome as it often involves the solvent as a reactant.2 In this webinar I will start by presenting the basic principles of GC-DFT, illustrating what it means in practice. Then, I will discuss a couple of use-cases, where GC-DFT has worked more or less hand-in-hand with experiments: on the one hand, I will discuss the prototypical case of sulfate adsorption on Au(111),3 where precise experimental information has been converted to atomic-resolution pictures of the arrangement of the overlayer. On the other hand, I will discuss screening of doping of MoS2-based HER catalysts.4 Finally, I will discuss various questions that we have addressed in view of the effort needed to come answer them, ranging from structural complexity5 to reaction pathways6 and covering metals, oxides and sulfides. Bibliography (1)Abidi, N.; Lim, K. R. G.; Seh, Z. W.; Steinmann, S. N. Atomistic Modeling of Electrocatalysis: Are We There Yet? WIREs Comput Mol Sci 2021, 11 (3), e1499. (2)Abidi, N.; Bonduelle-Skrzypczak, A.; Steinmann, S. N. Potential and Support-Dependent Hydrogen Evolution Reaction Activation Energies on Sulfur Vacancies of MoS2 from GC-DFT. Int. J. Hydrog. Energy 2023, 48, 8478–8488. (3)Fang, Y.; Ding, S.-Y.; Zhang, M.; Steinmann, S. N.; Hu, R.; Mao, B.-W.; Feliu, J. M.; Tian, Z.-Q. Revisiting the Atomistic Structures at the Interface of Au(111) Electrode–Sulfuric Acid Solution. J. Am. Chem. Soc. 2020, 142 (20), 9439–9446. (4)Abidi, N.; Bonduelle-Skrzypczak, A.; Steinmann, S. N. How to Dope the Basal Plane of 2H-MoS2 to Boost the Hydrogen Evolution Reaction? Electrochim. Acta 2023, 439, 141653. (5)Sahu, A.; Steinmann, S. N.; Raybaud, P. Size-Dependent Structural, Energetic, and Spectroscopic Properties of MoS3 Polymorphs. Cryst. Growth Des. 2020, 20 (12), 7750–7760. (6)Curutchet, A.; Colinet, P.; Michel, C.; Steinmann, S. N.; Le Bahers, T. Two-Sites Are Better than One: Revisiting the OER Mechanism on CoOOH by DFT with Electrode Polarization. Phys. Chem. Chem. Phys. 2020, 22 (13), 7031–7038.