Two-dimensional transition metal dichalcogenides (TMDCs) in contact with ionic liquid (IL) electrolytes will be used as the starting materials offering a new paradigm for electrocatalysis based on materials with low work function, significant overlap of the d-band partial density of states with the Fermi energy, and an electrolyte 'solvent' that protects rather than poisons the catalytic sites. Novel material combinations and structures will be predicted using computational tools and then synthesized using chemical vapor deposition, chemical vapor transport and colloidal chemistry. Atomic and electronic structure will be characterized using in-situ aberration-corrected scanning transmission electron microscopy (STEM). The information obtained from high-resolution STEM, including high-angle annular dark-field (HAADF) and annular bright-field (ABF) imaging, as well as electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (XEDS), will be used to confirm successful synthesis of the desired structures and to create starting configurations for the first-principles modeling efforts. Both ex-situ and in-situ electrochemical experiments will be conducted to measure the activity and selectivity of the synthesized materials. In particular, the study will utilize a novel graphene liquid cell, developed by one of the investigators, that enables atomic-resolution imaging and spectroscopy in a liquid environment. Mechanistic studies of the electrocatalytic reactions and transport measurements will be made utilizing in-situ differential electrochemical mass spectrometry (DEMS) together with a traditional silicon nitride based electrochemical stage for STEM characterization under operando conditions. Taken together, the advanced synthesis, characterization, and evaluation techniques, coupled with efficient computational search methods, will accelerate the discovery of 2D material-based-catalysts with superior activity and selectivity for various electrochemical reactions including the oxygen reduction reaction (important in fuel cell technology), and the hydrogen evolution reaction (important in water electrolysis).