Electrocatalysis underlies many emerging clean energy technologies, such as fuel cells, electrolyzers, and photocatalytic reactors. However, continued improvements in electrocatalyst activity, durability, and selectivity must be achieved for these technologies to accelerate society’s transition away from fossil fuels and towards a sustainable future based on fuels produced from renewable energy. In this seminar, I will describe design rules electrocatalytic systems for which the active electrocatalyst is encapsulated by nanoscopic overlayers consisting of semi-permeable oxide materials like silica. Electroanalytical and spectroscopic measurements show that these oxide overlayers can be selectively permeable to certain electroactive species and thereby leverage transport phenomena to enable efficient and selective electrocatalysis at the buried interface between the oxide overlayer and active catalyst. I will present several examples that show how the thickness, defects, and/or composition of oxide overlayers influence their transport properties and the performance of encapsulated electrodes. This talk will also describe characterization of the catalytic buried interface and discuss challenges and opportunities for tailoring active sites located there. Lastly, I will show that sub-micron thick proton-conducting oxide layers offer a promising opportunity to replace conventional Nafion membranes in zero-gap electrochemical reactors for the efficient production of hydrogen from water electrolysis.