Rational design of heterogeneous catalysts is of utmost importance to improve the efficiency of industrial chemical synthesis. In this thesis, we investigate two chemical reactions catalyzed by heterogeneous catalysts through theoretical modeling, the aerobic esterification of primary alcohols and the two electron oxygen reduction reaction. First, we develop a microkinetic modeling code, Micki, that both provides an easy-to-use interface for standard statistical mechanical methods for microkinetic modeling as well as novel ways to incorporate complex physics that influence the liquid-solid interface. Then we use Micki to determine the role of P block promoters for the aerobic esterification of alcohols. Tellurium atoms modify the electronic structure of the catalyst which reduces the barrier of the rate limiting step, C-H bond scission, as well as providing lower energy pathways for O2 reduction. Next, we develop a theoretical framework to evaluate the performance of cobalt dichalcogenides based on density functional theory calculations. Together with experimental collaborators, we discover the best 2e? ORR catalysts in acidic media to date as well as transferable physical principles. We apply these physical principles to nickel dichalcogenides and cobalt nickel dichalcogen alloys. We conclude that while nickel dichalcogenides show great promise for 2e? ORR, the alloy does not as neighboring metal centers have little electronic influence on each other. Finally we use Micki to develop an electrochemical microkinetic model of 2e? ORR on cobalt dichalcogenide catalysts and compare results to bulk electrolysis experiments. While significant work must be done to reach quantitative accuracy for electrochemical kinetic models, our results indicate qualitative trends are properly modeled and electrochemical kinetic models can be used to predict catalyst performance.