Coupling renewably generated electricity with waste chemicals to generate value-added products has potentially transformative benefits for society by curbing chemical emissions and mitigating climate change. One such waste chemical is excess ammonia from agricultural livestock production, which depletes nitrogen from the soil and has harmful health effects on human and aquatic life. Ammonia can be partially converted electrochemically to nitrate, and this mixture of ammonium nitrate can then be re-introduced into the nitrogen cycle as an upgraded form of fertilizer. In contrast to the reverse process nitrogen reduction, the mechanism of ammonia oxidation and in particular the formation of NOx species is comparatively less explored. In this talk, I will describe our recent efforts to map the reaction mechanism of electrochemical ammonia oxidation to dinitrogen, nitrite, and nitrate on oxidized Ni surfaces and discuss possible ways to direct selectivity toward oxygenated products using periodic density functional theory.