Various　exposed　facets　can　cause　a　huge　difference　in　the　catalytic　activity.　Here　we　prepared　Co3O4　hexagonal　nanosheets　with　exposed　{112},　{112}&{111},　and　{111}　facets　for　the　electrochemical　nitrate　reduction　reactions　(NO3RR).　The　reaction　pathways　of　the　NO3RR　on　Co3O4　{111}　and　{112}　facets　are　clarified　through　in　situ　electrochemical　characterizations　and　theoretical　analysis.　As　the　dominating　facet　of　Co3O4　transforms　from　{112}　to　{111},　the　rate-determining　step　changes　from　*NO2　→　*NO2H　to　*NO3H　→　*NO2,　with　the　energy　barrier　decreasing　to　0.48　eV.　And　the　{111}　facet　promotes　the　hydrogenation　of　NOx　and　NHx　intermediates.　Notably,　the　Co3O4-{111}　catalyst　shows　exceptional　NO3RR　performance,　achieving　an　NH3　yield　of　5.73　mg　mgcat.-1　h-1,　surpassing　the　majority　of　the　reported　activities.　©　2024　American　Chemical　Society.