The　nitrate　reduction　reaction　(NO3RR)　has　emerged　as　a　promising　approach　for　wastewater　treatment　and　ammonia　(NH3)　synthesis.　Poly(triazine　imide)/LiCl　(PTI/LiCl),　a　highly　crystalline　carbon　nitride　with　a　well-defined　structure,　has　shown　significant　potential　in　this　field.　In　this　study,　the　electronic　properties　and　catalytic　performance　of　PTI/LiCl　for　NO3RR　were　investigated　through　theoretical　calculations.　Band　structure　and　projected　density　of　states　(PDOS)　analyses　show　that　the　intercalation　of　Li+　and　Cl-　ions　within　the　PTI　pores　enhances　electronic　conductivity　and　improves　its　electronic　properties.　The　reduction　of　nitrate　to　NH3　through　a　series　of　intermediates　on　the　PTI/LiCl　(001)　surface　shows　exothermic　free　energy　changes　for　each　elementary　step.　The　catalyst　demonstrates　outstanding　selectivity　and　stability,　effectively　suppressing　the　competitive　hydrogen　evolution　reaction　and　byproduct　formation.　Charge　density　difference　and　PDOS　analyses　confirm　the　orbital　interactions　between　absorbed　NO3　and　Li　ions.　The　study　highlights　the　potential　of　PTI/LiCl　as　a　low-cost,　efficient　electrocatalyst　for　NO3RR　and　provides　theoretical　and　practical　insights　for　the　design　of　environmentally　friendly　catalysts.　©　2024　American　Chemical　Society.