Polymer-based　photoanodes　for　the　water　oxidation　reaction　have　recently　garnered　attention,　with　carbon　nitride　standing　out　due　to　its　numerous　advantages.　This　study　focuses　on　synthesizing　crystalline　carbon　nitride　photoanodes,　specifically　poly(heptazine　imide)　(PHI),　and　explores　the　role　of　salts　in　their　production.　Using　a　binary　molten　salt　system,　optimal　photocurrent　density　of　365　μA·cm−2　was　achieved　with　a　voltage　bias　of　1.23　V　versus　the　reversible　hydrogen　electrode　under　AM　1.5G　illumination,　this　performance　is　ca.　18　times　to　the　pristine　PCN　photoanode.　In　this　process,　NH₄SCN　facilitates　the　growth　of　SnS2　seeding　layers,　while　K2CO3　enhances　film　crystallinity.　In　situ　electrochemical　analyses　show　that　this　salt　combination　improves　photoexcited　charge　transfer　efficiency　and　minimizes　resistance　in　the　SnS2　layer.　This　study　clarifies　the　role　of　salts　in　synthesizing　the　PHI　photoanode　and　provides　insights　for　designing　high-crystallinity　carbon　nitride-based　functional　films.　©　Editorial　office　of　Acta　Physico-Chimica　Sinica.