PtS2　is　a　newly　developed　group　10　2D　layered　material　with　high　carrier　mobility,　wide　band　gap　tunability,　strongly　bound　excitons,　symmetrical　metallic　and　magnetic　edge　states,　and　ambient　stability,　making　it　attractive　in　nanoelectronic,　optoelectronic,　and　spintronic　fields.　To　the　aim　of　application,　a　large-scale　synthesis　is　necessary.　For　transition-metal　dichalcogenide　(TMD)　compounds,　a　thermally　assisted　conversion　method　has　been　widely　used　to　fabricate　wafer-scale　thin　films.　However,　PtS2　cannot　be　easily　synthesized　using　the　method,　as　the　tetragonal　PtS　phase　is　more　stable.　Here,　we　use　a　specified　quartz　part　to　locally　increase　the　vapor　pressure　of　sulfur　in　a　chemical　vapor　deposition　furnace　and　successfully　extend　this　method　for　the　synthesis　of　PtS2　thin　films　in　a　scalable　and　controllable　manner.　Moreover,　the　PtS　and　PtS2　phases　can　be　interchangeably　converted　through　a　proposed　strategy.　Field-effect　transistor　characterization　and　photocurrent　measurements　suggest　that　PtS2　is　an　ambipolar　semiconductor　with　a　narrow　band　gap.　Moreover,　PtS2　also　shows　excellent　gas-sensing　performance　with　a　detection　limit　of　similar　to　0.4　ppb　for　NO2.　Our　work　presents　a　relatively　simple　way　of　synthesizing　PtS2　thin　films　and　demonstrates　their　promise　for　high-performance　ultrasensitive　gas　sensing,　broadband　optoelectronics,　and　nanoelectronics　in　a　scalable　manner.　Furthermore,　the　proposed　strategy　is　applicable　for　making　other　PtX2　compounds　and　TMDs　which　are　compatible　with　modern　silicon　technologies.