Photocatalytic　selective　oxidation　of　alcohols　over　titania　supported　with　bimetallic　nanoparticles　represents　an　energy　efficient　and　sustainable　route　for　the　synthesis　of　esters.　Specifically,　the　bimetallic　PdAu/TiO2　system　was　found　to　be　highly　active　and　selective　toward　photocatalytic　production　of　methyl　formate　(MF)　from　gas-phase　methanol.　In　the　current　paper,　we　applied　the　electronic　structure　density　functional　theory　method　to　understand　the　mechanistic　aspects　and　corroborate　our　recent　experimental　measurements　for　the　photocatalytic　selective　oxidation　of　methanol　to　MF　over　the　PdAu/TiO2　catalyst.　Our　theoretical　results　revealed　the　preferential　segregation　of　Pd　atoms　from　initially　mixed　PdAu　nanoclusters　to　the　interface　of　PdAu/TiO2　and　subsequent　formation　of　a　unique　structure,　resembling　a　core@shell　architecture　in　close　proximity　to　the　interface.　The　analysis　of　the　calculated　band　gap　diagram　provides　an　explanation　of　the　superior　electron　hole　separation　capability　of　PdAu　nanoparticles　deposited　onto　the　anatase　surface　and　hence　the　remarkably　enhanced　photocatalytic　activity,　in　comparison　to　their　monometallic　counterparts.　We　demonstrated　that　facile　dissociation　of　molecular　oxygen　at　the　triple-point　boundary　site　gives　rise　to　in　situ　oxidation　of　Pd.　The　in　situ　formed　PdO/TiO2　is　responsible　for　total　oxidation　of　methanol　to　CO2　(no　MF　formation)　in　the　gas　phase.　Our　investigation　provides　theoretical　guidance　for　designing　highly　selective　and　active　bimetallic　nanoparticles-TiO2　catalysts　for　the　photocatalytic　selective　oxidation　of　methanol　to　MF.