The　industrially　important　selective　hydrogenation　of　alpha,beta-unsaturated　aldehydes　to　allyl　alcohol　is　still　challenging　to　realize　using　heterogenous　hydrogenation　catalysts.　Supported　Cu　catalysts　have　shown　moderate　selectivity,　yet　low　activity　for　the　reaction,　due　to　the　electronic　structure　of　Cu.　By　anchoring　atomically　dispersed　Pd　atoms　onto　the　exposed　Cu　surface　of　Cu@CeO2,　we　report　in　this　work　that　hydrogen　spillover　activates　the　inert　metal-oxide　interfaces　of　Cu@CeO2　into　highly　effective　and　selective　catalytic　sites　for　hydrogenation　under　mild　reaction　conditions.　The　as-prepared　catalysts　exhibit　much　higher　catalytic　activity　in　the　selective　hydrogenation　of　acrolein　than　Cu@CeO2.　Comprehensive　studies　reveal　that　atomically　dispersed　Pd　species　are　critical　for　the　activation　and　homolytic　splitting　of　H2.　The　activated　H　atoms　easily　spill　to　the　Cu-O-Ce　interfaces　as　Cu-H　delta-and　interfacial　Ce-O-H　delta+　species,　making　them　the　active　sites　for　hydrogenation　of　polar　C=O　bonds.　Moreover,　the　weak　adsorption　of　allyl　alcohol　on　the　Pd　and　Cu-O-Ce　interfacial　sites　prevents　deep　hydrogenation,　leading　to　selective　hydrogenation　of　several　alpha,beta-unsaturated　aldehydes.　Overall,　we　demonstrate　here　a　synergic　effect　between　single　atom　alloy　and　the　support　for　activation　of　an　inert　metal-　oxide　interface　into　selective　catalytic　sites.