Materials　with　different　Au-Pd　ratios　bimetallic　alloy　nanoparticles　(NPs)　supported　on　MgAl-LDH　(Au-Pd/LDH)　were　prepared　by　an　impregnation-reduction　method　and　developed　as　photocatalysts　for　the　selective　oxidation　of　benzyl　alcohol　to　benzaldehyde　under　visible　light　irradiation.　A　typical　sample　(Au9-Pd1/LDH)　showed　efficient　photocatalytic　activity　with　91.1%　conversion　and　99%　selectivity.　The　conversion　was　greatly　increased　from　3.6%　for　Au/LDH　and　1.5%　for　Pd/LDH,　respectively.　Moreover,　it　was　four　times　higher　than　that　for　Au9-Pd1/TiO2.　The　ESR　spectrum　demonstrated　that　the　main　reactive　species　were　superoxide　radicals　(O2-)　generated　by　the　transfer　of　hot　electrons　from　the　Au-Pd　alloy　NPs　to　the　surface　adsorbed　molecular　oxygen.　The　formation　of　hot　electrons　was　attributed　to　localized　surface　plasmon　resonance　(LSPR)　of　the　alloy　NPs.　Based　on　XPS　analysis,　a　synergistic　electron　effect　in　the　Au-Pd　alloy　was　observed　due　to　the　transfer　of　electrons　from　Pd　to　Au　atoms.　This　effect　enhances　the　adsorption　ability　of　Pd　atoms　to　oxygen　molecules　and　facilitates　the　formation　of　O2-.　The　results　from　CO2-TPD　and　in　situ　FT-IR　analyses　indicated　that　benzyl　alcohol　could　be　efficiently　activated　at　the　surface　base　sites　on　the　LDH　via　surface　coordination　to　form　a　metal-alkoxide　intermediate.　Here,　the　intermediate　could　be　more　easily　oxidized　by　O2-　to　form　benzaldehyde.　Finally,　a　possible　mechanism　based　on　the　cooperation　effect　between　the　alloy　NPs　and　the　surface　basic　sites　on　the　LDH　was　proposed　to　illustrate　the　photocatalytic　process.　©　2018　The　Royal　Society　of　Chemistry.