TiO2　films　on　Al　alloy　(Al),　indium-tin　oxide　glass　(ITO/glass),　and　glass　were　prepared　by　a　dip-coating　method.　ITO　is　found　to　have　a　higher　work　function,　while　the　work　function　for　Al　is　lower　than　that　of　TiO2　films.　An　electron　transfer　is　indicated　to　occur　in　the　interfaces　between　TiO2　films　and　conducting　substrate　Al　or　ITO,　which　results　in　an　Ohm　contact　or　Schottky　barrier　under　the　transient　equilibrium　UV　radiation　conditions.　Photocatalytic　measurements　showed　that　the　TiO2　films　on　Al　have　a　higher　activity　for　photocatalytic　oxidation　of　C2H4,　but　the　activity　for　photocatalytic　degradation　of　oleic　acid　is　lower　as　compared　with　TiO2　films　on　glass.　Alternatively,　TiO2　films　on　ITO　give　completely　contrary　photocatalytic　performance　to　those　on　Al.　These　observations　could　be　associated　with　the　electron　transfer,　in　which　Al　acts　as　an　electron　donor　and　offers　electrons　to　TiO2,　allowing　photocatalytic　oxidation　of　ethylene　to　proceed　by　the　photogenerated　electrons,　while　ITO　could　be　an　acceptor　for　the　photogenerated　electrons,　which　is　beneficial　to　photocatalytic　degradation　of　oleic　acid　by　the　photogenerated　holes.　This　electron-transfer　model　could　be　extended　to　other　photocatalytic　systems.