In　the　previous　work,　we　have　ever　found　that　the　photocatalytic　oxidation　of　a　reactant　gas　over　TiO2　would　be　somewhat　dependent　on　the　electron　transfer　behavior　between　the　adsorbed　gas　and　TiO2　under　UV　irradiation.　To　further　confirm　the　viewpoint,　in　this　work,　a　TiO2　(in-situ)　sample　was　prepared　by　an　in-situ　method,　and　was　tested　its　gas-sensing　performance　to　H2　and　its　photocatalytic　performance　of　oxidizing　H2　as　compared　to　a　TiO2　(commercial)　sample.　It　was　found　that　TiO2　(in-situ)　would　increase　the　conductivity　with　the　introduction　of　H2　under　UV　irradiation,　but　TiO2　(commercial)　would　decrease　the　conductivity　in　the　same　case.　Based　on　the　surface　structural　and　electrochemical　characteristics　of　samples,　it　was　proposed　that　the　existence　of　surface　defects　over　TiO2　(in-situ)　would　decrease　the　Fermi　level　(EF),　resulting　in　the　electron　transfer　from　the　adsorbed　H2　to　TiO2,　while　the　adsorbed　H2　accepted　electrons　from　TiO2　(commercial)　due　to　its　higher　EF.　Moreover,　the　adsorbed　H2　on　TiO2　(in-situ)　could　be　oxidized　under　UV　irradiation　but　that　on　TiO2　(commercial)　could　be　hardly.　This　indicated　that　the　photocatalytic　oxidation　of　H2　over　TiO2　would　be　dependent　on　the　electron　transfer　direction　between　the　adsorbed　H2　and　TiO2,　i.e.,　the　electron-donated　H2　could　be　oxidized,　while　the　electron-accepted　H2　could　be　not.　This　above　effect　induced　by　the　surface　defects　could　be　further　demonstrated　by　a　N-doped　TiO2　(N-TiO2)　sample.　This　N-TiO2　owned　a　lower　EF　than　TiO2　(in-situ)　due　to　the　introduction　of　a　more　impurity　defects,　resulting　in　a　more　electron　transfer　from　the　adsorbed　H2　to　N-TiO2　and　then　the　oxidation　of　more　H2.　This　study　also　indicated　that　the　adjustment　of　EF　could　improve　the　photocatalytic　activity　of　oxidizing　H2　by　changing　the　adsorbed　behavior　of　H2　over　TiO2,　which　may　be　applicable　for　investigating　other　reactants’　oxidation　behaviors　over　other　semiconductor　photocatalysts.　©　2019