• HYDROGEN YIELDS FROM WATER ADSORBED ON DIFFERENT OXIDE SURFACE PLOTTED VS. OXIDE BAND GAP SHOW MAXIMUM NEAR 5 eV • 5.1 eV IS AN ENERGY OF H-OH BOND BREAKING IN WATER MOLECULE
ACCORDING TO EFFECT ON THE H2 YIELD OXIDES CAN BE CLASSIFIED INTO THREE GROUPS:
INHIBITORS : G(H2)=10-3-10-1 (100eV)-1
Oxides which lower the H2 yield as compared with the radiolysis of pure gas-phase water:
MnO2 , Co3O4 ,CuO and Fe2O3
INDIFFERENT : G(H2)=0.1-3 (100eV)-1
Oxides with H2 yields which are similar to or slightly greater than radiolysis of pure gas-phase water:
MgO, CaO, SrO, BaO, ZnO, CdO, Cu2O, NiO, Cr2O3 , Cr(OH)3 , Al2O3 , CeO2 , SiO2 , TiO2 , Nb2O5 and WO3
PROMOTERS : G(H2) > 3 (100eV)-1 (up to 100-130)
Oxides which increase the H2 yield as compared with the radiolysis of pure gas-phase water:
Ga2O3 , Y2O3 , La2O3 , Nd2O3 , Sm2O3 , Eu2O3 , Gd2O3 , Yb2O3 , Er2O3 , HfO2 and ZrO2
NOTE: the G-values quoted above are defined in terms of the radiant energy adsorbed directly by the water molecules.