Mm. Khader et al., CATALYTIC EFFECTS FOR HYDROGEN PHOTOGENERATION DUE TO METALLIC DEPOSITION ON P-GAAS, International journal of hydrogen energy, 21(7), 1996, pp. 547-553
Citations number
40
Categorie Soggetti
Energy & Fuels","Environmental Sciences","Physics, Atomic, Molecular & Chemical
In continuation of our previous work on water photodissociation at sem
iconductor surfaces, we report on the catalytic effects of hydrogen ph
otogeneration due to metallic deposits on p-GaAs. These effects were i
nvestigated by measuring the current-voltage curves in 0.5 MH(2)SO(4)
solution, Metallic coating was performed electrochemically by depositi
ng an amount of a metal equivalent to five monolayers on GaAs. Such a
coverage has achieved a maximum positive shift in the onset-potential
of the photocurrent, E(p). Etching GaAs electrodes in (H2SO4 + H2O2 H2O) mixture improved the (J-E) characteristics, however temporarily b
y shifting E(p) towards positive potentials and also by increasing the
value of the limiting photocurrent density by approximately similar t
o 15%. The effect of etching is for the surface with an elemental comp
onent, possibly, arsenic, due to the preferential dissolution of the o
ther elemental component in the etching mixture. Coating with Pt, Ag a
nd Cu gave a positive shift in E(p), but coating with Pb gave a negati
ve shift. Whereas the shift of the onset potential of the photocurrent
was independent of the height of the Schottky barrier, which is expec
ted to be created at the metal/semiconductor interface, the magnitude
of this shift, towards positive potential, was proportional to the dar
k electrocatalytic activity for hydrogen evolution at the deposited me
tal. This activity has been found to be inversely proportional to the
magnitude of the Tafel slope of the metal. Copyright (C) 1996 Internat
ional Association for Hydrogen Energy