Kp. Quinlan, ELECTRON-TRANSFER PROPERTIES OF THE P-BENZOQUINONE-INP ELECTRODE SYSTEMS, Journal of electroanalytical chemistry [1992], 369(1-2), 1994, pp. 121-129
The reduction of p-benzoquinone (p-BzQ) has been studied at p- and n-I
nP electrodes. The p-InP/p-BzQ system exhibits a photocurrent density
multiplication factor of 1.2 when the pH ratio of the systems is 4.0/7
.0. This factor is constant at high and low light intensities. When th
e study is extended to higher pH values, e.g. using pH ratios of 8.0/8
.3, 4.0/8.3 etc., photocurrent multiplication factors of 2 or more are
observed. These results indicate that a possible pH-induced surface c
hange is the factor responsible for photocurrent doubling and not the
presence of the undissociated acid form of semibenzoquinone. The n-InP
electrodes with p-BzQ were studied in detail at pH values of 7 and 4
with electrodes having carrier concentrations of 7 x 10(18), 4 x 10(18
) and 5 x 10(15) cm-3. The ratios of the dark current density at pH 4
to that at pH 7 for the n-InP/p-BzQ systems ranged from 2 to 38 for th
e different n-InP electrodes. This wide range of dark current multipli
cation factors is possibly the result of a pH-induced surface change.
The energy level diagrams of the interfaces suggest the participation
of the conduction and valence bands in these processes.