Data from: Contactless measurement of the photovoltage in BiVO4 photoelectrodes

The power output of photoelectrochemical devices for solar energy-to-fuel
conversion is determined by the photovoltage of the junction under
illumination. In the presence of fast redox couples, the photovoltage can
be obtained directly from current-voltage measurements of the device.
However, for slow redox couples (H+/H2, O2/H2O) used in solar fuel
photoelectrodes, photovoltage measurements are not straightforward, due to
the kinetic overpotentials during charge transfer. Here we show that the
photovoltage of BiVO4 electrodes in contact with fast electron donors KI,
Na2SO3 or H2O2 or K4Fe(CN)6 can be measured in a contactless way with
vibrating Kelvin probe surface photovoltage (SPV) spectroscopy. The
photovoltage varies with illumination wavelength and intensity and matches
the open circuit potential of the electrodes, obtained separately from
electrochemical measurements. Plots of the photovoltage versus irradiance
can be used to predict the oxidizing power of each electrode under zero
applied bias. Except for K4Fe(CN)6, which causes shunting in the BiVO4
electrode, photovoltage values correlate well with the built-in potential
of each junction. The ability to obtain photovoltage information through
contactless SPV measurements will be useful in the search for solid-liquid
junctions with superior energy conversion properties.