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 ze..., Surface photovoltage (SPV) data was obtained with the vibrating Kelvin probe technique, using a semi-transparent (60%) 3.0 mm diameter gold Kelvin probe (Kelvin Probe S, Delta PHI Besocke) and a Besocke Kelvin Control.  Measurements were conducted in a custom-made chamber under vacuum (≤ 2 × 10-4 mbar) or in H2O-saturated N2 gas. Samples were coated  with 10-15 mL of liquid electrolytes using a micropipette and covered with a glass cover slip (Fisher Scientific, 0.17 to 0.25 mm thickness). For the acquisition of full spectra, n-GaP was illuminated through the Kelvin probe using light from a 300 W tungsten-halogen lamp filtered through an Oriel Cornerstone 130 monochromator (1-10 mW cm-2). Scans were performed from 9600 cm-1 to 40000 cm-1. The contact potential difference (CPD) data were corrected for drift effects by subtracting a fitted logarithmic curve of a dark scan from the spectral scan. Intensity-dependent measurements were performed with an air-cooled 400 nm LED array connected ..., , # Contactless Measurement of Photovoltage in BiVO4 Photoelectrodes

Access this dataset on Dryad(DOI:10.25338/B83H0K)

This set contains surface photovoltage spectra (Figs 3a-d), transient surface photovoltage data (Figs 3e-h, S3), Open circuit potential data (Fig 4, S5), Fermi level data (Fig. 5), short circuit current data (Fig S6). All data is organized in the same order as in the Figures in the source publication.

## Description of the data and file structure

The data is organized in csv format, as follows:

Surface photovoltage spectra of n-BiVO4

Fig3aVacuum

Column A: Photon energy / eV
Column B: Delta CPD signal / V

Fig3a005MI3

Column A: Photon energy / eV
Column B: Delta CPD signal / V

Fig3a0005MI3

Column A: Photon energy / eV
Column B: Delta CPD signal / V

Fig3bNa2SO3

Column A: Photon energy / eV
Column B: Delta CPD signal / V

Fig3cH2O2

Column A: Photon energy / eV
Column B: Delta CPD signal / V

Fig3dHCF

Column A: Photon energy / eV
Column B: Delta CPD signal / ...