The use of semiconducting materials, such as bismuth vanadate (BiVO4), as nanoparticulate catalysts for photocatalytic water-splitting depends on the nature of electronic-band bending phenomena at the semiconductor-liquid interface. Electric fields present at these interfaces reduce the concentration of majority charge carriers within a region of the semiconductor, establishing a depletion/space-charge region. A model produced from studies on bulk semiconductors is currently used to measure the width of this space-charge region and relates it to electronic characteristics such as carrier density and interface voltage. However, it is unknown whether this model accurately describes the space-charge region in nanoparticle systems. Here, we utilize the technique of surface photovoltage spectroscopy to probe the dimension of the space-charge region in BiVO4 particle films. Photoactive monoclinic-scheelite BiVO4 particles with an optical bandgap of 2.5eV were produced through a liquid-assisted solid-state synthesis. Films were prepared via drop-coating on gold-coated glass substrates and annealed before being characterized with surface profilometry and UV-Vis spectroscopy. The space-charge region width observed with surface photovoltage spectroscopy is projected to be orders of magnitude larger than that predicted using the existing model, similar to previous observations made by our group. The results of these characterizations are to be discussed and are expected to aid in the development of a model applicable to nanoscale systems.

Measurement of the space-charge region width in BiVO4 particle films with surface photovoltage spectroscopy

ACS Fall 2020 Virtual Meeting

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