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Title: Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO 4 Photoanodes

Abstract

Chemical transformations that occur on photoactive materials, such as photoelectrochemical water splitting, are strongly influenced by the surface properties as well as by the surrounding environment. Herein, we elucidate the effects of oxygen and water surface adsorption on band alignment, interfacial charge transfer, and charge-carrier transport by using complementary Kelvin probe measurements and photoconductive atomic force microscopy on bismuth vanadate. By observing variations in surface potential, we show that adsorbed oxygen acts as an electron-trap state at the surface of bismuth vanadate, whereas adsorbed water results in formation of a dipole layer without inducing interfacial charge transfer. The apparent change of trap state density under dry or humid nitrogen, as well as under oxygen-rich atmosphere, proves that surface adsorbates influence charge-carrier transport properties in the material. The finding that oxygen introduces electronically active states on the surface of bismuth vanadate may have important implications for understanding functional characteristics of water splitting photoanodes, devising strategies to passivate interfacial trap states, and elucidating important couplings between energetics and charge transport in reaction environments.

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Technische Univ. Munchen, Garching (Germany)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
OSTI Identifier:
1477400
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 10; Journal Issue: 41; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Eichhorn, Johanna, Kastl, Christoph, Schwartzberg, Adam M., Sharp, Ian D., and Toma, Francesca M. Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO 4 Photoanodes. United States: N. p., 2018. Web. doi:10.1021/acsami.8b11366.
Eichhorn, Johanna, Kastl, Christoph, Schwartzberg, Adam M., Sharp, Ian D., & Toma, Francesca M. Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO 4 Photoanodes. United States. doi:10.1021/acsami.8b11366.
Eichhorn, Johanna, Kastl, Christoph, Schwartzberg, Adam M., Sharp, Ian D., and Toma, Francesca M. Wed . "Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO 4 Photoanodes". United States. doi:10.1021/acsami.8b11366. https://www.osti.gov/servlets/purl/1477400.
@article{osti_1477400,
title = {Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO 4 Photoanodes},
author = {Eichhorn, Johanna and Kastl, Christoph and Schwartzberg, Adam M. and Sharp, Ian D. and Toma, Francesca M.},
abstractNote = {Chemical transformations that occur on photoactive materials, such as photoelectrochemical water splitting, are strongly influenced by the surface properties as well as by the surrounding environment. Herein, we elucidate the effects of oxygen and water surface adsorption on band alignment, interfacial charge transfer, and charge-carrier transport by using complementary Kelvin probe measurements and photoconductive atomic force microscopy on bismuth vanadate. By observing variations in surface potential, we show that adsorbed oxygen acts as an electron-trap state at the surface of bismuth vanadate, whereas adsorbed water results in formation of a dipole layer without inducing interfacial charge transfer. The apparent change of trap state density under dry or humid nitrogen, as well as under oxygen-rich atmosphere, proves that surface adsorbates influence charge-carrier transport properties in the material. The finding that oxygen introduces electronically active states on the surface of bismuth vanadate may have important implications for understanding functional characteristics of water splitting photoanodes, devising strategies to passivate interfacial trap states, and elucidating important couplings between energetics and charge transport in reaction environments.},
doi = {10.1021/acsami.8b11366},
journal = {ACS Applied Materials and Interfaces},
number = 41,
volume = 10,
place = {United States},
year = {2018},
month = {9}
}

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Cited by: 2 works
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Figures / Tables:

Figure 1 Figure 1: Oxygen and water adsorption on BiVO4 in dark conditions. (a) Time-resolved contact potential difference (CPD) measurements after exposure to humidity. The baseline in dry nitrogen environment is set to zero. Upon increasing the relative humidity to about 40%, the equilibrium ΔCPD is about -27 mV. (b) Schematic bandmore » diagram with Fermi level, vacuum level ($E$vac), conduction ($E$c) and valence band ($E$v). Non-dissociative water adsorption creates a dipole layer on the surface, and can lead to a reduced surface concentration of oxygen as a consequence of competitive adsorption/desorption events (red arrow). (c) CPD measurement after exposure to oxygen. An increase of the oxygen concentration to 21% yields a ΔCPD of about +40 mV. (d) Schematic illustration of the electron charge transfer from the surface of BiVO4 to O2 , which results in chemisorption of $O$ $^{-}_{2}$(brown arrow), thus increasing the band bending (brown lines) compared to dry nitrogen environment (black lines).« less

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