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Title: Quantification of the loss mechanisms in emerging water splitting photoanodes through empirical extraction of the spatial charge collection efficiency

Abstract

We present that the operando quantification of surface and bulk losses is key to developing strategies for optimizing photoelectrodes and realizing high efficiency photoelectrochemical solar energy conversion systems. This is particularly true for emerging thin film semiconductors, in which photocarrier diffusion lengths, surface and bulk recombination processes, and charge separation and extraction limitations are poorly understood. Insights into mechanisms of efficiency loss can guide strategies for nanostructuring photoelectrodes, engineering interfaces, and incorporating catalysts. However, few experimental methods are available for direct characterization of dominant loss processes under photoelectrochemical operating conditions. In this work, we provide insight into the function and limitations of an emerging semiconductor photoanode, γ-Cu 3V 2O 8, by quantifying the spatial collection efficiency (SCE), which is defined as the fraction of photogenerated charge carriers at each point below the surface that contributes to the measured current. Analyzing SCE profiles at different operating potentials shows that increasing the applied potential primarily acts to reduce surface recombination rather than to increase the thickness of the space charge region under the semiconductor/electrolyte interface. Comparing SCE profiles obtained with and without a sacrificial reagent allows surface losses from electronically active defect states to be distinguished from performance bottlenecks arising from slowmore » reaction kinetics. Combining these insights promotes a complete understanding of the photoanode performance and its potential as a water splitting photoanode. More generally, application of the SCE extraction method can aid in the discovery and evaluation of new materials for solar water splitting devices by providing mechanistic details underlying photocurrent generation and loss.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division and Joint Center for Artificial Photosynthesis
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division and Joint Center for Artificial Photosynthesis; Technische Universität München (Germany). Walter Schottky Institut and Physik Department
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), Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1477280
Grant/Contract Number:  
AC02-05CH11231; SC0004993
Resource Type:
Accepted Manuscript
Journal Name:
Energy & Environmental Science
Additional Journal Information:
Journal Volume: 11; Journal Issue: 4; Journal ID: ISSN 1754-5692
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 14 SOLAR ENERGY

Citation Formats

Segev, Gideon, Jiang, Chang-Ming, Cooper, Jason K., Eichhorn, Johanna, Toma, Francesca M., and Sharp, Ian D. Quantification of the loss mechanisms in emerging water splitting photoanodes through empirical extraction of the spatial charge collection efficiency. United States: N. p., 2018. Web. doi:10.1039/c7ee03486e.
Segev, Gideon, Jiang, Chang-Ming, Cooper, Jason K., Eichhorn, Johanna, Toma, Francesca M., & Sharp, Ian D. Quantification of the loss mechanisms in emerging water splitting photoanodes through empirical extraction of the spatial charge collection efficiency. United States. doi:10.1039/c7ee03486e.
Segev, Gideon, Jiang, Chang-Ming, Cooper, Jason K., Eichhorn, Johanna, Toma, Francesca M., and Sharp, Ian D. Tue . "Quantification of the loss mechanisms in emerging water splitting photoanodes through empirical extraction of the spatial charge collection efficiency". United States. doi:10.1039/c7ee03486e. https://www.osti.gov/servlets/purl/1477280.
@article{osti_1477280,
title = {Quantification of the loss mechanisms in emerging water splitting photoanodes through empirical extraction of the spatial charge collection efficiency},
author = {Segev, Gideon and Jiang, Chang-Ming and Cooper, Jason K. and Eichhorn, Johanna and Toma, Francesca M. and Sharp, Ian D.},
abstractNote = {We present that the operando quantification of surface and bulk losses is key to developing strategies for optimizing photoelectrodes and realizing high efficiency photoelectrochemical solar energy conversion systems. This is particularly true for emerging thin film semiconductors, in which photocarrier diffusion lengths, surface and bulk recombination processes, and charge separation and extraction limitations are poorly understood. Insights into mechanisms of efficiency loss can guide strategies for nanostructuring photoelectrodes, engineering interfaces, and incorporating catalysts. However, few experimental methods are available for direct characterization of dominant loss processes under photoelectrochemical operating conditions. In this work, we provide insight into the function and limitations of an emerging semiconductor photoanode, γ-Cu3V2O8, by quantifying the spatial collection efficiency (SCE), which is defined as the fraction of photogenerated charge carriers at each point below the surface that contributes to the measured current. Analyzing SCE profiles at different operating potentials shows that increasing the applied potential primarily acts to reduce surface recombination rather than to increase the thickness of the space charge region under the semiconductor/electrolyte interface. Comparing SCE profiles obtained with and without a sacrificial reagent allows surface losses from electronically active defect states to be distinguished from performance bottlenecks arising from slow reaction kinetics. Combining these insights promotes a complete understanding of the photoanode performance and its potential as a water splitting photoanode. More generally, application of the SCE extraction method can aid in the discovery and evaluation of new materials for solar water splitting devices by providing mechanistic details underlying photocurrent generation and loss.},
doi = {10.1039/c7ee03486e},
journal = {Energy & Environmental Science},
number = 4,
volume = 11,
place = {United States},
year = {2018},
month = {2}
}

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