Silicon Photoelectrode Thermodynamics and Hydrogen Evolution Kinetics Measured by Intensity-Modulated High-Frequency Resistivity Impedance Spectroscopy
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States); The Univ. of Texas at Austin, Austin, TX (United States)
Here, we present an impedance technique based on light intensity-modulated high-frequency resistivity (IMHFR) that provides a new way to elucidate both the thermodynamics and kinetics in complex semiconductor photoelectrodes. We apply IMHFR to probe electrode interfacial energetics on oxide-modified semiconductor surfaces frequently used to improve the stability and efficiency of photoelectrochemical water splitting systems. Combined with current density-voltage measurements, the technique quantifies the overpotential for proton reduction relative to its thermodynamic potential in Si photocathodes coated with three oxides (SiOx, TiO2, and Al2O3) and a Pt catalyst. In pH 7 electrolyte, the flatband potentials of TiO2- and Al2O3-coated Si electrodes are negative relative to samples with native SiOx, indicating that SiOx is a better protective layer against oxidative electrochemical corrosion than ALD-deposited crystalline TiO2 or Al2O3. Adding a Pt catalyst to SiOx/Si minimizes proton reduction overpotential losses but at the expense of a reduction in available energy characterized by a more negative flatband potential relative to catalyst-free SiOx/Si.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1402562
- Report Number(s):
- NREL/JA-5900-68410
- Journal Information:
- Journal of Physical Chemistry Letters, Vol. 8, Issue 21; ISSN 1948-7185
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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