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Performance and failure modes of Si anodes patterned with thin-film Ni catalyst islands for water oxidation

Sun, Ke and Ritzert, Nicole L. and John, Jimmy and Tan, Haiyan and Hale, William G. and Jiang, Jingjing and Moreno-Hernandez, Ivan and Papadantonakis, Kimberly M. and Moffat, Thomas P. and Brunschwig, Bruce S. and Lewis, Nathan S. (2018) Performance and failure modes of Si anodes patterned with thin-film Ni catalyst islands for water oxidation. Sustainable Energy and Fuels, 2 (5). pp. 983-998. ISSN 2398-4902. doi:10.1039/C7SE00583K.

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Silicon photoanodes patterned with thin-film Ni catalyst islands exhibited stable oxygen evolution for over 240 h of continuous operation in 1.0 mol L^(−1) KOH under simulated sunlight conditions. Buried-junction np^+-Si(111) photoanodes with an 18.0% filling fraction of a square array of Ni microelectrodes, np^+-Si(111)|NiμE_(18.0%), demonstrated performance equivalent to a Ni anode in series with a photovoltaic device having an open-circuit voltage of 538 ± 20 mV, a short-circuit current density of 20.4 ± 1.3 mA cm^(−2), and a photovoltaic efficiency of 6.7 ± 0.9%. For the np^+-Si(111)|NiμE_(18.0%) samples, the photocurrent density at the equilibrium potential for oxygen evolution was 12.7 ± 0.9 mA cm^(−2), yielding an ideal regenerative cell solar-to-oxygen conversion efficiency of 0.47 ± 0.07%. The photocurrent passed exclusively through the Ni catalyst islands to evolve O_2 with nearly 100% faradaic efficiency, while a passivating, insulating surface layer of SiO_x formed in situ on areas of the Si in direct contact with the electrolyte. The (photo)electrochemical behavior of Si electrodes patterned with varying areal filling fractions of Ni catalyst islands was also investigated. The stability and efficiency of the patterned-catalyst Si electrodes were affected by the filling fraction of the Ni catalyst, the orientation and dopant type of the substrates, and the measurement conditions. The electrochemical behavior at different stages of operation, including Ni catalyst activation, Si passivation, stable operation, and device failure, was affected by the dynamic processes of anodic formation and isotropic dissolution of SiO_x on the exposed Si. Ex situ and operando microscopic and spectroscopic studies revealed that these processes were three-dimensional and spatially non-uniform across the surface of the substrate, and occurred near the active catalyst islands. The patterned catalyst/substrate electrodes serve as a model system for accelerated studies of failure mechanisms in photoanodes protected by multifunctional catalytic coatings or other hole-conductive thin-film coatings that contain defects.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Sun, Ke0000-0001-8209-364X
John, Jimmy0000-0002-8772-8939
Moreno-Hernandez, Ivan0000-0001-6461-9214
Papadantonakis, Kimberly M.0000-0002-9900-5500
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© Royal Society of Chemistry 2018. The article was received on 05 Dec 2017, accepted on 03 Mar 2018 and first published on 06 Mar 2018. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under award no. DE-SC0004993. UV-vis spectroscopy was performed at the Molecular Materials Research Center (MMRC) in the Beckman Institute at the California Institute of Technology. This work was also supported by the Gordon and Betty Moore Foundation under award no. GBMF1225. We thank A. Carim, M. Shaner, F. Saadi, J. Velazquez, and C. Xiang from Caltech for stimulating discussions. We also thank K. Walczak (Lawrence Berkeley National Laboratory) for preparation of the ion-implanted Si n^+np^+ substrates. The NIST work was supported by the American Recovery and Reinvestment funds. N. L. R. acknowledges the National Institute of Standards and Technology-National Research Council research associateship program for a postdoctoral fellowship. Author contributions: K. S. and N. S. L designed research; K. S., N. R., J. J., H. T., W. G. H., J. J., I. A. M., and T. P. M. performed experiments; K. S., N. R., J. J., H. T., K. M. P., T. P. M., B. S. B., and N. S. L. analyzed data; and K. S., N. R., K. M. P., T. P. M., B. S. B., and N. S. L. wrote the paper. There are no conflicts to declare.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Gordon and Betty Moore FoundationGBMF1225
American Recovery and Reinvestment Act (ARRA)UNSPECIFIED
National Institute of Standards and Technology (NIST)UNSPECIFIED
National Research CouncilUNSPECIFIED
Issue or Number:5
Record Number:CaltechAUTHORS:20180328-133308643
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85483
Deposited By: George Porter
Deposited On:29 Mar 2018 14:35
Last Modified:15 Nov 2021 20:29

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