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

Published

March 6, 2018

Author(s)

Ke Sun, Nicole L. Ritzert, Jimmy John, Haiyan Tan, William G. Hale, Jingjing Jiang, Kimberly M. Papadantonakis, Thomas P. Moffat, Bruce S. Brunschwig, Nathan S. Lewis

Abstract

Silicon photoanodes patterned with Ni thin film catalyst islands exhibited stable oxygen evolution for over 240 h of continuous operation in 1.0 mol L-1 KOH(aq) 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)|NiuE18.0%, 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)|NiuE18.0% samples, the photocurrent density at the equilibrium oxygen evolution potential was 12.7 ± 0.9 mA cm-2, yielding an ideal regenerative cell solar-to-oxygen conversion efficiency of 0.47 ± 0.07%. A passivating, insulating surface layer of SiOx formed in situ on areas of the Si in direct contact with the electrolyte, whereas the photocurrent produced by the np+-Si(111)|NiuE18.0% device passed exclusively through the Ni catalyst islands to evolve O2(g) with nearly 100% faradaic efficiency. 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 observed electrochemical behavior at different stages of operation, including Ni catalyst activation, Si passivation, stable operation, and device failure is affected by the dynamic processes of anodic formation and isotropic dissolution of SiOx on the exposed Si.

Citation

Sustainable Energy & Fuels

Pub Type

Journals

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Citation

Sun, K. , Ritzert, N. , John, J. , Tan, H. , Hale, W. , Jiang, J. , Papadantonakis, K. , Moffat, T. , Brunschwig, B. and Lewis, N. (2018), Performance and failure modes of Si anodes patterned with thin-film Ni catalyst islands for water oxidation, Sustainable Energy & Fuels, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=923743 (Accessed October 3, 2024)