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Comparison of the Performance of CoP-Coated and Pt-Coated Radial Junction n+p‑Silicon Microwire-Array Photocathodes for the Sunlight-Driven Reduction of Water to H2(g)

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journal contribution
posted on 17.12.2015, 08:08 by Christopher W. Roske, Eric J. Popczun, Brian Seger, Carlos G. Read, Thomas Pedersen, Ole Hansen, Peter C. K. Vesborg, Bruce S. Brunschwig, Raymond E. Schaak, Ib Chorkendorff, Harry B. Gray, Nathan S. Lewis
The electrocatalytic performance for hydrogen evolution has been evaluated for radial-junction n+p-Si microwire (MW) arrays with Pt or cobalt phosphide, CoP, nanoparticulate catalysts in contact with 0.50 M H2SO4(aq). The CoP-coated (2.0 mg cm–2) n+p-Si MW photocathodes were stable for over 12 h of continuous operation and produced an open-circuit photovoltage (Voc) of 0.48 V, a light-limited photocurrent density (Jph) of 17 mA cm–2, a fill factor (ff) of 0.24, and an ideal regenerative cell efficiency (ηIRC) of 1.9% under simulated 1 Sun illumination. Pt-coated (0.5 mg cm–2) n+p-Si MW-array photocathodes produced Voc = 0.44 V, Jph = 14 mA cm–2, ff = 0.46, and η = 2.9% under identical conditions. Thus, the MW geometry allows the fabrication of photocathodes entirely comprised of earth-abundant materials that exhibit performance comparable to that of devices that contain Pt.