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A quantitative analysis of the efficiency of solar-driven water-splitting device designs based on tandem photoabsorbers patterned with islands of metallic electrocatalysts

Chen, Yikai and Sun, Ke and Audesirk, Heather A. and Xiang, Chengxiang and Lewis, Nathan S. (2015) A quantitative analysis of the efficiency of solar-driven water-splitting device designs based on tandem photoabsorbers patterned with islands of metallic electrocatalysts. Energy and Environmental Science, 8 (6). pp. 1736-1747. ISSN 1754-5692. doi:10.1039/c5ee00311c.

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The trade-off between the optical obscuration and kinetic overpotentials of electrocatalyst films patterned onto the surface of tandem light-absorber structures in model photoelectrosynthetic water-splitting systems was investigated using a 0-dimensional load-line analysis and experimental measurements. The electrocatalytic performance of the catalyst at high current densities, normalized to the electrocatalyst surface area, is an important factor in the dependence of the optimal solar-to-hydrogen (STH) conversion efficiency, η_(STH,opt), on the filling fraction (f_c) of the patterned catalysts, because even under conditions that produce minority-carrier current densities of ~10 mA cm^(−2) at the solid/liquid interface, the current density at catalyst-bearing sites can be >1–2 A cm^(−2) in low filling-fraction films. A universal current-density versus potential relationship, up to current densities of 10 A cm^(−2), was obtained experimentally for the hydrogen-evolution reaction (HER) using patterned Pt ultramicroelectrode (UME) arrays with a range of filling fractions and disc diameters. The η_(STH,opt) of system designs that utilize patterned electrocatalysts located on the illuminated side of tandem photoabsorbers was then evaluated systematically. The maximum STH conversion efficiency, η_(STH,max), using a hypothetical electrocatalyst that was optically transparent but which nevertheless exhibited a current-density versus potential behavior that is characteristic of the most active Pt films measured experimentally regardless of their optical obscuration, was 26.7%. By comparison, the maximum η_(STH,opt) of 24.9% for real patterned Pt electrocatalyst films closely approached this ideal-case limit. The performance and materials utilization of the patterned electrocatalysts and of the uniformly coated electrocatalysts on tandem photoabsorbers were also compared in this study. Hence, patterned electrocatalysts with very low filling fractions can provide a potentially promising path to the realization of efficient large-scale photoelectrolysis systems while minimizing the use of scarce noble metals.

Item Type:Article
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URLURL TypeDescription
Sun, Ke0000-0001-8209-364X
Xiang, Chengxiang0000-0002-1698-6754
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2015 The Royal Society of Chemistry. Received 29th January 2015, Accepted 23rd March 2015, First published online 23 Mar 2015. 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 Number DE-SC0004993. UV-VIS spectroscopy and AFM were performed at the Beckman Institute Molecular Materials Resource Center (MMRC) at the California Institute of Technology. We also thank E. Warren for stimulating discussions, Z. Huang for assistance with the AFM measurement and K. Papadantonakis for assistance on the editing of this manuscript.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Issue or Number:6
Record Number:CaltechAUTHORS:20150427-134904440
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57019
Deposited By: Tony Diaz
Deposited On:27 Apr 2015 21:01
Last Modified:10 Nov 2021 21:06

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