Si Microwire-Array Photocathodes Decorated with Cu Allow CO2Reduction with Minimal Parasitic Absorption of Sunlight

Paul A. Kempler, Matthias H. Richter, Wen Hui Cheng, Bruce S. Brunschwig, Nathan S. Lewis

Research output: Contribution to journalArticlepeer-review


High loadings of Cu were integrated on the light-facing side of Si microwire arrays used under simulated sunlight for the photoelectrochemical reduction of CO2(aq) to hydrocarbons in 0.10 M KHCO3(aq). Radial-junction n+p-Si microwire arrays decorated with Cu exhibited absolute photocurrent densities comparable to an uncovered Si surface. Moreover, with respect to a Cu foil electrode, the positive shift in the onset potential for hydrocarbon formation at n+p-Si/Cu microwire arrays was equal to or greater than the photovoltage of the semiconductor alone. Selective electrodeposition of Cu on the tips and sidewalls of Si microwires was responsible for the minimal parasitic reflection and absorption exhibited by the catalyst, such that light-limited, absolute current densities >25 mA·cm-2 were sustained for 48 h under simulated sunlight. Photoelectrodes prepared from semiconductors with low diode quality factors and electrocatalysts with large Tafel slopes are shown to benefit from increased microstructured surface area. Si microwire arrays are thus suitable for photoelectrochemical reactions requiring high loadings of metallic and reflective electrocatalysts.

Original languageEnglish
Pages (from-to)2528-2534
Number of pages7
JournalACS Energy Letters
Issue number8
Publication statusPublished - Aug 14 2020

ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Materials Chemistry

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