A High-Performance Si Microwire Photocathode Coupled with Ni–Mo Catalyst

Shaner, M. R., McKone, J. R., Gray, H. B. & Lewis, N. S. Functional integration of Ni–Mo electrocatalysts with i microwire array photocathodes to simultaneously achieve high fill factors and light-limited photocurrent densities for solar-driven hydrogen evolution. Energy & Environmental Science, DOI: 10.1039/C5EE01076D (2015).


Scientific Achievement

We have designed and demonstrated a H2-evolving Si microwire photocathode decorated with an opaque Ni–Mo electrocatalyst.  The system exhibits high light-limited photocurrent densities (Jph) and fill factor (ff).

Significance & impact

The microwire design overcomes limitations of other traditional photocathode designs.  The design enables the required loading of earth-abundant Ni–Mo catalyst, while minimizing parasitic optical absorption losses.

Top:  (a) Scanning-electron micrographs of a silicon microwire array with sequentially deposited layers of Ni–Mo nanopowder and TiO2 light-scattering particles; (b) Close-up image highlighted to delineate the Ni–Mo nanopowder (blue) layer beneath the layer of TiO2 particles (gray).

Bottom:  Current-density versus potential (J–E) behavior of the Si microwire-array devices, as well as Si microwires control samples without the catalyst (n+p-Si/TiO2) that utilize only a Pt electrode in the dark.

  Adapted from Shaner, M. R., McKone, J. R., Gray, H. B. & Lewis, N. S. Functional integration of Ni–Mo electrocatalysts with Si microwire array photocathodes to simultaneously achieve high fill factors and light-limited photocurrent densities for solar-driven hydrogen evolution. Energy & Environmental Science, DOI: 10.1039/C5EE01076D (2015) with permission of The Royal Society of Chemistry.

 

Adapted from Shaner, M. R., McKone, J. R., Gray, H. B. & Lewis, N. S. Functional integration of Ni–Mo electrocatalysts with Si microwire array photocathodes to simultaneously achieve high fill factors and light-limited photocurrent densities for solar-driven hydrogen evolution. Energy & Environmental Science, DOI: 10.1039/C5EE01076D (2015) with permission of The Royal Society of Chemistry.

Research Details

  • The design consists of a n+p-Si microwire array with a Ni–Mo/TiO2catalyst/light-scattering bi-layer structure.  TiO2 light-scattering nanoparticles are used to simultaneously achieve high fill factors and light-limited photocurrent densities from photocathodes that produce H2(g) directly from sunlight and water.
  • Photoelectrochemical characterization was performed in 1.0 M H2SO4 under simulated 1 Sun AMG1.5 conditions.
  • The best-performing microwire devices exhibit short-circuit photocurrent densities of −14.3 mA·cm−2, photovoltages of 420 mV, and a fill factor of 0.48, whereas the equivalent planar Ni–Mo-coated Si devices, without TiO2, display negligible photocurrent due to complete light blocking by the catalyst layer.

Contact: nslewis@caltech.edu

 

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