Stabilized Si Microwire Arrays for Solar-Driven H2O Oxidation

Shaner, M. R., Hu, S., Sun, K. & Lewis, N. S. Stabilization of Si microwire arrays for solar-driven H2O oxidation to O2(g) in 1.0 M KOH(aq) using conformal coatings of amorphous TiO2. Energy & Environmental Science 8, 203-207, DOI: 10.1039/c4ee03012e (2015).


Scientific Achievement

Atomic-layer deposition of TiO2combined with sputtering of NiCrOxoxygen-evolution catalyst on Si microwires yields robust microwire-array photoanodes.

Significance & impact

Si microwire arrays were protected from passivation and corrosion in 1.0 M KOH(aq) electrolyte, while generating O2 for >2200 h with near 100% Faradaic efficiency under simulated 1 Sun illumination.

 

  Adapted from Shaner, M. R., Hu, S., Sun, K. & Lewis, N. S. Stabilization of Si microwire arrays for solar-driven H2O oxidation to O2(g) in 1.0 M KOH(aq) using conformal coatings of amorphous TiO2. Energy & Environmental Science 8, 203-207, DOI: 10.1039/c4ee03012e (2015) with permission of The Royal Society of Chemistry.

 

Adapted from Shaner, M. R., Hu, S., Sun, K. & Lewis, N. S. Stabilization of Si microwire arrays for solar-driven H2O oxidation to O2(g) in 1.0 M KOH(aq) using conformal coatings of amorphous TiO2. Energy & Environmental Science 8, 203-207, DOI: 10.1039/c4ee03012e (2015) with permission of The Royal Society of Chemistry.

Left:  SEM Image of a fully processed Si microwire array; right:  current desntiy versus time for a Si microwire-array photoelectrode under 1 Sun simulated illumination in 1.0 M KOH(aq).

Research Details

  • Arrays of n-type and np+-radial junction Si microwires were coated with ~94 nm of TiO2 protective coating ~40 nm of NiCrOx catalyst.
  • 10-h interval stability tests show no significant change in photocurrent density, open-circuit potential, or fill factors.
  • Accounting for the 20% capacity factor of sunlight, the 2200 h of continuous operation contained the same amount of charge as would be passed during >1 year of outdoor operation.

 

Contact:  nslewis@caltech.edu