1 research outputs found
Tailoring n‑ZnO/p-Si Branched Nanowire Heterostructures for Selective Photoelectrochemical Water Oxidation or Reduction
We
report the fabrication of three-dimensional (3D) branched nanowire
(NW) heterostructures, consisting of periodically ordered vertical
Si NW trunks and ZnO NW branches, and their application for solar
water splitting. The branched NW photoelectrodes show orders of magnitudes
higher photocurrent compared to the bare Si NW electrodes. More interestingly,
selective photoelectrochemical cathodic or anodic behavior resulting
in either solar water oxidation or reduction was achieved by tuning
the doping concentration of the p-type Si NW core. Specifically, n-ZnO/p-Si
branched NW array electrodes with lightly doped core show broadband
absorption from UV to near IR region and photocathodic water reduction,
while n-ZnO/p<sup>+</sup>-Si branched NW arrays show photoanodic water
oxidation with photoresponse only to UV light. The photoelectrochemical
stability for over 24 h under constant light illumination and fixed
biasing potential was achieved by coating the branched NW array with
thin layers of TiO<sub>2</sub> and Pt. These studies not only reveal
the promise of 3D branched NW photoelectrodes for high efficiency
solar energy harvesting and conversion to clean chemical fuels, but
also developing understanding enabling rational design of high efficiency
robust photocathodes and photoanodes from low-cost and earth-abundant
materials allowing practical applications in clean renewable energy