P-type Cu--Ti--O nanotube arrays and their use in self-biased heterojunction photoelectrochemical diodes for hydrogen generation.
Copper and titanium remain relatively plentiful in the earth's crust; hence, their use for large-scale solar energy conversion technologies is of significant interest. We describe fabrication of vertically oriented p-type Cu-Ti-O nanotube array films by anodization of copper rich (60% to 74%) Ti metal films cosputtered onto fluorine doped tin oxide (FTO) coated glass. Cu-Ti-O nanotube array films 1 mum thick exhibit external quantum efficiencies up to 11%, with a spectral photoresponse indicating that the complete visible spectrum, 380 to 885 nm, contributes significantly to the photocurrent generation. Water-splitting photoelectrochemical pn-junction diodes are fabricated using p-type Cu-Ti-O nanotube array films in combination with n-type TiO 2 nanotube array films. With the glass substrates oriented back-to-back, light is incident upon the UV absorbing n-TiO 2 side, with the visible light passing to the p-Cu-Ti-O side. In a manner analogous to photosynthesis, photocatalytic reactions are powered only by the incident light to generate fuel with oxygen evolved from the n-TiO 2 side of the diode and hydrogen from the p-Cu-Ti-O side. To date, we find under global AM 1.5 illumination that such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 mA/cm (2), at a photoconversion efficiency of 0.30%.
Department of Electrical Engineering, and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Gopal K
GK
Mor
Oomman K
OK
Varghese
Rudeger H T
RH
Wilke
Sanjeev
S
Sharma
Karthik
K
Shankar
Thomas J
TJ
Latempa
Kyoung-Shin
KS
Choi
Craig A
CA
Grimes
D003300:Copper / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D054023:Lasers, Semiconductor; D008855:Microscopy, Electron, Scanning; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D010777:Photochemistry; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
D003300:Copper; D006859:Hydrogen; D014025:Titanium