Protection of p(+)-n-Si Photoanodes by Sputter-Deposited Ir/IrOx Thin Films.
Sputter deposition of Ir/IrOx on p(+)-n-Si without interfacial corrosion protection layers yielded photoanodes capable of efficient water oxidation (OER) in acidic media (1 M H2SO4). Stability of at least 18 h was shown by chronoamperomety at 1.23 V versus RHE (reversible hydrogen electrode) under 38.6 mW/cm(2) simulated sunlight irradiation (λ > 635 nm, AM 1.5G) and measurements with quartz crystal microbalances. Films exceeding a thickness of 4 nm were shown to be highly active though metastable due to an amorphous character. By contrast, 2 nm IrOx films were stable, enabling OER at a current density of 1 mA/cm(2) at 1.05 V vs. RHE. Further improvement by heat treatment resulted in a cathodic shift of 40 mV and enabled a current density of 10 mA/cm(2) (requirements for a 10% efficient tandem device) at 1.12 V vs. RHS under irradiation. Thus, the simple IrOx/Ir/p(+)-n-Si structures not only provide the necessary overpotential for OER at realistic device current, but also harvest ∼100 mV of free energy (voltage) which makes them among the best-performing Si-based photoanodes in low-pH media.
†Department of Physics, CINF and ‡Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
Bastian
B
Mei
†Department of Physics, CINF and ‡Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
Brian
B
Seger
†Department of Physics, CINF and ‡Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
Thomas
T
Pedersen
†Department of Physics, CINF and ‡Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
Mauro
M
Malizia
†Department of Physics, CINF and ‡Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
Ole
O
Hansen
†Department of Physics, CINF and ‡Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
Ib
I
Chorkendorff
†Department of Physics, CINF and ‡Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
Peter C K
PC
Vesborg
acidic electrolyte; oxygen evolution reaction (OER); photoelectrochemical water splitting; quartz crystal microbalance; stability