Gold Nanorods Coated Metallic Photonic Crystal for Enhanced Hot Electron Transfer in Electrochemical Cells
- PDF / 633,142 Bytes
- 7 Pages / 432 x 648 pts Page_size
- 89 Downloads / 169 Views
Gold Nanorods Coated Metallic Photonic Crystal for Enhanced Hot Electron Transfer in Electrochemical Cells A. Elfaer1,2, Y. Wang1, X. H. Li1, J. B. Chou1 and S-G. Kim1,* Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, U.S.A. 2 Dammam University, Saudi Arabia. 1
ABSTRACT We recently demonstrated a sub-bandgap photoresponse with our wafer-scale Au/TiO2 metallic-semiconductor photonic crystals (MSPhC). The sub-bandgap energy with 590 nm peak could be absorbed in the form of hot electron and injected to TiO2, which provides 5.28 times more energy for photolysis than that of energy absorbed to flat TiO2. If the solar energy already absorbed above 700 nm could be injected to the catalyst, higher than 10 times improvement will be achieved, and above 20% solar to fuel efficiency will be feasible with the robust but inefficient TiO2 catalyst. In order to achieve photocurrent near and above 700 nm spectrum, we deposited gold nanorods on the surface of MSPhC to incur localized surface plasmon (LSP) modes absorption and subsequent injection to the TiO2 catalyst. We used electrophoretic deposition (EPD) method to deposit nanorods on the top, sidewall and bottom well surface of the photonic nanocavities. The deposition of nanorods was achieved reasonably uniform and sparse not to block the optical cavities of MSPhC. Flat gold surfaces were tested at 4 different suspension densities to get the optimum gold nanorods density. Under 10V applied electric field, positively charged gold nanorods at the concentration of 6.52ൈ1013 #/mL could deposit MSPhC surface with the density of 230 #/μm2, which was reasonably uniform and sparse. Preliminary tests show an absorbance increase near 700 nm on flat device coated with gold nanorods. Photocurrent measurement is under way to demonstrate the enhanced hot electron transfer over full visible light and near-infrared solar spectrum. INTRODUCTION The wide bandgap oxide-based (such as TiO2) photocatalysts have been used for solar water splitting due to their robustness under oxygen environment. The performance of wide bandgap oxide-based (such as TiO2) photocatalytic cells, however, has been limited by the poor absorption of solar energy, utilizing less than 5% of the available solar energy. We recently developed metallic-semiconductor photonic crystals (MSPhC) where broadband solar absorption in the metal occurs [1]. If most of the absorbed photons (sub bandgap of TiO2) to metal can be transformed to hot electrons and injected to the catalytic layer, much higher energy efficiency can be achieved for photoelectrochemistry. The absorption and conversion of photons below the bandgap of a semiconductor can lead to significant advancements in photoelectrochemistry (PEC), solar driven water-splitting and thermal energy conversion [2]. We recently demonstrated a sub-bandgap photoresponse at 590 nm due to surface plasmon polariton with our wafer-scale Au/TiO2 MSPhC [3]. We also showed a photoresponse enhancement factor of 4.5 at 639 nm compared to a flat
Data Loading...
