KEYWORDS: Water splitting, Nanoparticles, Particles, Hydrogen, Diffusion, Scanning electron microscopy, Rhodium, Nanoprobes, Electrons, Electron microscopes
Solar-powered water splitting using nanoparticle photocatalyst suspensions is a promising route to a clean hydrogen economy. A key step in the water-splitting process is the transport of photo-excited electrons and holes to the photocatalyst surface, where they undergo redox reactions. Here we characterize charge transport in individual SrTiO3:Rh and BiVO4 nanoparticles using a nanoprobe within a scanning electron microscope, and directly map photocarrier diffusion lengths with electron-beam induced current. We find that performance in this system is limited by poor e-h transport within the hydrogen-evolving SrTiO3:Rh nanoparticles.
Solar-powered photochemical water splitting using suspensions of photocatalyst nanoparticles is an attractive route for economical production of green hydrogen. SrTiO3 based photocatalysts have been intensely investigated due to their stability and recently demonstrated near-100% external quantum yield at wavelengths below 400 nm. To extend the optical absorption into the visible range, SrTiO3 nanoparticles can be alloyed with various transition metals. Here we demonstrate that alloying SrTiO3 nanoparticles with ~1% Rh introduces mid-gap recombination centers that degrade the photocarrier lifetime from ~90 ps to ~1 ps, and lower the maximum achievable external quantum yield by an order of magnitude. By trapping the free conduction band electrons normally introduced by oxygen vacancies, Rh-induced traps change the charge transport mechanism from band to trap-mediated space-charge limited conduction, and drastically reduce the built-in electric fields needed for charge separation. Our results illustrate why and how the solar to hydrogen efficiency of Rh-doped SrTiO3 nanoparticles remains low despite extended optical absorption. Furthermore, the absence of built-in fields within Rh doped SrTiO3 nanoparticles suggests a new mechanism for photocatalytic reactions, where modest e-h separation can be achieved with a difference in mobility between electrons and holes.
Conference Committee Involvement (3)
Solar Hydrogen and Nanotechnology VI
23 August 2011 | San Diego, California, United States
Solar Hydrogen and Nanotechnology V
3 August 2010 | San Diego, California, United States
Solar Hydrogen and Nanotechnology IV
3 August 2009 | San Diego, California, United States
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.