Use of potential determining ions to control energetics and photochemical charge transfer of a nanoscale water splitting photocatalyst
By Chamousis, Rachel L. & Osterloh, Frank E.
Published in Energy Environ. Sci.
The Royal Society of Chemistry
2014
Abstract
Tetrabutylammonium (TBA) stabilized H[Ca2Nb3O10] nanosheets catalyze hydrogen evolution from aqueous methanol under illumination with UV light. Here we show that surface treatment with protons, potassium, and strontium potential-determining cations (PDIs) in aqueous solution modifies the electrostatic, energetic and photocatalytic properties of this nanomaterial. Attachment of cations to the nanocrystals was verified with elemental dispersive spectroscopy. Zeta potentials were measured as -40 mV (TBA+, pH = 4.8), -50 mV (K+, pH = 4.3), and -20 mV (Sr2+, pH = 4.4). Photoelectrochemical measurements in methanol containing 0.1 M tetraethylammonium chloride revealed anodic current photoonset potentials/Fermi energies ranging between -0.59 V (Sr2+) and -0.71 V (at pH = 7, vs. NHE). The photocatalytic proton reduction ability of the modified nanocrystals was assessed in aqueous methanol at pH = 1. Here, KxH1-x[Ca2Nb3O10] evolved hydrogen at 350 [small mu ]mol H2 h-1, SrxH1-2x[Ca2Nb3O10] at 70 [small mu ]mol H2 h-1, and H[Ca2Nb3O10] at 160 [small mu ]mol H2 h-1. In addition, the photocatalytic activity was found to increase (20-160 [small mu ]mol H2 h-1) with solution pH. These observed activity variations can be quantitatively understood using a linear free energy relationship between the proton reduction rate constant and the free energy of proton reduction. This shows that the photocatalytic activity of the nanocrystals depends on the electrochemical potentials/Fermi energies of the modified catalysts. The effect of the PDI charge on the nanomaterial energetics can be rationalized by considering the surface potential. The latter can be related to the particle surface charge and the concentration of counterions in solution using the Grahame equation. These results provide a quantitative basis for the understanding and manipulation of nanomaterial photocatalysts with PDIs.
Microsoft is Ending Support for Windows 7
Microsoft will discontinue support for Windows 7 on January 14, 2020 which means Gamry will also be discontinuing support for Windows 7. If you are upgrading to Windows 10, like many companies and institutions, you need to be running Version 7 of our s oftware . Please note that only USB and Ethernet-based instruments can run in Version 7. Eligible users can download the latest version of our software through our online Client Portal .
If you haven't already registered your instrument, you can do so through the Client Portal .
Please email Technical Support if you have any questions regarding this transition. Please be sure to include your instrument model and serial number when contacting us.