(Invited) Microreactors for Characterization and Benchmarking of Photocatalysts

Monday, 25 May 2015: 15:00
Boulevard Room C (Hilton Chicago)
P. C. K. Vesborg, F. Dionigi, D. Bøndergaard, T. Pedersen (Technical University of Denmark), K. Domen (ARPChem), K. Maeda (Tokyo Institute of Technology), S. Dahl, O. Hansen, and I. Chorkendorff (Technical University of Denmark)
In the field of photocatalysis the batch-nature of the typical benchmarking experiment makes it very laborious to obtain good kinetic data as a function of parameters such as illumination wavelength, irradiance, catalyst temperature, reactant composition, etc. 
Microreactors with on-line mass spectrometry, on the other hand, allow fast and automated acquisition of quantitative kinetic data. [1,2] As an example, we show how microreactor experiments on water splitting using Pt- or Rh-loaded GaN:ZnO photocatalysts quickly rank different catalysts according to their activity for gas-phase water splitting - but also how the activity scales with relative humidity and the crucial role of CrOx "capping" of the Pt- or Rh-co catalyst in order to prevent the loss of H2/O2 product via backward reaction on the precious metal. [3,4] The data suggests that protons transfer via the catalyst surface between the oxygen-evolving sites and the hydrogen evolving co-catalyst sites. 
Recently, the microreactor experimental platform is being developed to support in-situ UV-VIS-IR spectroscopy [5] and even the introduction of liquid aqueous electrolyte and electrodes - all while retaining high sensitivity time resolved mass spectrometric product detection. [6]
[1] Vesborg et al. Chemical Engineering Journal, 160, p. 738-741 (2010)
[2] Vesborg et al. J. Phys. Chem. C, 114, p. 11162-11168 (2010)
[3] Dionigi et al. Energy & Env. Sci., 4, p. 2937-2942 (2011)
[4] Dionigi et al. J. Catal., 292, p. 26-31 (2012)
[5] Dionigi et al. Rev. Sci. Instr., 84, p. 103910 (2013)
[6] Bøndergaard et al. "Fast and sensitive method for detecting volatile species in liquids", submitted