Plasmonic photocatalysts of the form Ag@AgCl/rGO have been shown to be stable and recyclable with regard to the degradation of a variety of refractory organic pollutants, however, the reusability and activity are closely dependent on the specific substrates, transformation of Ag species, and solution conditions with deactivation of the catalyst often occurring relatively quickly. We have investigated the interplay of semiconductor AgCl and plasmonic Ag nanoparticles and clusters by changing wavelength, co-doping redox active Fe and Cu species, supplying oxygen and chloride ions and found that the deactivation can be attributed mainly to the continuous reduction of Ag(I) to Ag(0).  The composite materials have been characterized using diffuse reflectance spectroscopy (DRS) and X-ray absorption spectroscopy (XAS) with XAS used to determine the oxidation state and speciation of silver under the various conditions of interest. The effectivity of the catalyst was attributed principally to the ability of the composite Ag0/AgCl system to absorb light in the visible wavelength region and to retard the recombination of electron-hole pairs. While the presence of the reduced graphene oxide (rGO) support may also have contributed to a reduction in rate of electron-hole pair recombination, the effect was not found to be particularly significant. While photogenerated holes decay via reaction with chloride ions, photogenerated electrons decay via a pathway other than reaction with oxygen.  Although this system has potential for the oxidative degradation of contaminants, greater understanding of the factors that promote excessive Ag(I) reduction, concomitant formation of Ag(0) and eventual deactivation of the catalyst is required.Reference:Yu, H.; Miller, C. J.; Ikeda-Ohno, A.; Waite, T. D., Photodegradation of contaminants using Ag@AgCl/rGO assemblages: Possibilities and limitations. Catalysis Today 2014, 224, (0), 122-131

Photodegradation of contaminants using Ag@AgCl/rGO assemblages: Photo-corrosion and control

248th National Meeting (2014)

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