Exploiting the inherent surface chemical reactivity of semi-conductor photocatalysts may be a promising route to controlling reaction selectivity, reducing photon-energy requirements, and coupling photo and thermal catalysis. In this study, we have investigated the role of surface chemical reactivity in the photocatalytic reduction of CO2 and H2O over a suite of classic and state-of-the-art semiconductor photocatalysts. Using a combination of quantum chemical modeling, Electron Energy Loss Spectroscopy (EELS), in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), and non-model catalyst performance studies, we have determined several specific material properties that appear to dictate the aforementioned aspects of a photocatalytic reaction. Specifically, we find that a greater degree of surface chemical reactivity stabilizes surface bound organic fragments and enhances the production of reduced C1 products. On the other hand, a less reactive semiconductor surface favors the raw production of H2 and CO from H2O and CO2, respectively. We also find that the unexcited oxidation state of adsorbed atomic hydrogen is dictated by the electronic structure of the semi-conductor and correlates with its proclivity to hydrogenate surface bound organic fragments or to leave as H2. Critical advances in rationally tuning the selectivity of a noble metal-free semiconductor will also be discussed. In this regard, we will show that the surface reaction site of a single material (beta-SiC) can be identified and modified such that its selectively switches from producing CH4 to H2.

Isolating and controlling the nature of surface reaction sites of semiconductor photocatalysts: Selectivity in the photocatalytic reduction of CO2 and H2O to H2 and reduced C1 molecules

249th National Meeting (2015)

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