Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

Abstract

Photocatalytic hydrogen prodn. from ethanol as an example of biofuel is studied over 0.5 wt% Rh/SrTiO3 and 0.5 wt% Pt/SrTiO3 perovskite materials. The rate of hydrogen prodn., rH2, over Pt/SrTiO3 is found to be far higher than that obsd. over Rh/SrTiO3 (4 × 10-6 mol of H2 gcatal.-1 min-1 (1.1 × 10-6 mol of H2 mcatal.-2 min-1) compared to 0.7 × 10-6 mol of H2 gcatal.-1 min-1 (5.5 × 10-8 mol of H2 mcatal.-2 min-1), resp., under UV excitation with a flux equiv. to that from the sun light (ca. 1 mW cm-2). Analyses of the XPS Rh3d and XPS Pt4f indicate that Rh is mainly present in its ionic form (Rh3+) while Pt is mainly present in its metallic form (Pt0). A fraction of the non-metallic state of Rh in the catalyst persisted even after argon ion sputtering. The tendency of Rh to be oxidized compared to Pt might be the reason behind the lower activity of the former compared to the later. On the contrary, a larger amt. of methane are formed on the Rh contg. catalyst compared to that obsd. on the Pt contg. catalyst due to the capacity of Rh to break the carbon-carbon bond of the org. compd. [on SciFinder(R)]