Extended Data Figure 6: XPS characterization of 2%Pt/α-MoC and 0.2%Pt/α-MoC.
From: Low-temperature hydrogen production from water and methanol using Pt/α-MoC catalysts
a, XPS spectra of the platinum 4f regions (the binding energy of pure platinum foil is 71.2 eV) and b, the molybdenum 3d regions of 2%Pt/α-MoC before and after exposure to methanol/water vapour at 190 °C for 1 hour. Ptδ+ denotes a partial positive charge on Pt. c, XPS spectra of the platinum 4f and d, molybdenum 3d regions of 0.2%Pt/α-MoC before and after exposure to methanol/water vapour at 190 °C for 1 hour. After the reaction, we detected no oxidation of platinum in either catalyst (as compared with the fresh catalysts); however, we did observe oxidation of a small amount of molybdenum, as shown by the generation of weak components in the high-energy region. These findings show that: first, platinum is not oxidized during the reaction; and second, perhaps only the MoC domain that is far from the Pt1 species is oxidized by the dissociated water, while oxygen-containing groups on the MoC domain adjacent to Pt1 will be converted to CO2 and H2 through the ongoing reaction cycles.
