All-in-one catalytic sites for the methanol steam reforming as electron-poor copper nanoparticles on amorphous zirconia-silica

Copper on zirconia catalysts are a benchmark for the methanol steam reforming reaction (MSR) because of the simultaneous presence of Cu0 and Cu+ sites responsible for the molecular hydrogen formation and intermediates dehydrogenation, respectively, the latter being adsorbed on the zirconia support [1]. A system so conceived, although active, is intrinsically limited as copper does not participates to all the reaction steps. By means of in-situ XRPD, XPS and FT-IR analyses, we found that by adding a specific amount of silica (10 wt.%) in the zirconia support, the copper reduction is inhibited and leads to nanoparticles in the range of 2-3 nm. Such small nanoparticles are in the metallic state but feature a markedly electron-poor surface on which methanol preferentially adsorbs. This catalyst showed a hydrogen productivity almost four times higher than a classical zirconia-supported catalyst because both the dehydrogenation of the intermediates and the subsequent molecular hydrogen evolution are carried out by the same site. The drawback of having different adsorption sites and two distinct Cu0 and Cu+ sites is thus overcome thanks to this all-in-one catalytic site and the amount of copper actually participating to all the reaction is maximized [2].