Preferential oxidation of carbon monoxide in hydrogen using zinc oxide photocatalysts promoted and tuned by adsorbed copper ions

Photo-PROX: Preferential oxidation of CO in H2 by photocatalysis using Cu(II) on spheroidal ZnO as the catalyst. [Display omitted] ► Spheroidal (22nm×47nm) and rod-like ZnO (80nm×443nm) were synthesized. ► 0.5% of Cu2+-adsorbed spheroidal ZnO was a semiconductor with bandgap of 3.17eV. ► Cu–spheroidal ZnO was most effective for photo-PROX of CO in H2. ► Cu–ZnO reduced 63Pa of CO to 2.3mPa (0.35ppm) in 6.3kPa of H2 for 5h. ► CuII trapped photogenerated electrons and would oxidize formate species to CO2. Preferential oxidation of CO (63Pa) and O2 (76Pa) in H2 (6.3kPa) using spheroidal ZnO nanoparticles (22nm×47nm) converted 52% of CO into CO2, and selectivity to CO2 was 92mol% under UV–visible light for 5h. When 0.5wt.% of Cu2+ was adsorbed on ZnO, 91% of CO was converted into CO2 with a selectivity of 99mol% under UV–visible light for 3h. CO (63Pa) was photocatalytically decreased to 2.3mPa (0.35ppm) in O2 (150Pa) and H2 (6.3kPa) for 5h with a selectivity of 94mol%. As evident from a XANES peak at 8983.1eV, the surface CuII sites trapped photogenerated electrons. Furthermore, O2-derived species were reduced by accepting electrons from CuI and protons from the neighboring formate species, as indicated by the FT-IR peaks at 2985, 2879, 1627, 1587, and 1297cm−1.