Abstract
In this study, evidence is provided that isolated surface vanadia (VO4) species on SiO2 can similarly act as a thermal heterogeneous catalyst and as a heterogeneous photocatalyst. Structurally identical surface VO4 species catalyze the selective oxidation of methanol both by thermal activation and by UV-light induction. Selectivity to formaldehyde appears to be unity. For the photocatalytic reaction at room temperature, formaldehyde desorption is rate limiting. With larger agglomerates or V2O5 nanoparticles, on the contrary, only the thermal reaction is feasible. This is tentatively attributed to the different positions of electronic states (HOMO/LUMO, valence/conduction band) on the electrochemical energy scale owing to the quantum size effect. Besides providing new fundamental insight into the mode of action of nanosized photocatalysts, our results demonstrate that tuning the photocatalytic reactivity of supported transition-metal oxides by adjusting the degree of agglomeration is feasible.
Original language | English |
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Pages (from-to) | 2360-2364 |
Number of pages | 5 |
Journal | ChemCatChem |
Volume | 10 |
Issue number | 11 |
DOIs | |
State | Published - 7 Jun 2018 |
Externally published | Yes |
Keywords
- oxidation
- photocatalysis
- quantum size effect
- structure–activity relationships
- vanadium