The novel p-Co3O4/n-I-Fe2O3 nano hollow spheres with the enhanced photocatalytic activity

Tailored Co3O4-Based Nanosystems: Toward Photocatalysts for Air Purification

“…The latter are produced from the reaction of adsorbed NO molecules with surface hydroxyl groups chemisorbed on oxygen vacancies (see above and Figure S1 in the Supporting Information). 24 25,29,32,42,45,56,67 and (b) Z-scheme Heterojunction. 5,7,33 CB and VB: Conduction and Valence Band Edges, Respectively Based on the obtained results, the main chemical reactions occurring during the target De-NO x process can be described as follows.…”

“…28 To overcome the disadvantages exhibited by single photocatalysts, including limited Vis light absorption (as for TiO 2 1,3,20,24 ) and/or detrimental electron−hole recombination, 8,20,29−31 a valuable tool is provided by the construction of heterojunctions between different semiconductors. 6,16,26,27,29,32 The latter enable, in principle, to extend the radiation absorption range and favorably enhance charge carrier separation at the junction interfaces. 5,15,19,33 An additional important issue is the development of supported photocatalysts, scarcely investigated so far at variance with the homologous powdered counterparts, 9,15,22 which allow to reduce the active material amount and are less hazardous, more stable, and more easily recoverable after use than the homologous powders.…”

“…In addition, we present a proof-of-principle investigation on the possibility of tuning material performances by the formation of Co 3 O 4 /SnO 2 and Co 3 O 4 /Fe 2 O 3 heterojunctions, which have been scarcely investigated for photocatalytic applications up to date. 29,32,37,40,45,46 The choice of SnO 2 , recently exploited in organic pollutant photodegradation even in combination with Co 3 O 4 , 40,46 is further motivated by the matched band potentials with Co 3 O 4 to form type-II semiconductor heterojunctions. 32 On the other hand, Fe 2 O 3 introduction is driven by its promising performances as a photocatalyst for different processes.…”

“…Over the last decade, semiconductor metal oxide nanosystems have been investigated as De-NO x photocatalysts, thanks to their favorable chemico-physical properties, relatively low cost, and good chemical stability. ,, In fact, the assembly of high-area nanocrystalline and defective structures positively affects material reactivity and charge transport phenomena, paving the way to an improved photocatalytic activity. ,,,,, Most literature works have involved the use of TiO 2 , ,,,, ZnO, ,,, and Fe 2 O 3 -containing systems, − ,, whereas other studies have focused on materials based on C 3 N 4 , , Mn 3 O 4 , SnO 2 , InVO 4 , ZnFe 2 O 4 , ZnWO 4 , Bi 2 GeO 5 , Bi 2 MoO 6 , Bi 2 Mo 3 O 12 , and Bi 2 WO 6 . To overcome the disadvantages exhibited by single photocatalysts, including limited Vis light absorption (as for TiO 2 ,,, ) and/or detrimental electron–hole recombination, ,,− a valuable tool is provided by the construction of heterojunctions between different semiconductors. ,,,,, The latter enable, in principle, to extend the radiation absorption range and favorably enhance charge carrier separation at the junction interfaces. ,,, An additional important issue is the development of supported photocatalysts, scarcely investigated so far at variance with the homologous powdered counterparts, ,, which allow to reduce the active material amount and are less hazardous, more stable, and more easily recoverable after use than the homologous powders. ,, …”

“…Scheme 2. Schematic Representation of Energy-Level Diagrams for Co 3 O 4 -SnO 2 (Left) and Co 3 O 4 -Fe 2 O 3 Systems (Right), Highlighting the Processes Occurring upon Irradiation: (a) Type-II Heterojunction25,29,32,42,45,56,67 and (b) Z-scheme Heterojunction 5,7,33. CB and VB: Conduction and Valence Band Edges, Respectively…”