Insight into the role of copper in the promoted photocatalytic removal of NO using Zn2-xCuxCr-CO3 layered double hydroxide

Tailored Co3O4-Based Nanosystems: Toward Photocatalysts for Air Purification

“…Photocatalyst recycling tests (Figure 5b) showed that the NO removal efficiency decayed during the first four cycles, a phenomenon attributed to the progressive passivation of Co 3 O 4 surface by nitrites/nitrates (compare DRIFTS data below). 24 Indeed, these species can be eliminated by rinsing the sample in water, yielding a good recovery of the pristine performances at the fifth utilization cycle and highlighting the catalyst recyclability. These results demonstrate that Co 3 O 4 can be successfully used as an air purification photocatalyst.…”

“…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.…”

“…1,2,8,18,21 Although various research works have been aimed at the development of De-NO x photocatalysts, 1,3,14 key problems still far from being completely overcome are related to the low activity and the generation of undesired/toxic byproducts, 1,5 in particular, the NO 2 intermediate. 6,13,20,22,23 Hence, an important goal to be fulfilled for an efficient NO x degradation, an actual open challenge, 2,4,10,[14][15][16]24 is the obtainment of a high selectivity toward harmless nitrates (NO 3 − ) as the major process products. 1,13,17,19,21 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.…”

“…4,9,13,20,22,25 Most literature works have involved the use of TiO 2 , 1,12,13,20,26 ZnO, 1,14,22,27 tems, [2][3][4]15,20 whereas other studies have focused on materials based on C 3 N 4 , 21,26 Mn 3 O 4 , 5 SnO 2 , 6 InVO 4 , 7 ZnFe 2 O 4 , 19 ZnWO 4 , 10 Bi 2 GeO 5 , 8 Bi 2 MoO 6 , 18 Bi 2 Mo 3 O 12 , 16 and Bi 2 WO 6 . 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.…”

“…Although various research works have been aimed at the development of De-NO x photocatalysts, ,, key problems still far from being completely overcome are related to the low activity and the generation of undesired/toxic byproducts, , in particular, the NO 2 intermediate. ,,,, Hence, an important goal to be fulfilled for an efficient NO x degradation, an actual open challenge, ,,,− , is the obtainment of a high selectivity toward harmless nitrates (NO 3 – ) as the major process products. ,,,, …”