Some physical investigations on NiCo2O4 thin films for potential applications

Development of Three-Dimensional Nickel–Cobalt Oxide Nanoflowers for Superior Photocatalytic Degradation of Food Colorant Dyes: Catalyst Properties and Reaction Kinetic Study

“…Owing to partially filled high-energy e g orbitals, the electrons can be excited from t 2g to e g of the 3d orbital of Co and Ni cations after light absorption, while internal electronic-transitions in 3d orbitals of both Co and Ni cations contribute to band structures resulting in excellent catalytic performance of F-NCO nanosheets. , Based on Tauc plot estimation, the band structure was projected using variable band-gaps of F-NCO nanosheets. Thus photocatalytic performance of NiCo 2 O 4 nanosheets can be explained by the exciton-diffusion and charge-separation which produce a synergistic and coupling-effect between two band-gaps of F-NCO nanosheets. , Based on band theory, photons are excited from the VB (O 2p orbitals) to CB of 3d orbitals (t 2g and e g ) of nickel or cobalt cations under UV light irradiation.…”

“…LC–mass spectra (Figure S5b,c) were collected for fresh dye solution (at zero time, red color) and degraded dye solution (colorless) after 10 min light exposure at room temperature. From mass plots, a sharp peak was observed at a molar mass ( m/z ) of ∼498 (Figure S5b) of AR dye (molecular weight (MW): 496.4, chemical formula: C 18 H 14 N 2 Na 2 O 8 S 2 ) as a molecular ion peak. − However, the food colorant, AR dye produces amine degradation products (Figure S5c) after azo bond breakage as a sodium salt or pure form of the benzene-based moiety (C 8 H 10 NSNaO 4 , MW: 239.22, or C 8 H 10 NSO 4 , MW: 217.36) along with the naphthene-based moiety (C 10 H 8 NSNaO 4 , MW: 261.23 or C 10 H 8 NSO 4 , MW: 238.43) as byproducts. From the LC–MS spectrum, the AR dye shows three sharp degradation peaks of m/z at 317, 340, and 361 peaks after 10 min of light exposure. , Among them, the base peak at m/z of 317 (Figure S5c) belongs to the benzene-derived amine product (C 8 H 10 NSO 4 , MW: 216.22) after removal of sodium ions.…”

“…48 For F-NCO nanosheets, estimated optical band-gaps lie in the range between ∼2.05 and ∼1.58 eV (Figure S4b) which are consistent with earlier reports of NCO nanomaterials. 48,49 The bulk cobalt-oxide nanomaterials exhibit two band-gaps because of the presence of nonstoichiometric metal cations (Co +2 and Co +3 cations) and nonuniform size of nanoparticles. Again, the two variable band-gaps of F-NCO nanosheets result from size-dependent optical properties and morphology of semiconducting metal oxide nanomaterials. )…”

“…Thus photocatalytic performance of NiCo 2 O 4 nanosheets can be explained by the exciton-diffusion and charge-separation which produce a synergistic and coupling-effect between two band-gaps of F-NCO nanosheets. 49,50 Based on band theory, photons are excited from 52 The recombination of excitons (h + /e − pair) might hinder to improve the catalytic property of the F-NCO catalyst, and holes transferred to nickel−cobalt oxides are trapped by H 2 O to produce OH − species. 51,52 During catalytic degradation, the F-NCO catalyst absorbs light to excite electrons from the VB to CB resulting in exciton (Figure 6) formation.…”