Boosting Photochemical Activity by Ni Doping of Mesoporous CoO Nanoparticle Assemblies

Mesoporous Ni-implanted CoO nanoparticle assemblies possessing a suitable electronic structure and large mesoporosity deliver highly efficient photocatalytic Cr(vi) reduction and water oxidation activity.


Supporting Figures
Fig. S1 TGA profiles of (a) as-prepared containing surfactant (black line) and (b) mesoporous CoO MNAs recorded under N 2 flow (~200 mL min -1 ).The differential thermogravimetric (DTG) curve (dotted line) for as-prepared material is also given.
Fig. S2 XRD pattern of the inorganic residue obtained after TGA analysis of the CoO mesoporous sample (up to 600 o C, in Ν 2 ).All diffraction peaks could be indexed to the metallic Co with a face-centered cubic (JCPDS No. 15-0806) and hexagonal close-packed (JCPDS No. 05-0727) structure.

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Fig. S3 (a) Typical TEM images and (b) SAED pattern of CoO MNAs.

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Fig. S5 O 1s XPS spectrum of the polycrystalline NiO material.

Fig. S7
Fig. S7 Powder XRD pattern of the reused Co 0.98 Ni 0.02 O MNAs catalyst.All the diffraction peaks in the XRD pattern can be assigned to the cubic phase of CoO (JCPDS No. 43-1004).

Fig. S8
Fig. S8 N 2 adsorption-desorption isotherms at -196 o C (Inset: the corresponding NLDFT poresize distribution, indicating an average pore size of ~4.6 nm) of the Co 0.98 Ni 0.02 O MNAs catalyst retrieved after the cycling test.Analysis of the adsorption data indicate a BET surface area of 92 m 2 g -1 and a pore volume of 0.13 cm 3 g -1 .

Fig. S10
Fig. S10 O 2 evolution transient with light on/off for Co 0.98 Ni 0.02 O MNAs catalyst under λ > 360 nm light irradiation.

Fig. S11
Fig. S11 (a, b) Fluorescence spectra of coumarin in water and (c) time evolution of the fluorescence intensity ratio of umbelliferone emission (455 nm) to coumarine emission (398 nm) for CoO and Co 0.98 Ni 0.02 O MNAs catalysts.The emission peaks at ~398 nm and ~455 nm correspond to the coumarin and umbelliferone, respectively.All the •OH radical formation tests were performed similarly to the photocatalytic Cr(VI) reduction reactions, but with the addition of coumarin in the solution.Reaction conditions: 0.3 g L -1 catalyst, 10 mM coumarin, 50 mg L -1 Cr (VI) solution, pH = 2, UV-vis light (λ > 360 nm) irradiation, 20 o C. Fluorescence emission spectra obtained with an excitation wavelength of 332 nm.

Fig. S12
Fig. S12 (a) Photocatalytic reduction of aqueous Cr(VI) and (b) kinetic profiles over Co 0.98 Ni 0.02 O MNAs catalyst in the presence 1 equiv. of phenol, citric acid or EDTA under  > 360 nm light irradiation.Reaction conditions: 0.3 g L -1 catalyst, 50 mg L -1 Cr(VI) solution, pH = 2, 20 o C. In panel (b), the red lines are fit to the data.

Table S2 .
EIS equivalent circuit fitted parameters of pure and Ni-doped CoO MNAs catalysts.