Molecular-Level Understanding of Selectively Photocatalytic Degradation of Ammonia via Copper Ferrite/N-Doped Graphene Catalyst under Visible Near-Infrared Irradiation

Abstract

Developing photocatalysts with molecular recognition function is very interesting and desired for specific applications in the environmental field. Copper ferrite/N-doped graphene (CuFe 2 O 4 /NG) hybrid catalyst was synthesized and characterized by surface photovoltage spectroscopy, X-ray powder diffraction, transmission electron microscopy, Raman spectroscopy, UV-Vis near-infrared diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The CuFe 2 O 4 /NG catalyst can recognize ammonia from rhodamine B (RhB) in ammonia-RhB mixed solution and selectively degrade ammonia under visible near-infrared irradiation. The degradation ratio for ammonia reached 92.6% at 6 h while the degradation ratio for RhB was only 39.3% in a mixed solution containing 100.0 mg/L NH 3 -N and 50 mg/L RhB. Raman spectra and X-ray photoelectron spectra indicated ammonia adsorbed on CuFe 2 O 4 while RhB was adsorbed on NG. The products of oxidized ammonia were detected by gas chromatography, and results showed that N 2 was formed during photocatalytic oxidization. Mechanism studies showed that photo-generated electrons flow to N-doped graphene following the Z-scheme configuration to reduce O 2 dissolved in solution, while photo-generated holes oxidize directly ammonia to nitrogen gas.to graphene [6], TiO 2 [7], AgBr [8] and Ag 3 PO 4 [9] to fabricate composites for degrading organic pollutants. Wang and co-workers utilized CuFe 2 O 4 as a photocatalyst to selectively degrade methylene blue in the presence of methylene orange, rhodamine B and rhodamine 6G, and the authors attributed the selective degradation to the specific interaction of active sites of catalyst with the methylene blue molecule [10]. To the best of our knowledge, however, the coupling of CuFe 2 O 4 to nitrogen-doped graphene (NG) for the selective photocatalytic oxidization of NH 3 has not been reported.Graphene is a two-dimensional sp2-hybridized carbon material with unique properties such as excellent charge transport, outstanding transparency, huge specific surface area, high mechanical strength and superior thermal conductivity, so it was often used as a co-catalyst [11][12][13][14][15][16][17]. Moreover, molecular tailoring (nitrogen atoms were doped into graphene framework) can module its intrinsic properties to meet the rapidly increasing demand for practical applications in various fields. For example, nitrogen doping can tailor its electrical properties, open a band gap and allow it to show semiconducting properties. As a result, nitrogen doping can significantly improve the catalytic activity toward photocatalytic reactions due to the enhanced electron transportation from semiconductors to NG and the reduced recombination of the photogenerated electron-hole pairs [18][19][20]. In the work, we coupled CuFe 2 O 4 to NG to prepare CuFe 2 O 4 /NG hybrid catalyst, it is expected that the Cu-based hybrid catalyst can recognize ammonia via coordination effect since the formation constant of Cu(NH 3 ) 4 2+ approached 1.1 × 10 13 . This large constant implies...

An Efficient Nanocatalyst Cobalt Copper Zinc Ferrite for the Thermolysis of Ammonium Nitrate

“…The ferrites are widely explored for their catalytic effect on the degradation of organic compounds, where the optical band gap of the ferrites widely influences their catalytic efficiency and which is affected by substitution with different metal ions in the ferrite system. − Spinel ferrite has two interstitial sites, tetrahedral and octahedral, in its crystal structure, that may support a wide variety of cations, allowing ferrites to have a wide range of characteristics. Other divalent metal ions can be substituted for M, resulting in a variety of spinel ferrites. − Previous literature has suggested that Al 3+ substitution in cobalt ferrite nanoparticles alters the electromagnetic characteristics of CoFe 2 O 4 which can be a potential candidate for microwave and power devices applications . Substitution of Zn in MgFe 2 O 4 increases the resistivity and the magnetic property decreases .…”

“…Other divalent metal ions can be substituted for M, resulting in a variety of spinel ferrites. 29 − 31 Previous literature has suggested that Al 3+ substitution in cobalt ferrite nanoparticles alters the electromagnetic characteristics of CoFe 2 O 4 which can be a potential candidate for microwave and power devices applications. 32 Substitution of Zn in MgFe 2 O 4 increases the resistivity and the magnetic property decreases.…”