Smart photocatalytic removal of ammonia through molecular recognition of zinc ferrite/reduced graphene oxide hybrid catalyst under visible-light irradiation

• Published in: Catalysis science & technology 2017, Vol.7 (15), p.3210-3219
• Main Authors: Liu, Shou-Qing, Zhu, Xiao-Lei, Zhou, Yang, Meng, Ze-Da, Chen, Zhi-Gang, Liu, Cheng-Bao, Chen, Feng, Wu, Zheng-Ying, Qian, Jun-Chao
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/C7CY00797C

Zinc ferrite loaded with reduced graphene oxide (ZnFe 2 O 4 /rGO) and zinc ferrite (ZnFe 2 O 4 ) catalysts were synthesized via a one-spot method. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, surface photovoltage spectroscopy and X-ray photoelectron spectroscopy. Results revealed that the as-synthesized ZnFe 2 O 4 /rGO and ZnFe 2 O 4 particles were cubic spinel-type ZnFe 2 O 4 with space group number of Fd 3 m , and that their average diameters were 7.4 and 7.0 nm, respectively. The photocatalytic results indicated that the ZnFe 2 O 4 /rGO hybrid catalyst possesses higher activity than that of the single ZnFe 2 O 4 component under visible-light irradiation. More importantly, the ZnFe 2 O 4 /rGO catalyst could recognize ammonia from an organic pollutant-ammonia mixed solution and selectively degrade ammonia and nitrogen gas based on the coordination recognition between Zn cations on ZnFe 2 O 4 and ammonia in solution. Fourier-transform infrared, Raman and X-ray photoelectron spectra confirmed that ammonia was selectively adsorbed on ZnFe 2 O 4 particles. The shifts of Zn 2p3/2 and Zn 2p1/2 binding energies confirmed the coordination between Zn cations and ammonia. The surface photovoltage spectra revealed that the photo-generated holes moved to the surface of ZnFe 2 O 4 particles upon incident visible-light irradiation, and degraded ammonia adsorbed on the catalyst surface. These findings will encourage more investigations of photocatalysis based on coordination recognition.