In this article, the catalyst Au/γ-Fe2O3@hydroxyapatite (Au/γ-Fe2O3@HAP) consisting of Au nanoparticles supported on the core–shell structure γ-Fe2O3@HAP was prepared through a deposition–precipitation method. The catalyst was characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, N2 adsorption–desorption and atomic absorption spectrometry. The as-prepared Au/γ-Fe2O3@HAP exhibited excellent performance for the reduction of 4-nitrophenolate (4-NP) to 4-aminophenolate (4-AP) in the presence of NaBH4 at room temperature. Thermodynamic and kinetic data on the reduction of 4-NP to 4-AP catalyzed by the as-prepared catalyst were studied. The as-prepared catalyst could be easily separated by a magnet and recycled 6 times with over 92% conversion of 4-NP to 4-AP. In addition, the as-prepared catalyst showed excellent catalytic performance on other nitrophenolates. The TOF value of this work on the reduction of 4-NP to 4-AP was 241.3 h−1. Au/γ-Fe2O3@HAP might have a promising potential application on the production of 4-AP and its derivatives.
Yue Qin,Huiyu Li,Yaxin Sun,Shiquan Guo,Chunhong Shi,Yuanfeng Liu,Congju Li
Sluggish kinetics of the cathodic oxygen reduction reaction (ORR) is one of the major challenges hindering the development of microbial fuel cells (MFCs). In this work, a three-dimensional (3D) cellular scaffolds structure is fabricated by in-situ growth of conductive Ni/Co-catecholate bimetal metal-organic frameworks (MOFs) on multiwalled carbon nanotubes (NiCo-CAT/MWCNTs). Such specific structure successfully achieves favorable electronic channels and fast charge-transfer capacity and displays an ultra-low ohmic internal resistance of 7.27 Ω. Meanwhile, NiCo-CAT/MWCNTs exhibit a superior ORR half-wave potential (−0.442V vs. Hg/HgCl 2 ), onset potential (−0.064V vs. Hg/HgCl 2 ) and high limiting current density (8.25 mA cm −2 ), which exceed that of commercial Pt/C. In the MFC with the NiCo-CAT/MWCNTs cathode, the maximum power density is 130% higher than Pt/C cathode. The outstanding performance of MFC is mainly due to the optimized electronic structure and fully exposure of the Ni, Co synergistic catalytic active sites. In addition, oxygen permeability is greatly improved by electrospun polyvinylidene fluoride (PVDF) air diffusion layer replacing the traditional carbon cloth cathode. This study provides a new perspective for MFCs performance improvement by ORR conductive MOFs catalysts.
Jinping Zhang,Haijun Chen,Meijiang Liu,Tianliang Lu,Beibei Gao,Xiaomei Yang,Lipeng Zhou,Hongji Li,Yunlai Su
Surface charge-transfer complex formed by TiO 2 and phenols has showed a great potential in visible-light photocatalysis. However, back electron transfer limits the charge transfer efficiency and the activation of phenols in surface complex. Herein, we disclosed the efficient activation of phenols in surface complex by introducing the base. Both homocoupling reactions and butylated hydroxytoluene-trapped experiments clearly demonstrated the generation of phenolic radicals from various lignin-derived substrates. The addition of base caused the blue-shifted absorption of surface complex, while increased the visible light-induced electron excitation from substrate to TiO 2 . Vibrational spectra suggested that the interaction between phenolate and TiO 2 was stronger than the interaction between neutral phenol and TiO 2 . This base-triggered strategy may be conducive to useful transformations or degradation of phenols via surface complex.
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