Qian Xu,Qian Xue,Shengmei Tan,Zhiliang Cheng,Xueqiang Qi,Chaoqun Yan
A low band gap and visible light-responsive heterogeneous Photo-Fenton catalyst of γ-Fe 2 O 3 /CQDs micron composite was prepared under the one-pot hydrothermal method. The Photo-Fenton degradation of γ-Fe 2 O 3 /CQDs towards dye solution of rhodamine B(RhB), methyl blue (MB), and methyl orange (MO) was studied comparatively with α-Fe 2 O 3 . The γ-Fe 2 O 3 /CQDs exhibited remarkable catalytic performance for various dyes and with a first-order rate ( k ) of 14 times higher than that of initial α-Fe 2 O 3 with a low concentration of H 2 O 2 of 0.049 mmol . L −1 and a wider pH range of 3.1–7.1. The microstructure of the compounds was observed by XRD, SEM, TEM, FT-IR, and XPS characterization results suggested that the γ-Fe 2 O 3 /CQDs nanocomposite was formed through the stable Fe–O–C bonds, thus, the band gap decreased, and it is more favorable for the distance of holes and electrons. The free radical trapping experiment and EPR analysis indicated that •OH and 1 O 2 were the major active species during the typical photo-Fenton reaction. What's more, the γ-Fe 2 O 3 /CQDs also exhibited good stability and magnetic properties. DFT conclusion shows that the mechanism of the potential determination step (PDS) on α-Fe 2 O 3 (220) is the cleavage of H 2 O 2 with an energy barrier of only 0.08 eV, which is 0.54 eV lower than that of OH* on γ-Fe 2 O 3 (220). Thus it can be deemed that γ-Fe 2 O 3 /CQDs perform much higher catalytic activity for the dissociation of H 2 O 2 than α-Fe 2 O 3 . This work gives a feasible and economical countermeasure of visible light Photo-Fenton dispose of dye wastewater with a recyclable magnetic γ-Fe 2 O 3 /CQDs micron catalyst.
Flexible asymmetric supercapacitors (FASCs) have attracted increasing interest in portable and wearable electronics. The practical application of FASCs in high energy density devices is limited by their low specific capacity, which can be effectively addressed by designing electrode materials hierarchically on the micro-nanoscale. Herein, well-defined 3D porous hierarchical CuCo 2 O 4 @carbon quantum dots (CQDs) and Fe 2 O 3 @CQDs architectures are rationally synthesized through a simple CQDs-induced hydrothermal self-assembly technique. Both of the as-prepared CuCo 2 O 4 @CQDs and Fe 2 O 3 @CQDs electrodes exhibit improved specific capacity, desirable rate capability and complementary potential range. A FASC (CuCo 2 O 4 @CQDs//Fe 2 O 3 @CQDs) on graphite paper delivers a high operation voltage of 1.55 V, an energy density of 39.5 Wh kg −1 at 1203.7 W kg −1 , and long cycling lifespan. The excellent performance is ascribed to the good electronic conductivity with the assistance of CQDs and their unique 3D mesoporous structures with extraordinary specific surface area, which could provide fruitful active sites for electrochemical reactions . The newly developed FASC based on the Faradaic-type electrodes is inspiring, and would be promising for the applications in wearable electronic devices.
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