Yan Zhang,Ming-Ming Gao,Xin-Hua Wang,Shu-Guang Wang,Rui-Ting Liu
An electro-Fenton process was developed for wastewater treatment in which hydrogen peroxide was generated in situ with a rotating graphite disk electrode as cathode. The maximum H 2 O 2 generation rate for the RDE reached 0.90 mg/L/h/cm 2 under the rotation speed of 400 rpm at pH 3, and −0.8 V vs SCE. The performance of this electro-Fenton reactor was assessed by tetracycline degradation in an aqueous solution. Experimental results showed the rotation of disk cathode resulted in the efficient production of H 2 O 2 without oxygen aeration, and excellent ability for degrading organic pollutants compared to the electro-Fenton system with fixed cathode. Tetracycline of 50 mg/L was degraded completely within 2 h with the addition of ferrous ion (1.0 mM). The chronoamperometry analysis was employed to investigate the oxygen diffusion on the rotating cathode. The results demonstrated that the diffusion coefficients of dissolved oxygen is 19.45 × 10 −5 cm 2 /s, which is greater than that reported in the literature. Further calculation indicated that oxygen is able to diffuse through the film on the rotating cathode within the contact time in each circle. This study proves that enhancement of oxygen diffusion on RDE is benefit for H 2 O 2 generation, thus provides a promising method for organic pollutants degradation by the combination of RDE with electro-Fenton reactor and offers a new insight on the oxygen transform process in this new system.
Yiqiao Wang,Siyuan Pan,Huan Li,Dewang Li,Yong Guo,Sijia Chi,Chuannan Geng,Shichao Wu,Quan-Hong Yang
Despite lithium–air batteries having unprecedented theoretical energy supremacy, rambling Li2O2 growth typically impedes O2 diffusion and electron transfer, causing low capacity, poor charging kinetics and short cycle life. Herein, we propose synergistic catalysis in the cathode by engineering the crystal facet of Fe2O3 nanoplates and introducing a visible light-excited photochemical effect. The growth of Li2O2 is regulated with a uniform distribution, mitigating local product aggregation and thus reducing the barriers of O2 diffusion and electron transfer. The improved reaction kinetics lead to ∼420% capacity improvement, low charge potential, superior rate performance, and long-term stability (300 cycles) in actual air. We reveal a mechanism that photoelectrons around each catalyst node and the resultant homogeneous internal electric field increase charge transfer, decrease soluble intermediates, and enable high electrochemical reversibility of amorphous Li2O2 with an ordered process. This study provides inspiring insights for future research into controlling product ordering in Li–air batteries.
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