Jinxin Li,Dan Zhong,Feiyu Li,Kefei Li,Wencheng Ma,Jun Ma,Jingna Zhang,Aoshuang Sun
A bifunctional electro-Fenton (EF) cathode with Fe 3 O 4 -LaFeO 3 /C embedded graphite felt (GF) was synthesized through a hydrothermal process, which was used for in situ electrochemical formation of active oxygen species (ROS) for coal pyrolysis wastewater (CPW) removal. Experimental results illustrated that the mineralization efficiency of dimethylphenol (DMP) was achieved at 90.7 % within 150 min reaction. On the basis of quenching test and free radical detection, the ∙OH and ∙O 2 − were the detectable ROS in the hetero-EF system for DMP removal. Meanwhile, the formed oxygen vacancies (OVs) and the redox of Fe 2+ /Fe 3+ promoted the oxygen adsorption and H 2 O 2 activation. Density functional theory (DFT) calculations further discussed that the Fe 3 O 4 -LaFeO 3 interface possessed more downward spin density of states in the conduction band, resulting in a higher total density of states (DOS) value near the Fermi level. Moreover, the Fe 3 O 4 -LaFeO 3 /C/GF cathode displayed good recyclability with low metal ion dissolution for 5 times (99.5 % DMP removal and 78.6 % TOC removal) and underlying actual CPW application potential (80.2 % of COD removal and 100 % of total phenol (Tph) removal). Overall, this work invented a novel and stable bifunctional cathode for the efficient removal of refractory CPW in the hetero-EF system.
In the present work, an indirect Z-schematic heterojunction system of TiO 2 and LaFeO 3 (LFO) with a solid state electron mediator (RGO) is proposed and applied for photocatalytic hydrogen (H 2 ) evolution. Through a facile 2-step synthesis strategy including adsorption of LFO on GO sheets and growth of TiO 2 between the LFO-GO frameworks, a Ti-O-C bonds strongly linked sandwich-like TiO 2 /RGO/LFO composite is obtained. The structure, morphology, optical properties and catalytic mechanism of the Z-scheme heterojunction are thoroughly investigated. The obtained visible light responded TiO 2 /RGO/LFO composite displays significantly elevated photocatalytic performance for H 2 evolution with excellent stability, and its H 2 production rate (0.893 mmol h −1 g -1 ) is approximately 3.2, 14.4 and 11.4 times superior to the direct Z-scheme TiO 2 /LFO composite, pure TiO 2 and LFO, respectively. The sandwich-like structure with strong interaction between three components and short diffusion distance for impactful separation of e--h + pairs bring about a vast improvement in H 2 evolution performance of TiO 2 /RGO/LFO composite. In addition, Ti-O-C bonds could also enhance electronic conductivity and structure stability as a bridge of photogenerated carriers. Based on the investigation results, possible mechanisms for synthesis and photocatalytic charge transfer pattern for TiO 2 /RGO/LFO are developed.
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