Construction Of MoS₂-based Catalysts And Their Bio-Photo-Electrocatalytic Performances In Degradation Of Levofloxacin

Photoelectrocatalysis is a green chemical technology based on solar energy coupling electrocatalytic strategy that can simultaneously utilize solar energy and electric field,to achieve effectively contaminant removal and energy conversion hydrogen generation.Due to its mild reaction conditions and environmentally friendly route,it has attracted broad applications in the fields of environmental wastewater treatment and energy catalysis.In terms of low-energy efficiency and limited electrode materials,how to develop high-efficiency photoelectrocatalytic materials is still a key issue in the field of photoelectrocatalysis.Compared with the traditional photoelectrocatalysis,microbial fuel cell(MFC)has attracted widespread attention,which depends on utilizing exoelectrogens as biocatalysts to recover electricity and valued-chemical products from wastewater.Additionally,considering single-mode and unclear degradation mechanisms of the photoelectrocatalysis coupled with microbial fuel cell(PEC-MFC),how to realize effectively degradation pollutant in a multi-technology coupling system is an urgent problem to be solved in the environmental field.Based on the development of high catalytically materials-based PEC-MFC system,in this paper,focusing on the treatment of antibiotic levofloxacin(LEV)wastewater,three-dimensional(3D),two-dimensional(2D)and zero-dimensional(0D)of MoS2 catalysts have been designed to regulate and optimize the active sites,aiming at improving its microscopic and electronic structure for enhancing LEV degradation efficiency.The microstructure and catalytic activity are systematically discussed by multi-characterization methods and theoretical calculations.Besides,enhanced PEC-MFC systems have been constructed to investigate the LEV degradation mechanism in oxidation and reduction modes,respectively.The detailed findings are as follows:(1)Self-assembled 3D flower-like MoS2 microsphere-modified TiO2 nanotube arrays electrodes were successfully prepared by a facile hydrothermal assisted anodic oxidation method,in the absence of surfactant or template assistance.The as-prepared 3D-1D MoS2/TiO2 heterojunction structure was proposed to explain the charge transfer on the interface of 3D/1D hybrid and photocatalytic degradation of LEV performance.These results demonstrated that the flower-like MoS2 catalyst not only broadened the photo-response range of the original TiO2 nanotube arrays to 630 nm,but also improved the separation efficiency of photo-induced charge over the interface(6.5 times).Under visible light irradiation(?>420 nm),the electrode synergistic catalytic degradation rate of LEV was achieving to 2.0×10-2 min-1.The active species in the catalytic reaction was studied by multi-spectral methods,such as electron paramagnetic resonance combined with fluorescent probes methods.It was found that ·OH and ·O2-were mainly active free radicals in the catalytic process.In terms of the energy band structures and DFT,the proposed mechanism of pollutant degradation over the 3D-1D MoS2/TiO2 catalyst was deeply explained.(2)Aiming at the issues of extracellular electron transfer interface,the lifetime of electroactive microorganisms over the cathode catalyst in the MFC,a low-cost and stable porous FePO4 catalyst was constructed and assembled into an air-cathode single-chamber MFC device.Under the optimal carbon source(3 mM sodium acetate),the bioelectrochemical performance was investigated during 0.1-1000 ?g L-1 antibiotics LEV.The relationship between concentration and current/voltage was built and an online system for LEV detection in water was also constructed.Regardless of the selectivity or other similar antibiotic interference conditions(norfloxacin,ciprofloxacin),this constructed biosensor showed a good detection performance on 0.1-100 ?g L-1 LEV.Also,it presented the highest LEV removal rate(>35%)in the range of 600-800 ?g L-1 for 10 min.The mechanism of LEV detection and degradation was elucidated through the biofilm dynamic balance resulting in the limited cathode oxygen reduction reaction by output voltage signals and theoretical calculations.(3)MoS2 quantum dots(QDs)were synthesized by the Top to Down method,then the 0D-1D MoS2/TiO2 electrode was successfully constructed by an electrostatic adsorption strategy,which effectively broadened the visible light absorption range(690 nm)and improved the photoconversion efficiency,which was 9.15 times than that of pure TiO2.Compared with the traditional photoelectrocatalytic system,the sequential microbial fuel cell coupled photocatalytic device(S-SCMFC-PEC)simultaneously realized photoelectrocatalytic and bioelectrocatalytic dual-degradation of LEV and exhibited excellent removal efficiency.The possible degradation pathways and mechanisms were investigated by LC/TOF/MS and density functional theory calculations(DFT)in-depth,explaining that the pollutant attack sites(piperazine ring and F position)and mineralization pathways in SCMFC-PEC coupled system.(4)A coupling system based on photo-driven microbial fuel cell(PMFC)was constructed to controllably synthesize different sizes of MoS2 nanomaterials in situ and the corresponding MoS2/PDA/TiO2 electrodes.Under the optimized conditions(6 h,visible-light-driven),the enhanced radical oxygen species(·OH and·O2-),the incorporation of a dual-electron(ebio-/epho-)route,as well as improved hydrophilic behavior could effectively promote the LEV rapid degradation(5.2×10-2 min-1)and efficient hydrogen generation(0.003 m3 m-3 min-1)during the PMFC-PEC coupling system.The possible dual-electron driven mode has been elucidated.