Study On The Performance Of 2D MoS₂ Modified Bismuth-based Composite Photoanode-based Photocatalytic Fuel Cell

At present,the world is facing serious environmental problems and energy crisis.Therefore,finding an efficient and environmentally friendly alternative to fossil fuels has become an important issue of common concern to governments and the scientific community all over the world.As an efficient and environmentally friendly photocatalyst,bismuth semiconductor photocatalyst has been widely favored by researchers,but its inherent material defects limit its application in the field of photocatalysis.In this thesis,bismuth-based semiconductors were used as basic materials,and the heterostructures were constructed by compounding with two-dimensional MoS₂ to explore the application of composite photoanodes in solar-driven photocatalytic fuel cells（Photocatalytic fuel cell,PFC）.The main research contents are as follows:（1）FTO was pretreated by impregnation method,and BiOBr/FTO photoanode was prepared by one-step solvothermal method.On this basis,M-BiVO₄/FTO photoanode was synthesized by improved MOD method,and compared with C-BiVO₄ prepared by traditional hydrothermal method.The experimental results show that because of its unique spatial structure,good crystallinity,wide visible light absorption range,excellent charge transfer resistance and band potential,M-BiVO₄ photoanode can improve the optical absorption capacity and photocarrier separation efficiency,photocurrent density and power generation performance.The photocurrent density of M-BiVO₄ photoanode can reach 2.78m A/cm² at 1.23 V（vs.RHE）,which is 1.8 times higher than that C-BiVO₄（1.53 m A/cm²）prepared by traditional hydrothermal method.Then,the M-BiVO₄ photoanode was constructed into a PFC system,and the effects of different types,concentrations and pH of pollutants on its power generation performance were discussed.Under the condition of MB as pollutant,concentration of 50 ppm and pH of 11,the PFC system achieved the best power generation performance,with J_sc and P_max values of 0.514 m A/cm²,0.0483 m W/cm² and FF of 20.3%,respectively.（2）MoS₂/BiOBr composite photoanode was synthesized by solvothermal and hydrothermal methods.The experimental results show that the synthesized tetragonal nano-flower-like BiOBr has good electron transport efficiency.XPS,UV-vis DRS and energy band calculation show that 2H phase MoS₂ nanowires are combined with BiOBr nanoclusters,and MoS₂/BiOBr photoelectrodes with typeⅡheterojunctions are successfully constructed with excellent photoabsorptivity and photogenerated carrier separation rate.The photoelectrochemical performance of the composite photoanode was evaluated by electrochemical performance characterization.When the concentration of MoS₂ precursor solution was 0.05 M（MBO-3）,the photoanode had the best photoelectrochemical performance.At 1.23 V（vs.RHE）,the photocurrent density reaches 3.7 m A/cm²,which is about 5.4 times higher than that of pure BiOBr（0.5 m A/cm²）.Subsequently,the MoS₂/BiOBr-Pt PFC system was successfully constructed to explore the power generation performance of PFC system under different pollutant types,concentrations and pH conditions.It was found that phenol had the best effect when phenol was used as a simulated pollutant.Under the condition of 10 ppm and 7 pH,the values of J_sc、P_max and FF reached0.532 m A/cm²,0.0835 m W/cm² and 21.1%,respectively.（3）MoS₂/BiVO₄ composite photoanode was constructed on M-BiVO₄/FTO photoanode by hydrothermal method.The phase composition and morphology were characterized by XRD,SEM and XPS.The results show that MoS₂ nanowires are uniformly distributed on the BiVO₄/FTO film,forming a dense porous film-like structure,which is beneficial to improve the specific surface area and light absorption ability of the photoanode materials.Through the calculation of XPS and Tacu diagram,it is determined that the MoS₂/BiVO₄ composite photoanode material also forms a typeⅡheterojunction,which forms a built-in electric field,which promotes the migration and separation of photogenerated carriers between different semiconductors,thus inhibiting the recombination of e^--h⁺pairs.In addition,the photoelectrochemical properties of MoS₂/BiVO₄ composite photoanode materials were evaluated by electrochemical methods,and compared with pure BiVO₄ photoanode materials.The results show that MoS₂/BiVO₄ composite photoanode materials exhibit higher photocurrent density under visible light.The MBV-4 sample obtained a maximum photocurrent of 6.02 m A/cm² at 1.23 V（vs.RHE）,which is about 2.2times the maximum photocurrent density of the bare BiVO₄ photoanode（2.78 m A/cm²）,indicating its higher photocatalytic activity and stability.Then a PFC system was built with MBV-4 as the photoanode and Pt cathode,and the effects of different pollutant types,concentrations and pH on the PFC system power production performance were investigated.The results showed that the MBV-4-Pt PFC system exhibited the best electrical generation performance with Rh B as the sacrificial agent,reaching the highest J_sc、P_max and FF of0.619 m A/cm²、0.0987 m W/cm² and 23.8%at 50 ppm and pH of 6.8,respectively.