Synthesis Of Two Carbon-Based Composites And Their Photoelectrochemical Sensing And Catalytic Applications

Carbon-based materials have excellent light absorption capability,electrical conductivity,thermal and chemical stability and other advantages,as well as rich sources,green non-toxic,low cost,etc.,which have been widely applied in the fields of photo/electro catalysis and biosensor detection.However,in the field of photoelectrochemistry,the properties and applications of carbon-based materials remain to be studied.In this paper,two heterogeneous structures including Ti₃C₂/Cu₂O and g-C₃N₅/BiOBr,are constructed in combination with different semiconductors based on two carbon-based materials,Ti₃C₂ and g-C₃N₅.Their structures and properties have been explored and were further applied to PEC sensing and catalysis.The main content of this article is as follows:1.The mixed solution involving LiF and HCl etched the Al in Ti₃AlC₂ away by agitating in a closed atmosphere at 37°C for 24 h to obtain a regularly arranged organ-like Ti₃C₂,the glucose was used as a reducing agent to reduce the CuSO₄ at 80°C,therefore preparing Ti₃C₂/Cu₂O.Octahedral Cu₂O was evenly distributed on the surface of Ti₃C₂,thus a heterostructure with enhanced PEC properties was obtained under the synergistic effect.Excellent PEC performance and sensitive response to glucose made Ti₃C₂/Cu₂O a favorable substitute for glucose oxidase.Based on this,we constructed a non-enzymatic PEC sensor based on Ti₃C₂/Cu₂O heterostructure for glucose detection.Under the optimal detection conditions,the detection range was 0.5 nM to 0.5 mM,and the detection limit was 0.17 nM.In addition,the glucose in standard samples and human serum had been detected by the proposed Ti₃C₂/Cu₂O based PEC non-enzyme sensor successfully.The experiments prove the application prospect of heterostructure materials in PEC sensors,and provide new ideas for the design and construction of PEC sensing platforms.2.Nitrogen vacancy（NV）g-C₃N₅ was synthesized by NaOH etching and calcination,and then the NV-g-C₃N₅/BiOBr heterostructure was synthesized with BiOBr by solvothermal method.A non-enzymatic PEC sensor was constructed based on this composite material for monitoring the cytochrome c（Cyt c）,which is highly sensitive to Cyt c.The electron transfer between the Fe（Ⅲ）/Fe（Ⅱ）-heme redox active sites of Cyt c weakened the photocurrent intensity.Photocurrent values and Cyt c showed different linear calibration curves at lower concentrations of 0.1nM to 0.1μM and relatively higher concentrations of 0.1μM to 0.1 mM,which is I=0.018LogC-0.029 and I=0.043LogC+0.094,respectively.The experimental results show that the sensor not only has excellent sensitivity to Cyt c but also can be used to monitor the transfer of Cyt c from mitochondria to cytoplasm.3.Based on the strong photoelectric conversion efficiency from the above synthesized NV-g-C₃N₅/BiOBr with built-in double-electron transfer mechanism（DETM）,it is applied to photoelectrochemical nitrogen reduction（NRR）.Experiments shown that nitrogen vacancies can effectively narrow the band gap of the original g-C₃N₅ and enhance the visible light collection ability of NV-g-C₃N₅.At the same time,nitrogen vacancies can also serve as chemisorption sites to adsorb N₂ and act as a catalytic site for the activation and reduction of N₂.In addition,due to the matching band structure,NV-g-C₃N₅/BiOBr further separated the photo-induced electrons and holes.The DETM effectively prevented the recombination of charge carriers and ensured continuous supply of high-quality electrons,which enabled NV-g-C₃N₅/BiOBr to obtain excellent PEC NRR performance without the addition of noble metals.The constructed DETM shows the potential of non-noble metal materials in PEC NRR and lays the foundation for the design of a more affordable and efficient NRR photocathode.