Biomass Microwave-assisted Construction Of Carbonbased Sensor And Its Application In Hydrogen Peroxide Detection

In the process of agricultural development,in order to ensure the quality of agricultural products,it is essential to use some chemical reagents to increase their production.Hydrogen peroxide（H₂O₂）is widely used in chemical,medical,food and other industries due to its strong oxidation.Under normal circumstances,hydrogen peroxide can decompose into oxygen moreover water without causing environmental pollution,which also makes it closely concerned by researchers in the field of agriculture.H₂O₂ is of great significance to plant seeds,seedlings in addition agricultural environmental protection.However,it has also become a significant research topic for how to avoid the secondary pollution of hydrogen peroxide to the agricultural environment in practical utilization.Because these residues will flow into the human body directly or indirectly through the environment,endanger the ecological environment,and even threaten people’s lives.Therefore,the realization of accurate detection of hydrogen peroxide not only can curb the emergence of residual from the source,but also can dynamically detect the changes of hydrogen peroxide in agricultural environment,to provide important data support for agricultural development.There are many existing detection techniques,of which high performance liquid chromatography is accurate as well as low detection limit,on the contrary the instrument is expensive and the analysis cost is high;chemical titration method is simple,even if the sensitivity is low and not conducive to outdoor detection;electrochemical method has fast detection speed and wide linear range,however usually the electrode materials are overpriced.Based on the strengths and weaknesses of these methods,aiming at the problem of high cost,low sensitivity and poor stability of hydrogen peroxide detection in agriculture,this study makes use of lignocellulosic agricultural waste as feedstock,develops a variety of high performance electrochemical sensing platforms based on electrochemistry and microwave-assisted synthesis strategy,and realizes rapid and accurate analysis of hydrogen peroxide both for experimental conditions and actual sample detection.In this work,biochar was prepared by microwave-assisted pyrolysis of bagasse,and a variety of carbon-based nanocomposites with high performance were synthesized by microwave-assisted hydrothermal synthesis method.The reproducibility,selectivity and stability of the sensor were tested by cyclic voltammetry in addition to i-t method,and the detection mechanism of hydrogen peroxide by the developed sensor material was explored to achieve high sensitivity detection of hydrogen peroxide.This paper includes the following three parts:1)Biochar（MPC）prepared by microwave-assisted pyrolysis of sugarcane bagasse was used as the substrate,and then Co nanoparticles were introduced by microwave-assisted solvothermal method,and then calcined at high temperature to form a highly dispersive Co/MPC material,and the prepared material was limited to glassy carbon.On the electrode surface,a cobalt-based sensing platform（Co/MPC/GCE）was built.Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on the carbon-based skeleton with the performance of microwave-asisted hydrothermal synthesis approach,providing high-activity space.On the basis of this constructed sensing platform,the linear equation was fitted by the concentration change of current signal I and H₂O₂.The linear range was 0.55-100.05 m M,the detection limit was 1.38μM（S/N=3）and the sensitivity was 103.45μA cm^-2 m M^-1.Besides,this sensor was also applied to detect H₂O₂ in actual water samples by using the standard addition recovery method,results disclosed that the recovery rate and RSD of H₂O₂ in tap water samples were 94.0-97.6%and 4.1-6.5%,respectively.2)In order to improve the sensitivity and stability of the material for the detection of hydrogen peroxide,according to the work completed in the first part,Ni/N/MPC nanocomposites were synthesized by Ni-based biomass doped with nitrogen.Nickel atom and cobalt atom are in transition metal region,as well as both have the advantages of good catalytic activity and low price;nitrogen doping is conducive to the formation of stable hybrid structures and the formation of rich functional groups on the surface of nanocomposites.Among them,the linear equation was fitted with the variation of current signal I and H₂O₂ concentration,with the linear range of 0.05-240.15 m M as well as the detection limit of 0.84μM（S/N=3）.For Ni/GCE and Ni/N/GCE sensors,the electrochemical signals were much lower than those of the composite materials under the test of cyclic voltammetry.In the actual sample detection,the recovery rate and RSD of H₂O₂ in tap water samples were 97.2-98.6%and 5.5-6.4%,respectively.The Ni/N/MPC/GCE sensing platform has better stability and higher sensitivity.3)Based on the above two parts,the performance of the sensor for detecting H₂O₂ was further improved.At the same time,three elements Co,Ni and N were introduced into the carbon-based materials to construct the Co/Ni/N/MPC sensor with multiple electrochemical active signal sites.Under the microwave-assisted synthesis performance,carbon-based skeleton was used to uniformly disperse Co and Ni atoms,forming metal-metal bonds with stronger activity than single metal.Nitrogen doping could also stabilize the carbon-based skeleton and promote electron transfer efficiency.In order to explore the effect of different metal ratios on catalytic performance,the sensitivity of Co₁/Ni₂/N/MPC/GCE,Co₁/Ni₁/N/MPC/GCE and Co₂/Ni₁/N/MPC/GCE to detect H₂O₂ was investigated in this chapter.The results showed that Co₁/Ni₁/N/MPC/GCE had the highest sensitivity,and the linear equation was fitted by the change of current signal I and H₂O₂ concentration.The linear range was 0.05-272.15 m M,and the detection limit was 0.56μM（S/N=3）,which was used in the actual sample detection.The recovery and RSD of H₂O₂ in tap water samples were 98.3-98.9%and 2.6-4.2%,respectively.In this chapter,bimetal as well as nitrogen doping were used to improve the activity likewise stability of the material,expand the sensitivity of the material,in the meanwhile realize the high sensitivity detection of H₂O₂ in water.It provides a theoretical basis for the development of low-cost and high-performance sensing elements,and opens up a new pathway.