Research Of Nafion-based Fuel Cell Type Hydrogen Sulfide Sensor

A fuel cell type H₂S sensor using Nafion proton membrane as a solid electrolyte was developed in this paper.The sensor has advantages such as room temperature operation,intrinsic safety,environmental friendliness,zero power consumption,good mechanical and chemical stability,etc.It has good application prospects in flammable and explosive fields such as sewage treatment and dye preparation.This thesis starts with the core component of the sensor,the membrane electrode,and improves the catalytic activity of sensing electrode materials through component sensitization of material alloying and improved process sensitization of the preparation method.The H₂S sensor with fast response recovery speed,large test range and excellent selectivity was developed through a two-stage sensitization strategy.The main research contents are as follows:First,H₂S sensor based on platinum?Pt?-rhodium?Rh?nanoparticle sensing electrodes supported on carbon fibers were developed.Carbon fiber-supported Pt-Rh nanoparticles were prepared by sodium borohydride reduction method,and a membrane electrode assembly?MEA?was prepared by hot pressing method.X-ray diffraction?XRD?and field emission scanning electron microscope?FESEM?were used to analyze the structure and morphology of the prepared electrode materials.The effects of Pt-Rh alloying and carbon fiber surface remodeling on the performance of the sensor were mainly studied,and the optimal ratio of Pt and Rh and the optimal carbon fiber corrosion process were explored.The results showed that:when the ratio of Pt to Rh is 1:1,the gas sensing performance was the best.The surface remodeling of carbon fiber increased the load of precious metal nanoparticles,which improved the sensitivity from-0.158?A/ppm to-0.191?A/ppm.The sensor could detect H₂S as low as 0.1 ppm,and the response current in the range of 1 to 200 ppm had a good linear relationship with the concentration of H₂S.The response and recovery time of the sensor to 50 ppm H₂S were 10 s and 16 s,respectively,enabling real-time monitoring of H₂S.In addition,this fuel cell-type sensor also exhibited good repeatability and humidity resistance as well as excellent selectivity and stability.Second,the H₂S sensor based on platinum?Pt?-tin?Sn?nanoparticle sensing electrodes supported by carbon fibers was developed.The research focused on the improvement of sensing electrode material preparation technology and the effect of alloying in Pt-Sn materials on sensor performance.Pt/C materials?Pt/C?NaBH₄?,Pt/C?EG??were prepared by sodium borohydride reduction method and ethylene glycol method.The results showed that the ethylene glycol method was a better preparation method.The sensing electrode material has a more uniform distribution of precious metal particles,and the Nafion-based sensor based on the corresponding sensing electrode material had higher sensitivity.Next,the Pt-Sn/C sensing electrode material was prepared by the ethylene glycol method.The material was characterized by X-ray diffraction?XRD?,transmission electron microscope?TEM?,and energy dispersive X-ray spectrometer?EDS?.The results showed that the material is a multi-phase combination of Pt,Pt₃Sn,and SnO₂,and the surface was rougher.The gas sensing performance of Pt/C?NaBH₄?,Pt/C?EG?,and Pt-Sn/C was studied.The results showed that the sensor based on Pt-Sn/C had the highest sensitivity?-0.276?A/ppm?.The sensor could linearly detect H₂S in the concentration range of 0.2-100 ppm.More importantly,the response and recovery time to 50 ppm H₂S was 10 s and 8 s,respectively.This result is the leading level in hydrogen sulfide sensors operating at room temperature.In addition,in the selectivity study,it was found that compared to traditional Pt/C catalysts,alloying of Pt and Sn can effectively suppress the response to interfering gases such as CO and SO₂,and improve long-term stability;at the same time,the sensor also performed outstanding repeatability and moisture resistance.This article mainly studies the effect of the composition of sensing electrode materials and the method of material preparation on the gas sensing performance of the sensor.It was found that the glycol method is significantly better than the sodium borohydride reduction method.The alloying of precious metals in electrode materials can significantly improve the selectivity and stability of the sensor.Combining the two-stage sensitization strategy of component sensitization and industrial sensitization,a Nafion-based fuel cell type H₂S sensor with the advantages of room temperature operation,high sensitivity,fast response recovery speed and strong stability was developed.It has good application potential in flammable and explosive environments.