Preparation Of Ru-based Bimetallic Nanocrystals And Their Effects On Gas Sensing Properties Of SnO₂

Metal-oxide-semiconductor gas sensors have great application potential in the fields of environmental monitoring and protection,security,medical and health due to their simple structure,adjustable performance,and portability.Among them,SnO₂ is regarded as one of the important gas-sensing materials due to its extremely high electron mobility,wide band gap,high sensitivity,high conductivity,and strong stability.However,the single SnO₂material still needs improvement in terms of selectivity,stability,and trace gas detection.The modification of precious metals on metal oxide semiconductor materials is a relatively common modification method,but the scarcity and high price of precious metals limit their large-scale commercial applications.Bimetallic nanoparticles have unique synergistic effects.They have more excellent physical and chemical properties than the corresponding single metals,and play an important role in replacing single precious metals and improving catalytic activity.As a member of the platinum group metals,Ru not only has good catalytic performance,but also is not easy to be poisoned.Alloying Ru with another metal can not only effectively reduce the cost by reducing the modification ratio of noble metals,but also significantly improve the utilization rate of the catalyst in the reaction and improve the sensing performance of the material.In this paper,SnO₂ nanoparticle cluster materials with high specific surface area were synthesized by hydrothermal method,RuCu and Pd Ru bimetallic nanoparticles were synthesized by liquid phase method,and Ru-based bimetallic materials were used as surface modification materials to composite with SnO₂ nanoparticles.The unique synergistic effect and excellent catalytic performance of bimetals can improve the gas sensing properties of SnO₂ materials.The details are as follows:(1)RuCu bimetallic nanoparticles were synthesized by solvothermal method.The bimetallic nanoparticles were about 5 nm in diameter and consisted of crystalline Ru and amorphous Cu,then they were decorated with high-purity SnO₂ nanoparticle clusters prepared by hydrothermal method.After a series of gas-sensing tests,we found that 0.3 wt%RuCu-SnO₂ exhibited excellent gas-sensing performance for n-pentanol at an operating temperature of 200°C.The response to 50 ppm n-pentanol is as high as217.8,which is 20 times higher than that of the pure SnO₂ gas sensor.The improvement of the sensor performance is mainly attributed to the chemical sensitization and electronic sensitization of RuCu bimetallic nanoparticles.In addition,compared with pure Ru-modified SnO₂,the improvement of its gas sensing performance is mainly due to the synergistic effect of RuCu bimetals,which can provide more reactant molecules or intermediates with different binding configurations compared with single metal.The multiple catalytic sites promote oxygen adsorption and electron transfer.(2)Pd Ru bimetallic nanocrystals with good dispersibility and a particle diameter of about 8 nm were synthesized and then modified on the surface of high-purity SnO₂nanoparticle clusters to prepare a series of Pd Ru-SnO₂ gas sensing materials.Among them,the gas sensor based on 0.2 wt%Pd Ru-SnO₂ has a response of up to 78.3 for 100ppm trimethylamine at an operating temperature of 230°C,with a response/recovery time of 10 s/81 s,respectively,which is comparable to other gases such as NH₃,triethylamine,ethanol.In contrast,it has the best response to trimethylamine,and also has considerable performance in terms of repeatability and moisture resistance.The research results in this paper show that the controllable synthesis of Ru-based bimetallic alloy nanoparticles can be realized by the liquid phase method.When the alloy types are different,the Ru-based bimetals show different selective catalytic properties.The combination of a small amount of Ru-based bimetallic and SnO₂materials can significantly improve the selectivity and sensitivity to VOCs gases(n-pentanol,trimethylamine).The work of this paper provides an idea for the study of new oxide semiconductor materials.