NiO/Fe_(2)O_(3)复合材料制备与气敏性综合实验设计

Comprehensive experimental design about preparation and gas sensing properties of NiO/Fe_(2)O_(3) composites

该综合实验通过煅烧金属有机框架材料制备中空NiO/Fe_(2)O_(3)纳米材料,并对材料的形貌、物相进行了结构表征。通过调整Ni和Fe的含量,对比了不同材料对正丙醇等气体的气敏性能,并提出可能的气敏机理。此实验将科研成果与实验教学相融合,旨在激发学生的科研兴趣,培养创新型、复合型和应用型高素质人才。

[Objective]Gas sensors are pivotal in intelligent detection systems and have broad applications in medicine,indoor and outdoor air quality monitoring systems,environmental science,the automotive industry,and the military.In particular,semiconductive metal oxides have become the main choice for designing advanced gas sensors with high sensitivity,high stability,and low cost owing to their inherent physical and chemical properties.Compared with single-component materials,heterostructured bimetallic oxides offer superior features such as fast electron transfer,high carrier concentration,and low grain boundary potential barriers.These advantages often result in enhanced gas sensing performance.In addition,hollow structures with an inner cavity provide a more accessible surface and shorten the diffusion distance of target molecules,enabling effective surface reactions.Consequently,the integration of heterostructure and hollow structure serves as an effective strategy for enhancing gas sensing performance.[Methods]This paper proposes the preparation of an advanced hollow heterostructure for gas sensing using a metal–organic precursor.A primitive metal–organic precursor assembly was selected,using Ni^(2+)ions,anionic ligand(H_(2)BDC),and neutral ligand(DABCO).Another metallic Fe element,with varying content,was introduced using the impregnation method to form bimetallic precursors(HXR-Fe).Following thermal annealing in air,bimetallic NiO/Fe_(2)O_(3)-1∶1,NiO/Fe_(2)O_(3)-1∶2,and NiO/Fe_(2)O_(3)-1∶4 heterostructures were obtained and further employed as sensing materials.The sensing devices were fabricated by coating the sensing materials on the outer surfaces of alumina ceramic tubes.The sensing devices were then placed in a sealed gas box with a controllable working temperature and alternating gases,i.e.,air and target gas,for gas sensing measurement.[Results]The experimental results from both the materials synthesis and characterization revealed that the HXR-Fe sample exhibits hexagonal nanorods,with lateral dimensions ranging from 400 to 500 nm and longitudinal dimensions of approximately 200 nm.The NiO/Fe_(2)O_(3) heterostructures retain the hexagonal morphology and clearly show a hollow structure.Depending on the Fe element content,the ratio between NiO and Fe_(2)O_(3) can be modulated.The resistance values decreased from pure NiO to NiO/Fe_(2)O_(3) heterostructures,demonstrating the formation of a p–n heterojunction.Our experimental results from gas sensing measurements have yielded significant insights.Notably,we found the following:i)the optimal working temperature for each sensing device is 150℃;ii)heterostructure materials outperform pure NiO in terms of responsive values,with NiO/Fe_(2)O_(3)-1∶1 demonstrating the highest responsiveness;iii)NiO/Fe_(2)O_(3)-1∶1 presents the largest response value to 100-ppm n-propanol and maintains good cyclic stability across six alternating cycles;iv)NiO/Fe_(2)O_(3)-1∶1 presents the largest response value to 100-ppm n-propanol among other gases,indicating excellent selectivity.Furthermore,the NiO/Fe_(2)O_(3)-1∶1 sensor exhibits representative p-type semiconductor behavior,with holes serving as the main carriers in gas sensing reactions.This experiment integrates emerging research areas such as nanomaterials and gas sensing into comprehensive experimental teaching.As a result,students can deepen their understanding of fundamental concepts in fields like inorganic and structural chemistry,as well as semiconductor physics.This comprehensive experiment also enhances students’experimental skills.In addition,students gain firsthand experience with research methodologies used for the synthesis,structure,and performance of gas sensors.This experience provides them with a clearer understanding of the future trajectory of gas sensor technology within the chemical industry,particularly in the context of smart living.[Conclusions]This hands-on experiment not only stimulates students’interest in learning but also fosters their comprehensive practical abilities.It encourages them to develop problem-solving skills,bolsters their engineering capabilities,and nurtures innovative thinking.Ultimately,this experiment contributes to the cultivation of innovative talent in line with the evolving demands of new engineering disciplines.