基于富氧缺陷氧化锌多级纳米结构的甲烷室温传感技术与机理

Methane sensing is crucial for monitoring of the coal mine gas. Considering the high working temperature and the un-stability of the present methane sensors based on catalytic combustion, a novel strategy is proposed for methane sensing at room temperature using defect-rich ZnO nano-architectures, which can be quickly fabricated by super-saturation induced method, as the sensitive material. How to keep the sensitivity, selectivity and sensing response to methane at room temperature is important. The sensitivity and selectivity are expected to be improved by regulation of oxygen defects and BET of ZnO nano-architectures which favor the adsorption of methane or by loading of catalysts which favor the oxidation of methane at room temperature; the sensing response is expected to be accelerated by constructing ZnO/graphene nanocomposites using graphene with high conductance as the conductive network. The influences of the oxygen defect and BET of ZnO nano-architectures, the loading of catalysts and the structure of graphene network on the sensing behaviors will be revealed by in-situ monitoring, the structure/surface/electric analyses and molecular simulation. The corresponding mechanisms will be revealed and the theoretical models will be established to guide the optimization for the effective methane sensing at room temperature.

甲烷传感是煤矿瓦斯监控的关键。针对现有催化燃烧型甲烷传感器工作温度高且性能不稳定等问题，借鉴已有过饱和度诱导的氧化锌多级纳米结构快速组装技术，本课题提出基于富氧缺陷氧化锌多级纳米结构的甲烷室温传感新思路。如何实现室温条件下对甲烷的灵敏、选择、快速响应是关键。拟通过调控纳米氧化锌氧缺陷浓度和比表面促进甲烷吸附，通过负载催化剂促进甲烷室温氧化，由此提高甲烷传感灵敏性和选择性；通过调控石墨烯导电网络结构，构建氧化锌/石墨烯纳米复合材料，促进室温快速响应。综合利用原位检测、结构/表面表征、电学性质分析和分子模拟等手段，从构效关系角度系统研究氧化锌氧缺陷/比表面，催化负载和石墨烯构型与传感行为关系，建立相应理论模型并指导工艺优化，为甲烷室温传感提供新途径和基础数据。

甲烷传感是煤矿瓦斯监控的关键。针对现有催化燃烧型甲烷传感器工作温度高且性能不稳定等问题，本课题提出基于富氧缺陷氧化锌多级纳米结构的甲烷低温传感新思路：以提高氧化锌表面吸附氧（O-，O2-）的数量及活性、强化甲烷表面催化为核心，在晶种辅助的氢氧化锌碱溶转化法制备的高比表面（35 m2/g，普通ZnO<10 m2/g）多级结构氧化锌基础上，利用高温氢气还原法制备了富氧缺陷氧化锌（OV ZnO），利用氧缺陷处气体的吸附强化提高吸附氧数量。进一步在OV ZnO上以银纳米颗粒为载体，利用电化学还原法制备了高分散性钯纳米颗粒，得到银钯负载的富氧缺陷氧化锌（Pd@Ag@OV ZnO），利用钯对氧气的溢流效应及对碳氢键的催化裂解，提高氧化锌表面吸附氧的数量及活性，促进甲烷催化氧化。在470nm可见光下，利用Ag受光激发产生的热电子向氧化锌的转移，同时氧缺陷引入的中间能级显著降低热电子向氧化锌的转移能垒，使热电子与吸附氧结合显著提高吸附氧活性。在80℃，470nm光照下，Pd@Ag@OV ZnO对0.1%甲烷响应值达68.5%，响应/恢复时间为2.6/2.3min，实现了低温甲烷传感。进一步地，在Pd@Ag@OV ZnO包覆ZIF-8（二甲基咪唑锌盐，C8H10N4Zn），利用其0.4-0.42nm的筛分孔径显著降低了1ppm NO2（分子动力学直径：0.45nm）对甲烷（分子动力学直径：0.38nm）的干扰（响应值由255.7%降至17.3%），提高了甲烷传感选择性。