Preparation And Performance Study Of Hydrogen Sensor Based On ZnO Electrode

Hydrogen is a clean and efficient energy source,which is widely used in various industries such as industry,transportation and electric power.But at the same time,hydrogen is a flammable and explosive gas with wide explosion limit,and once it leaks,it is very easy to have fire and explosion and other dangerous accidents,which seriously threaten public safety.Accurate detection of hydrogen concentration and timely sensing of hydrogen leakage are the keys to ensure safe hydrogen production,safe hydrogen storage and transportation,safe hydrogen refueling and safe hydrogen energy application.The mixed potential hydrogen sensor is an effective means to detect hydrogen,but there are still problems of low sensitivity and high lower detection limit,which cannot detect hydrogen at low concentration with high sensitivity.The sensitive electrode and the reference electrode are two important factors affecting the sensitivity of hydrogen sensors,and it is expected to significantly improve the sensitivity of hydrogen sensors by optimizing the shape of the sensitive electrode and changing the composition of the reference electrode to achieve highly sensitive detection of hydrogen.Based on this,a hybrid potential hydrogen sensor was prepared using zeolitic imidazolium framework-8（ZIF-8）-derived Zn O as the sensitive electrode,and the optimal Zn O electrode morphology was determined to achieve fast,highly sensitive and highly selective detection of ppm-level or even ppb-level hydrogen gas;two metal oxides with different physicochemical properties were used to replace the traditional Pt reference electrode and paired with Zn O nanocage electrode to prepare Two mixed-potential hydrogen sensors were prepared,and the reference electrode with anomalous potential polarity was paired with the Zn O nanocage electrode to further improve the response value,sensitivity,and lower lower limit of hydrogen detection.This thesis achieves highly sensitive detection of hydrogen gas at ppb level in a simple and low-cost manner,which is important for ensuring public safety,as follows:1.Three different morphologies of ZIF-8 were synthesized by regulating the addition of cetyltrimethylammonium bromide（CTAB）in the hydrothermal process,and three morphologies of Zn O were prepared by high-temperature calcination using ZIF-8as a sacrificial template.The four mixed potential hydrogen sensors were prepared with three different shapes of ZIF-8 and conventional nanoparticulate ZIF-8 as sensitive electrodes,Ce_0.8Gd_0.2O_1.9（GDC）as solid electrolyte and Pt as reference electrode,respectively.The results showed that the ZIF-8-derived Zn O nanocages showed a hollow porous polyhedral structure with an average size of 390 nm and an average pore size of 32.84 nm when CTAB was added at 0.35 wt%;the response value of the Zn O nanocage sensor to 500 ppm hydrogen at 450℃was-99.55 m V and the response time was 26 s,which was 78%higher than that of the Zn O The response time was 26 s,which was 78%higher and 90.44%shorter than that of the Zn O nanoparticle sensor;the Zn O sensor had a high response value（-10.62 m V）for 0.3 ppm hydrogen,and the calculated lower detection limit was 56 ppb;in addition,the Zn O sensor also had excellent interference immunity and repeatability;by comparing the AC impedance spectra,it was found that the Zn O sensor corresponded to the smallest interfacial impedance,and the hydrogen with the highest electrochemical catalytic activity.Therefore,the ZIF-8-derived Zn O sensor can achieve fast,highly sensitive and selective detection of hydrogen at ppm and ppb levels compared to Zn O nanoparticles.2.To further optimize the performance of the nano-cage Zn O sensor,two metal oxides with different physicochemical properties,cobalt oxide（Co₃O₄）and strontium iron cobaltate(Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ,BSCF),were used to replace the conventional Pt electrode as the reference electrode and paired with the Zn O sensitive electrode,and two mixed potential hydrogen sensors with GDC as the solid electrolyte were prepared.Two mixed potential hydrogen sensors with bimetallic oxide electrodes were prepared using GDC as a solid electrolyte,and the sensitivity characteristics of the sensors with single and bimetallic oxide electrodes to hydrogen were systematically investigated and compared.The results show that the electron conductor Co₃O₄has the same polarity as the Zn O potential,and the mutual pairing of the two cancels part of the hydrogen response and reduces the response value and sensitivity to hydrogen.The response value to 800 ppm hydrogen at 400℃is-20.69 m V,which is 39.47%lower than that of the Zn O sensor under the same conditions;the electron-ion hybrid conductor BSCF has the opposite polarity to the The electron-ion hybrid conductor BSCF with opposite polarity of Zn O increased the response value and sensitivity to hydrogen,and the response value at 450℃to 800 ppm hydrogen was-94.38 m V,and the sensitivity was-44.43 m V/Dec,which increased the response value and sensitivity to hydrogen by 34%and 58.87%,respectively,compared with the Zn O sensor under the same conditions,and significantly enhanced the sensitivity to hydrogen.sensitive characteristics.Therefore,the use of BSCF with anomalous potential polarity as a reference electrode paired with conventional polarity sensitive electrode is an effective means to optimize the detection effect of hydrogen and achieve highly sensitive detection of low concentration of hydrogen gas.