Research On Preparation And Process Optimization Of Hydrogen Sensor Based On Pd Nano-rings/TiO₂ Nanotubes Composite Structure

Hydrogen is a type of renewable clean energy,which have been wildly applied in the national living and national defense science and technology fields.Preparation of a hydrogen sensor with short response time,high sensitivity and good stability to ensure the safety in the process of preparation,transportation,storage and utilization of hydrogen is very urgent and necessary.In this paper,the preparation and process optimization of hydrogen sensor based on Pd nano-rings/TiO₂ nanotubes composite are studied.Anodic oxidation method was used to prepare highly ordered TiO₂ nanotube arrays in ammonium fluoride?NH4F?/ethylene glycol electrolyte on the Ti foil.The effect of water content on the surface morphology of TiO₂ nanotube arrays was studied.It was shown that the diameter and gap of TiO₂ nanotubes increased with the increase of water content.On that basis,the surface morphology of TiO₂ nanotubes could be controlled by water content,and the performance of hydrogen sensor affected by surface morphology of TiO₂ nanotubes had been researched.The results show that the sensitivity of the composite structure hydrogen sensor increases first and then decreases with the increase of the gap.The surface morphology of the TiO₂ nanotubes prepared by the electrolyte with 17.5wt.% water is ordered.The TiO₂ nanotubes composite with the Pd nano-rings to fabricate a hydrogen sensor has high sensitivity of 88% at 1.6% hydrogen concentration.We also investigated the effect of the annealing atmosphere on the sensor's hydrogen response characteristics.And we found that the annealed sensor in the nitrogen atmosphere had a faster response time and higher sensitivity than in the air atmosphere.But,the sensor annealed in the nitrogen atmosphere also has many problems,like drifting too much and lack of stability.In addition,we also studied the impact of the air environment on the performance of the hydrogen sensor,the sensor showed good stability after stored in the air environment more than a month.On the basis of the preparation and optimization of hydrogen sensor based on Pd nano-rings/TiO₂ nanotubes composite structure,we propose a physical-catalytic compound mechanism model based on this composite structure.The results show that Pd nano-rings play a role in catalysis effect and break-junction effect.Finally,the feasibility study of the flexible hydrogen sensor based on Pd nano-rings/TiO₂ nanotubes composite structure had been finished in this paper.The problem of stripping off the TiO₂ nanotube thin film prepared by anodic oxidation method on Ti substrate had been successfully solved.And then transferred thin film to PDMS flexible substrate.The metal Pd was sputtered by magnetron sputtering to prepare flexible hydrogen sensor.The results show that the hydrogen sensor is sensitive to hydrogen,but the measured image noise is very large and the jitter of waveform is serious,the sensor still need to be further improved.