Dynamic Reaction Mechanism of P–N-Switched H₂-Sensing Performance on a Pt-Decorated TiO₂ Surface

Abstract

Pt decoration is known to be one of the most promising strategies to enhance the performance of TiO2 hydrogen gas sensors, while the effect of Pt-decorating concentration on the sensing performance of TiO2 and the specific interaction between Pt and TiO2 have not been fully investigated. Here, a series of TiO2 nanoarray thin films with differing amounts of Pt decorated (Pt/TiO2) is fabricated, and the H2-sensing performance is evaluated. A switch in the response from P-type to N-type is observed with increasing Pt decoration. The response additionally depends on the H2 concentration: resistance increases in low H2 concentrations and decreases in hydrogen concentrations higher than 40 ppm. This is explained by the competitive adsorption of hydrogen between the Pt nanoparticles (Pt NPs) and the exposed TiO2 surface. The preference for H2 adsorption and splitting between Pt and TiO2 is established by DFT calculations. Humidity brings preferential adsorption of H2O on the surface of Pt, which affects the following adsorption and splitting of H2, thus resulting in a P–N switch of the sensing performance. The detailed dynamic reaction process is described according to the findings.

Bimetallic Au and Pd Nanoparticles Modified WO3 Nanosheets for Enhancing the Sensitivity and Selectivity of Formaldehyde Assessment in Aquatic Products

“…The bond dissociation energy of H–CHO is 364 kJ/mol, which is smaller than other interference gases in Figure a. , In the gas-sensing process of 2.0% AuPd/WO 3 NS based sensors at comparatively low operating temperature (210 °C), the H–CHO bond is prone to breakage due to the lower bond dissociation energy, resulting in an active surface reaction between formaldehyde molecules and the sensing materials. Owing to competitive adsorption effect of different gas molecules on the surface of sensing materials, when formaldehyde begins to be adsorbed and reacting onto 2.0% AuPd/WO 3 NS, the material’s adsorption of other interference gases greatly weakens. , Based on the above reasons, the 2.0% AuPd/WO 3 NS-based sensors achieved highly sensitive and selective detection of formaldehyde.…”

“…Owing to competitive adsorption effect of different gas molecules on the surface of sensing materials, when formaldehyde begins to be adsorbed and reacting onto 2.0% AuPd/WO 3 NS, the material's adsorption of other interference gases greatly weakens. 61,62 Based on the above reasons, the 2.0% AuPd/WO 3 NS-based sensors achieved highly sensitive and selective detection of formaldehyde.…”

A CuO/TiO2 Heterojunction Based CO Sensor with High Response and Selectivity

“…The TiO 2 layer was prepared by a hydrothermal method as described in our previous study. [35][36][37] The prepared TiO 2 films were annealed at 400 °C for 20 min in air, and then used as the substrate to grow the CuO layer. CuO thin films were prepared by a water bath method.…”

Gas Sensing Technology for the Detection and Early Warning of Battery Thermal Runaway: A Review

“…Combining different MOSs (two or more) to construct heterostructures (p–n junction, p–p junction, and n–n junction) can effectively improve gas sensitivity, which may benefit from the introduction of more electron depletion layers, the change of energy band structure, the increase of adsorption sites, or the improvement of the catalytic activity of materials. − However, the construction of heterostructures will also lead to an increase in operating temperature in some cases due to a higher activation barrier at the material interfaces. , This feature is conducive to the gas sensors being applied in some high-temperature conditions but will inevitably increase the power consumption. Kumaresan et al synthesized nanofibers with n-WO 3 /n-TiO 2 heterostructure by simple spin-coating method, in which WO 3 nanoparticles were uniformly loaded on the surface of TiO 2 NFs.…”