Insight into the Mechanism of CO Oxidation on WO3(001) Surfaces for Gas Sensing: A DFT Study

Abstract

The mechanism of CO oxidation on the WO3(001) surface for gas sensing performance has been systematically investigated by means of first principles density functional theory (DFT) calculations. Our results show that the oxidation of CO molecule on the perfect WO3(001) surface induces the formation of surface oxygen vacancies, which results in an increase of the surface conductance. This defective WO3(001) surface can be re-oxidized by the O2 molecules in the atmosphere. During this step, the active O2− species is generated, accompanied with the obvious charge transfer from the surface to O2 molecule, and correspondingly, the surface conductivity is reduced. The O2− species tends to take part in the subsequent reaction with the CO molecule, and after releasing CO2 molecule, the perfect WO3(001) surface is finally reproduced. The activation energy barriers and the reaction energies associated with above surface reactions are determined, and from the kinetics viewpoint, the oxidation of CO molecule on the perfect WO3(001) surface is the rate-limiting step with an activation barrier of about 0.91 eV.

IoT-Enabled Gas Sensors: Technologies, Applications, and Opportunities

“…The poisoning symptoms are easily mistaken with fatigue. Depending on the exposition time and concentrations of this gas, it can be lethal or reduce lifetime, causing cardiovascular diseases and brain damage [19,20,[35][36][37][38].…”

“…These sensors operate at high temperatures, the reaction with the target gas generates a variation on its internal resistance and the sensor responds with a proportional output tension, according to the concentration of the gas it is sensing; the sensors are normally designed within a heater. The transducers are sensitive to more than one gas and the temperature of operation is a key to determine the gas that will be sensed [28,29,38,120,121].…”

“…The heating process must be adequate to the target gas, as the sensor will respond to different gases if the temperature is not suitable for the gas of interest. A physical gas filter, to eliminate interference from other gases, can be added to the sensing element, upgrading the performance of the measurements [28,38,119,120].…”

“…The poisoning symptoms are easily mistaken with fatigue. Depending on the exposition time and concentrations of this gas, it can be lethal or reduce lifetime, causing cardiovascular diseases and brain damage [19,20,[35][36][37][38].Volatile organic compounds (VOCs) are carbon-based organic compounds, in a vapor state at room temperature, generated by the combustion of fossil fuels, or natural emissions, where some compounds are toxic, affecting human health by causing irritation of the respiratory system and eyes, diseases as cardiovascular and respiratory malfunctions, or even cancer [39,40].Liquefied petroleum gas (LPG) is a fossil fuel composed of a mixture of hydrocarbon gases, used in domestic situations and industry, to generate electricity, power heating systems, vehicular combustible and cooking. It is a highly flammable gas, capable of severe damage if a leakage is followed by an ignition; major explosions and fire incidents were reported in the literature, due to its gas leakage, in numerous countries, such as the 2011 Karakopru incident, where an entity plant was destroyed due to an explosion.…”

Tungsten-Embedded Graphene: Theoretical Study on a Potential High-Activity Catalyst toward CO Oxidation

“…The results indicated the tungsten was bonded to single vacancy tightly to form a stable substitution system, they believe this embedded graphene can be used in nano electronics, spintronics, and magnetic storage devices. Jin et al [ 33 ] have investigated the mechanism of CO oxidation on the WO 3 (001) surface systematically, their calculation results show that this tungsten oxide is one of the most promising gas sensor candidates due to its high activity toward CO oxidation. To the best of our knowledge, the mechanism of CO oxidation on tungsten-embedded graphene is still lacking in experimental and theoretical investigations.…”