Facet-engineered CeO₂/graphene composites for enhanced NO₂gas-sensing

Abstract

An effective approach to enhance the gas sensing performance of CeO2/graphene composites at room temperature is demonstrated and discussed.

Porous reduced graphene oxide (rGO)/WO3 nanocomposites for the enhanced detection of NH3 at room temperature

“…The response and recovery times of the sensor are respectively dened as the times taken to reach 90% of its stable resistance value on exposure to target vapour and to reach 10% of its baseline resistance value when exposed to an air atmosphere. [47][48][49] The pure WO 3 sensor shows a response time of 165 s and recovery time of 132 s, which are shown for comparison in Fig S6(e). † However, the response and recovery times of the prepared sensor are 18 s and 24 s respectively.…”

Oxygen Vacancy Enhanced Gas-Sensing Performance of CeO2/Graphene Heterostructure at Room Temperature

“…According to Scherer's equation, the average sizes of CeO 2 nanoparticles in the composites are calculated to be about 20, 19, 16, 13, and 4 nm for samples (a) to (e), respectively. Figure S4 displays the Raman spectra of graphene, 22 CeO 2 , and CeO 2 /graphene composites, the evident D and G bands confirm the presence of graphene. 29,30 The G-band is attributed to the first-order scattering of the E 2g mode, 31 while the D-band is associated with the structural defects or functional groups adsorbed on the carbon basal plane.…”

“…64 Based on DFT calculations, the work function of CeO 2 (6.14 eV) is much larger than that of graphene (4.54 eV), large Schottky barrier height exists between graphene and CeO 2 , making it difficult for the electrons to transfer between them, and the system exhibits poor gas sensing performance (Figure S18b-c). 22 Since the electronegativity of Ce 3+ ions is lower, the introduction of Ce 3+ ions in CeO 2 will lower the work function and thus the difference of work function between CeO 2 {111} facets and graphene decreases. Hence, the Schottky barrier height (SBH) is lower.…”

“…For example, the composites of graphene and CeO 2 nanocubes with {100} facets exhibit high gas sensing performance, the sensitivity to 100 ppm of NO 2 at room temperature is 33%, which is enhanced by 200% as compared to the reported results (10.39%). 22 However, the {100} facets with high surface energy are usually replaced by low-energy {111} facets during growth. Therefore, how to enhance the gas sensing activity of CeO 2 nanoparticles enclosed by the most stable {111} facets is crucial for the practical application.…”

Prototyping a Gas Sensors Using CeO2 as a Matrix or Dopant in Oxide Semiconductor Systems

“…The oxygen vacancies can significantly enhance the adsorption of oxygen molecules and electrons will transfer from the oxygen vacancies from CeO 2 to the oxygen molecules, resulting in more oxygen species (especially O 2À ). These oxygen species will react with NO 2 , resulting in an abrupt change in the conductivity of the sensor [71]. The graphene sheets by their good properties as: high surface area 2630 m 2 /g, thermal conductivity in the range of 3000-5000 W/mK at room temperature carrier mobility up to 200,000 cm 2 /Vs [72], electrical conductivity of 7200 S/m [73], coming from their structure two-dimensional (2D) single atom layer is used in gas sensing and in the composite leads to increase of the electrical conductivity of CeO 2 and thus improve the performance to gas sensing room temperature [71].…”