Remarkably Enhanced Room-Temperature Hydrogen Sensing of SnO2 Nanoflowers via Vacuum Annealing Treatment

Abstract

In this work, SnO2 nanoflowers synthesized by a hydrothermal method were employed as hydrogen sensing materials. The as-synthesized SnO2 nanoflowers consisted of cuboid-like SnO2 nanorods with tetragonal structures. A great increase in the relative content of surface-adsorbed oxygen was observed after the vacuum annealing treatment, and this increase could have been due to the increase in surface oxygen vacancies serving as preferential adsorption sites for oxygen species. Annealing treatment resulted in an 8% increase in the specific surface area of the samples. Moreover, the conductivity of the sensors decreased after the annealing treatment, which should be attributed to the increase in electron scattering around the defects and the compensated donor behavior of the oxygen vacancies due to the surface oxygen adsorption. The hydrogen sensors of the annealed samples, compared to those of the unannealed samples, exhibited a much higher sensitivity and faster response rate. The sensor response factor and response rate increased from 27.1% to 80.2% and 0.34%/s to 1.15%/s, respectively. This remarkable enhancement in sensing performance induced by the annealing treatment could be attributed to the larger specific surface areas and higher amount of surface-adsorbed oxygen, which provides a greater reaction space for hydrogen. Moreover, the sensors with annealed SnO2 nanoflowers also exhibited high selectivity towards hydrogen against CH4, CO, and ethanol.

A Low‐Power CuSCN Hydrogen Sensor Operating Reversibly at Room Temperature

“…When compared to the relevant literature, our Pd-based CuSCN sensor offers attractive attributes including, high sensitivity, reliable cyclic hydrogen sensing at room temperature and relatively fast response and recovery times over a broad range of analyte concentrations. [24,29,[50][51][52][53][54][55]65] Among those, the ability to operate at room temperature continuously or intermittently, at low power, are all very attractive and could prove enabling characteristic for numerous emerging applications aiming at monitoring H 2 concentrations using distributed sensing nodes as part of the emerging Internet of Things device ecosystem. To objectively compare the various technologies found in the literature, we have summarized (Figure 6) the key operating parameters of the best-performing hydrogen sensors that are able to operate at room temperature.…”

Recent Advances and Challenges of Nanomaterials-Based Hydrogen Sensors

“…However, the SnO 2 based gas sensors exhibited poor selectivity, long response/recovery time, and a need for high operating temperature, high power consumption and complex integration structure accordingly [110]. To resolve these issues, researchers have devoted their efforts to improve the sensing performance of SnO 2 by applying various methods, such as morphological modifications [105,106,111] and metallic doping [87,[112][113][114][115]. Since the gas-sensing performance of SnO 2 -based gas sensors depends strongly on the fabrication morphology, Shen et al in [105] investigated nanofilms, nanorods and nanowires at various hydrogen concentrations at high ambient temperatures, as presented in Figure 21a,f.…”

“…Liu et al in 2018 developed a hydrogen gas sensor based on hydrothermal synthesized SnO 2 nanoflowers [111]. This nanostructure increased the effective surface significantly for oxygen adsorption.…”

Acetone Sensing Properties and Mechanism of SnO2 Thick-Films

“…Among the semiconductor metal oxides used in gas sensors, SnO 2 has received considerable attention in science and technology for many years. SnO 2 with a wide band gap of 3.6 eV is a significant functional material applicable for solar cells, catalysis, transparent electrodes, and, particularly, in gas sensor devices because of its unique optical, catalytic, and electrical properties [ 1 , 2 , 3 , 4 , 5 , 6 ]. It has been widely used to detect toxic chemicals such as CH 4 , H 2 , C 2 H 5 OH, gasoline, CO, C 2 H 2 , NO 2 , NO, and H 2 S [ 7 ].…”