An operando FT-IR study of the NOx SCR over Co-HFER and Fe-HFER using acetylene as a reducing agent

The Role of Nitrate on the Sol-Gel Spread Self-Combustion Process and Its Effect on the NH3-SCR Activity of Magnetic Iron-Based Catalyst

“…At the same time, the bidentate nitrates (1002 and 1547 cm −1 ), M-NO2 formed by the reaction between M-OH and NOx (1350 and 3639 cm −1 ) and the bridging nitrate (1618 cm −1 ) species appeared [44][45][46][47]. As shown in Figure 8B, after nitrogen oxide species adsorption and N2 purge at 250 °C, Fe85Ce10W5-CP-CA showed several bands ascribed to M-NO2 formed by the reaction between M-OH and NOx (1353 cm −1 ), bidentate nitrates (1560 cm −1 ), and bridging nitrate (1621 cm −1 ), respectively [48][49][50]. After the introduction of NH3 for 10 s, the intensity of adsorption peaks of M-NO2 (1353 cm −1 ) and bridging nitrate (1621 cm −1 ) became weakened, and the band at 1560 cm −1 Figure 7.…”

“…As illustrated in Figure 8A, after NH 3 adsorption and N 2 purge at 250 • C, Fe 85 Ce 10 W 5 -CP-CA showed several bands located at 1188, 1406, 1587, 3256, and 3351 cm −1 . The bands located at 1188 and 1587 cm −1 can be attributed to the coordinated NH 3 on the Lewis acid sites, and the band located at 1406 cm −1 can be ascribed to the ionic NH 4 + bound to the Brønsted acid site, while the bands of 3256 and 3351 cm −1 corresponded to the N-H stretching modes of the coordinated NH 3 connected to the Lewis acid sites [27,[44][45][46][47][48]. After the introduction of NO + O 2 for 10 s, the adsorption peaks of the coordinated NH 3 on the Lewis acid sites (located at 1188 and 1587 cm −1 ) and the N-H stretching modes of coordinated NH 3 connected to the Lewis acid sites (located at 3256 and 3351 cm −1 ) disappeared, and the intensity of ionic NH 4 + bound to the Brønsted acid site at 1406 cm −1 also became weakened.…”

“…After the introduction of NH 3 for 10 s, the intensity of adsorption peaks of M-NO 2 (1353 cm −1 ) and bridging nitrate (1621 cm −1 ) became weakened, and the band at 1560 cm −1 ascribed to the bidentate nitrates disappeared. The IR bands assigned to the coordinated NH 3 on the Lewis acid sites (1189 and 1587 cm −1 ), the ionic NH 4 + bound to the Brønsted acid site (1439 cm −1 ), and the N-H stretching modes of the coordinated NH 3 connected to the Lewis acid sites (3255 and 3364 cm −1 ) appeared [27,[47][48][49][50]. Figure 8C shows the experimental results of the introduction of NH 3 + NO+O 2 gases over Fe 85 Ce 10 W 5 -CP-CA at 250 • C. It can clearly be seen that the IR bands ascribed to the coordinated NH 3, the N-H stretching modes of the coordinated NH 3 and the ionic NH 4 + appeared, and their intensity gradually became stronger with the increase in the NH 3 + NO + O 2 introduction.…”

“…ascribed to the bidentate nitrates disappeared. The IR bands assigned to the coordinated NH3 on the Lewis acid sites (1189 and 1587 cm −1 ), the ionic NH4 + bound to the Brønsted acid site (1439 cm −1 ), and the N-H stretching modes of the coordinated NH3 connected to the Lewis acid sites (3255 and 3364 cm −1 ) appeared [27,[47][48][49][50]. Figure 8C shows the experimental results of the introduction of NH3 + NO+O2 gases over Fe85Ce10W5-CP-CA at 250 °C.…”

Controlled preparation of multiple mesoporous CoAl-LDHs nanosheets for the high performance of NOx detection at room temperature

“…When the sensor was exposed to air, oxygen could easily be adsorbed on its outer surface layers, and easily diffused into the pores of CA2-1, thus capturing the free electrons to form chemically adsorption oxygen, reducing the conductivity of the materials, and placing them in a state of high resistance. 45 Similarly, when the sensor was exposed to NO x gas, it could capture free electrons directly from the sensor surface to form NO À /NO 2 À and react with O 2 À to form NO 2 À / NO 3 À , which would eventually increase the hole density on the surface and rapidly reduce the resistivity (Scheme 1f). 46 The reaction equation on the surface of the sensor is described as follows (see eqn (4)-(6)):…”