Single Mo atoms paired with neighbouring Ti atoms catalytically decompose ammonium bisulfate formed in low-temperature SCR

Abstract

We developed a TiO2-supported single-atom Mo catalyst (Mo1/TiO2) where single Mo atoms paired with the neighboring surface Ti atoms function as Mo–Ti acid–base dual sites, realizing the decomposition of ABS at ∼225 °C.

Abatement of Nitrogen Oxides via Selective Catalytic Reduction over Ce1–W1 Atom-Pair Sites

“…As shown in Figure a, Ce 1 –W 1 /TiO 2 possesses abundant strong Lewis acid sites, characteristic of the bands at 1172–1240 cm –1 , ,, and the Lewis acid sites have also been reported to be active sites of CeO 2 -based , or traditional V–W/TiO 2 SCR catalysts. − After comparing the DRIFT spectrum of Ce 1 –W 1 /TiO 2 to those of W 1 /TiO 2 , Ce 1 /TiO 2 , and TiO 2 , it is convincing that the W anchoring leads to the generation of abundant strong Lewis acid sites on Ce 1 –W 1 /TiO 2 , similar to the previously reported results on Ce–W/TiO 2 . , Only Lewis acid sites are observed on the surface of Ce 1 –W 1 /TiO 2 and W 1 /TiO 2 , indicating that the monotungstate species are predominant on these catalysts, consistent with the results in STEM. Although Ce 1 –W 1 /TiO 2 and Ce 1 /TiO 2 presented a similar CeO 4 tetragonal motif (Figure S7), Brønsted acid sites characteristics of the broad bands at 1386–1480 cm –1 are observed on Ce 1 /TiO 2 ,, but are absent on the surfaces of Ce 1 –W 1 /TiO 2 , also implicating the existence of the synergy within Ce 1 –W 1 atom pairs.…”

“…6,33 Only Lewis acid sites are observed on the surface of Ce 1 −W 1 /TiO 2 and W 1 /TiO 2 , indicating that the monotungstate species are predominant on these catalysts, 12 consistent with the results in STEM. Although Ce 1 −W 1 /TiO 2 and Ce 1 /TiO 2 presented a similar CeO 4 tetragonal motif (Figure S7), Brønsted acid sites characteristics of the broad bands at 1386−1480 cm −1 are observed on Ce 1 /TiO 2 5,26,34 but are absent on the surfaces of Ce 1 −W 1 /TiO 2 , also implicating the existence of the synergy within Ce 1 −W 1 atom pairs. We further investigated the adsorption ability of the acidic sites to NH 3 in a range of SCR operating temperatures and used in situ DRIFT spectra to directly compare the evolution of adsorbed NH 3 over Ce 1 −W 1 /TiO 2 and Ce 1 /TiO 2 in a temperature-programmed mode (Figure 3b,c).…”

“…The oxidation states of W and Ti for Ce 1 –W 1 /TiO 2 and W 1 /TiO 2 almost remain unchanged after the Ce anchoring (Figure S6). A peak attributed to OH appeared in the O 1s XPS spectra of Ce 1 /TiO 2 at ∼ 532.8 eV (Figure S6c), indicating the formation of Ce–O­(H)–Ti structures on Ce 1 /TiO 2 (Figure S7).…”

“…The oxidation states of W and Ti for Ce 1 −W 1 /TiO 2 and W 1 /TiO 2 almost remain unchanged after the Ce anchoring (Figure S6). A peak attributed to OH appeared in the O 1s XPS spectra of Ce 1 /TiO 2 at ∼ 532.8 eV (Figure S6c), 26 Although the oxidation states of W are not changed after the Ce anchoring, the synergy makes the frontier orbital electrons of W delocalized in comparison to those of the isolated W of W 1 /TiO 2 (Figure 2b). This delocalized electron structure often favors O 2 activation with a multielectron transfer process.…”

Integrating Atomically Dispersed Sites with Versatile Oxide Supports to Construct Efficient Thermocatalysts: Toward Comprehensive Treatment of Flue Gas Pollutants

“…(i) Initiation temperature of SO 2 release over ABS deposited catalysts. Reproduced with permission from ref . Copyright 2022, Royal Society of Chemistry.…”