In situ DRIFTS and temperature-programmed technology study on NH3-SCR of NO  over Cu-SSZ-13 and Cu-SAPO-34 catalysts

Ma, Lei; Cheng, Yunhui; Cavataio, Giovanni; McCabe, Robert W.; Fu, Lixin; Li, Junhua

doi:10.1016/j.apcatb.2014.03.048

Cited by 317 publications

(238 citation statements)

References 58 publications

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“…On this basis they assigned both these peaks to different unspecified types of Cu sites. Ma et al attributed this peak to a combination of both Brønsted and Lewis acid sites [4]. This shows that there has not been a consensus on assignment of the TPD peaks.…”

Section: Uv-vis Spectroscopy and H 2 -Tprmentioning

confidence: 97%

“…Assignment of the other two peaks is more complex. Earlier studies have observed the presence of both Peak 1 and 2 with Cu/SSZ-13 and H/ SSZ-13 catalysts [2][3][4][5]. Some of these studies assigned the high temperature peak to NH 3 strongly bound to Brønsted acid sites [2,4,5].…”

Section: Uv-vis Spectroscopy and H 2 -Tprmentioning

confidence: 99%

“…The general trend of all three peaks appears to be increasing height with increasing copper loading. Peak 3 at 175-198 °C can probably be assigned to desorption of loosely bound ammonia not removed during the purge step [2,4,5]. Assignment of the other two peaks is more complex.…”

Section: Uv-vis Spectroscopy and H 2 -Tprmentioning

confidence: 99%

“…In the case of Cu/ SSZ-13, two peaks are typically seen at ~250-350 and ~450-500 °C. There is no consensus as to the assignment of these: the former has been attributed to ammonia stored either on Cu 2+ sites [2,3] or both Brønsted and Lewis acid sites [4] and the latter to either Brønsted acid sites [2,4,5] or copper sites [3]. It has been shown that Cu/SSZ-13 can contain copper sites in two different locations: the 6-membered rings (6MR) and chabazite cages (8-membered rings or 8MR) [6].…”

Section: Introductionmentioning

confidence: 99%

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Ammonia Desorption Peaks Can Be Assigned to Different Copper Sites in Cu/SSZ-13

et al. 2017

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Section: Uv-vis Spectroscopy and H 2 -Tprmentioning

confidence: 97%

Section: Uv-vis Spectroscopy and H 2 -Tprmentioning

confidence: 99%

Section: Uv-vis Spectroscopy and H 2 -Tprmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ammonia Desorption Peaks Can Be Assigned to Different Copper Sites in Cu/SSZ-13

et al. 2017

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“…Thus, a number of studies have been published on Cu/SAPO-34 synthesised via one-pot synthesis or solid state ion exchange and on commercially-produced catalysts [11,12]. However, very few details are available as to the procedure of aqueous ion exchange for Cu/SAPO-34.…”

Section: Introductionmentioning

confidence: 99%

Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

et al. 2017

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Abstract:We developed a procedure for aqueous ion exchange to obtain different Cu loadings of Cu/SAPO-34 (between 0 and 2.6 wt %). The catalysts were washcoated on monoliths and characterised with respect to their activity and selectivity under standard selective catalytic reduction (SCR), fast SCR, NH 3 oxidation and NO oxidation reactions. They were further characterised using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), H 2 -temperature programmed reduction (H 2 -TPR), ultraviolet (UV)-vis spectroscopy and NH 3 adsorption. As expected, activity of all reactions increased with copper loading, due to increased number of active sites. However, the N 2 O formation during standard and fast SCR yielded interesting mechanistic information. We observed that N 2 O formation at low temperature increased with copper loading for the standard SCR reaction, while it decreased for fast SCR. The low-temperature N 2 O formation during fast SCR thus occurs predominantly over Brønsted sites. Species responsible for N 2 O formation during standard SCR, on the other hand, are formed on the copper sites. We further found that the fast SCR reaction occurs to a significant extent even over the H/SAPO-34 form. The Brønsted sites in SAPO-34 are thus active for the fast SCR reaction.

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Intrinsic Electron Localization of Metastable MoS₂ Boosts Electrocatalytic Nitrogen Reduction to Ammonia

et al. 2021

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The advancement of efficient electrocatalysts toward the nitrogen reduction reaction (NRR) is critical in sustainable ammonia synthesis under ambient pressure and temperature. Manipulating the electronic configuration of electrocatalysts is particularly vital to form metal–nitrogen (MN) bonds during the NRR through regulating the active electronic states of sites. Here, in sharp contrast to stable 2H MoS2 without metal chains, MoMo bonding in metastable polymorphs of MoS2 bulk (zigzag chain in the 1T′ phase and diamond chain in the 1T″′ phase) is discovered to significantly increase intrinsic electron localization around the metal chains. This can enhance the charge transfer from the adsorbed nitrogen molecule to the metal chains, allowing for boosted NRR kinetics. The electrochemical experiments show that the NH3 yield rate and the faradaic efficiency of the metastable 1T″′ MoS2 rich with abundant Mo–Mo bonds are about 9 and 12 times above average than those of 2H MoS2, correspondingly. Theoretical simulations reveal the high local electron density surrounding the MoMo chains and sites can promote π back‐donation, which is beneficial for increasing nitrogen adsorption, strengthening the MN bonds, and reducing the cleavage barrier of the triple NN bond.

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In situ DRIFTS and temperature-programmed technology study on NH3-SCR of NO over Cu-SSZ-13 and Cu-SAPO-34 catalysts

Cited by 317 publications

References 58 publications

Ammonia Desorption Peaks Can Be Assigned to Different Copper Sites in Cu/SSZ-13

Ammonia Desorption Peaks Can Be Assigned to Different Copper Sites in Cu/SSZ-13

Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

Intrinsic Electron Localization of Metastable MoS₂ Boosts Electrocatalytic Nitrogen Reduction to Ammonia

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In situ DRIFTS and temperature-programmed technology study on NH3-SCR of NO over Cu-SSZ-13 and Cu-SAPO-34 catalysts

Cited by 317 publications

References 58 publications

Ammonia Desorption Peaks Can Be Assigned to Different Copper Sites in Cu/SSZ-13

Ammonia Desorption Peaks Can Be Assigned to Different Copper Sites in Cu/SSZ-13

Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

Intrinsic Electron Localization of Metastable MoS2 Boosts Electrocatalytic Nitrogen Reduction to Ammonia

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Intrinsic Electron Localization of Metastable MoS₂ Boosts Electrocatalytic Nitrogen Reduction to Ammonia