Pyrolysis of mass-selected (V₂O₅)_NO⁻ (N = 1–6) clusters in a high-temperature linear ion trap reactor

Abstract

A high-temperature linear ion trap that can stably run up to 873 K was newly designed and installed into a homemade reflectron time-of-flight mass spectrometer coupled with a laser ablation cluster source and a quadrupole mass filter. The instrument was used to study the pyrolysis behavior of mass-selected (V2O5) NO− ( N = 1−6) cluster anions and the dissociation channels were clarified with atomistic precision. Similar to the dissociation behavior of the heated metal oxide cluster cations reported in literature, the desorption of either atomic oxygen atom or molecular O2 prevailed for the (V2O5) NO− clusters with N = 2−5 at 873 K. However, novel dissociation channels involving fragmentation of (V2O5) NO− to small-sized V xO y− anions concurrent with the release of neutral vanadium oxide species were identified for the clusters with N = 3−6. Significant variations of branching ratios for different dissociation channels were observed as a function of cluster size. The kinetic studies indicate that the dissociation rates of (V2O5) NO− monotonically increased with the increase of cluster size. The internal energies carried by the (V2O5) NO− clusters at 873 K as well as the energetics data for dissociation channels have been theoretically calculated to rationalize the experimental observations. The decomposition behavior of vanadium oxide clusters from this study can provide new insights into the pyrolysis mechanism of metal oxide nanoparticles that are widely used in high temperature catalysis.

Filtration of the preferred catalyst for reverse water-gas shift among Rhn−(n= 3–11) clusters by mass spectrometry under variable temperatures

“…The Rh n − and Rh n O − cluster anions were generated by laser ablation of a rotating and translating Rh disk in the presence of pure helium carrier gas (99.9999% purity) and 0.001% O 2 seeded in the He, respectively, with a backing pressure of about 5.0 standard atmospheres. The Rh n − and the Rh n O − ( n = 3–11) clusters were mass-selected using a quadrupole mass filter 31 and then entered into a high-temperature linear ion trap (LIT) 30 reactor where they were confined and heated to a controlled temperature by collisions with a pulse of buffer gas (He) and then interacted with another pulse of pure (or diluted) CO 2 and diluted H 2 , respectively. In addition, the reactions of CO 2 (or H 2 ) pre-adsorbed products Rh n CO 2 − (or Rh n H 2 − ) with H 2 (or CO 2 ) were performed to explore the impact of co-adsorption.…”

“…The temperature was monitored using a thermocouple positioned in the LIT holder. 30 The cluster ions ejected from the LIT were detected using a reflectron TOF-MS, 32 which was used to measure the masses and the abundance of the reactant and product ions.…”

“…27,28 The endothermic nature of CO 2 hydrogenation requires external energies, while related conversions mediated with gas-phase species under high temperatures have rarely been reported. 29 Herein, by employing a homemade time-of-flight mass spectrometer (TOF-MS) coupled with a newly-developed high-temperature ion trap reactor that can trap ions to react with reactants at a temperature up to 873 K, 30 the catalysis of the RWGS mediated with the Rh n − ( n = 3–11) clusters was identified under variable temperatures (298–783 K) and the critical temperature that each elementary step (Rh n − + CO 2 and Rh n O − + H 2 ) requires to take place was identified. These experiments demonstrate that Rh 4 − strikingly surpasses other Rh n − clusters to drive the RWGS reaction at a mild starting temperature (∼440 K), while the co-adsorption of reactants on Rh n − suppresses the catalysis by inhibiting H 2 oxidation and/or CO desorption steps, emphasizing the significance to separate the injection of reactants into the reactor.…”

Selective Reduction of NO into N2 Catalyzed by Rh1-Doped Cluster Anions RhCe2O3–5–

“…In addition to room-temperature experiments, the temperature-controllable experiments were performed by introducing the cluster-source generated and mass-selected RhCe 2 O 4,5 – clusters into a newly designed high-temperature LIT reactor, where they were confined and heated to variable temperatures ( T = 298–723 K) by collisions with a pulse of preheated buffer gas (He) and then interacted with another pulse of CO. The reactions of mass-selected RhCe 2 O 3,5 – clusters with the mixture of NO and CO were also performed in a single-ion-trap reactor under different temperatures (298, 523, and 573 K).…”

Size-Dependent Reactivity of Con– (n = 5–25) Cluster Anions toward Carbon Dioxide

“…The Co n – clusters of interest ( n = 5–25) were mass-selected using a quadrupole mass filter (QMF) and then entered into a high-temperature LIT reactor, where they were confined and heated to a controlled temperature by collisions with a pulse of buffer gas (He) and then interacted with another pulse of CO 2 . The high-temperature LIT was formed by a set of hexapole rods and two cap electrodes that were heated by a resistive heater. The temperature was monitored by using a thermocouple positioned in the LIT holder.…”