Single-Atom Pt⁺ Derived from the Laser Dissociation of a Platinum Cluster: Insights into Nonoxidative Alkane Conversion

Abstract

The Pt:SC2H4Ph clusters were synthesized via a modified approach in our previous work. 1 Typically, 0.1 mmol H2PtCl6 and 0.1 mmol phenylethanethiol were added to a 15 mL THF solution. After stirring for 20 min, an aqueous solution of NaBH4 (1.5 mmol) was added. Then, (ratio of thiol/Pt: 1/1) was added, and some black precipitates were immediately formed. Then the precipitates were thoroughly washed with methanol and extracted with CH2Cl2 to give Pt clusters, which are characterized by HR-MS analyses. Generation of single-atom Pt + for the non-oxidative alkane conversionThe Exactive plus EMR MS system (Thermo) is implemented with an ultraviolet laser dissociation module (Scheme S1A), where the charge detector at the back of high-energy collision dissociation (HCD) chamber was removed and an MgF2 window was implemented. The 193 nm laser of 1~2 mJ/pulse (a pulse width of 5 ns), generated by an ArF excimer laser (Gam laser, Orlando, FL, USA), was coaxially introduced into the HCD dissociation chamber though the MgF2 window. The laser beam was focused with a diameter about 2 mm. The Pt clusters were dissolved in an electrospray solution (70 v% CH2Cl2/30 v% methanol) with a concentration of 1 mg/mL. The Pt cluster ions were formed by nanoflow electrospray ionization (nano-ESI) with a spray voltage of 1.5 kV in positive MS mode and the sample injection flowrate was about 300 nL/min. The Pt + cluster ions were transferred into the HCD chamber. The excimer laser was operated in pulsed mode with pulse length of 5 ns and frequency of 3 Hz (with about 300 ms interval between S3/S39 adjacent shots), which was roughly synchronized with the duty cycle of the MS analysis and avoided the photoionization of the conversion intermediates and products.The Pt cluster dissociation-HRMS characterization experiment included following steps (Scheme S1B): the ligand-protected Pt clusters were firstly ionized by nano-ESI and guided into the HCD chamber (no activation energy was applied during the process); then, 5 ns single-shot laser was applied to dissociated the ligand-protected Pt clusters and generate the single-atom Pt cations, which was kept off during conversion and detection to avoid post-activation and ionization of the conversion intermediate and product ions; the Pt + were trapped in the HCD chamber and in-situ reacted with the alkane gas reagents (1 v% alkane gas mixed with 99 v% N2, about 20 mTorr in total; 298 K) for about 100 ms; the conversion intermediate and product ions were transfers to the orbitrap analyser in about 10 ms and characterized with a mass resolution of 140,000 (m/z = 200) before the arrive of next laser shot pulse. HRMS data were collected in a profile mode (continuous mode). 195 Pt + was utilized as the internal standard to calibrate the detected m/z values of alkane conversion species. No collision and activation energy were applied to the Pt + species during the whole alkane conversion process. DFT calculationAll DFT calculations have been performed using Gaussian 16 package 2 . B3LYP functional [3][4] ...

Propylene Synthesis: Recent Advances in the Use of Pt-Based Catalysts for Propane Dehydrogenation Reaction

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“…The addition of H 2 seems to help maintain the surface states of the active metals in the Pt-Sn/SiO 2 catalysts under the reaction conditions. [13]. Moreover, Pt-Pt ensembles seem to be responsible for the propylene deep dehydrogenation and hydrogenolysis, so the insolation of Pt atoms could be an effective strategy to inhibit the side reactions [14].…”

Simple and high-yield preparation of carbon-black-supported ∼1 nm platinum nanoclusters and their oxygen reduction reactivity

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A Revealing Insight into Gold Cluster Photocatalysts: Visible versus (Vacuum) Ultraviolet Light

“…To understand the atomistic details of the photoreactions of Au25 , we performed PD-MS on a homemade system of a Thermo Exactive plus EMR HRMS instrument (Figure S1) using different lasers (e.g., 455, 193, and 154 nm). , Note that the effect of the P25 support was omitted here, as the absorption of P25 occurs at <400 nm. Figure S5 showed that a single MS peak at 4252.58 Da was ascribed to the intact Au25 cluster.…”