Thermal stable Pt clusters anchored by K/TiO_(2)—Al_(2)O_(3)for efficient cycloalkane dehydrogenation

Catalytic dehydrogenation of cycloalkanes is considered a valuable endothermic process for alleviating the thermal barrier issue of hypersonic vehicles.However,conventional Pt-based catalysts often face the severe problem of metal sintering under high-temperature conditions.Herein,we develop an efficient K_(2)CO_(3)-modified Pt/TiO_(2)—Al_(2)O_(3)(K—Pt/TA)for cycloalkane dehydrogenation.The optimized K—Pt/TA showed a high specific activity above 27.9 mol·mol^(-1)·s^(-1)(H_(2)/Pt),with toluene selectivity above 90.0%at 600℃with a high weight hourly space velocity of 266.4 h^(-1).The introduction of alkali metal ions could generate titanate layers after high-temperature hydrogen reduction treatment,which promotes the generation of oxygen vacancy defects to anchored Pt clusters.In addition,the titanate layers could weaken the surface acidity of catalysts and inhibit side reactions,including pyrolysis,polymerization,and isomerization reactions.Thus,this work provides a modification method to develop efficient and stable dehydrogenation catalysts under high-temperature conditions.

Enhanced performance for propane dehydrogenation through Pt clusters alloying with copper in zeolite

Metal alloys have been widely applied for heterogeneous catalysis,especially alkane dehydrogenation.However,the catalysts always suffer from sintering and coke deposition due to the rigorous reaction conditions.Herein,we described an original approach to prepare a catalyst where highly dispersed Pt clusters alloying with copper were encapsulated in silicalite-1(S-1)zeolite for propane dehydrogenation(PDH).The introduction of Cu species significantly enhances the catalytic activity and prolongs the lifetime of the catalyst.0.1Pt0.4CuK@S-1 exhibits a propane conversion of 24.8%with 98.2%selectivity of propene,and the specific activity of propylene formation is up to 32 mol·gPt^(−1)·h^(−1)at 500℃.No obvious deactivation is observed even after 73 h on stream,affording an extremely low deactivation constant of 0.00032 h^(−1).The excellent activity and stability are ascribed to the confinement of zeolites and the stabilization of Cu species for Pt clusters.

Highly dispersed Pt clusters encapsulated in MIL-125-NH_(2) via in situ auto-reduction method for photocatalytic H_(2) production under visible light

Efficient hydrogen production via photocatalysis with high utilization efficiency of Pt cocatalyst is of great importance for sustainable development. In this work, we report an in situ auto-reduction strategy to encapsulate highly dispersed Pt clusters inside the cages of MIL-125-NH_(2). The amino groups in MIL-125-NH_(2) first react with formaldehyde to form reducing groups (i.e.,–NH-CH_(2)OH), which can in situ auto-reduce the confined Pt^(2+) ions to ultrasmall Pt clusters within the cavities. With optimized Pt content, photocatalytic H_(2) production over the obtained Pt(1.5)/MIL-125-NH-CH_(2)OH catalyst with 1.43 wt.% Pt loading achieved as high as 4,496.4 µmol·g^(-1)·h^(-1) under visible light (λ > 420 nm) due to the facilitated transfer and separation of the photo-induced charger carriers arising from the synergetic effects between highly dispersed Pt clusters and MIL-125-NH-CH_(2)OH framework. This in situ auto-reduction strategy may be extended to encapsulate various kinds of metal or alloy clusters/nanoparticles within amino-functioned metal-organic frameworks (MOFs) with superior properties and excellent performance.

Fully-exposed Pt clusters stabilized on Sn-decorated nanodiamond/graphene hybrid support for efficient ethylbenzene direct dehydrogenation

The pursuit of energy conservation and environmental protection has always been a hot topic in the catalytic fields,which is inseparable from the rational designing of efficient catalysts and an in-depth understanding of the catalytic reaction mechanism.In this work,fully-exposed Pt clusters were fabricated on the atomically dispersed Sn decorated nanodiamond/graphene(Sn-ND@G)hybrid support and employed for direct dehydrogenation(DDH)of ethylbenzene(EB)to styrene(ST).The detailed structural characterizations revealed the fully-exposed Pt clusters were stabilized on Sn-ND@G,assisted by the spatial separation of atomically dispersed Sn species.The as-prepared Pt/Sn-ND@G catalyst showed enhanced ST yield(136.2 molEB·molpt-1·h-1 EB conversion rate and 99.7%ST selectivity)and robust long-term stability at 500℃for the EB DDH reaction,compared with the traditional ND@G supported Pt nanoparticle catalyst(Pt/ND@G).The ST prefers to desorb from the fully-exposed Pt clusters,resulting in the enhanced DDH catalytic performance of the Pt/Sn-ND@G catalyst.The present work paves a new way for designing highly dispersed and stable supported metal catalysts for DDH reactions.

Interplay between geometric and electronic structures of Pt entities over TiO_(2) for CO oxidation

Monodispersed Pt colloids with a mean size of 2 nm were deposited uniformly on the {110} facets of a rod-shaped rutile TiO_(2),forming a well-defined Pt/TiO_(2) system.Oxidative treatment of this precursor at elevated temperatures re-dispersed the Pt particles into clusters and single-atoms.Air-calcination at 673 K partially oxidized the Pt particle surface,while calcination at 773 K yielded Pt Oxclusters of 1.6 nm in 7–8 atomic layers.Further calcination at 873 K formed a mixture of raft-like PtO_(x) clusters(1.6 nm,1–2 atomic layers) and cationic single-atoms.When tested for CO oxidation at 373 K,the Pt particles showed a higher activity than the Pt Oxclusters,whereas the cationic single-atoms were much less active.Subsequent H_(2)-reduction at 473 K converted the partially oxidized Pt particles into the metallic species,but they were encapsulated by TiO_(2)–xoverlayers because of the strong metal–support interactions,which decreased the activity dramatically.H_(2)-reduction of the PtO_(x) clusters at473 K enhanced the fraction of metallic Pt species without changing the size and geometry,and promoted the activity substantially.H_(2)-treatment of Pt single-atoms at 473 K increased the activity only moderately because most Pt species still kept at cationic species.These results straightforwardly differentiated the catalytic behavior of Pt particles,clusters and single-atoms at the same metal loading and over the same TiO_(2) support,and further demonstrated that the electronic structures of Pt entities played a decisive role in the catalytic oxidation,in addition to the specified sizes.

Assembling molybdenum-doped platinum clusters into a coral-like nanostructure for highly enhanced oxygen reduction

Regulating the electronic and geometric structures of electrocatalysts is an effective strategy to boost their catalytic properties.Herein,a coral-like nanostructure is assembled with Mo-doped Pt clusters to form a highly active catalyst toward the oxygen reduction reaction(ORR).The advantages of a Mo-doped porous skeleton,grain boundaries,and MoOx species on the Pt cluster surfaces synergistically boost the electrocatalytic performance.This unique architecture delivers 3.5-and 2.8-fold higher mass and specific activities,respectively,than commercial Pt/C.Density functional theory calculations reveal that the Mo-doped Pt clusters have an optimized Pt–O bond length of 2.110Å,which weakens the adsorption energy of the intermediate O*to yield great ORR activity.Moreover,the catalyst shows a decay in the half-wave potential of only 8 mV after 10,000 cycles of accelerated durability testing.The high stability arises from the increased dissociation energy of Pt atoms and the stable architecture of the coral-like structure of clusters.

Enhanced production of hydrogen via catalytic methane decomposition on a Pt_(7)-Ni(110)substrate:a reactive molecular dynamics investigation

Numerous researchers in the energy field are engaged in a competitive race to advance hydrogen as a clean and environmentally friendly fuel.Studies have been conducted on the different aspects of hydrogen,including its production,storage,transportation and utilization.The catalytic methane decomposition technique for hydrogen production is an environmentally friendly process that avoids generating carbon dioxide gas,which contributes to the greenhouse effect.Catalysts play a crucial role in facilitating rapid,cost-effective and efficient production of hydrogen using this technique.In this study,reactive molecular dynamics simulations were employed to examine the impact of Pt7 cluster decoration on the surface of a Ni(110)catalyst,referred to as Pt7-Ni(110),on the rates of methane dissociation and molecular hydrogen production.The reactive force field was employed to model the atomic interactions that enabled the formation and dissociation of chemical bonds.Our reactive molecular dynamics simulations using the Pt7-Ni(110)catalyst revealed a notable decrease in the number of methane molecules,specifically~11.89 molecules per picosecond.The rate was approximately four times higher than that of the simulation system utilizing a Ni(110)catalyst and approximately six times higher than that of the pure methane,no-catalyst system.The number of hydrogen molecules generated during a simulation period of 150000 fs was greater on the Pt7-Ni(110)surface than in both the Ni(110)and pure methane systems.This was due to the presence of numerous dissociated hydrogen atoms on the Pt7-Ni(110)surface.

Enhanced Catalysis of Pt_(3) Clusters Supported on Graphene for N–H Bond Dissociation

We report an in-depth study of catalytic N–H bond dissociation with typical platinum clusters on gra-phene supports.Among all the pristine graphene-and defective graphene-supported Pt clusters of different sizes that were studied,the Pt_(3)/G cluster possesses the highest reactivity and lowest activa-tion barriers for each step of N–H dissociation in the decomposition of ammonia.

A DFT＋U Investigation on Methylamine Decomposition Catalyzed by Pt4 Cluster Supported on Oxygen Defective Rutile（110） TiO2

The adsorption and decomposition mechanisms of methylamine catalyzed by Pt4 cluster supported on ruffle（110） titania[namely, Pt4/TiO2-R（110）] were investigated via density functional theory slab calculations with Hubbard corrections（DFT＋U）. The adsorption energies under the most stable configuration of the possible species and the energy barriers of the possible elementary reactions involved in methylamine decomposition were obtained. Through systematic calculations for the reaction mechanism of methylamine decomposition on the PtVTiO2-R（110）, the most possible decomposition path is CHaNH2→CH2NH2＋H→CH2NH＋2H→CHNH＋3H→HCN＋4H→CN＋5H, which is similar to that of methylamine dissociation catalyzed by Pt（100） surface.