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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Stepwise synthesis, characterization, and electrochemical properties of ordered mesoporous carbons containing well-dispersed Pt nanoparticles using a functionalized template route

A stepwise method is described for the accurately controlled growth of Pt nanoparticles supported on ordered mesoporous carbons (Pt-OMC) by the nanocasting of carbon and metal precursors in the pore channels of mesoporous silicas functionalized with Si-H groups. Results obtained from N{sub 2} adsorption/desorption isotherms and transmission electron microscopy showed well-dispersed Pt nanoparticles (2-3 nm) on Pt-OMC with high surface area (837 m{sup 2} g{sup -1}) and regular pore channels (2.9 nm), which facilitate reactant/product diffusion. X-ray diffraction and X-ray photoelectron spectroscopy indicated that Pt nanoparticles in the Pt-OMC sample were mostly present in the metallic form of a face-centered cubic (fcc) crystalline structure. The Pt-OMC catalyst was found to have superior electrocatalytic properties during oxygen reduction reaction as compared to typical commercial electrocatalysts. - Graphical abstract: A novel procedure has been developed to synthesize ordered carbon mesoporous carbons (OMC) containing well-dispersed and highly electrocatalytic Pt nanoparticles (Pt-OMC) for oxygen reduction reaction. Highlights: > A novel method to incorporate nanosized Pt particles on nanostructure carbons. > Functionalized silica templates were used to control size and distribution of Pt nanoparticles. > Electrochemical measurements of oxygen reduction demonstrated high catalytic activity compared to common commercial catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Directly patternable SnO{sub 2} thin films incorporating Pt nanoparticles

Highlights: • Direct-patterning of SnO{sub 2} films incorporated with Pt nanoparticles. • Pt incorporated SnO{sub 2} thin films by using photochemical solution deposition. • Reduction catalytic behavior of Pt nanoparticles. • Progress reduction of SnO{sub 2} with increasing amount of Pt nanoparticles. • Enhanced electrical conductivity of SnO{sub 2} films with Pt nanoparticles incorporation. - Abstract: Direct-patterning of SnO{sub 2} films incorporating Pt nanoparticles was performed by using a photochemical solution deposition without a photoresist or dry etching. Incorporating Pt nanoparticles into these films had a slight effect on their crystallinity and almost no effect on their transmittance. The inclusion of Pt nanoparticles enhanced the electrical conductivity of the SnO{sub 2} thin films compared to their pristine forms. The chemical bonding state of the films was analyzed by X-ray photoelectron spectroscopy to investigate the effect of the Pt nanoparticles on the carrier concentration in the film. It was concluded that the reduction of SnO{sub 2} thin films by Pt nanoparticles progressed as a result of the presence of the Pt nanoparticles, causing an oxygen deficiency to develop in SnO{sub 2} and thereby influencing the carrier concentration of the film.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Ordered Pt 3 Co Intermetallic Nanoparticles Derived from Metal–Organic Frameworks for Oxygen Reduction

Highly ordered Pt alloy structures are proved effective to improve their catalytic activity and stability for the oxygen reduction reaction (ORR) for proton exchange membrane fuel cells. Here, we report a new approach to preparing ordered Pt 3 Co intermetallic nanoparticles through a facile thermal treatment of Pt nanoparticles supported on Co-doped metal-organic framework (MOF)-derived carbon. In particular, the atomically dispersed Co sites, which are originally embedded into MOF-derived carbon, diffuse into Pt nanocrystals and form ordered Pt 3 Co structures. It is very crucial for the formation of the ordered Pt 3 Co to carefully control the doping content of Co into the MOFs and the heating temperatures for Co diffusion. The optimal Pt 3 Co nanoparticle catalyst has achieved significantly enhanced activity and stability, exhibiting a half-wave potential up to 0.92 V vs. RHE and only losing 12 mV after 30,000 potential cycling between 0.6 and 1.0 V. The highly ordered intermetallic structure was retained after the accelerated stress tests evidenced by atomic-scale elemental mapping. Fuel cell tests further verified the high intrinsic activity of the ordered Pt 3 Co catalysts. Unlike the direct use of MOF-derived carbon supports for depositing Pt, we utilized MOF-derived carbon containing atomically dispersed Co sites as Co sources to prepare ordered Pt 3 Co intermetallic catalysts. Finally, the new synthesis approach provides an effective strategy to develop active and stable Pt alloy catalysts by leveraging the unique properties of MOFs such as 3D structures, high surface areas, and controlled nitrogen doping.

25 ENERGY STORAGE↗
DOE OSTI2018

Ultrathin Pt x Sn 1–x Nanowires for Methanol and Ethanol Oxidation Reactions: Tuning Performance by Varying Chemical Composition

Pt-based alloys denote promising catalysts for the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR), due to their enhanced activity toward alcohol-oxidation reactions and reduced cost as compared with Pt alone. Among all of these binary systems, PtSn has been reported to exhibit superior methanol/ethanol oxidation activity. In this paper, we deliberatively tailor chemical composition, reduce size, and optimize morphology of the catalyst in an effort to understand structure–property correlations that can be used to improve upon the electrocatalytic activity of these systems. Previous work performed by our group suggested that Pt-based catalysts, possessing an ultrathin one-dimensional (1D) structure, dramatically promote both cathodic and anodic reactions with respect to their zero-dimensional (0D) counterparts. Herein, a novel set of ultrathin binary Pt–Sn 1D nanowire (NW) catalysts with rationally controlled chemical compositions, i.e., Pt 9 Sn 1 , Pt 8 Sn 2 , and Pt 7 Sn 3 , has been synthesized using a facile, room-temperature, wet-solution-based method. The crystallinity and chemical composition of these as-prepared samples were initially characterized using XRD, XPS, and EDX. Results revealed that this synthetic protocol could successfully generate PtSn alloys with purposely tunable chemical compositions. TEM and HRTEM verified the structural integrity of our ultrathin 1D NW morphology for our Pt 9 Sn 1 , Pt 8 Sn 2 , and Pt 7 Sn 3 samples. The effects of varying Sn content within these alloy samples toward the electro-oxidation reaction of methanol and ethanol were probed using cyclic voltammetry (CV) in acidic media. Finally, within this series, we find that the optimized chemical composition for both the MOR and the EOR is Pt 7 Sn 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enhanced Electrocatalytic Hydrogen Evolution Activity in Single-Atom Pt-Decorated VS 2 Nanosheets

Enhancing catalytic activity by decorating noble metals in catalysts provides an opportunity for promoting the electrocatalytic hydrogen evolution reaction (HER) application. However, there are few systematic studies on regulating the structures of noble metals in catalytic materials and investigating their influence on HER. Herein, Pt catalysts with different structures including single atoms (SAs), clusters, and nanoparticles well-controllably anchored on VS 2 nanosheets through a cost-effective optothermal method are reported, and their HER performance is studied. The most efficient Pt-decorated VS 2 catalyst (with both Pt SAs and clusters) delivers an overpotential of 77 mV at 10 mA cm –2 , close to that of Pt/C (48 mV). However, the optimal mass activity of Pt (normalizing to Pt content) is obtained from only SA Pt-decorated VS 2 (i.e., 22.88 A mg Pt –1 at 200 mV) and is 12 times greater than that of the Pt/C (1.87 A mg Pt –1 ), attributed to the greatly enhanced Pt utilization. Additionally, the theoretical simulations reveal that Pt SA decoration makes the adsorption free energy of H* closer to the thermoneutral value and improves the charge-transfer kinetics, significantly enhancing HER activity. Furthermore, this work offers a pathway to prepare the desired catalyst based on synergy of Pt structures and VS 2 and reveals the intrinsic mechanism for enhancing catalytic activity, which is important for HER applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural and electronic properties of Au{sub n−x}Pt{sub x} (n = 2–14; x ⩽ n) clusters: The density functional theory investigation

The structural evolutions and electronic properties of bimetallic Au{sub n–x}Pt{sub x} (n = 2–14; x ⩽ n) clusters are investigated by using the density functional theory (DFT) with the generalized gradient approximation (GGA). The monatomic doping Au{sub n–1}Pt clusters are emphasized and compared with the corresponding pristine Au{sub n} clusters. The results reveal that the planar configurations are favored for both Au{sub n–1}Pt and Au{sub n} clusters with size up to n = 13, and the former often employ the substitution patterns based on the structures of the latter. The most stable clusters are Au{sub 6} and Au{sub 6}Pt, which adopt regular planar triangle (D{sub 3h}) and hexagon-ring (D{sub 6h}) structures and can be regarded as the preferential building units in designing large clusters. For Pt-rich bimetallic clusters, their structures can be obtained from the substitution of Pt atoms by Au atoms from the Pt{sub n} structures, where Pt atoms assemble together and occupy the center yet Au atoms prefer the apex positions showing a segregation effect. With respect to pristine Au clusters, Au{sub n}Pt clusters exhibit somewhat weaker and less pronounced odd-even oscillations in the highest occupied and lowest unoccupied molecular-orbital gaps (HOMO-LUMO gap), electron affinity (EA), and ionization potential (IP) due to the partially released electron pairing effect. The analyses of electronic structure indicate that Pt atoms in AuPt clusters would delocalize their one 6s and one 5d electrons to contribute the electronic shell closure. The sp-d hybridizations as well as the d-d interactions between the host Au and dopant Pt atoms result in the enhanced stabilities of AuPt clusters.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A first-principles study of Pt thin films on SrTiO{sub 3}(100): Support effects on CO adsorption

Density functional theory was used to study CO adsorption on thin Pt metal films supported on SrO- and TiO{sub 2}-terminated SrTiO{sub 3}(100) surfaces. Regardless of substrate-termination, significant enhancement in CO binding occurred on the Pt monolayer compared to the bulk Pt(100) surface. We also observed CO-coverage dependent shifting of Pt atoms, influenced by the nature of underlying oxide atoms. These oxide-induced effects become negligible after depositing more than 2 monolayers of Pt. Evaluating the electronic structures of oxide-supported Pt showed that the interaction of filled Pt d{sub xz+yz} and empty Pt d{sub z{sup 2}} states with CO molecular orbitals can be directly related to CO adsorption on the Pt/SrTiO{sub 3}(100) surface. A hybrid d-band model is able to capture the CO adsorption trends for systems that do not show large lateral distortion except for the case of Pt adsorbed above the Sr atom on the SrO-termination. For this case, charge transfer from adjacent Pt atoms leads to a large filled d{sub z{sup 2}} peak below the Fermi level that weakens the Pt–CO σ bonding due to Pauli repulsion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

High-temperature ferromagnetism in Cr 1+x Pt 5-x P

In this work, we present the growth and basic magnetic and transport properties of Cr 1+x Pt 5-x P. We show that single crystals can readily be grown from a high-temperature solution created by adding dilute quantities of Cr to Pt-P based melts. Like other 1-5-1 compounds, Cr 1+x Pt 5-x P adopts a tetragonal P4/mmm, structure composed facesharing CrPts like slabs that are broken up along the c-axis by sheets of P atoms. EDS and X-ray diffraction measurements both suggest Cr 1+x Pt 5-x P has mixed occupancy between Cr and Pt atoms, similar to what is found in the closely related compound CrPtg, giving real compositions of Cr 1.5 Pt 4.5 P (x = 0.5). We report that Cr 1.5 Pt 4.5 P orders ferromagnetically at T c = 464.5 K with a saturated moment of ≈ 2.1 μs/Cr at 1.8 K. Likely owing to the strong spin-orbit coupling associated with the large quantity of high Z, Pt atoms, Cr 1.5 Pt 4.5 P has exceptionally strong planar anisotropy with estimated anisotropy fields of 345 kOe and 220 kOe at 1.8 K and 300 K respectively. The resistance of Cr 1.5 Pt 4.5 P has a metallic temperature dependence with relatively weak magnetoresistance. Electronic band structure calculations show that CrPt 5 P has a large peak in the density of states near the Fermi level which is split into spin majority and minority bands in the ferromagnetic state. Furthermore, the calculations suggest substantial hybridization between Cr-3d and Pt-5d states near the Fermi level, in agreement with the experimentally measured anisotropy.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nonoxidative dehydrogenation of propane using boron-incorporated silica-supported Pt Sites synthesized by atomic layer deposition

Nonoxidative dehydrogenation of propane to propylene using Pt-based supported catalysts is an active research area in catalysis because catalyst attributes of Pt sites can be controlled by careful design of active sites. One way to achieve this is by the addition of a second metal that may impart a change in the electron density of active sites, which in turn affects catalytic performance. In this study, bimetallic Pt and B sites were deposited on powder SiO2 using atomic layer deposition (ALD). Boron was first deposited on SiO2 via half-cycle ALD using triisoproplyborate as the B source. Following calcination, Pt deposition was performed via half-cycle ALD using trimethyl(methylcyclopentadienyl)platinum(IV) as the Pt source. The synthesized catalysts were reduced under H2 at 550 °C and characterized using inductively coupled plasma optical emission spectroscopy for elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO to examine the properties of Pt, and time-resolved X-ray absorption near edge structure spectroscopy to examine the changes in the reducibility of Pt sites. The samples were then tested for nonoxidative dehydrogenation of propane at 550 °C using a fixed-bed plug-flow reactor to examine the role of B on the catalytic performance. Characterization results showed that the addition of B imparted an increase in electron density and affected the reducibility of Pt sites. In addition, incorporating B on SiO2 created anchoring sites for Pt ALD. The amount of Pt deposited on B/SiO2 was 2.2 times that on SiO2. Catalytic activity results revealed the addition of B did not change the initial activity of Pt sites significantly, but improved propylene selectivity from 80% to 87% and stability almost threefold. The enhanced selectivity and stability of PtB/SiO2 is most presumably due to favored desorption of propylene and mitigating coke formation under reaction conditions, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Programmable Exposure of Pt Active Facets for Efficient Oxygen Reduction

Pt-based materials are the state-of-the-art catalysts for oxygen reduction reaction (ORR), but their high cost and scarcity remain the major obstacles for large-scale applications in renewable energy industries. To produce efficient ORR catalysts with low Pt content, PtNi porous films (PFs) with sufficiently exposed Pt active sites were rationally designed through a programmable approach combining electrochemical bottom-up (electrodeposition) and topdown (anodization) processes. The unique dynamic oxygen-bubble template (DOBT) programmably controlled by square-wave potential was utilized to tune the catalyst morphology and expose Pt active facets in PtNi PFs. Here, the surface-bounded species such as hydroxyl anions (OH*, *=surface site) on the exposed PtNi PFs surfaces were adjusted by the applied anodic voltage, further affecting the dynamic oxygen (O 2 ) bubbles adsorption on Pt. As a result, PtNi PF with enriched Pt (111) facets (denoted as Pt 3.5% Ni PF) was obtained, showing prominent ORR activity with an onset potential of 0.92 V (vs. RHE) at an ultra-low Pt loading (0.015 mg cm -2 ). The adsorbed OHads coverage estimation shows fewer OHads on Pt 3.5% Ni PF than other PtNi PFs, indicating that enriched Pt (111) facets in the catalysts enable facilitated O 2 adsorption for oxygen reduction and thus leading to superior ORR activity

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Highly efficient Pt catalyst on newly designed CeO 2 -ZrO 2 -Al 2 O 3 support for catalytic removal of pollutants from vehicle exhaust

Pt-CeO 2 catalysts have been widely studied for the vehicle emission control. Designing novel CeO 2 based supports with improved physical-chemical properties has become a research hotspot to further promote the catalytic performance and stability of Pt-CeO 2 catalysts. In this work, through utilizing a unique, two-step incipient wetness impregnation (T-IWI) method for ceria-zirconia-alumina (CZA-T) support preparation, a Pt single site catalyst (Pt/CZA-T) with excellent thermal stability was synthesized. Higher oxidation activity and Oxygen storage capacity (OSC) were achieved on activated Pt/CZA-T, comparing to Pt catalysts on regular CeO 2 /Al 2 O 3 (Pt/CA) and one-step prepared CeZrO x /Al 2 O 3 (Pt/CZA). Via the modification of hydrophilic/hydrophobic properties of γ-Al 2 O 3 by this unique T-IWI method, finer Ce 0.9 Zr 0.1 O 2 particles with higher density of surface defects were formed on CZA-T, on which a higher Pt dispersion and stronger Pt-O-Ce interaction were achieved. Upon activation, smaller, well-dispersed Pt clusters on CZA-T were generated. It was concluded that the CO oxidation performance and OSC were highly related to the size of Pt clusters on different supports that we have developed. Finally, more Pt sites located at Pt cluster-CeZrO x interfaces, which were the real active sites, were responsible for the highest OSC function and CO oxidation activity of activated Pt/CZA-T catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Rationalization of Au concentration and distribution in AuNi@Pt core-shell nanoparticles for oxygen reduction reaction

Improving the activity and stability of Pt-based core–shell nanocatalysts for proton exchange membrane fuel cells while lowering Pt loading has been one of the big challenges in electrocatalysis. Here, using density functional theory, we report the effect of adding Au as the third element to enhance the durability and activity of Ni@Pt core–shell nanoparticles (NPs) during the oxygen reduction reaction (ORR). Our results show that the durability and activity of a Ni@Pt NP can be finely tuned by controlling Au concentration and distribution. For a NiAu@Pt NP, the durability can be greatly promoted by thermodynamically favorable segregation of Au to replace the Pt atoms at vertex, edge, and (100) facets on the shell, while still keeping the ORR activity on the active Pt(111) shell as high as that of Ni@Pt nanoparticles. Such behavior strongly depends on a direct interaction with the Ni interlayer. The results not only highlight the importance of interplay between surface strain on the shell and the interlayer–shell interaction in determining the durability and activity but also provide guidance on how to maximize the usage of Au to optimize the performance of core–shell (Pt) nanoparticles. As a result, such understanding has allowed us to discover a novel NiAu@Pt nanocatalyst for the ORR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Pt 8 cluster on alumina under a pressure of hydrogen: Support-dependent reconstruction from first-principles global optimization

Alumina supported Pt nano clusters under hydrogen environment play a crucial role for many heterogeneous catalysis applications. As such, we conducted grand canonical genetic algorithm (GCGA) simulations for supported Pt 8 clusters in hydrogen gas environment to study the intra-cluster, cluster-support, and cluster-adsorbate interactions. Two alumina surfaces, α-Al 2 O 3 (0001) and $γ$-Al 2 O 3 (100), and two conditions T=600°C, p H2 = 0.1bar and T=25°C, p H2 = 1.0 bar were considered corresponding to low and high hydrogen chemical potential $μ$ H , respectively. The low free energy ensemble of Pt 8 is decorated by a medium (2–12 H), resp. high (20–30 H), number of hydrogen atoms under equilibrium at low $μ$ H , respectively, high $μ$ H , and undergoes different morphology transformations on the two surfaces. On α-Al2O3(0001), Pt8 is mostly 3D but very fluxional in structure at low μH and converts to open one-layer 2D structures with minimal fluxionality at high μH, whereas on $γ$-Al 2 O 3 (100), the exact opposite occurs, and Pt 8 clusters present one-layer 2D shapes at low $μ$ H and switch into compact 3D shapes under high $μ$ H , during which the Pt 8 cluster preserves moderate fluxionality. Further analysis reveals similar Pt–Pt bond length increase when switching from low $μ$ H to high $μ$ H on both surfaces, though morphology transformations are different. Electronic structure analysis shows the existence of bonding interactions between Pt and Lewis acidic Al 3+ sites along with the Pt – O interaction, which implies the necessity to include Al neighbors to discuss the electronic structure of small Pt clusters.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Tailoring the Local Environment of Platinum in Single‐Atom Pt 1 /CeO 2 Catalysts for Robust Low‐Temperature CO Oxidation

Abstract A single‐atom Pt 1 /CeO 2 catalyst formed by atom trapping (AT, 800 °C in air) shows excellent thermal stability but is inactive for CO oxidation at low temperatures owing to over‐stabilization of Pt 2+ in a highly symmetric square‐planar Pt 1 O 4 coordination environment. Reductive activation to form Pt nanoparticles (NPs) results in enhanced activity; however, the NPs are easily oxidized, leading to drastic activity loss. Herein we show that tailoring the local environment of isolated Pt 2+ by thermal‐shock (TS) synthesis leads to a highly active and thermally stable Pt 1 /CeO 2 catalyst. Ultrafast shockwaves (>1200 °C) in an inert atmosphere induced surface reconstruction of CeO 2 to generate Pt single atoms in an asymmetric Pt 1 O 4 configuration. Owing to this unique coordination, Pt 1 δ+ in a partially reduced state dynamically evolves during CO oxidation, resulting in exceptional low‐temperature performance. CO oxidation reactivity on the Pt 1 /CeO 2 _TS catalyst was retained under oxidizing conditions.

Jiang, Dong↗
DOE OSTI2021

Tailoring the Local Environment of Platinum in Single-Atom Pt 1 /CeO 2 Catalysts for Robust Low-Temperature CO Oxidation

A single-atom Pt 1 /CeO 2 catalyst formed by atom trapping (AT, 800 degrees C in air) shows excellent thermal stability but is inactive for CO oxidation at low temperatures owing to over-stabilization of Pt 2+ in a highly symmetric square-planar Pt 1 O 4 coordination environment. Reductive activation to form Pt nanoparticles (NPs) results in enhanced activity; however, the NPs are easily oxidized, leading to drastic activity loss. In this work, we show that tailoring the local environment of isolated Pt 2+ by thermal-shock (TS) synthesis leads to a highly active and thermally stable Pt 1 /CeO 2 catalyst. Ultrafast shockwaves (>1200 degrees C) in an inert atmosphere induced surface reconstruction of CeO 2 to generate Pt single atoms in an asymmetric Pt 1 O 4 configuration. Owing to this unique coordination, Pt 1 δ+ in a partially reduced state dynamically evolves during CO oxidation, resulting in exceptional low-temperature performance. CO oxidation reactivity on the Pt 1 /CeO 2 _TS catalyst was retained under oxidizing conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Pt Nanoparticle Disintegration at Oxide Interfaces Enhances CO Oxidation Catalysis

Understanding how supported metal nanoparticles dynamically evolve under reaction conditions is critical for controlling their catalytic function. Here, the mechanism behind the dynamic disintegration of Pt nanoparticles (NPs) supported on CeOx-TiO2 (CT) during CO oxidation is elucidated, leading to the formation of single atoms (SAs) and/or sub-nanometer clusters. Density functional theory (DFT) calculations reveal that strong Pt-CO interactions weaken Pt─Pt cohesion, while electronic coupling between Pt and Ce ions stabilizes Pt-CO* intermediates at the oxide interface. Surface oxygen vacancies kinetically trap Pt-CO*, but the vacancies are replenished under oxygen-rich conditions, enabling Pt-CO* surface diffusion and subsequent structural reorganization. In situ spectroscopic analyses confirm the oxygen-driven transformation of Pt NPs, correlating with a threefold increase in mass-specific activity at 150 °C. These findings demonstrate that interfacial oxygen dynamics and metal-support interactions can be leveraged to induce nanoparticle disintegration and optimize catalytic performance, highlighting the catalytic potential of interface-engineered Pt nanostructures.

CO oxidation↗
DOE OSTI2023

Crowded supported metal atoms on catalytically active supports may compromise intrinsic activity: A case study of dual-site Pt/α-MoC catalysts

Increasing the surface population of supported catalytic sites, assuming these sites are stable, is considered a straightforward approach to improving the overall catalytic performance. Here, we report an exception represented by the Pt/α-MoC catalysts featuring atomically dispersed Pt. The Pt/α-MoC catalysts display very high activity for the reverse water gas shift reaction with near 100% CO selectivity for CO 2 :H 2 ratios from 0.25 to 4 and from 250 to 400 °C. Despite the excellent performance, the intrinsic activity per Pt-centric catalytic center declines as the Pt loading increases from 0.1 to 1.0 wt%. With the dispersed Pt evolving from isolated atoms to fully exposed ensembles, the shrinking inter-Pt-atom space impedes CO 2 activation at the critical Pt-Mo interfaces, where the Pt shall temporarily take the -O intermediates. The Pt, even as atomically dispersed without noticeable sintering, is underutilized in such a crowded state. This caution for high-loading catalyst design is translational to other systems where the direct catalytic roles of the supports are crucial.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗