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Showing papers on "Platinum published in 2020"


Journal ArticleDOI
TL;DR: McCrum et al. as discussed by the authors showed that Pt decorated with Ru atoms at the step edge is 65 times more active for the hydrogen evolution reaction (HER) than is the bare Pt step.
Abstract: The bifunctional mechanism that involves adsorbed hydroxide in the alkaline hydrogen oxidation and evolution reactions, important in hydrogen fuel cells and water electrolysers, is hotly debated. Hydroxide binding has been suggested to impact activity, but the exact role of adsorbed hydroxide in the reaction mechanism is unknown. Here, by selectively decorating steps on a Pt single crystal with other metal atoms, we show that the rate of alkaline hydrogen evolution exhibits a volcano-type relationship with the hydroxide binding strength. We find that Pt decorated with Ru at the step edge is 65 times more active for the hydrogen evolution reaction (HER) than is the bare Pt step. Simulations of electrochemical water dissociation show that the activation energy correlates with the OH* adsorption strength, even when the adsorbed hydroxide is not a product, which leads to a simulated volcano curve that matches the experimental curve. This work not only illustrates the alkaline HER mechanism but also provides a goal for catalyst design in targeting an optimum hydroxide binding strength to yield the highest rate for the alkaline HER. A three-dimensional (H and OH adsorbed species) HER activity volcano and the implications for hydrogen oxidation are discussed. The appropriate descriptors for a catalyst’s hydrogen evolution activity in alkaline electrolyte are debated. Combining simulations and single-crystal studies of metal-decorated Pt surfaces, McCrum and Koper show that activity exhibits a volcano-type relationship with the hydroxide binding strength of the catalyst, providing a target for catalyst design.

301 citations


Journal ArticleDOI
TL;DR: It is shown that nanoparticulate zirconium nitride (ZrN) can replace and even surpass Pt as a catalyst for ORR in alkaline environments and is shown to deliver a greater power density and cyclability than Pt/C in a zinc–air battery.
Abstract: Platinum (Pt)-based materials are important components of microelectronic sensors, anticancer drugs, automotive catalytic converters and electrochemical energy conversion devices1. Pt is currently the most common catalyst used for the oxygen reduction reaction (ORR) in devices such as fuel cells and metal–air batteries2,3, although a scalable use is restricted by the scarcity, cost and vulnerability to poisoning of Pt (refs 4–6). Here we show that nanoparticulate zirconium nitride (ZrN) can replace and even surpass Pt as a catalyst for ORR in alkaline environments. As-synthesized ZrN nanoparticles (NPs) exhibit a high oxygen reduction performance with the same activity as that of a widely used Pt-on-carbon (Pt/C) commercial catalyst. Both materials show the same half-wave potential (E1/2 = 0.80 V) and ZrN has a higher stability (ΔE1/2 = −3 mV) than the Pt/C catalyst (ΔE1/2 = −39 mV) after 1,000 ORR cycles in 0.1 M KOH. ZrN is also shown to deliver a greater power density and cyclability than Pt/C in a zinc–air battery. Replacement of Pt by ZrN is likely to reduce costs and promote the usage of electrochemical energy devices, and ZrN may also be useful in other catalytic systems. Platinum catalysts are widely used for oxygen reduction reactions in electrochemical devices but scalability is restricted by scarcity, cost and vulnerability to poisoning. Zirconium nitride nanoparticles now exhibit an oxygen reduction performance with similar activity to that of Pt on carbon.

253 citations


Journal ArticleDOI
09 Sep 2020-Nature
TL;DR: It is found that the silanol nests enable the rare-earth elements to exist as single atomic species with a substantially higher chemical potential compared with that of the bulk oxide, making it possible for them to diffuse onto Pt through the H2 reduction route.
Abstract: Platinum is a much used catalyst that, in petrochemical processes, is often alloyed with other metals to improve catalytic activity, selectivity and longevity1-5. Such catalysts are usually prepared in the form of metallic nanoparticles supported on porous solids, and their production involves reducing metal precursor compounds under a H2 flow at high temperatures6. The method works well when using easily reducible late transition metals, but Pt alloy formation with rare-earth elements through the H2 reduction route is almost impossible owing to the low chemical potential of rare-earth element oxides6. Here we use as support a mesoporous zeolite that has pore walls with surface framework defects (called 'silanol nests') and show that the zeolite enables alloy formation between Pt and rare-earth elements. We find that the silanol nests enable the rare-earth elements to exist as single atomic species with a substantially higher chemical potential compared with that of the bulk oxide, making it possible for them to diffuse onto Pt. High-resolution transmission electron microscopy and hydrogen chemisorption measurements indicate that the resultant bimetallic nanoparticles supported on the mesoporous zeolite are intermetallic compounds, which we find to be stable, highly active and selective catalysts for the propane dehydrogenation reaction. When used with late transition metals, the same preparation strategy produces Pt alloy catalysts that incorporate an unusually large amount of the second metal and, in the case of the PtCo alloy, show high catalytic activity and selectivity in the preferential oxidation of carbon monoxide in H2.

175 citations


Journal ArticleDOI
01 Oct 2020
TL;DR: In this paper, a combination of operando techniques and density functional theory analysis is used to capture the evolution of single platinum atoms on CeO2 during CO, C3H6 and CH4 oxidation.
Abstract: Platinum single sites are highly attractive due to their high atom economy and can be generated on CeO2 by an oxidative high-temperature treatment. However, their location and activity are strongly debated. Furthermore, reaction-driven structural dynamics have not been addressed so far. In this study, we were able to evidence platinum-induced CeO2 surface restructuring, locate platinum single sites on CeO2 and track the variation of the active state under reaction conditions using a complementary approach of density functional theory calculations, in situ infrared spectroscopy, operando high-energy-resolution fluorescence detected X-ray absorption spectroscopy and catalytic CO (as well as C3H6 and CH4) oxidation. We found that the onset of CO oxidation is linked to the migration of platinum single sites from four-fold hollow sites to form small clusters containing a few platinum atoms. This demonstrates that operando studies on single sites are essential to assess their fate and the resulting catalytic properties. Single-atom catalysts hold great promise for process optimization by reducing metal utilization. However, their structure–activity properties remain elusive. Here, a combination of operando techniques and density functional theory analysis is used to capture the evolution of single platinum atoms on CeO2 during CO, C3H6 and CH4 oxidation.

169 citations


Journal ArticleDOI
TL;DR: A structurally well-defined model complex with Pt-O bonding to enable efficient H2 evolution electrocatalysis is shown and complements the knowledge boundary of Pt-based electrocatalytic HER, and suggests another way to update the state-of-the-art electrocatalyst.
Abstract: The oxidized platinum (Pt) can exhibit better electrocatalytic activity than metallic Pt0 in the hydrogen evolution reaction (HER), which has aroused great interest in exploring the role of oxygen in Pt-based catalysts. Herein, we select two structurally well-defined polyoxometalates Na5[H3Pt(IV)W6O24] (PtW6O24) and Na3K5[Pt(II)2(W5O18)2] (Pt2(W5O18)2) as the platinum oxide model to investigate the HER performance. Electrocatalytic experiments show the mass activities of PtW6O24/C and Pt2(W5O18)2/C are 20.175 A mg−1 and 10.976 A mg−1 at 77 mV, respectively, which are better than that of commercial 20% Pt/C (0.398 A mg−1). The in situ synchrotron radiation experiments and DFT calculations suggest that the elongated Pt-O bond acts as the active site during the HER process, which can accelerate the coupling of proton and electron and the rapid release of H2. This work complements the knowledge boundary of Pt-based electrocatalytic HER, and suggests another way to update the state-of-the-art electrocatalyst. While converting water to H2 with a catalyst offers a renewable means to produce carbon-neutral fuels, understanding the catalytic active sites has proven challenging. Here, authors show a structurally well-defined model complex with Pt-O bonding to enable efficient H2 evolution electrocatalysis.

166 citations


Journal ArticleDOI
TL;DR: An atomic-scale defect engineering approach to form and control traps for platinum SA sites as co-catalyst for photocatalytic H2 generation is described, finding that only on the thin-film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing.
Abstract: Single-atom (SA) catalysis is a novel frontline in the catalysis field due to the often drastically enhanced specific activity and selectivity of many catalytic reactions. Here, an atomic-scale defect engineering approach to form and control traps for platinum SA sites as co-catalyst for photocatalytic H2 generation is described. Thin sputtered TiO2 layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA platinum, the TiO2 layers are reduced in Ar/H2 under different conditions (leading to different but defined Ti3+ -Ov surface defects), followed by immersion in a dilute hexachloroplatinic acid solution. HAADF-STEM results show that only on the thin-film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA-Pt decoration can enhance the normalized photocatalytic activity of a TiO2 sputtered sample by 150 times in comparison to a conventional platinum-nanoparticle-decorated TiO2 surface. HAADF-STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt on TiO2 . Importantly, the density of the relevant surface exposed defect centers-thus the density of Pt-SA sites, which play the key role in photocatalytic activity-can be precisely optimized.

153 citations


Journal ArticleDOI
TL;DR: Platinum is a nearly perfect catalyst for the hydrogen evolution reaction, and its high activity has conventionally been explained by its close-to-thermoneutral hydrogen binding energy (G ∼ 0) as discussed by the authors.
Abstract: Platinum is a nearly perfect catalyst for the hydrogen evolution reaction, and its high activity has conventionally been explained by its close-to-thermoneutral hydrogen binding energy (G ∼ 0). How...

145 citations


Journal ArticleDOI
TL;DR: It is shown that a nickel-molybdenum nanoalloy with tetragonal MoNi4 phase can catalyze the ultrafast hydrogen oxidation reaction (HOR) efficiently in alkaline electrolytes and has the capability to tolerate carbon monoxide poisoning.
Abstract: Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi4 phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi4 catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction. The lack of efficient and cost-effective catalysts for hydrogen oxidation reaction (HOR) hampers the application of hydroxide exchange membrane fuel cells. Here, authors reported bimetallic MoNi4 and WNi4 nanoalloys with marked HOR activity in alkali, among which MoNi4 outperforms the Pt/C catalyst.

141 citations


Journal ArticleDOI
TL;DR: A low-temperature NH 4 Cl-treatment strategy is reported to efficiently etch out graphene-encapsulated nanoparticles from metal-N-C catalysts without destruction of co-existed atomically dispersed metal- N x sites.
Abstract: The development of metal-N-C materials as efficient non-precious metal (NPM) catalysts for catalysing the oxygen reduction reaction (ORR) as alternatives to platinum is important for the practical use of proton exchange membrane fuel cells (PEMFCs). However, metal-N-C materials have high structural heterogeneity. As a result of their high-temperature synthesis they often consist of metal-Nx sites and graphene-encapsulated metal nanoparticles. Thus it is hard to identify the active structure of metal-N-C catalysts. Herein, we report a low-temperature NH4 Cl-treatment to etch out graphene-encapsulated nanoparticles from metal-N-C catalysts without destruction of co-existing atomically dispersed metal-Nx sites. Catalytic activity is much enhanced by this selective removal of metallic nanoparticles. Accordingly, we can confirm the spectator role of graphene-encapsulated nanoparticles and the pivotal role of metal-Nx sites in the metal-N-C materials for ORR in the acidic medium.

126 citations


Journal ArticleDOI
TL;DR: A novel synthetic strategy to directly produce highly dispersed MPt alloy nanoparticles (M = Fe, Co, or Ni) on various carbon supports with high catalyst loading is reported, featuring a unique bimetallic compound that evenly decomposes on carbon surface and forms uniformly sized intermetallic nanoparticles with a nitrogen-doped carbon protection layer.
Abstract: Compared to nanostructured platinum (Pt) catalysts, ordered Pt-based intermetallic nanoparticles supported on a carbon substrate exhibit much enhanced catalytic performance, especially in fuel cell...

122 citations


Journal ArticleDOI
TL;DR: In this paper, a new Pt SA strongly coupled with amorphous MoOX (Pt-SA/ɑ-MoOx) is rationally designed, and the synergistic effect between unsaturated Pt atoms and defective MoOx can significantly lower the reaction barrier contributing to the fast HER reaction kinetics.

Journal ArticleDOI
22 Apr 2020-ACS Nano
TL;DR: Pt catalysts with different structures including single atoms, clusters, and nanoparticles well-controllably anchored on VS2 nanosheets through a cost-effective optothermal method are reported, and their HER performance is studied.
Abstract: 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...

Journal ArticleDOI
02 Mar 2020
TL;DR: It is demonstrated that platinum single atoms on carbon carriers are substantially more stable than their gold counterparts, enabling facile and scalable preparation and precise tuning of their coordination environment by simple temperature control.
Abstract: The worldwide replacement of the toxic mercuric chloride catalyst in vinyl chloride manufacture via acetylene hydrochlorination is slowed by the limited durability of alternative catalytic systems at high space velocities. Here, we demonstrate that platinum single atoms on carbon carriers are substantially more stable (up to 1,073 K) than their gold counterparts (up to 473 K), enabling facile and scalable preparation and precise tuning of their coordination environment by simple temperature control. By combining kinetic analysis, advanced characterization, and density functional theory, we assess how the Pt species determines the catalytic performance and thereby identify Pt(ii)−Cl as the active site, being three times more active than Pt nanoparticles. We show that Pt single atoms exhibit outstanding stability in acetylene hydrochlorination and surpass the space–time yields of their gold-based analogues after 25 h time-on-stream, qualifying them as a candidate for sustainable vinyl chloride production. Platinum nanoparticles have been neglected as a catalyst for acetylene hydrochlorination due to their limited activity. Here, the authors show that nanostructuring to the single-atom level renders platinum on carbonaceous supports a superior catalyst for this important industrial process.

Journal ArticleDOI
TL;DR: At atomic-scale insight into well-defined single-crystalline, thin-film and nanoscale surfaces exposed Pt dissolution trends that governed the design and synthesis of durable materials, leading to the design of PtAu catalysts with suppressed dissolution.
Abstract: A remaining challenge for the deployment of proton-exchange membrane fuel cells is the limited durability of platinum (Pt) nanoscale materials that operate at high voltages during the cathodic oxygen reduction reaction. In this work, atomic-scale insight into well-defined single-crystalline, thin-film and nanoscale surfaces exposed Pt dissolution trends that governed the design and synthesis of durable materials. A newly defined metric, intrinsic dissolution, is essential to understanding the correlation between the measured Pt loss, surface structure, size and ratio of Pt nanoparticles in a carbon (C) support. It was found that the utilization of a gold (Au) underlayer promotes ordering of Pt surface atoms towards a (111) structure, whereas Au on the surface selectively protects low-coordinated Pt sites. This mitigation strategy was applied towards 3 nm Pt3Au/C nanoparticles and resulted in the elimination of Pt dissolution in the liquid electrolyte, which included a 30-fold durability improvement versus 3 nm Pt/C over an extended potential range up to 1.2 V. Deployment of proton-exchange membrane fuel cells is limited by the durability of Pt-nanoscale catalysts during cathodic oxygen reduction reactions. Dissolution processes on single crystalline and thin film surfaces are now correlated leading to the design of PtAu catalysts with suppressed dissolution.

Journal ArticleDOI
TL;DR: In this paper, a series of bifunctional composites with excellent electrochemical activity and durability based on platinum with the perovskite Sr(Co0.8Fe0.2)(0.95)P0.05O3-delta (SCFP) are synthesized via a facile but effective strategy.
Abstract: Constructing highly active electrocatalysts with superior stability at low cost is a must, and vital for the large-scale application of rechargeable Zn-air batteries. Herein, a series of bifunctional composites with excellent electrochemical activity and durability based on platinum with the perovskite Sr(Co0.8Fe0.2)(0.95)P0.05O3-delta (SCFP) are synthesized via a facile but effective strategy. The optimal sample Pt-SCFP/C-12 exhibits outstanding bifunctional activity for the oxygen reduction reaction and oxygen evolution reaction with a potential difference of 0.73 V. Remarkably, the Zn-air battery based on this catalyst shows an initial discharge and charge potential of 1.25 and 2.02 V at 5 mA cm(-2), accompanied by an excellent cycling stability. X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and extended X-ray absorption fine structure experiments demonstrate that the superior performance is due to the strong electronic interaction between Pt and SCFP that arises as a result of the rapid electron transfer via the Pt-O-Co bonds as well as the higher concentration of surface oxygen vacancies. Meanwhile, the spillover effect between Pt and SCFP also can increase more active sites via lowering energy barrier and change the rate-determining step on the catalysts surface. Undoubtedly, this work provides an efficient approach for developing low-cost and highly active catalysts for wider application of electrochemical energy devices.

Journal ArticleDOI
TL;DR: The recent advances in platinum-free and/or metal-free electrocatalysts for electrochemical redox reactions at the electrodes of especially fuel cells and broadly energy devices were thoroughly rev...
Abstract: The recent advances in platinum-free and/or metal-free electrocatalysts for electrochemical redox reactions at the electrodes of especially fuel cells and broadly energy devices were thoroughly rev...

Journal ArticleDOI
TL;DR: The hydroisomerization of n-heptane demonstrates that the bifunctional catalysts with platinum particles on the binder, which separates platinum and acid sites at nanoscale distance, surprisingly offers a higher yield of desired isomers than catalystswith platinum particles inside the zeolite crystals.
Abstract: Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the "intimacy criterion" for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants.

Journal ArticleDOI
TL;DR: Optically pure pillar[5]arene-based platinum chiral metallacycles formed by coordination with 60° and 90° Pt(II) acceptors were self-assembled efficiently and characterized by multiple spectroscopic techniques, indicating that they had chiral properties.
Abstract: Chiral metal-organic complexes hold great promise as new functional materials that exhibit unique stereochemical and optical properties. Here, we report the formation of optically pure pillar[5]arene-based platinum chiral metallacycles. By coordination with 60° and 90° Pt(II) acceptors, planar chiral platinum triangles were self-assembled efficiently and characterized by multiple spectroscopic techniques. Optical studies indicated that these metallacycles had chiral properties: pS enantiomers showed a negative Cotton effect, and pR enantiomers exhibited a positive Cotton effect. In addition, these metallacycles also exhibited circularly polarized luminescence.

Journal ArticleDOI
TL;DR: The CVD synthesis sheds some light on the mass production of single metal site catalysts towards advanced electrocatalysis and features an optimal CVD-derived Fe-N-C catalyst featured with atomically dispersed FeN4 sites with increased Fe loading relative to other catalysts from wet-chemistry synthesis.
Abstract: Atomically dispersed and nitrogen coordinated single metal sites (M-N-C, M=Fe, Co, Ni, or Mn) are the popular platinum group-metal (PGM)-free catalysts for many electrochemical reactions. Traditional wet-chemistry catalyst synthesis often requires complex procedures with unsatisfied reproducibility and scalability. Here, we report a chemical vapor deposition (CVD) strategy to synthesize the promising single metal site (M-N-C) catalysts. The deposition of gaseous 2-methylimidazole onto ZnO substrates doped with M, followed by an in-situ thermal activation, was proved effective in generating single metal sites well dispersed into porous carbon. In particular, an optimal CVD-derived Fe-N-C catalyst is featured with atomically dispersed FeN4 sites with increased Fe loading relative to other catalysts from wet-chemistry synthesis. The catalyst exhibited outstanding oxygen-reduction activity in acidic electrolytes, which was further studied in proton-exchange membrane fuel cells with encouraging performance. The CVD synthesis sheds some light on the mass production of single metal site catalysts towards advanced electrocatalysis.

Journal ArticleDOI
TL;DR: In this article, the separation of Pt, Pd and rhodium by ion exchange resins from various solutions while considering the presence of other metals such as other PGMs, Au, Ag and base metals.

Journal ArticleDOI
TL;DR: The selective loading strategy employed in this work not only provides an effective approach for constructing controllable active sites in HER catalysts but should also be applicable in the fabrication of other atomic catalysts.
Abstract: High-performance electrocatalysts for the hydrogen evolution reaction (HER) have an important role to play in the development of renewable energy. Despite the enormous efforts to find cheaper alternative materials, platinum remains the most efficient known HER electrocatalyst. Therefore, it is necessary to find ways to maximize Pt utilization in actual practical applications. Here we demonstrate a facile strategy for synthesizing RuCeO x -supported selectively loaded atomic Pt (0.49 wt.%) (denoted Pt/RuCeO x -PA) by photoactivation at ambient temperature and pressure. Due to the photoelectron transfer at the Mott-Schottky heterojunction in RuCeO x , Pt atoms became directionally embedded into the RuO 2 lattice. The resulting selectively loaded Pt-O-Ru moieties in Pt/RuCeO x -PA exhibit a stronger hydrogen spillover effect than Pt complexes randomly loaded by either chemical activation or thermal activation. As a result, Pt/RuCeO x -PA shows superior HER performance to the materials prepared by random loading and is even better than a commercial Pt/C catalyst with much higher Pt loading (20 wt.%) at high current densities (from 50-600 mA cm -2 ). The selective loading strategy employed in our work not only provides an effective approach for constructing controllable active sites in HER catalysts but should also be applicable in the fabrication of other atomic catalysts.

Journal ArticleDOI
TL;DR: In this paper, the photophysical behaviors of luminescent platinum(II) and gold(III) complexes are described, as well as their recent advances in using these complexes for various applications.

Journal ArticleDOI
TL;DR: In this paper, a novel strategy to stabilize atomic Pt catalysts in alloyed platinum cobalt nanosheets with trapped interstitial fluorine (SA-PtCoF) for ZABs was proposed.
Abstract: Recently, considerable attention has been paid to the stabilization of atomic platinum (Pt) catalysts on desirable supports in order to reduce Pt consumption, improve the catalyst stability, and thereafter enhance the catalyst performance in renewable energy devices such as fuel cells and zinc-air batteries (ZABs). Herein, we rationally designed a novel strategy to stabilize atomic Pt catalysts in alloyed platinum cobalt (PtCo) nanosheets with trapped interstitial fluorine (SA-PtCoF) for ZABs. The trapped interstitial F atoms in the PtCoF matrix induce lattice distortion resulting in weakening of the Pt–Co bond, which is the driving force to form atomic Pt. As a result, the onset potentials of SA-PtCoF are 0.95 V and 1.50 V for the oxygen reduction and evolution reactions (ORR and OER), respectively, superior to commercial Pt/C@RuO2. When used in ZABs, the designed SA-PtCoF can afford a peak power density of 125 mW cm−2 with a specific capacity of 808 mA h gZn−1 and excellent cyclability over 240 h, surpassing the state-of-the-art catalysts.

Journal ArticleDOI
TL;DR: A nanoporous crystal is reported that can firmly stabilize Pt single atoms in its surface cavities for efficient catalytic hydrogenation of nitroarenes with a much higher turnover frequency than well-studied Pt-based catalysts.
Abstract: Single-atom catalysts (SACs) have attracted significant attention because they exhibit unique catalytic performance due to their ideal structure. However, maintaining atomically dispersed metal under high temperature, while achieving high catalytic activity remains a formidable challenge. In this work, we stabilize single platinum atoms within sub-nanometer surface cavities in well-defined 12CaO·7Al2O3 (C12A7) crystals through theoretical prediction and experimental process. This approach utilizes the interaction of isolated metal anions with the positively charged surface cavities of C12A7, which allows for severe reduction conditions up to 600 °C. The resulting catalyst is stable and highly active toward the selective hydrogenation of nitroarenes with a much higher turnover frequency (up to 25772 h−1) than well-studied Pt-based catalysts. The high activity and selectivity result from the formation of stable trapped single Pt atoms, which leads to heterolytic cleavage of hydrogen molecules in a reaction that involves the nitro group being selectively adsorbed on C12A7 surface. Stabilize the active metal single atoms under harsh conditions is critical for the development of single atom catalysts. Here the authors report a nanoporous crystal, 12CaO·7Al2O3, that can firmly stabilize Pt single atoms in its surface cavities for efficient catalytic hydrogenation of nitroarenes.

Journal ArticleDOI
TL;DR: Benefited from rich Fe(III)-OH-Pt interfaces, the Fe(OH) x /Pt catalysts exhibit high catalytic performance towards a broad range of substituted nitroarenes.
Abstract: Catalytic hydrogenation of nitroaromatics is an environment-benign strategy to produce industrially important aniline intermediates Herein, we report that Fe(OH)x deposition on Pt nanocrystals to give Fe(OH)x /Pt, enables the selective hydrogenation of nitro groups into amino groups without hydrogenating other functional groups on the aromatic ring The unique catalytic behavior is identified to be associated with the FeIII -OH-Pt interfaces While H2 activation occurs on exposed Pt atoms to ensure the high activity, the high selectivity towards the production of substituted aniline originates from the FeIII -OH-Pt interfaces In situ IR, X-ray photoelectron spectroscopy (XPS), and isotope effect studies reveal that the Fe3+ /Fe2+ redox couple facilitates the hydrodeoxygenation of the -NO2 group during hydrogenation catalysis Benefitting from FeIII -OH-Pt interfaces, the Fe(OH)x /Pt catalysts exhibit high catalytic performance towards a broad range of substituted nitroarenes

Journal ArticleDOI
TL;DR: Se-hun Kwon et al. as discussed by the authors proposed a high-performance Pt/carbon catalyst for PEMFCs using fluidized bed reactor atomic layer deposition (FBR-ALD) that was realized by an effective matching of the carbon supports for the FBR -ALD process and an optimization of the ionomer content during the preparation of the membrane electrode assembly.
Abstract: The performance of proton exchange membrane fuel cells (PEMFCs) depends on the controlled size, dispersion and density of Pt nanoparticles (NPs) on carbon supports, which are strongly affected by the carbon characteristics and fabrication methods. Here, we demonstrated a high-performance Pt/carbon catalyst for PEMFCs using fluidized bed reactor atomic layer deposition (FBR-ALD) that was realized by an effective matching of the carbon supports for the FBR-ALD process and an optimization of the ionomer content during the preparation of the membrane electrode assembly (MEA). For this, the synthesis of Pt NPs was conducted on two porous supports (Vulcan XC-72R and functionalized carbon) by FBR-ALD. The functionalized carbon possessed a higher surface area with a large pore volume, abundant defects in a disordered structure and a large number of oxygen functional groups compared to those of the well-known Vulcan carbon. The favorable surface characteristics of the functionalized carbon for nucleation produced Pt particles with an increased uniformity and density and a narrow size range, which led to a higher electrochemical surface area (ECSA) than that of Pt/Vulcan carbon and commercial Pt/carbon. The PEMFC test of the respective Pt/carbon samples was investigated, and highly dense and uniform Pt/functionalized-carbon showed the highest performance through optimization of the higher ionomer content compared to that for the ALD Pt growth on Vulcan carbon and commercial Pt/carbon. In addition, the Pt catalyst using ALD demonstrated a significant long-term stability for the PEMFC. This finding demonstrates the remarkable advantages of FBR-ALD for the fabrication of Pt/carbon and the ability of functionalized carbon supports to achieve a high PEMFC efficiency and an enhanced durability. Small tweaks to techniques used to manufacture platinum catalysts can have a big impact on the long-term stability of fuel cells. Platinum nanoparticle catalysts help fuel cells turn hydrogen and oxygen into water and electricity, but their small size makes them tricky to manipulate. Se-Hun Kwon from Pusan National University in Busan, South Korea, and colleagues have now optimized a high-tech procedure for attaching these tiny nanocatalysts to large, porous materials known as carbon supports. Their process coats various supports with platinum nanoparticles, less than one monolayer at a time, until the desired thicknesses are reached. Various factors including the physical textures of the supports and leftover chemical impurities were shown to significantly affect coating uniformity. Adjusting these factors enabled the team to generate supports with greater durability than commercial platinum–carbon composites. Very efficient, fast and scalable Fluidized Bed Reactor Atomic Layer Deposition (FBR-ALD) of highly dense and uniform Pt nanoparticles (NPs) on the functionalized carbon were successfully demonstrated for the proton exchange membrane fuel cell (PEMFC) application. The textural properties, functional groups and structural defects of the carbon supports significantly influenced Pt NPs deposition. A proper carbon supporter matching for FBR-ALD of Pt resulted in excellent electrochemical properties, long-term durability and fuel cell performance.

Journal ArticleDOI
TL;DR: A general and simple method was developed to prepare flower-like platinum-cobalt-ruthenium alloy nanoassemblies by using murexide and cetyltrimethylammonium chloride as the co-structure-directing agents, and the as-prepared PtCoRu NAs displayed remarkably enhanced electrocatalytic performance for the HER in 1.0 M KOH.

Journal ArticleDOI
TL;DR: In this paper, an ultralow-temperature solution reduction approach is developed to anchor atomically dispersed Pt atoms on carbon nanotubes (Pt-CNTs), which decelerates the diffusion rate of PtCl62− ion reached onto the carbon nanotsubes and lowers the free energy of Pt atoms in the solution to reduce the probability of the Pt aggregation.

Journal ArticleDOI
TL;DR: It is demonstrated that under-coordinated Pt atoms at the edges of the first cluster layer are rendered cationic by direct contact with the Al 2 O 3 support, which affects the overall CO oxidation activity.
Abstract: Platinum nanocatalysts play critical roles in CO oxidation, an important catalytic conversion process. As the catalyst size decreases, the influence of the support material on catalysis increases which can alter the chemical states of Pt atoms in contact with the support. Herein, we demonstrate that under-coordinated Pt atoms at the edges of the first cluster layer are rendered cationic by direct contact with the Al2O3 support, which affects the overall CO oxidation activity. The ratio of neutral to cationic Pt atoms in the Pt nanocluster is strongly correlated with the CO oxidation activity, but no correlation exists with the total surface area of surface-exposed Pt atoms. The low oxygen affinity of cationic Pt atoms explains this counterintuitive result. Using this relationship and our modified bond-additivity method, which only requires the catalyst–support bond energy as input, we successfully predict the CO oxidation activities of various sized Pt clusters on TiO2. Platinum nanocatalysts play critical roles in CO oxidation. Herein, the authors discover that under-coordinated Pt atoms at the edges of the first cluster layer are rendered cationic by direct contact with the Al2O3 support, which affects the overall CO oxidation activity.

Journal ArticleDOI
TL;DR: In this article, high-quality platinum nanocubes (Pt-NCs) with 4.5-nm size were achieved by facile hydrothermal synthesis, and the physical morphology and structure of Pt-NC was exhaustively characterized, revealing that PtNCs with special {100} facets have excellent uniformity, good dispersity and high crystallinity.