Electronic State Of Pt Research Articles

Strong Metal-Support Interaction – a Tool for Enhancing the Hydrogen Evolution Reaction Performance

Renewable and green energy transition and meeting ever-increasing energy demands are among modern society's most pressing challenges. Currently, the world's energy systems rely on fossil fuels, leading to significant environmental pollution, including anthropogenic CO2 emissions and subsequent climate changes. The concept of hydrogen economy was first proposed half a century ago as a way to overcome these challenges by using hydrogen as the primary energy carrier instead of fossils.1 However, hydrogen production remains one of the significant obstacles to realizing the hydrogen economy, as steam reforming of methane derived from natural gas is still the dominant method of industrial-scale production, contributing significantly to the undesired emissions. Water electrolysis powered by renewables such as wind and sun energy is a sustainable way to produce high-purity hydrogen. In electrolyzers, hydrogen is obtained at the cathode side through the electrochemical hydrogen evolution reaction (HER), while the oxygen evolution reaction (OER) occurs at the anode. The HER is one of the most intensely studied electrochemical processes as it is of paramount importance for both fundamental and applicable aspects of electrocatalysis and physical chemistry in general. Traditionally, Pt has been known as the best monometallic HER catalyst due to its close-to-optimal interaction with adsorbed hydrogen atoms, which are reaction intermediates.2 However, due to its scarcity and high price, significant research efforts are being invested in designing alternative Pt-free electrocatalysts for (not only) HER. While promising results have been reported with different abundant materials such as sulfides, nitrides, carbides, and phosphides, their applicability is still challenged by rather inferior activity with respect to Pt and rapid deactivation, especially in corrosive acidic media. Currently, state-of-the-art HER catalysts are based on Pt nanoparticles dispersed over high-surface-area carbon supports (Pt/C). The main downside of such composites is the weak interaction between carbon and Pt particles, which means that support cannot affect the intrinsic activity of Pt sites. Moreover, this weak interaction results in the degradation of Pt/C due to particle detachment, agglomeration, or coalescence during HER. Upgrading the overall performance of Pt/C may be achieved by employing alternative supports able to trigger strong metal-support interaction (SMSI). SMSI can alter the electronic structure of the metallic active sites and increase their activity, while also it can lead to the stronger anchoring of nanoparticles with the support, improving stability. Different materials, such as pre-functionalized carbons, carbides, and metal oxides, have been reported to be able to provide SMSI.In this work, we investigated HER on a carbon-ceramic catalyst composed of Pt nanoparticles supported on titanium oxynitride (TiONx) embedded on reduced graphene oxide nanoribbons (Pt/TiONx).3 TiONx was obtained by incorporating nitrogen into TiO2 and provides the main merits of carbon supports, such as electrical conductivity and high surface area, combined with the ability to trigger SMSI. The screening of the electrocatalytic performance of the Pt/TiONx composite for HER revealed enhancement with respect to the Pt/C benchmark, which we ascribe to the effect of the TiONx substrate via SMSI. To confirm this, XPS was performed to compare the electronic states of Pt in Pt/TiONx and Pt/C catalysts, which revealed the ability of TiONx to trigger SMSI. DFT calculation provided additional confirmation of SMSI between the TiONx support and Pt nanoparticles and its impact on both HER activity and stability enhancement. The results presented in this work open up a perspective of using TiONx as an alternative support able to improve the catalytic performance of various active sites for different electrochemical reactions. References (1) Bockris, J. O. M. The Hydrogen Economy: Its History. Int J Hydrogen Energy 2013, 38 (6), 2579–2588. https://doi.org/10.1016/j.ijhydene.2012.12.026.(2) Hansen, J. N.; Prats, H.; Toudahl, K. K.; Mørch Secher, N.; Chan, K.; Kibsgaard, J.; Chorkendorff, I. Is There Anything Better than Pt for HER? ACS Energy Lett 2021, 1175–1180. https://doi.org/10.1021/acsenergylett.1c00246.(3) Smiljanić, M.; Panić, S.; Bele, M.; Ruiz-Zepeda, F.; Pavko, L.; Gašparič, L.; Kokalj, A.; Gaberšček, M.; Hodnik, N. Improving the HER Activity and Stability of Pt Nanoparticles by Titanium Oxynitride Support. ACS Catal 2022, 12 (20), 13021–13033. https://doi.org/10.1021/acscatal.2c03214. Figure 1

Phosphorus-doped activated carbon as a platinum-based catalyst support for electrocatalytic hydrogen evolution reaction

Carbon is an excellent support that may influence the electronic structure of metal particles. However, carbon lacks functional groups on its surface, making it unsuitable for carrying catalysts, resulting in metal agglomeration. This can be solved by heteroatom doping to effectively optimize ligand structure and electronic characteristics of carbon materials, as well as enhance the intrinsic activity and steadiness of Pt/C catalysts. Herein, phosphorus-doped activated carbon (P-AC) was prepared as support for Pt catalysts to enhance the hydrogen evolution reaction (HER) under alkaline conditions. The main doped form of P-AC by potassium dihydrogen phosphate was identified as C3-PO, considered the most stable phosphorus-oxygen functional group in the carbon lattice with a key role in the HER process. The existence of C3-PO enhanced the interaction between P-AC and Pt nanoparticles, thereby tuning the electronic state of Pt and further optimising the adsorption of H* on Pt. Consequently, the resulting Pt/P-AC catalysts exhibited excellent HER activity (Tafel slope: 33.0 mV·dec−1, overpotential: 36.1 mV), with 4.6-fold incremented mass activity (1.220 A·mgpt−1) at a voltage of 70 mV than commercial catalysts containing 40 wt% Pt/C (0.266 A·mgpt−1). Moreover, a remarkable electrochemically active surface area (ECSA) of 66.95 m2·gPt−1 was observed in the Pt/P-AC catalysts. The Pt/P-AC catalysts also displayed high stability with better activity loss than commercial 40% Pt/C after 10,000 cycles. In sum, the proposed method looks promising for future syntheses of novel HER catalysts with high HER performance under alkaline conditions.

The coupling synergy of active Pt species and oxygen vacancy induced by PtCu for enhanced performance towards the removal of NO and CO

Both the Pt electronic state and oxygen vacancy within supports play an important role in catalytic reactions. However, it remains a challenge for simultaneous achievement of modulating Pt electronic state as well as tuning oxygen vacancy content. In this work, we have prepared a series of PtCu-CeO2 catalysts with different Pt/Cu ratios. The electronic state of Pt is modulated by means of Pt-Cu alloy effect, while the oxygen vacancy content is tuned by the constructed PtCu-CeO2 interfaces. When the as-prepared PtCu-CeO2 catalysts are used for the reduction of NOx by CO, the one with Pt/Cu ratio of 1 (Pt1Cu1-CeO2) possesses twice higher NO conversion and superior N2 selectivity below 200℃than that of monometallic Pt-CeO2. The characterization results illustrate that Pt1Cu1-CeO2 catalyst exhibits a moderate strength for CO adsorption and a fast NO dissociation ability, resulting in the formation of N2 rather than N2O intermediate. This work is expected to open an alternative avenue for boosting the catalytic performances by simultaneous modulation of Pt electronic state and oxygen vacancy content.

Improved electrocatalytic activity of Pt on carbon nanofibers for glucose oxidation mediated by support oxygen groups in Pt perimeter

Support effects in supported metal catalysts are well studied for thermocatalytic reactions, but less studied for electrocatalytic reactions. Here, we prepared a series of Pt supported on carbon nanofiber catalysts which vary in their Pt particle size and the content of oxygen groups on the surface of the CNF. We show that the activity of these catalysts for electrocatalytic glucose oxidation relates linearly with the content of support oxygen groups. Since the electronic state of Pt (XAS) and Pt surface structure (CO-stripping) were indistinguishable for all materials, we conclude that sorption effects of glucose play a crucial role in catalytic activity. This was further confirmed by establishing a relation between the annulus of the Pt particles and the activity.

Nanoengineered design of inside-heating hot nanoreactor surrounded by coolenvironment for selective hydrogenations.

Catalysts with designable intelligent nanostructure may potentially drive the changes of chemical reaction techniques. Herein, we designed a multi-function integrating nanocatalyst, Pt-containing magnetic yolk-shell carbonaceous structure, having catalysis function, microenvironment heating, thermalinsulation and elevated pressure into a whole, which induces selective hydrogenation within heating-constrained nanoreactors surrounded by ambient environment.As a demonstration, carbonyl of α, β-unsaturated aldehydes/ketones are selectively hydrogenated to unsaturated alcohols with a >98% selectivity at a nearly complete conversion under mild conditions of 40°C and 3bar instead of harsh requirements of 120°C and 30bar. We creatively demonstrate that the locally increased temperature and endogenous pressure (estimated as ∼120°C, 9.7bar) in the nano-sized space greatly facilitates the reaction kinetics under an alternating magnetic field. The outward-diffused products to the "cool environment" retain thermodynamically stable, avoiding the over-hydrogenation often occurs under constantly heated conditions of 120°C. Regulation of the electronic state of Pt by sulfur doping of carbon allows selective chemical adsorption of the -C = O group and consequently leads to selective hydrogenation. It is expected that such a multi-function integrated catalyst provides an ideal platform for precisely operating a variety of organic liquid-phase transformations under mild reaction conditions. This article is protected by copyright. All rights reserved.

Tailoring the electronic states of Pt by atomic layer deposition of Al2O3 for enhanced CO oxidation performance: Experimental and theoretical investigations

Herein, atomic layer deposition (ALD)-Al2O3 films were applied as a medium to modulate the electronic states of the supported Pt. Based on the sacrificial template of ZIF-67, the ternary Co3O4/Pt/Al2O3 catalyst exhibited better performance in catalytic CO oxidation than the binary Co3O4/Pt catalyst. Both experimental and calculation results indicate the existence of charge transport between the Pt and the ALD-Al2O3 films, leading to electron-rich Pt, enhanced O2 affinity, and reduced activation energy. Interestingly, the oxidation resistance of Pt nanoparticles was visualized when annealing Co3O4/Pt/Al2O3 catalyst at high temperatures. Mechanism studies indicate the typical LH mechanism occurred in CO oxidation, showing that the co-adsorbed CO and O2 could be converted to carbonate-type *OCOO intermediates via low energy barriers. At low temperatures, CO2 was mainly produced by the lattice oxygen-mediated M-vK mechanism based on isotope labeling experiments. Our findings provide an alternative way to regulate the electronic states of noble metals by the ALD technique.

Al-Pt intermetallic compounds: HAXPES study.

Intermetallic compounds in the Al-Pt system were systematically studied via hard X-ray photoelectron spectroscopy, focusing on the positions of Pt 4f and Al 2s core levels and valence band features. On one hand, with increasing Al content, the Pt 4f core levels shift towards higher binding energies (BE), revealing the influence of the atomic interactions (chemical bonding) on the electronic state of Pt. On the other hand, the charge transfer from Al to Pt increases with increasing Al content in Al-Pt compounds. These two facts cannot be combined using the standard "chemical shift" approach. Computational analysis reveals that higher negative effective charges of Pt atoms are accompanied by reduced occupancy of Pt 5d orbitals, leading to the limited availability of these electrons for the screening of the 4f core hole and this in turn explains the experimentally observed shift of 4f core levels to higher BE.

Development and catalytic mechanism of a highly efficient Pt/Kβ catalyst for n-Heptane aromatization

Development of a high-performance naphtha aromatization catalyst has been paid many attentions as this reaction is generally employed to elevate the octane number of FCC gasoline and Fischer-Tropsch-synthesized oil. Here, a hierarchical porous Pt/Kβ catalyst is developed. It shows much higher activity, selectivity and stability than conventional Pt/KL. The catalytic performance of Pt/Kβ depends on Brϕnsted acidity and mesoporosity of zeolite β and nanoparticles (NPs) size and electronic state of Pt. The catalytic mechanism was investigated by combining TPSR, GC–MS, reaction kinetic studies and DFT calculations. Pt NPs catalyze dehydrogenations of alkanes/cycloalkenes to alkenes and dienes, while Brϕnsted acid sites facilitate alkene cyclization and ring-expansion of cycloalkenes despite that they can also dehydrogenate alkanes/alkenes through hydrogen transfer reactions. The n-heptane is mainly aromatized by dehydrogenating to 1-heptene and 2-heptene, 1,6- and 1,5-cyclizing into methylcyclohexane and ethyl-cyclopentane, and successively ring-expanding and/or dehydrogenating to toluene that may be further dealkylated to benzene.

Enhanced Activity of Oxygen Reduction Reaction on Pr6O11-Assisted PtPr Alloy Electrocatalysts.

Pt-based alloy catalysts for oxygen reduction reaction (ORR) with outstanding performance have been well-studied in recent years. Among these, Pt-lanthanide alloy catalysts have been developed with quite a competitive ORR activity. However, to promote practical applications of a proton-exchange membrane fuel cell (PEMFC), catalysts with superior activity are still being explored. Herein, we present the Pr6O11-assisted Pt-Pr catalyst exhibiting further improved ORR activity than the state-of-the-art Pt/C. A simple annealing treatment is applied after the synthesis of the Pt-Pr alloy, obtaining Pr6O11 nanoparticles attached to the surface of the Pt-Pr alloy to form a Pt-Pr/Pr6O11 composite catalyst. Experimental and theoretical studies reveal that the electronic state of Pt in the Pt-Pr/Pr6O11 system is modified. It was found that the strong oxophilicity of Pr adjusts the active site of Pt and promotes the adsorption and dissociation of O2. The preeminent intrinsic ORR activity on the Pt-Pr/Pr6O11 catalyst reaches the promoted specific activity (2.01 mA cm-2) and mass activity (1.3 A mgPt-1), which were 5.91- and 5.90-fold higher than those obtained by the state-of-the-art Pt/C catalyst (0.34 mA cm-2 and 0.22 A mgPt-1). This study provides us with an idea that the ORR performance of Pt-based alloy could be enhanced with the assistance of the metal oxide phase.

Synergistic effects of PtFeV alloy-decorated functionalized CNTs on performance of polymer fuel cell investigated by specially designed cathodic half-cell

In this study, functionalized carbon nanotube decorated with PtFeV tri-metallic electrocatalysts (PtFeV/FCNT) by different concentrations are prepared using the ethylene glycol reduction method in order to minimize electrocatalyst load and enhance the performance of the fuel cell cathodic electrode, simultaneously. The homogeneous distribution of PtFeV catalysts on the FCNT substrate and also the change in the electronic states of Pt, Fe and V elements is confirmed with characterization analyses. Electrode half-cell tests simulating the cathodic compartment of a polymer fuel cell show that the 2 mM PtFeV/FCNT electrode increases the maximum power density by about 500% compared to the commercial Pt/C 20% wt catalyst (from 4.43 to 27.31 mW/cm2). The increase in maximum power density along with the decrease in charge transfer resistance specified by the electrochemical impedance tests confirm the synergistic effects of alloying Pt with Fe and V and the application of FCNTs. In fact, in addition to the exceptional specific surface area and electrical conductivity of FCNTs, the increase in PtFeV/FCNT electrode performance can be attributed to the improved electrocatalytic activity of PtFeV tri-metallic nanoparticle alloy, resulting from the valence alterations and the Pt network compression during alloying.

Effects of second metals (M = Fe, Cu, Ga, In, Sn) on the geometric and electronic properties of platinum for the direct dehydrogenation of propane

Supported Pt-based bimetallic catalysts are representative types of dehydrogenation catalysts used for alkanes to olefins conversion. The platinum in these catalysts exhibits unique structural features accompanied with changes in electronic states due to the addition of the second metal. To investigate the impact of each effect on the activity for propane dehydrogenation, a series of Pt-M/SiO 2 (M= Fe, Cu, Ga, In and Sn) catalysts were prepared and used for propane dehydrogenation. Utilizing various characterization techniques, the geometric and electronic properties of these catalysts were studied. The relationships between the specific activity of bimetallic platinum catalysts in propane dehydrogenation and atomic sizes of alloys (i) and the total density of unoccupied d bands in platinum (ii) were considered. Via alloy formation, it was found that dilution of the active metal Pt occurred in these SiO 2 supported bimetallic catalysts, and the lattice parameter of Pt-M alloys decreased on Pt-Fe, Pt-Cu and Pt-Ga alloys, but increased on Pt-In and Pt-Sn alloys when compared with that of Pt foil. Catalytic activity was evidently shown to not be a function of the lattice parameters of Pt-M alloys, but appears closely related with the d -holes of Pt in Pt-M bimetallic catalysts. More d holes show favorably high activity. Among the studied Pt-M/SiO 2 (M= Fe, Cu, Ga, In and Sn) catalysts, the prominent and primary role of the electronic effect was demonstrated. • Mansour’method was used to quantitatively determine the electronic state of Pt. • Pt-Ga/SiO 2 catalyst exhibits biggest d -holes and highest initial conversion of propane. • The electronic effect plays a crucial role in studied systems.

Isostructural M 2pt (M = Al, Ga, In, Sn) As OER Anode Materials

Looking for the future energy infrastructure, hydrogen will play an important role as energy carrier molecule. Among different physical and chemical methods of hydrogen production, water electrolysis has numerous advantages. However, the sluggish kinetics of anodic oxygen evolution reaction (OER) hinders its large-scale implementation. The intensive search for new OER electrocatalytic materials is limited by harsh oxidative conditions and instability/ changes of electrocatalyst under reaction conditions. Platinum is characterized by pronounced stability against dissolution compared to other noble metals. However, the OER activity of Pt is one of the lowest one. Combining the platinum with main group elements in form of M 2Pt intermetallic compound will lead to the different electronic state of Pt and, correspondingly, different OER activity.The compounds M2 Pt (M = Al, Ga, In, Sn) crystallize with cubic anti-CaF2 type of crystal structure [1]. Due to the pronounced charge transfer from M to Pt, Pt atoms are negatively charged in these compounds. There is only one type of strongly polar covalent interactions between M and Pt atoms. The OER activity decreases in the following sequence In2Pt > Ga2Pt > Al2Pt. This trend is governed by the chemical nature of the counterpart elements M (M = Al, Ga, In) and their leaching rates under OER conditions. The leaching of M into the electrolyte leads to formation of composite material of intermetallic M2 Pt and Pt-rich phase in the near-surface region. The inactivity of Sn2Pt is due to the formation of passivating SnO2 layer with poor electrical conductivity.The study of OER activity of M 2Pt materials under different electrochemical treatments was combined with surface- and bulk characterization of electrodes after electrochemical experiments, elemental analysis of electrolyte and quantum chemical calculations. This allows to investigate the influence of chemical nature of counterpart element M onto the OER performance of isostructural M 2Pt electrode materials [2].[1]. Antonyshyn, I., Barrios Jiménez, A.M., Sichevych, O., Burkhardt, U., Veremchuk, I., Schmidt, M., Ormeci, A., Spanos, I., Tarasov, A., Teschner, D., Algara-Siller, G., Schlögl, R., Grin, Yu. // Angew. Chem. Int. Ed. 59, 16770–16776 (2020).[2]. Barrios Jiménez, A.M., Burkhardt, U., Altendorf, S.G., Kaiser, F., Veremchuk, I., Ormeci, A., Auffermann, G., Antonyshyn, I., Grin, Yu., submitted.

Stabilizing the isolated Pt sites on PtGa/Al2O3 catalyst via silica coating layers for propane dehydrogenation at low temperature

Catalytic conversion of propane to propylene can be achieved by non-oxidative propane dehydrogenation (PDH) by Pt-based catalysts under 550–700 °C. In this work, we report a strategy to decrease the Pt loading amount to only 0.1 wt% for obtaining a stable catalyst via silica coating for high PDH activity at a temperature as low as of 450 °C. The as-prepared 2.5%Si@PtGa/Al2O3 catalyst shows outstanding catalytic activity (propylene productivity rate 0.5 mol/gcat.·h) close to its equilibrium conversion (24.5%) with much better stability (deactivation constant: 0.007 h−1) at 450 °C. The interface between catalyst and silica coating changes the strong metal-support interaction (SMSI) to immobilize the Ga oxide clusters, further tightly anchoring the Pt catalytic sites for PDH process. Moreover, the electronic state of Pt is also influenced by the silica coating layers. This work demonstrates a new method to harnessing the metal-support interaction in catalysis.

Tungsten Oxide/Reduced Graphene Oxide Aerogel with Low-Content Platinum as High-Performance Electrocatalyst for Hydrogen Evolution Reaction.

Designing cost-effective, highly active, and durable platinum (Pt)-based electrocatalysts is a crucial endeavor in electrochemical hydrogen evolution reaction (HER). Herein, the low-content Pt (0.8 wt%)/tungsten oxide/reduced graphene oxide aerogel (LPWGA) electrocatalyst with excellent HER activity and durability is developed by employing a tungsten oxide/reduced graphene oxide aerogel (WGA) obtained from a facile solvothermal process as a support, followed by electrochemical deposition of Pt nanoparticles. The WGA support with abundant oxygen vacancies and hierarchical pores plays the roles of anchoring the Pt nanoparticles, supplying continuous mass transport and electron transfer channels, and modulating the surface electronic state of Pt, which endow the LPWGA with both high HER activity and durability. Even under a low loading of 0.81 μgPt cm-2 , the LPWGA exhibits a high HER activity with an overpotential of 42mV at 10mA cm-2 , an excellent stability under 10000-cycle cyclic voltammetry and 40 h chronopotentiometry at 10mA cm-2 , a low Tafel slope (30mV dec-1 ), and a high turnover frequency of 29.05s-1 at η= 50mV, which is much superior to the commercial Pt/C and the low-content Pt/reduced graphene oxide aerogel. This work provides a new strategy to design high-performance Pt-based electrocatalysts with greatly reduced use of Pt.

Insight into the nature of Brönsted acidity of Pt-(WOx)n-H model catalysts in glycerol hydrogenolysis

In glycerol hydrogenolysis, the conventional preparation methods for Pt-WOx catalysts on active supports usually result in the coexistence of various active sites, causing complex reaction network and declining the atom efficiency of W toward 1,3-propanediol (1,3-PDO) production. Herein, we report Pt-(WOx)n-H model catalyst prepared via strong metal–oxide interaction (SMOI) behavior on inert SiO2 support, which shows both high performance and W efficiency for 1,3-PDO. The W efficiency as high as 5.786 h−1 was obtained on 2W4Pt/SiO2 at 160 °C under 8.0 MPa. Furthermore, these model catalysts also give the advantage in revealing the Brönsted acidity of Pt-(WOx)n-H sites. Structure characterizations and DFT calculation confirm the Brönsted acid strength of Pt-(WOx)n-H is significantly sensitive to both the polymerization and reduction degree of WOx domains. The high catalytic efficiency of 2W4Pt/SiO2 originates from the strong Brönsted acidity and its synergism with Pt metal. The correlation between Brönsted acidity and electronic state of Pt-(WOx)n-H is also discussed by electron density difference analysis and XPS.

Recent progress in Pt and Pd-based hybrid nanocatalysts for methanol electrooxidation.

Although Pt and Pd nanocrystals are among the most popular candidates for anode catalysts in direct methanol fuel cells, their catalytic properties still need to be further improved in order to reduce the costs. In view of this, fabricating hybrid nanomaterials by integrating noble metal nanocrystals and other species turns out to be a powerful way to produce unprecedented catalysts which could combine the merits of different components and modulate the electronic states of Pt or Pd at the same time. In this review, we list recent studies in the construction of heterostructured hybrid nanocatalysts through introducing external components into the noble metal nanocrystals. The mentioned external components include heteroatom doped carbon nanomaterials, metal oxides and hydroxides, as well as transition metal carbides, nitrides, phosphides, and sulfides. The construction methodologies and functions that these introduced species played in the catalytic processes of methanol electrooxidation are discussed. The attempts to maximize the catalytically active interfaces and utilization efficiencies of noble metals are also presented. Finally, the conclusions and existing problems in relevant nanocatalysts are provided.

Support induced charge transfer effects on electrochemical characteristics of Pt nanoparticle electrocatalysts

The electrokinetic properties of Pt nanoparticles supported on Carbon (Pt/C) and Boron Carbide-Graphite composite (Pt/BC) are compared over a wide potential range. The influence of the support on the electronic state of Pt was investigated via in-situ X-ray Absorption Spectroscopy. Pt d-band filling, determined from XANES white line analysis, was lower and nearly constant between 0.4 and 0.95V vs. RHE for Pt/BC, indicating more positively charged particles in the double layer region and a delay in the onset of oxide formation by about 0.2V compared to the Pt/C catalyst, which showed a marked increase in d-band vacancies above 0.8V vs. RHE. Moreover, Δμ analysis of the XANES data indicated a lack of sub-surface oxygen for the Pt/BC catalyst compared to the Pt/C catalyst above 0.9V vs. RHE. Additional anion adsorption on the Pt/BC in the double layer region, detected by CO displacement, was also confirmed by XANES analysis of the d-band occupancy. The H2 oxidation activities of electrodes with low catalyst loadings were assessed under high mass transport conditions using the floating electrode methodology. The metal-support interaction between the Pt and BC support improved the maximum hydrogen oxidation current density by 1.4 times when compared to Pt/C.

Platinum loaded on dual-doped TiO2 as an active and durable oxygen reduction reaction catalyst

In this work, dual-doped TiO2 was successfully synthesized by using tungsten or niobium as the cation and nitrogen as the anion and, as compared with single-doped TiO2, provided a higher electron conductivity and improved physical properties. Platinum (Pt) nanoparticles loaded on these materials showed better electrochemical performance, and the Pt/Ti0.9Nb0.1NxOy and Pt/Ti0.8W0.2NxOy catalysts were 2.6–3.7 times more active than the Pt/Ti0.9Nb0.1Oy and Pt/Ti0.8W0.2Oy catalysts without nitrogen doping. Additionally, there was an activity loss of 22.9% as compared with 81% in Pt/C after 30 000 cyclic voltammetry cycles, a value exceeding the US Department of Energy (DOE) stability target. Dual doping not only enhances the electron conductivity but also changes the electronic state of Pt on the support materials, thus allowing for more active and stable catalysts. Both X-ray absorption spectroscopy (XAS) and density functional theory (DFT) studies were undertaken to demonstrate how defect formation affects the interactions between Pt and the single- or dual-doped TiO2 supports and manipulates the physical and chemical properties of the resulting catalysts. Thus, these catalytic supports are strong candidates for proton exchange membrane fuel cell applications.

Improvement of Electrochemical ORR Activity and Its Durability with Pt Electrocatalyst Nanoparticles Anchored on MOx/Cup-Stacked Carbon Nanotube in Acidic Aqueous Media

In order to prepare the sample that exhibits the enhancement of oxygen reduction reaction (ORR) and improvement of its durability for the ORR in acidic aqueous solutions, Pt nanoparticles (NPs) were deposited on TiO2 moieties which was coated on a cup-stacked carbon nanotube (CSCNT) as a electron-conducting support material. The TiO2 moieties on which Pt NPs were deposited contribute to both enhancement of ORR and improvement of durability of ORR electrocatalytic activity by the electronic interaction between Pt NPs and TiO2 and anchor effect of rough TiO2 by which Pt NPs are anchored, resulting in the inhibition of aggregation of Pt NPs during potential cycling. The two functions of TiO2 moieties could realize large improvement of the electrocatalytic performance for ORR in Pt NPs/TiO2/CSCNT. The formation of nanostructure of Pt NPs on TiO2 and surface structure of the Pt NPs were characterized with transmission electron microscope (TEM). The electronic states of Pt and Ti atoms were measured with X-ray photoelectron spectroscopy (XPS). The results obtained with TEM and XPS supported our consideration on the improvement of ORR activity and its durability.

Mesoporous Pt–Ni catalyst and their electro catalytic activity towards methanol oxidation

Mesoporous Pt/Ni architecture has been prepared by template assisted electrochemical deposition of Pt–Ni over anodized aluminum oxide template followed by controlled de-alloying with nitric acid. Surface characteristics of the ordered bimetallic mesoporous Pt/Ni structure were systematically characterized through XRD, SEM, AFM and XPS analyses. It is designated by XPS analysis that presence of Ni significantly modifies surface characteristics and electronic states of Pt accompanied with a downshift in the d-band character of Pt. Mesoporous morphology is highly beneficial to offer readily accessible Pt catalytic sites for methanol oxidation reaction. The prepared bimetallic Pt/Ni was used as electro catalyst for DMFC. Comparison of electrocatalytic activity of bimetallic mesoporous Pt/Ni with bimetallic smooth Pt/Ni was interrogated using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy analyses. Distinctly enhanced electrocatalytic activity with improved CO tolerance associated with bimetallic mesoporous Pt/Ni electrode towards methanol oxidation stems from a synergy existing between mesoporous structure with bi-metallic composition.