PtNi Nanoparticles Research Articles

Application of Hydrogenated Graphitic Supports in Electrocatalysts: Effects on Carbon Support Surface Chemistry, Nanoparticle Growth, and Electrocatalytic Activity.

One of the key technical challenges before the widespread adoption of proton exchange membrane fuel cells (PEMFCs) is increasing the durability of the platinum catalyst layer to meet a target of 8000 operating hours with only a 10% loss of performance. Carbon corrosion, one of the primary mechanisms of degradation in fuel cells, has attracted attention from researchers interested in solving the durability problem. As such, the development of catalyst supports to avoid this issue has been a focus in recent years, with interest in hydrophobic supports such as highly graphitized carbons. In this research, we propose a method to increase the durability of carbon supports by way of exploiting hydrogenated graphene's hydrophobic properties. By performing a Birch reduction on graphene nanoplatelets, we were able to synthesize hydrogenated graphene nanoplatelets which were used as support for hollow porous PtNi nanoparticles. The structure of these nanoparticle-carbon composites was characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy coupled with scanning transmission electron microscopy (STEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). We found that hydrogenation can strongly affect the morphology of nanoparticles formed as well as increase the electrochemical stability of the composites. Accelerated stress tests for 6000 cycles between 1.0 and 1.6 V vs RHE at 25 °C demonstrated that a hydrogenated support for PtNi increased the retained electrochemical surface from 36.8% to 61.9% when compared to the pristine graphene nanoplatelets. Moreover, the retained activity was increased from 26.6% to 53.0% by use of the hydrogenated carbon support. To confirm that hydrogenation enhanced durability, stress tests combined with Raman spectroscopy showed minimal change in the ID/IG ratio of the hydrogenated composite. Finally, identical location transmission electron microscopy (IL-TEM) was used to support the results of the electrochemical stress tests.

Durability and Structural Transformation of Pt Alloy Nanowires and Nanoparticles for the Oxygen Reduction Reaction in Acidic Media

The oxygen reduction reaction (ORR) is catalyzed at the cathode in polymer electrolyte fuel cells (PEFCs). Since the ORR is sluggish and the electrocatalytic activity of the ORR catalyst determines the overall performance of PEFCs, highly active and durable ORR electrocatalysts have been intensively studied. The combination of alloying and nanostructuring of Pt is one of the promising approaches to develop such ORR electrocatalysts. Among the Pt-based shape-controlled electrocatalysts, Pt or Pt–M alloy nanowires (M = Ni and Co) are known to exhibit high ORR activity in the half cell [1,2]. Since nanowires have larger contact areas and therefore potentially higher adhesion to the carbon support than conventional nanoparticles, Pt-based nanowires should have higher durability. However, details of the effect of durability testing (potential cycles) on the structure of nanowires remain unclear.In this work, we report synthesis of PtNi alloy nanowires at different temperatures under different atmospheres, and their structural transformation after potential cycles. PtNi nanowires were prepared at 433 K under Ar and air [3]. The difference in atmosphere affects the presence or absence of PtNi nanoparticles with PtNi nanowires: both PtNi nanowires and nanoparticles are produced under the inert condition of Ar, whereas PtNi nanowires are exclusively produced under the oxidative condition of air. PtNi nanowires with and without PtNi nanoparticles were converted into branched nanostructures after durability tests. PtNi nanowires were also prepared at different temperatures of 433, 493 and 553 K under Ar [4]. The Ni content in the PtNi nanowires increases from <5 at.% up to about 15 at.% with increasing synthesis temperature. The number of PtNi nanoparticles also decreases with increasing synthesis temperature. The PtNi nanowires in the co-presence of PtNi nanoparticles prepared at 493 K gave highly durable beads-on-nanowires with the Pt skin via Ostwald ripening of coexisting PtNi nanoparticles. This structural transformation is coupled with changes in the surface electronic structure, confirmed by in situ X-ray absorption spectroscopy. Understanding such a structural transformation will help us to design and develop highly durable Pt alloy nanostructured electrocatalysts for the ORR.References.[1] M. Li et al., Science, 354, 1414 (2016).[2] Z. Zhao et al., Adv. Mater.,31, 1808115 (2019).[3] M. Kato, Y. Iguchi, T. Li, Y. Kato, Y. Zhuang, K. Higashi, T. Uruga, T. Saida, K. Miyabayashi, I. Yagi, ACS Catal., 12, 259 (2022).[4] Y. Zhuang, Y. Iguchi, T. Li, Y. Kato, M. Kato, Y. A. Hutapea, A. Hayashi, T. Watanabe, I. Yagi, ACS Catal., 14, 1750 (2024).

Effect of Annealing Time on Various PtNi/C Binary Alloy Catalysts for ORR in PEFCs

Introduction PEFCs are attracting attention as a power source for automobiles, residential, and portable devices due to their low environmental impact and high energy efficiency 1-2). However, the cathode of PEFCs requires a large amount of platinum to accelerate the ORR reaction. The high cost of Pt has hindered the extensive development of PEFCs for large-scale commercialization. Therefore, the research that combines reduced Pt usage with the high activity of electrocatalysts is highly desirable. A commonly applied approach to develop highly efficient and low-cost electrocatalysts is to reduce the Pt loading in the catalysts supported on high specific surface area carbon and to alloy Pt with transition metals, which could lead to a significant improvement in the cell performance. In this study, the PtNi nanoparticle alloy catalysts were synthesized as the cathode catalysts using high specific surface area carbon, utilizing Ni, which is an inexpensive metal, and their catalytic activity was evaluated. Experimental A Pt/C catalyst was prepared with loadings of 35% and 50% weight by ethanol reduction method 3). Briefly, nickel nitrate precursor was precipitated into the Pt/C powder by controlling pH at 10. Drying black powder then annealed at 900 °C for 15, 30, 60, 90 min in H2/Ar flow. The resulting powder was noted as PtNi/C(BT). To obtain Pt rich surface, acid treatment was performed in 0.5 M H2SO4 at 80 °C. The resulting powder was noted as PtNi/C(AT). The physical characteristics were evaluated by using various techniques such as TEM, XRD, and XRF. CV was measured to calculate the ECSA in 0.1 M HClO4 at room temperature. LSV was performed to evaluate the ORR mass activity and initial activity of the PtNi/C catalyst. Finally, the I-V cell performance of the PtNi/C catalyst was evaluated using MEA as a cathode for ORR in PEFCs. Results and Discussion TEM images revealed that the PtNi/C catalyst particles were homogeneously dispersed. The average particle sizes increased with increasing annealing time. Fig.1 shows the XRD patterns obtained for the 39.7 ° peak on the Pt(111) plane was shifted to a wider angle, indicating the formation disordered fcc-phase of PtNi alloy. The peaks became sharper with increasing annealing time, suggesting higher crystallinity. The crystalline size was calculated by using the Scherrer equation (3.73 nm, 5.21 nm, 5.94 nm and 6.49 nm), respectively. The ECSA of all PtNi/C catalysts was higher compared to the commercial PtCo/C catalysts. Acid treatment would cause Ni leaching from the surface, leading to a Pt-enriched surface, which could result in higher ECSA. The ECSA values decreased with increasing the annealing time, possibly due to particle growth and larger particle size with longer annealing time. The ORR activity for all PtNi/C catalysts was improved and higher than commercial PtCo/C. This increase in ORR activity would be due to the internal alloying of Ni and the improved electronic structure resulting from annealing at 900 °C. Fig.2 shows similar I-V performance was observed for 60 and 90 min annealing time in PtNi/C catalysts. Instead, the PtNi/C catalyst annealed for 15 min had lower performance, which could be attributed to Ni leaching and particle agglomeration. After ADT, the cell voltage at high current density region (1.0 A cm−2) for 60 min catalysts of PtNi/C (AT) was lower degradation compared to the commercial PtCo/C catalyst, indicating improved durability. In this study, the improvement of ORR activity was investigated at different annealing times, and it was found that 60 minutes of annealing time showed better durability and activity.This study was partly supported by NEDO, Japan. References (1) S. Maiti, et al., Energy Environ. Sci., 14, 3717 (2021).(2) R. Borup, et al., Chem. Rev., 107, 3904 (2007).(3) N. Narischat, et al., J. Phys. Chem. C, 118, 23003, (2014). Figure 1

Sub-10 nm PdNi@PtNi Core–Shell Nanoalloys for Efficient Ethanol Electro-Oxidation

By controlling the structure and composition of Pt-based nanoalloys, the ethanol oxidation reaction (EOR) performances of Pt alloy catalysts can be effectively improved. Herein, we successfully synthesis sub-10 nm PdNi@PtNi nanoparticles (PdNi@PtNi NPs) with a core–shell structure by a one-pot method. The sub 10 nm core–shell nanoparticles possess more effective atoms and exhibit a synergistic effect which can lead to a shift in the d-band center and alter binding energies toward adsorbates. Due to the synergistic effect and unique core–shell structure, the PdNi@PtNi NP catalysts exhibit excellent electrocatalytic performance for ethanol oxidation reactions in alkaline, achieving 9.30 times more mass activity and 7.05 times more specific activity that of the state-of-the-art Pt/C catalysts. Moreover, the stability of PdNi@PtNi NPs was also greatly improved over PtNi nanoparticles, PtPd nanoparticles, and commercial Pt/C. This strategy provides a new idea for improving the electrocatalytic performance of Pt-based catalysts for EORs.

Formation Characteristics of Pt-Ni Alloy Nanoparticles Fabricated by Nanolamination of Atomic Layer Deposition in Hydrogen.

Forced-flow atomic layer deposition nanolamination is employed to fabricate Pt-Ni nanoparticles on XC-72, with the compositions ranging from Pt94Ni6 to Pt67Ni33. Hydrogen is used as a co-reactant for depositing Pt and Ni. The growth rate of Pt is slower than that using oxygen reactant, and the growth exhibits preferred orientation along the (111) plane. Ni shows much slower growth rate than Pt, and it is only selectively deposited on Pt, not on the substrate. Higher ratios of Ni would hinder subsequent stacking of Pt atoms, resulting in lower overall growth rate and smaller particles (1.3-2.1nm). Alloying of Pt with Ni causes shifted lattice that leads to larger lattice parameter and d-spacing as Ni fraction increases. From the electronic state analysis, Pt 4f peaks are shifted to lower binding energies with increasing the Ni content, suggesting charge transfer from Ni to Pt. Schematic of the growth behavior is proposed. Most of the alloy nanoparticles exhibit higher electrochemical surface area and oxygen reduction reaction activity than those of commercial Pt. Especially, Pt83Ni17 and Pt87Ni13 show excellent mass activities of 0.76 and 0.59AmgPt -1, respectively, higher than the DOE target of 2025, 0.44AmgPt -1.

Understanding the Growth of Electrodeposited PtNi Nanoparticle Films Using Correlated In Situ Liquid Cell Transmission Electron Microscopy and Synchrotron Radiation.

Electrodeposition is a versatile method for synthesizing nanostructured films, but controlling the morphology of films containing two or more elements requires a detailed understanding of the deposition process. We used liquid cell transmission electron microscopy to follow the electrodeposition of PtNi nanoparticle films on a carbon electrode during cyclic voltammetry. These in situ observations show that the film thickness increases with each cycle, and by the fourth cycle, branched and porous structures could be deposited. Synchrotron studies using in situ transmission X-ray microscopy further revealed that Ni was deposited in the oxide phase. Ex situ studies of bulk electrodeposited PtNi nanoparticle films indicated the number of cycles and the scanning rate were the most influential parameters, resulting in a different thickness, a different homogeneity, a different nanoparticle size, and a different surface structure, while the precursor concentration did not have a significant influence. By varying the potential range, we were able to obtain films with different elemental compositions.

Synthesis of platinum-nickel nanoparticles supported by carbon and titanium oxide structures for efficient and enhanced formic acid oxidation

In this study, Platinum Nickel (PtNi) nanoparticles was synthesized using the chemical reduction method and functionalized multi-walled carbon nanotube (f-MWCNT) was synthesized by handling multi-walled carbon nanotube (MWCNT) with weak acid using the arc discharge method. To be evaluated in formic acid oxidation, f-MWCNT supported by PtNi (PtNi@f-MWCNT) and titanium oxide (TiO2) supported by PtNi (PtNi@TiO2) catalysts were synthesized using chemical reduction method. The comparison of PtNi, PtNi@f-MWCNT, and PtNi@TiO2 catalysts obtained in the study for formic acid oxidation is presented and their characterizations were carried out by X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), and Fourier Transform Infrared Spectrometer (FTIR). According to TEM results; PtNi, PtNi@f-MWCNT, and PtNi@TiO2 particle sizes were found to be 12.00 nm, 7.37 nm, and 5.38 nm, respectively. According to the CV results obtained for formic acid oxidation, the anodic peak peaks for PtNi, PtNi@f-MWCNT, and PtNi@TiO2 were 61.20 mA.cm−2, 80.17 mA.cm−2 and 65.07 mA.cm−2, respectively. These results showed that the addition of f-MWCNT and TiO2 support exhibited 1.30 and 1.06 times higher electrocatalytic activity for formic acid oxidation and higher resistance to CO poisoning with If/Ib ratios of 0.97 and 1.48, respectively. With the long-term stability tests obtained, it was observed that the f-MWCNT-supported catalyst showed approximately 9 times more current at the end of 5000 s and provided faster charge transfer with EIS. These findings demonstrated that a more cost-effective catalyst with high electrocatalytic activity was synthesized by obtaining f-MWCNTs from MWCNTs using the arc discharge method. It has also been revealed that TiO2 and f-MWCNT supports exhibit very high potential for fuel cell applications.

Synergistic growth of nickel and platinum nanoparticles via exsolution and surface reaction

Bimetallic catalysts combining precious and earth-abundant metals in well designed nanoparticle architectures can enable cost efficient and stable heterogeneous catalysis. Here, we present an interaction-driven in-situ approach to engineer finely dispersed Ni decorated Pt nanoparticles (1-6 nm) on perovskite nanofibres via reduction at high temperatures (600-800 oC). Deposition of Pt (0.5 wt%) enhances the reducibility of the perovskite support and promotes the nucleation of Ni cations via metal-support interaction, thereafter the Ni species react with Pt forming alloy nanoparticles, with the combined processes yielding smaller nanoparticles that either of the contributing processes. Tuneable uniform Pt-Ni nanoparticles are produced on the perovskite surface, yielding reactivity and stability surpassing 1 wt.% Pt/γ-Al2O3 catalysts for CO oxidation. This approach heralds the possibility of in-situ fabrication of supported bimetallic nanoparticles with engineered compositional distributions and performance.

Microstructure, mechanical and electrical properties of a novel low-cost high-strength Pt-xAu-5Ni alloy

The present study designed and prepared a novel platinum alloy system Pt-xAu-5Ni (x = 0, 2, 5, wt.%) with high strength and good electrical resistivity. The mechanical, electrical properties and related microstructure during the cold deformation and subsequent aging process were investigated. The cold-deformed Pt–5Ni alloy obtained the yield strength of 581 MPa, the ultimate tensile strength of 828 MPa, the hardness of 283 HV, and the electrical resistivity of 23.9 μΩ⋅cm. The subsequent aging process and the Au addition into Pt–5Ni alloy were found to both enhance the mechanical properties. Therefore, with the dual strengthening effect of the subsequent aging and the Au addition, Pt–5Au–5Ni alloy achieved the high yield strength of 889 MPa, the high ultimate tensile strength of 1117 MPa, the high hardness of 361 HV with the electrical resistivity of 26.7 μΩ⋅cm. The precipitation of L12-type Pt3Ni nanoparticles and L11-type CSRO dominated the age-strengthening behavior of Pt–2Au–5Ni and Pt–5Au–5Ni alloys after cold deformation. The Au addition refined the grains via the experimental observations, and predictably favored the L12-type Pt3Ni nanoprecipitation based on the thermodynamical calculations, thus the Au addition effectively strengthened Pt–5Ni alloy. This study provides a novel platinum alloy system with excellent mechanical and electrical properties, which has potential application in the electrical contact field.

Synthesis of PtNi Nanoparticles to Accelerate the Oxygen Reduction Reaction.

We report the synthesis of core-shell Ni-Pt nanoparticles (NPs) with varying degrees of crystallographic facets and surface layers rich in Pt via a seed-mediated thermolytic approach. Mixtures of different surfactants used during synthesis resulted in preferential surface passivation, which in turn dictated the size, chemical composition, and geometric evolution of these PtNi NPs. Electrochemical investigations of these pristine core-shell Ni-Pt structures in the oxygen reduction reaction (ORR) show that their catalytic functionalities outperform the commercial Pt/C reference catalyst. The enhanced electrocatalytic ORR performances of these Pt-based PtNi NPs are correlated with the weakened oxygen binding strength or surface-adsorbed hydroxyl (OH) species on active Pt surface sites induced by the downshift of the d-band center as a result of compressive strain effects. Our studies offer a robust synthetic approach for the development of core-shell nanostructures for enhanced ORR catalysis.

Ultrathin Ni–N–C layer modified Pt–Ni alloy nanoparticle catalysts for enhanced oxygen reduction

Accelerating the commercialization of fuel cells requires the development of Pt-based alloy cathode catalysts with high ORR operation, low price, and excellent reliability. However, it is a challenging task to fabricate uniformly dispersed, low-loaded, and small-sized Pt-based alloy catalysts to resolve the contradiction between activity and stability. Here, sub-3 nm N-doped PtNi nanoparticles (NPs) are synthesized as high-performance PEMFC cathode catalysts. PtNi/Ni-NC exhibits excellent electrocatalytic activity (0.51 A mgPt−1@0.8 V and peak power density of 328 mW cm−2) as well as stability (only 15 mV loss in E1/2 after 5000 cycles of ADT tests) in oxygen reduction reaction (ORR). The experimental results show that N doping modulates the electronic structure around Pt and optimizes the lattice compressive strain, thus attenuating the adsorption of oxygen intermediates on the surface Pt and enhancing the ORR activity. Meanwhile, the encapsulation of PtNi NPs by the constructed ultrathin Ni–N–C layer accounts for the improved stability. This work offers a novel perspective f for raising the stability and catalytic performance of Pt-based catalysts.

Effects of Zr dopants on properties of PtNi nanoparticles for ORR catalysis: A DFT modeling.

Pt-based alloys, such as Pt3Ni, are among the best electrocatalysts for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells. Doping of PtNi alloys with Zr was shown to enhance the durability of the operating ORR catalysts. Rationalizing these observations is hindered by the absence of atomic-level data for these tri-metallic materials, even when not exposed to the fuel cell operation conditions. This study aims at understanding structure-property relations in Zr-doped PtNi nanoparticles as a key to their ORR function. In particular, we calculated, using a method based on density functional theory, the most stable chemical orderings of pristine and Zr-doped Pt3Ni particles containing over 400 atoms. We thus clarify (i) preferential location and charge states of Zr atoms in the Pt3Ni NPs; (ii) effect of doping Zr atoms on the stability of the Pt skin of the Pt3Ni NPs; (iii) charge redistribution induced by Zr dopants; (iv) layer-by-layer atomic ordering in the Pt3Ni/Zr NPs with the increasing Zr content; and (v) effect of Zr atoms on the adsorption energies of O and OH species as indicators of the ORR activity.

Solvothermal Synthesis of PtNi Nanoparticle Thin Film Cathode with Superior Thermal Stability for Low Temperature Solid Oxide Fuel Cells

Solvothermal Synthesis of PtNi Nanoparticle Thin Film Cathode with Superior Thermal Stability for Low Temperature Solid Oxide Fuel Cells

Synergistic interaction between NiPt nanoparticles and phosphorus-doped graphene support boosts hydrogen generation from hydrazine borane

The Ni0.6Pt0.4/P-rGO catalyst exhibits excellent catalytic activity and recycling stability for hydrazine borane dehydrogenation at 323 K.

Bifunctional bimetallic PtNi, PtCu, and NiCu nanoparticles: Electrocatalytic activities for hydrogen evolution reaction and magnetic properties

Pt-based materials are commonly used in sustainable energy technologies and fuel cells due to their catalytic ability. In this study, we synthesized bifunctional bimetallic PtNi, PtCu, and NiCu nanoparticles using the modified polyol method to investigate their catalytic for hydrogen evolution reactions (HER) and magnetic properties. X-ray diffraction and Rietveld refinement analyses revealed that all samples exhibited a face-centered cubic structure with a Fm3¯m space group. The chemical compositions of PtNi, PtCu, and NiCu bimetallic NPs were determined to be Pt28Ni72, Pt25Cu75, and Ni27Cu73, via stoichiometric calculations using the energy-dispersive X-ray spectroscopy data. The nanostructure and size were characterized by scanning electron microscopy, and the average particle size was found to be between 10 and 13 nm for all three catalysts with a narrow size distribution. The Pt28Ni72 catalyst exhibited the highest HER activity, with a minimum overpotential of −33 mV at −10 mA cm−2 and Tafel slopes with 55 mV dec-1 revealing the Volmer– Heyrovsky HER mechanism. The HER performance of the catalysts revealed that the highest HER activity is Pt28Ni72 > Pt25Cu75 > Ni27Cu73. The magnetic results revealed that the PtNi NPs exhibited a ferromagnetic to paramagnetic transition with a large coercive field of 628 Oe at 5 K. In this work, the addition of magnetic Ni in the structure resulted in multifunctional materials such as magnetically reusable bimetallic PtNi, PtCu, and NiCu catalysts with potential biomedical applications.

Impact of Pt-Ni Nanoparticle Architecture on Electrocatalytic Oxidation Reaction in Fuel Cells

This paper investigates how the aggregation of bimetallic nanoparticles (NPs) influences the electronic condition of the surface adsorption site and, hence, the performance of materials during the electrooxidation of fuels in an alkaline medium. First, we synthesized Pt-Ni NPs in three configurations: ordered intermetallic, ordinary alloy, and core-shell. The NPs contained Pt and Ni close to a 1:1 Pt/Ni atomic ratio. They had similar particle sizes, which allowed us to evaluate their performance without the influence of these physical parameters. Depending on the structural arrangement of the Pt and Ni atoms in the NP, the electronic condition of the surface adsorption site (Pt) changed significantly. Consequently, the performance of the materials varied whenever they were used as anode material for the electrooxidation of hydrogen, methanol, ethanol, ethylene glycol, and glycerol in an alkaline solution. The electronic condition of the surface site strongly affected the adsorption characteristics of the reactants, intermediates, and products, consequently impacting the material's performance during the electrochemical processes. The approach adopted here could contribute to a better understanding of electrocatalytic processes and the design of selective electrocatalysts.

Exploring the Surface Segregation of Rh Dopants in PtNi Nanoparticles through Atom Probe Tomography Analysis

Exploring the Surface Segregation of Rh Dopants in PtNi Nanoparticles through Atom Probe Tomography Analysis

In Situ Single Particle Reconstruction Reveals 3D Evolution of PtNi Nanocatalysts During Heating.

Tailoring nanoparticles' composition and morphology is of particular interest for improving their performance for catalysis. A challenge of this approach is that the nanoparticles' optimized initial structure often changes during use. Visualizing the three dimensional(3D) structural transformation in situ is therefore critical, but often prohibitively difficult experimentally. Although electron tomography provides opportunities for 3D imaging, restrictions in the tilt range of in situ holders together with electron dose considerations limit the possibilities for in situ electron tomography studies. Here, an in situ 3D imaging methodology is presented using single particle reconstruction (SPR) that allows 3D reconstruction of nanoparticles with controlled electron dose and without tilting the microscope stage. This in situ SPR methodology is employed to investigate the restructuring and elemental redistribution within a population of PtNi nanoparticles at elevated temperatures. The atomic structure of PtNi is further examined and a heat-induced transition is found from a disordered to an ordered phase. Changes in structure and elemental distribution are linked to a loss of catalytic activity in the oxygen reduction reaction. The in situ SPR methodology employed here can be extended to a wide range of in situ studies employing not only heating, but gaseous, aqueous, or electrochemical environments to reveal in-operando nanoparticle evolution in 3D.

Tailoring the electronic structure of PtNi nanoalloy for boosting methanol electro-oxidation reaction

Tailoring the electronic structure of Pt-based catalysts can effectively facilitate their methanol oxidation reaction (MOR). Despite a great deal of effort, the fabrication of Pt-based catalysts with both tunable electronic structure and well-dispersion is still challenging. Herein, the PtNi alloy nanoparticles supported on poly (3, 4-ethylenedioxythiophene) modified multi-walled carbon nanotubes (PtNi/PEDOT-MWCNTs) was prepared for MOR. Transmission electron microscopy reveals the successful synthesis of PtNi nanoparticles (3.5 nm) by the reduction of H2. The X-ray photoelectron spectroscopy confirmed the strong electronic interaction between Ni and Pt, and the electronic environment of Pt atoms can be tailored by alloying different atomic content of Ni. Thus, the obtained PtNi/PEDOT-MWCNTs was suitable to design an effective electro-catalyst. As revealed through the electrochemical measurements, the fabricated PtNi/PEDOT-MWCNTs catalyst displayed higher peak current density, better stability, and excellent CO-tolerance than those of Pt nanoparticles dispersed on PEDOT-MWCNTs, MWCNTs, and commercial carbon black. The surface/interface engineering tactic highlights the tailoring of the electronic structure of Pt-based catalysts, which can be applied in various fields, including methanol fuel cells and other catalytic reactions.

Depositing the PtNi nanoparticles on niobium oxide to enhance the activity and CO-tolerance for alkaline methanol electrooxidation

Direct methanol fuel cells have the advantages of simple system, convenient operation, high conversion rate and low carbon emission, which are considered as the environmental and friendly energy conversion devices. However, the low activity, CO-tolerance and high cost of anode catalysts restrict the large-scale commercial applications. Therefore, it is of great practical significance to design and construct the anodic catalysts with high activity, stability and low cost for methanol oxidation reaction. In this work, the PtM/Nb2O5–C (M = Co, Sn, Ni) catalysts are synthesized by the ethylene glycol solvothermal method using transition metal oxide Nb2O5 as the support. The catalytic performance of different catalysts is further evaluated for alkaline MOR. The results show that the introduction of Ni (existing in Ni2+ and Ni3+) has the most obvious improvement for alkaline MOR performance. By adjusting the doped ratio of Pt:Ni, it is shown that PtNi/Nb2O5–C has the highest mass activity (3877.9 mA·mgPt−1), 12 times that of the commercial Pt/C catalyst. CV, LSV, Tafel and EIS analyses show that PtNi/Nb2O5–C has the lowest onset potential and charge transfer resistance, and the fastest electrocatalytic oxidation rate of methanol. CA tests show that the electrochemical stability is also significantly improved with the introduction of Nb2O5 and Ni. Combined with the structural characterization and electrochemical tests, it is found that the evident electronic effect among Pt and Ni, Nb2O5 and the hydroxyl brought from Ni species are mainly ascribed for enhancing the activity, CO resistance and stability of PtNi/Nb2O5–C.