Mass Specific Activity Research Articles

Phase-Controlled Ruthenium Nanocrystals on Colloidal Polydopamine Supports and Their Catalytic Behaviors in Aerobic Oxidation Reactions.

The past decade has witnessed rapidly growing interest in noble metal nanostructures adopting unconventional metastable crystal phases. In the case of Ru, chemically synthesized nanocrystals typically form thermodynamically favored hexagonal close-packed (hcp) crystal lattices, whereas it remains significantly more challenging to synthesize Ru nanocrystals in the metastable face-centered cubic (fcc) phase. In this work, we have synthesized polydopamine (PDA)-supported hcp and fcc Ru nanocrystals in a phase-selective manner through one-pot thermal reduction of appropriate Ru(III) precursors in a polyol solvent. Benefiting from the unique surface-adhesion function of PDA, we have been able to grow phase-controlled sub-5 nm Ru nanocrystals directly on colloidal PDA supports without prefunctionalizing the particle surfaces with any molecular linkers or surface-capping ligands. Success in phase-controlled synthesis of capping ligand-free Ru nanocrystals dispersed on the same support material enables us to systematically compare the intrinsic mass-specific and surface-specific activities of fcc and hcp Ru nanocatalysts toward the aerobic oxidation of a chromogenic molecular substrate, 3,3',5,5'-tetramethylbenzidine (TMB), under a broad range of reaction conditions. We use UV-vis absorption spectroscopy to monitor the conversion of the reactant molecules into the one-electron and two-electron oxidation products in real time during Ru-catalyzed oxidation of TMB, which is found to be a mechanistically complex molecule-transforming process involving multiple elementary steps. The apparent reaction rates and detailed kinetic features are observed to be not only intimately related to the crystalline structures of the Ru nanocatalysts but also profoundly influenced by several other critical factors, such as the pH of the reaction medium, the initial concentration of TMB, Ru coverage on the PDA supports, and degree of nanoparticle aggregation.

Tailored Lattice Compressive Strain of Pt-Skins by the L12 -Pt3 M Intermetallic Core for Highly Efficient Oxygen Reduction.

The sluggish kinetics of oxygen reduction reaction (ORR) and unsatisfactory durability of Pt-based catalysts are severely hindering the commercialization of proton-exchange-membrane fuel cells (PEMFCs). In this work, the lattice compressive strain of Pt-skins imposed by Pt-based intermetallic cores is tailored for highly effective ORR through the confinement effect of the activated nitrogen-doped porous carbon (a-NPC). The modulated pores of a-NPC not only promote Pt-based intermetallics with ultrasmall size (average size of <4nm), but also efficiently stabilizes intermetallic nanoparticlesand sufficient exposure of active sites during the ORR process. The optimized catalyst (L12 -Pt3 Co@ML-Pt/NPC10 ) achieves excellent mass activity (1.72 A mgPt -1 ) and specific activity (3.49mA cmPt -2 ), which are 11- and 15-fold that of commercial Pt/C, respectively. Besides, owing to the confinement effect of a-NPC and protection of Pt-skins, L12 -Pt3 Co@ML-Pt/NPC10 retains 98.1% mass activity after 30000 cycles, and even 95% for 100000 cycles, while Pt/C retains only 51.2% for 30000 cycles. Rationalized by density functional theory, compared with other metals (Cr, Mn, Fe, and Zn), L12 -Pt3 Co closer to the top of "volcano" induces a more suitable compressive strain and electronic structure on Pt-skin, leading to an optimal oxygen adsorption energy and a remarkable ORR performance.

Facile synthesis of PtCo nanoparticles/three-dimensional graphene hybrid material as a highly active and stable electrocatalyst for oxygen reduction reaction

To further promote the widespread commercialization of proton exchange membrane fuel cells (PEMFCs), high performance oxygen reduction reaction (ORR) catalysts with high activity and stability must be developed to accelerate its sluggish kinetic process. Here, we report a successful synthesis of a novel hybrid material - highly synergistic PtCo nanoparticles (NPs) attached to three-dimensional graphene (PtCo @3DG). The PtCo @3DG exhibits excellent ORR performance, and the mass activity and specific activity measured at 0.9 V vs. RHE were 0.801 A/mgPt and 1.250 mA/cm2 respectively, which are 6.8 and 6.2 times higher than commercial Pt/C. High stability of this new material is achieved, which has demonstrated a loss of only 1.87% after an extensive 10,000 cycles test. The superior performance of PtCo @3DG can be primarily attributed to several key features, including its ultrathin size, a high Pt utilization, and a beneficial alloy effect. Additionally, the 3D graphene possesses an open and interconnected porous structure that facilitates efficient charge and mass transfer, which accelerates the desorption process of intermediates and exposes more active sites.

Oxygen vacancy induced interaction between Pt and TiO2 to improve the oxygen reduction performance

In proton exchange membrane fuel cells (PEMFCS), a Pt-based catalyst has been plagued by activity and durability, making it difficult to implement in large-scale commercial applications. In this paper, a composite material formed by titanium dioxide and carbon black containing oxygen vacancies (TiO2(OV)-C) was used as a functional support to successfully load Pt nanoparticles (NPS). The introduction of oxygen vacancies induces the formation of a connection between Pt and TiO2, which not only strengthens the fixation of Pt by the composite support but also optimizes the local charge density of Pt. Compared with Pt/C (0.842 V) and Pt/TiO2-C (0.841 V), the half-wave potential (E1/2) of Pt/TiO2(OV)-C (0.862 V) is increased by 20 mV and 21 mV, respectively. After a long-term durability test, the E1/2 of Pt/TiO2(OV)-C is only attenuated by 5 mV. In addition, the mass activity (MA) and specific activity (SA) decreased from 183.4 mA mg−1 and 0.565 mA cm−2 to 144.4 mA mg−1 and 0.483 mA cm−2 at 0.85 V, only decreasing by 21% and 17 %, showing good stability. X-ray photoelectron spectroscopies (XPS) and density functional theory (DFT) calculations show that the interaction between Pt and TiO2 reduces the d-band center of Pt, thereby improving the desorption of intermediates *OH, which in turn promotes the activity of alkaline ORR. This study not only shows that OV plays a key role in the process of inducing interaction, but also deeply studies the influence of this interaction on the active site Pt, which provides more choices for the design of excellent multiphase catalysts.

Pd‐Enriched‐Core/Pt‐Enriched‐Shell High‐Entropy Alloy with Face‐Centred Cubic Structure for C1 and C2 Alcohol Oxidation

AbstractHigh‐entropy alloy nanoparticles (HEA NPs) have aroused great interest globally with their unique electrochemical, catalytic, and mechanical properties, as well as diverse activity and multielement tunability for multi‐step reactions. Herein, a facile low‐temperature synthesis method at atmospheric pressure is employed to synthesize Pd‐enriched‐HEA‐core and Pt‐enriched‐HEA‐shell NPs with a single phase of face‐centred cubic structure. Interestingly, the lattice of both Pd‐enriched‐HEA‐core and Pt‐enriched‐HEA‐shell enlarge during the formation process of HEA, with tensile strains included in the core and shell of HEA. The as‐obtained PdAgSn/PtBi HEA NPs show excellent electrocatalytic activity and durability for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The specific (mass) activity of PdAgSn/PtBi HEA NPs for MOR is 4.7 mA cm−2 (2874 mA mg(Pd+Pt)−1), about 1.7 (5.9) and 1.5 (4.8) times higher than that of commercial Pd/C and Pt/C catalysts, respectively. Additional to high‐entropy effect, Pt sites and Pd sites on the interface of the HEA act synergistically to facilitate the multi‐step process towards EOR. This study offers a promising way to find a feasible route for scalable HEA manufacturing with promising applications.

Pd-Enriched-Core/Pt-Enriched-Shell High-Entropy Alloys Nanoparticles with a Face-Centred Cubic Structure for C1 and C2 Alcohol Oxidation.

Recently, high-entropy alloy nanoparticles (HEA NPs) have aroused great interest globally with their unique electrochemical, catalytic, and mechanical properties, as well as diverse activity and multielement tunability for multi-step reactions. Herein, a facile low-temperature synthesis method at atmospheric pressure is employed to synthesize Pd-enriched-HEA-core and Pt-enriched-HEA-shell NPs with a single phase of face-centred cubic structure for promoting the oxidation of C1 and C2 alcohols. Interestingly, the lattice of both Pd-enriched-HEA-core and Pt-enriched-HEA-shell enlarge during the formation process of HEA, with tensile strains included in the core and shell of HEA. Strikingly, the as-made PdAgSn/PtBi HEA NPs show excellent electrocatalytic activity and durability for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Especially, the specific (mass) activity of PdAgSn/PtBi HEA NPs for MOR is 4.7 mA/cm2 (2874 mA mg(Pd+Pt)-1), about 1.7 (5.9) and 1.5 (4.8) times higher than that of commercial Pd/C and Pt/C catalysts, respectively. Combined with high-entropy effect, Pt sites and Pd sites on the interface of the HEA act synergistically to facilitate the multi-step process towards EOR. This study offers a promising way to find a feasible route for scalable HEA manufacturing with promising applications.

Amorphous nickel hydroxide shell tailors local chemical environment on platinum surface for alkaline hydrogen evolution reaction.

In analogy to natural enzymes, an elaborated design of catalytic systems with a specifically tailored local chemical environment could substantially improve reaction kinetics, effectively combat catalyst poisoning effect and boost catalyst lifetime under unfavourable reaction conditions. Here we report a unique design of 'Ni(OH)2-clothed Pt-tetrapods' with an amorphous Ni(OH)2 shell as a water dissociation catalyst and a proton conductive encapsulation layer to isolate the Pt core from bulk alkaline electrolyte while ensuring efficient proton supply to the active Pt sites. This design creates a favourable local chemical environment to result in acidic-like hydrogen evolution reaction kinetics with a lowest Tafel slope of 27 mV per decade and a record-high specific activity and mass activity in alkaline electrolyte. The proton conductive Ni(OH)2 shell can also effectively reject impurity ions and retard the Oswald ripening, endowing a high tolerance to solution impurities and exceptional long-term durability that is difficult to achieve in the naked Pt catalysts. The markedly improved hydrogen evolution reaction activity and durability in an alkaline medium promise an attractive catalyst material for alkaline water electrolysers and renewable chemical fuel generation.

Plasmonic synthesis of Non-homogeneous AuPd alloy for efficient electrocatalyst

Improving electrocatalyst performance is key to the large-scale application of fuel cells. Here, we constructed non-homogeneous AuPd alloy nanoparticles with excellent electrocatalytic activity based on the localized surface plasmon resonance (LSPR) effect of Au nanoparticles for the first time. The mass activity and specific activity of the non-homogeneous AuPd alloy for ethanol oxidation reaction can reach 18.14 A/mgPd and 20.28 mA cm−2, respectively, 10.67 and 3.75 times higher than that of commercial Pd/C. Experimental characterizations and theoretical simulations show that Pd precursor is reduced and deposited on the surface of Au NPs, and the localized temperature field drives the atomic interdiffusion. Finite element simulation results indicate a large temperature gradient around the laser-irradiated Au NPs, and the effective reduction of the Pd precursor is confined to the 2.5 nm thick shell region. This work demonstrates the heterogeneous nucleation and growth of nanocrystals driven by LSPR, providing a promising strategy for the rational design of bimetal nanoparticles.

PtCu anchored on N,S-codoped electrospinning porous carbon nanofibers for oxygen reduction reaction

A facile and general strategy for preparing carbon supports with ideal sintering resistance using electrospinning and sulfidation treatment is reported in this paper. The strong interaction between PtCu and N,S-codoped electrospinning porous carbon nanofibers can stabilize PtCu nanoparticles (NPs) below 4 nm to 800 °C. The as-prepared PtCu-800/NS-PCNFs exhibit superior catalytic performances for oxygen reduction reaction (ORR). The PtCu-800/NS-PCNFs presents the mass activity (MA) and specific activity (SA) of 0.4785 A mg−1 and 0.6343 mA cm−2, which is 3.1 times and 2.4 times that of commercial Pt/C. More important, the electrochemical surface area (ECSA) of PtCu-800/NS-PCNFs is 1.3 times larger than that of commercial Pt/C. Therefore, the improved ORR activity can be ascribed to the synergistic interaction between Pt and Cu and the uniform distribution of catalyst nanoparticles.

Few layers graphene-based electrocatalysts for ORR synthesized by electrochemical exfoliation methods

Graphene-based materials were synthesized by electrochemical exfoliation method (cathodic method) starting from a graphite sheet. In the established methodology, an initial immersion in H2SO4 was applied, followed by cathodic expansion in potassium sulphate, where the effect of the applied voltage was studied. Finally, by ultrasound treatment, the exfoliation was achieved to produce a dispersion of few layer graphene material. Once the optimum procedure was established, Pt nanoparticles were incorporated using H2PtCl6.6H2O. This incorporation was studied at each stage of the graphene-based material synthesis to determine which was the most adequate to obtain the highest Pt dispersion and the best distribution of the Pt nanoparticles. In this sense, the incorporation of Pt in the graphene-based material colloidal dispersion by stirring for 3 h and sonication for 1 h, results in Pt nanoparticles with an average size of around 1 nm with an excellent distribution in the carbon material. The performance of this catalyst was compared with the commercial Pt/C electrocatalyst, showing a great oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) activity, exceeding it by far when comparing the mass-specific activity (A gPt−1) In addition, it presents excellent stability and selectivity toward the 4-electron pathway in ORR, which is the most energy-efficient, and using half of the platinum loading compared to the commercial material.

Ionic Nickel Embedded in Ceria with High Specific CO2 Methanation Activity.

CO2 hydrogenation to methane is gaining increasing interest as one of the most promising ways to store intermittent renewable energy in the form of chemical fuels. Ni particles supported on CeO2 represent a highly efficient, stable and inexpensive catalyst for this reaction. Herein, Ni-doped CeO2 nanoparticles were tested for CO2 methanation showing an extremely high Ni mass-specific activity and CH4 selectivity. Operando characterization reveals that this performance is tightly associated with ionic Νi and Ce3+ surface sites, while formation of metallic Ni does not seem to considerably promote the reaction. Theoretical calculations confirmed the stability of interstitial ionic Ni sites on ceria surfaces and highlighted the role of Ce-O frustrated Lewis pair (FLP), Ni-O classical Lewis pair (CLP) and Ni-Ce pair sites to the activation of H2 and CO2 molecules. To a large extent, the theoretical predictions were validated by in situ spectroscopy under H2 and CO2 : H2 gaseous environments.

PtFeCoNiCu High-Entropy Alloy Catalyst for Aqueous-Phase Hydrogenation of Maleic Anhydride

High-entropy alloys (HEAs), as new heterogeneous catalytic materials, possess remarkable catalytic performance in numerous reactions. However, rational and controllable synthesis of these complex structures remains a challenge. In this work, bulk and carbon nanotube (CNT)-supported ultrasmall PtFeCoNiCu HEA nanoparticles with an average particle size of 1.58 nm are prepared by lithium naphthalenide-driven reduction under mild conditions. The supported PtFeCoNiCu/CNT catalyst exhibits high catalytic activity in the aqueous-phase hydrogenation of maleic anhydride to succinic acid with a selectivity of 98% at full conversion of maleic acid (the hydrolysis product of maleic anhydride), a low apparent activation energy (Ea = 49 kJ mol-1), and excellent stability. Moreover, a much higher mass-specific activity of Pt in the catalyst is displayed over PtFeCoNiCu/CNT (1515.4 mmolmaleicacid gPt-1 h-1) than that of 5 wt % Pt/CNT (388.0 mmolmaleicacid gPt-1 h-1). This work provides a strong support for HEAs as advanced heterogeneous catalysts and will be of great significance for promoting the research and application of HEAs in the field of selective hydrogenation.

Ternary CuZnPd Nanoalloys Achieving the Synergy of an Electronic Interaction and Bifunctional Catalysis for Efficient Ethanol Electrooxidation

Rationally constructing nanoalloys achieving the synergy of multiple interactions among different constituents could substantially enhance the electrocatalytic performance of an active metal for a given chemical reaction. In this context, we design and synthesize well-controlled ternary CuZnPd alloy nanoparticles, in which the Cu atoms modify the electronic configuration of Pd atoms through the ligand effect or the lattice strain effect, while the Zn atoms clean their neighboring Pd sites through a bifunctional mechanism, and the synergy of these two benefits endows the ternary CuZnPd alloy nanoparticles with exceptional electrocatalysis for a room-temperature ethanol oxidation reaction (EOR). In specific, at an appropriate 1/1/1 molar ratio for Cu/Zn/Pd, the as-prepared ternary CuZnPd alloy nanoparticles exhibit both the highest specific activity and mass activity of 17.3 mA cm–2 and 11.8 A mg–1, respectively, which outperform those of their CuPd, ZnPd alloy counterparts and the commercial Pd/C catalyst, as well as the majority of recently reported Pd-based catalysts. Density functional theory calculations verify that the key CO* and CH3CHO* intermediates generated during the EOR have the lowest adsorption energy on the ternary CuZnPd alloy nanoparticles, which is responsible for their boosted EOR electrocatalysis.

Regulating the electronic structure through charge redistribution in dense single-atom catalysts for enhanced alkene epoxidation

Inter-site interaction in densely populated single-atom catalysts has been demonstrated to have a crucial role in regulating the electronic structure of metal atoms, and consequently their catalytic performances. We herein report a general and facile strategy for the synthesis of several densely populated single-atom catalysts. Taking cobalt as an example, we further produce a series of Co single-atom catalysts with varying loadings to investigate the influence of density on regulating the electronic structure and catalytic performance in alkene epoxidation with O2. Interestingly, the turnover frequency and mass-specific activity are significantly enhanced by 10 times and 30 times with increasing Co loading from 5.4 wt% to 21.2 wt% in trans-stilbene epoxidation, respectively. Further theoretical studies reveal that the electronic structure of densely populated Co atoms is altered through charge redistribution, resulting in less Bader charger and higher d-band center, which are demonstrated to be more beneficial for the activation of O2 and trans-stilbene. The present study demonstrates a new finding about the site interaction in densely populated single-atom catalysts, shedding insight on how density affects the electronic structure and catalytic performance for alkene epoxidation.

Modulation of iron-based perovskites for enhanced electrocatalytic oxygen evolution reaction by a multi-method approach

Perovskite oxides have been a hot topic of research in the field of water electrolysis due to their tunable construction; however, the poor conductivity and insufficient electrocatalytic activity of extensively studied iron-based perovskites have hindered their widespread availability. While most reported schemes focus on a stand-alone measure to modulate the physicochemical properties of perovskite oxides, herein, we utilize a multi-method approach to improving the parent perovskite SrFeO3-δ (SF). A novel perovskite oxide with a nominal composition of Sr0.9Fe0.6Co0.2Ni0.2O3-δ (S9FCN) is formulated for efficiently catalyzing oxygen evolution reaction (OER) in alkaline electrolytic water, employing the B-site co-doping with the dynamic cations Co, Ni and the A-site Sr deficiency from a highly tunable construction management to enhance the electrocatalytic activity of the targeted perovskite sample. Utilizing this concept, encouragingly, the constructed S9FCN perovskite catalyst exhibits excellent OER catalytic activity with low overpotential of 340 mV at 10 mA cm-2, high mass activity (153.32 A gcatalyst-1) and specific activity (1.91 mA cmBET-2 and 0.11 mA cmECSA-2) under a 400 mV overpotential, along with outstanding electrochemical durability without obvious degradation up to 40 h, which is much superior to that of its parent SF and stoichiometric SFCN counterparts. The improvement of electrochemical performance of iron-based perovskite catalysts by a multi-method approach stands a chance of speeding up the practical application of OER electrocatalysts.

Oxygen reduction stability of graphene-supported electrocatalyst: Electrochemical and morphological evidences

Graphene has been proposed as support or as co-support for Proton Exchange Membrane Fuel cells (PEMFCs) electrocatalysts due to its high electronic conductivity, corrosion stability and high specific surface area compared to common carbon blacks, such as Vulcan. Despite such outstanding properties, comprehensive studies on long-term stability of graphene-supported Oxygen Reduction Reaction (ORR) catalysts are still unavailable or limited.The stability of graphene as support is now studied and compared with carbon black in terms of electrochemical performance and degradation mechanisms. Catalytic layers with Pt/G were prepared and subjected to a set of three different Accelerated Stress Tests (ASTs): cycling at high potentials, Open Circuit Potential (OCP) holding and cycling at low potentials. This study aims to assess if and why graphene is a better candidate as support.The Pt/G catalyst outperformed the reference catalyst in all ASTs, delivering both higher electrochemical active surface area (ECSA) and ORR mass-specific activity. Such electrochemical performance was correlated with morphological evidences associated to the support itself and with Pt nanoparticles.

One-pot hydrothermal synthesis of Pt–TiO2–Carbon as a highly active and stable electrocatalyst for oxygen reduction reaction

Energy conversion from chemical to electrical energy through electrochemical processes using fuel cells is a promising advanced technology to address global environmental issues. However, the development of cathode materials for proton exchange membrane fuel cells (PEMFCs) still faces challenges due to their practical requirements for activity and stability. Introducing oxides into the electrocatalysts is an important way to improve performance. Here, we propose a one-pot hydrothermal synthesis to load Pt and TiO2 nanoparticles (NPs) onto the treated carbon (TC). Through the TiO2 reconciliation between the Pt NPs and the carbon support, the tightly bound Pt–TiO2–TC electrocatalyst shows excellent activity and stability in the oxygen reduction reaction (ORR) due to the strong electronic interaction. At 0.9 V vs. reversible hydrogen electrode, the Pt–TiO2–TC electrocatalyst has about twice the specific activity (SA) and mass activity (MA) of commercial Pt/C. Moreover, the decline of Pt- SA and MA in Pt–TiO2-TC after the accelerated durability test (ADT) was 4.2% and 12.3%, respectively. Therefore, we strongly recommend hybrid metal-oxide-carbon materials with high conductivity, electronic interaction, and carbon corrosion resistance as support materials for Pt NPs to develop Pt-based electrocatalysts for fuel cell applications.

Improving Oxygen Reduction Performance of Surface-Layer-Controlled Pt-Ni Nano-Octahedra via Gaseous Etching.

This study demonstrates an atomic composition manipulation on Pt-Ni nano-octahedra to enhance their electrocatalytic performance. By selectively extracting Ni atoms from the {111} facets of the Pt-Ni nano-octahedra using gaseous carbon monoxide at an elevated temperature, a Pt-rich shell is formed, resulting in an ∼2 atomic layer Pt-skin. The surface-engineered octahedral nanocatalyst exhibits a significant enhancement in both mass activity (∼1.8-fold) and specific activity (∼2.2-fold) toward the oxygen reduction reaction compared with its unmodified counterpart. After 20,000 potential cycles of durability tests, the surface-etched Pt-Ni nano-octahedral sample shows a mass activity of 1.50 A/mgPt, exceeding the initial mass activity of the unetched counterpart (1.40 A/mgPt) and outperforming the benchmark Pt/C (0.18 A/mgPt) by a factor of 8. DFT calculations predict this improvement with the Pt surface layers and support these experimental observations. This surface-engineering protocol provides a promising strategy for developing novel electrocatalysts with improved catalytic features.

One-pot synthesis of ultrafine trimetallic PtPdCu alloy nanoparticles decorated on carbon nanotubes for bifunctional catalysis of ethanol oxidation and oxygen reduction

Bifunctional catalysts for ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) with high noble-metal utilization are highly beneficial to direct ethanol fuel cells (DEFCs). This study developed a ternary bifunctional catalyst composed of ultrafine PtPdCu alloy nanoparticles and carbon nanotubes (CNTs) support through a facile surfactant-free solvothermal route. The carboxyl terminal groups on CNTs ensure the confined growth of PtPdCu alloys (∼5 nm) and suppress Ostwald ripening of metallic active sites during electrochemical cycling. Consequently, PtPdCu/CNTs exhibits high mass activity (1.95 A mg−1) and specific activity (4.08 mA cm−2) toward EOR, which are 7.8 and 8.9 times higher, respectively, than those of commercial Pt/C. Furthermore, PtPdCu/CNTs displays superior stability toward EOR compared with its bimetallic counterparts (PtPd/CNTs and PtCu/CNTs). In addition, PtPdCu/CNTs exhibits the highest half-wave potential of 0.888 V among all electrocatalysts, indicating high ORR activity. Density functional theory calculations reveal that Pd and Cu mediate the electronic structure of Pt, leading to enhanced catalytic activity of PtPdCu/CNTs. The excellent catalytic property of PtPdCu/CNTs can also be attributed to the bifunctional effects of Pd/Cu and the interaction between metal and the carbon support. The proposed material is a contribution to the family of efficient ternary-alloy electrocatalysts for fuel cells.

How Size and Strain Effect Synergistically Improve Electrocatalytic Activity: A Systematic Investigation Based on PtCoCu Alloy Nanocrystals.

To reveal how the size effect and strain effect synergistically regulate the mass activity (MA) and specific activity (SA) of Pt alloy nanocrystal catalysts in oxygen reduction reaction (ORR), remains to be difficult due to the highly entangled factors. In this work, six ternary PtCoCu catalysts with sequentially changed composition, size, and compression strain are prepared. It is found that the smaller the alloy particles, the higher the electrochemical active surface area (ECSA) and MA values, that is, the particle size plays a decisive role in the size of the ECSA and MA. While, along alloy size decrease, the intrinsic activity SA first increases, then remains unchanged, and finally rapidly increases again. This detailed analysis shows that for the alloys above 4nm, it is the surface coordination number that decides the SA, while for those below 4nm, it is the well-regulated compression strain that determines the SA. Particularly, Pt47 Co26 Cu27 demonstrates the MA of 1.19 A mgPt -1 and SA of 1.48mA cm-2 , being 7.9 and 6.4 times those of commercial Pt/C respectively, representing an especially superior ORR catalyst.