Enhancing by Weakening: Electrooxidation of Methanol on Pt3Co and Pt Nanocubes

Shape-Controlled Synthesis of Platinum-Based Nanocrystals and Their Electrocatalytic Applications in Fuel Cells

To achieve environmentally benign energy conversion with the carbon neutrality target via electrochemical reactions, the innovation of electrocatalysts plays a vital role in the enablement of renewable resources. Nowadays, Pt-based nanocrystals (NCs) have been identified as one class of the most promising candidates to efficiently catalyze both the half-reactions in hydrogen- and hydrocarbon-based fuel cells. Here, we thoroughly discuss the key achievement in developing shape-controlled Pt and Pt-based NCs, and their electrochemical applications in fuel cells. We begin with a mechanistic discussion on how the morphology can be precisely controlled in a colloidal system, followed by highlighting the advanced development of shape-controlled Pt, Pt-alloy, Pt-based core@shell NCs, Pt-based nanocages, and Pt-based intermetallic compounds. We then select some case studies on models of typical reactions (oxygen reduction reaction at the cathode and small molecular oxidation reaction at the anode) that are enhanced by the shape-controlled Pt-based nanocatalysts. Finally, we provide an outlook on the potential challenges of shape-controlled nanocatalysts and envision their perspective with suggestions.

Toward Electrocatalytic Methanol Oxidation Reaction: Longstanding Debates and Emerging Catalysts

The study of direct methanol fuel cells (DMFCs) has lasted around 70 years, since the first investigation in the early 1950s. Though enormous effort has been devoted in this field, it is still far from commercialization. The methanol oxidation reaction (MOR), as a semi-reaction of DMFCs, is the bottleneck reaction that restricts the overall performance of DMFCs. To date, there has been intense debate on the complex six-electron reaction, but barely any reviews have systematically discussed this topic. To this end, the controversies and progress regarding the electrocatalytic mechanisms, performance evaluations as well as the design science toward MOR electrocatalysts are summarized. This review also provides a comprehensive introduction on the recent development of emerging MOR electrocatalysts with a focus on the innovation of the alloy, core-shell structure, heterostructure, and single-atom catalysts. Finally, perspectives on the future outlook toward study of the mechanisms and design of electrocatalysts are provided.

Surfactant-Free Monodispersed Pd Nanoparticles Template for Core-Shell Pd@PdPt Nanoparticles as Electrocatalyst towards Methanol Oxidation Reaction (MOR)

An eco-friendly two-step synthetic method for synthesizing Pd@PdPt/CNTs nanoparticles was introduced and studied for the methanol oxidation reaction. The Pd@PdPt alloy core-shell structure was synthesized by preparing a surfactant-free monodispersed Pd/CNTs precursor through the hydrolysis of tetrachloropalladate (II) ion ([PdCl₄]²⁻) in the presence of carbon nanotubes (CNTs) and the subsequent hydrogen reduction and followed by a galvanic replacement reaction. This method opens up an eco-friendly, practical, and straightforward route for synthesizing monometallic or bimetallic nanoparticles with a clean surfactant-free electrocatalytic surface. It is quite promising for large-scale preparation. The Pd@PdPt/CNTs electrocatalyst demonstrated a high specific mass activity for methanol oxidation (400.2 mAmg_Pt⁻¹) and excellent stability towards direct methanol oxidation compared to its monometallic counterparts.

Cu assisted loading of Pt on CeO2 as a carbon-free catalyst for methanol and oxygen reduction reaction

The widely studied Pt/C catalyst for direct methanol fuel cells (DMFCs) suffers severe carbon corrosion under operation, which undermines the catalytic activity and durability. It is of great importance to develop a carbon-free support with co-catalytic functionality for improving both the activity and durability of Pt-based catalysts. The direct loading of Pt on the smooth surface of oxides may be difficult. Herein, the Cu assisted loading of Pt on CeO2 is developed. Cu pre-coated CeO2 was facilely synthesized and Pt was electrochemically deposited to fabricate the carbon-free PtCu/CeO2 catalyst. The PtCu/CeO2 catalyst has a mass activity up to 1.84 and 1.57 times higher than Pt/C towards methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), respectively. Better durability is also confirmed by chronoamperometry and accelerated degradation tests. The strategy in this work would be greatly helpful for developing an efficient carbon-free support of Pt-based catalysts for applications in DMFCs.

Strategies to enhance the electrochemical performances of Pt-based intermetallic catalysts

The need for improving the energy conversion efficiency of proton exchange membrane fuel cells (PEMFCs) has motivated the development of advanced electrocatalysts with desirable activity and durability. Pt-Based intermetallic compounds, featuring atomically ordered structures, have long been considered to be very promising alternatives to widely employed Pt and Pt alloy (solid solutions) catalysts. To facilitate the practical application of Pt-based intermetallics in PEMFCs, effective strategies have been developed to further improve their catalytic activity and durability over the last decade. This feature article overviews the recent advances on the strategies for enhancing the electrochemical performances of Pt-based intermetallic catalysts, which include size control, surface engineering, and composition tuning. Thermodynamic and kinetic perspectives on the formation of the intermetallic phases are summarized to better design the synthesis conditions and realize the size control. After this, the size-control approaches (e.g. coating protection, matrix protection) are illustrated and discussed. We highlight the positive effect of surface engineering and discuss the recently developed methods for surface engineering. Finally, we discuss the thermodynamic feasibility of composition tuning and recent work based on composition-tunable intermetallic electrocatalysts.

Pt-Co truncated octahedral nanocrystals: a class of highly active and durable catalysts toward oxygen reduction

We report a facile and scalable synthesis of Pt-Co truncated octahedral nanocrystals (TONs) by employing Pt(acac)2 and Co(acac)2 as precursors, together with CO molecules and Mn atoms derived from the decomposition of Mn2(CO)10 as a reductant and a {111} facet-directing agent, respectively. Both the composition and yield of the Pt-Co TONs could be varied through the introduction of CHCl3. When tested at 80 °C using membrane electrode assembly (MEA), the 4 nm Pt2.6Co TONs gave a mass activity of 294 A gPt-1 at beginning-of-life (BOL) and it increased to 384 A gPt-1 during recovery cycles. The mass activity at BOL only dropped by 24% after 30 000 voltage cycles at end-of-life (EOL) in a metal dissolution accelerated stress test. The Pt2.6Co/C catalyst outperformed the commercial TKK Pt3Co/C (230 A gPt-1 at BOL and 40% loss after 30 000 cycles at EOL) in terms of both activity and durability. Our systematic analysis suggested that the enhancement in activity can be attributed to the combination of small, uniform size and well-defined {111} facets. This new class of catalysts holds promise for applications in proton-exchange membrane fuel cells.

Efficient polyalcohol oxidation electrocatalysts enabled by PtM (M = Fe, Co, and Ni) nanocubes surrounded by (200) crystal facets

Due to the high-density (200) crystal planes and abundant active sites, cubic platinum nanomaterials have become outstanding electrocatalysts in promoting fuel cell reactions. However, because of the fact that the facet-controlled synthesis is difficult, it is still a grand challenge to synthesize a sequence of Pt-based nanocubes via a universal method. Herein, we report a general and simple eco-friendly solvothermal method to prepare (200)-enclosed PtM nanocubes. Different from the other nanomaterials, nanocubes are conducive to mass transfer. Moreover, the synergistic and electronic effects between M and Pt are profitable to improve the utilization of precious metals. We used (200)-encapsulated nanocrystals to evaluate their electrocatalytic performance towards glycerol and ethylene glycol oxidation reactions in an alkaline medium. In particular, Pt4Co nanocubes showed superior mass activities in glycerol and ethylene glycol oxidation reactions, which are 6.2- and 5.0-fold higher than those obtained for commercial Pt/C catalysts, respectively. Meanwhile, Pt4M catalysts manifested excellent stability in the endurance test, which is attributed to the alloying effect promoting the electrooxidation of intermediates. Our study provides an ideal method for the construction of Pt-based bimetallic nanocubes, which can be used for anode reactions of polyol fuel cells and beyond.

Monodisperse Pt-Co/GO anodes with varying Pt: Co ratios as highly active and stable electrocatalysts for methanol electrooxidation reaction

The intense demand for alternative energy has led to efforts to find highly efficient and stable electrocatalysts for the methanol oxidation reaction. For this purpose, herein, graphene oxide-based platinum-cobalt nanoparticles (Pt100-xCox@GO NPs) were synthesized in different ratios and the synthesized nanoparticles were used directly as an efficient electrocatalyst for methanol oxidation reaction (MOR). The characterizations for the determination of particle size and surface composition of nanoparticles were performed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The structure of the catalysts was detected as face-centered cubic and the dispersion of them on graphene oxide was homogenous (distributed narrowly (4.01 ± 0.51 nm)). Cyclic voltammetry (CV) and chronoamperometry (CA) was utilized for testing electrocatalytic activities of all prepared NPs for the methanol oxidation reaction. It was detected that the newly produced NPs were more active and stable than commercially existing Pt(0)/Co nanomaterial in methanol electro-oxidation in acidic media.

PtMn/PtCo alloy nanofascicles: robust electrocatalysts for electrocatalytic hydrogen evolution reaction under both acidic and alkaline conditions

Herein, PtMn and PtCo nanofascicles were prepared by ultrathin nanofibers using a versatile method, and can be employed as effective electrocatalysts toward the HER under both acidic and alkaline conditions.

Bifunctional PtCu electrocatalysts for the N2 reduction reaction under ambient conditions and methanol oxidation

PtCu nanoalloys were employed as bifunctional electrocatalysts in both the N₂ reduction and methanol oxidation, in which the electrocatalytic activity and stability is composition dependent and highly improved compared to their counterpart.

Trimetallic palladium-copper-cobalt alloy wavy nanowires improve ethanol electrooxidation in alkaline medium

Recently, engineering high performance Pd-based nanocatalysts for alkaline ethanol fuel cells has attracted wide attention. Here, we report a one-pot synthesis of low-palladium ternary palladium-copper-cobalt (PdCuCo) alloy nanowires (NWs) with a diameter of ∼4.0 nm to improve the mass activity (MA) of ethanol electrooxidation in alkaline medium. The MA (7.45 A mg^-1) of the Pd₃₁Cu₆₁Co₈ NWs is 8.5-fold and 12.4-fold that of commercial Pd black and Pd/C, respectively. The reaction mechanism of the EOR and the reasons for the activity enhancement on Pd₃₁Cu₆₁Co₈ NWs are elucidated based on the results of in situ Fourier transform infrared spectroscopy and structure characterization. Besides the electronic effect and surface defect sites, the coexistence of surface Cu and Co that have high capacities to activate water to produce reactive oxygen species is another key factor. This study shows an example of how to design low-palladium ternary PdCuCo NWs as improved anode electrocatalysts for alkaline direct ethanol fuel cells with high mass activity.

Synthesis of low- and high-index faceted metal (Pt, Pd, Ru, Ir, Rh) nanoparticles for improved activity and stability in electrocatalysis

Driven by the quest for future energy solution, faceted metal nanoparticles are being pursued as the next generation electrocatalysts for renewable energy applications. Thanks to recent advancement in solution phase synthesis, different low- and high-index facets on metal nanocrystals become accessible and are tested for specific electrocatalytic reactions. This minireview summarises the key approaches to prepare nanocrystals containing the most catalytically active platinum group metals (Pt, Pd, Ru, Ir and Rh) exposed with low- and high-index facets using solution phase synthesis. Electrocatalytic studies related to the different facets are highlighted to emphasise the importance of exposing facets for catalysing these reactions, namely oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), alcohol oxidation including methanol (MOR) and ethanol oxidation reactions (EOR), formic acid oxidation reaction (FAOR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The future outlook discusses the challenges and opportunities for making electrocatalysts that are even more active and stable.

Polyhedron-Assembled Ternary PtCuCo Nanochains: Integrated Functions Enhance the Electrocatalytic Performance of Methanol Oxidation at Elevated Temperature

Recently, the preparation of a high-performance one-dimensional alloy nanostructure for fuel cells has been given increasing attention due to its smart-structure merits and electronic effect triggered by alloying different kinds of metals at the nanoscale. In this study, unique ternary PtCuCo nanochains assembled with small polyhedra are first achieved and used as high-performance anode electrocatalysts toward methanol oxidation at elevated temperature (60 °C) that is closer to the operating temperature of direct methanol fuel cells than room temperature. The specific activity/mass activity of Pt₄₅Cu₃₅Co₂₀ one-dimensional nanochains can reach up to 18.24 mA cm^-2/4.19 A mg^-1_Pt that is 9.25/10.47 times that of commercial Pt black in sulfuric acid medium. After a 3600 s durability test, the remaining current density of Pt₄₅Cu₃₅Co₂₀ one-dimensional nanochains is 73.3 times that of commercial Pt black. The structure characterizations show that the high density of surface active sites, d-band center of the Pt downshift, moderate strain effect, and synergetic effect are jointly responsible for the enhanced electrocatalytic performance of one-dimensional ternary PtCuCo nanochains.

Recent Progress on Catalysts for the Positive Electrode of Aprotic Lithium-Oxygen Batteries †

Rechargeable aprotic lithium-oxygen (Li-O2) batteries have attracted significant interest in recent years owing to their ultrahigh theoretical capacity, low cost, and environmental friendliness. However, the further development of Li-O2 batteries is hindered by some ineluctable issues, such as severe parasitic reactions, low energy efficiency, poor rate capability, short cycling life and potential safety hazards, which mainly stem from the high charging overpotential in the positive electrode side. Thus, it is of great significance to develop high-performance catalysts for the positive electrode in order to address these issues and to boost the commercialization of Li-O2 batteries. In this review, three main categories of catalyst for the positive electrode of Li-O2 batteries, including carbon materials, noble metals and their oxides, and transition metals and their oxides, are systematically summarized and discussed. We not only focus on the electrochemical performance of batteries, but also pay more attention to understanding the catalytic mechanism of these catalysts for the positive electrode. In closing, opportunities for the design of better catalysts for the positive electrode of high-performance Li-O2 batteries are discussed.

Recent Progress in Graphene-Based Noble-Metal Nanocomposites for Electrocatalytic Applications

The fast industrialization process has led to global challenges in the energy crisis and environmental pollution, which might be solved with clean and renewable energy. Highly efficient electrochemical systems for clean-energy collection require high-performance electrocatalysts, including Au, Pt, Pd, Ru, etc. Graphene, a single-layer 2D carbon nanosheet, possesses many intriguing properties, and has attracted tremendous research attention. Specifically, graphene and graphene derivatives have been utilized as templates for the synthesis of various noble-metal nanocomposites, showing excellent performance in electrocatalytic-energy-conversion applications, such as the hydrogen evolution reaction and CO₂ reduction. Herein, the recent progress in graphene-based noble-metal nanocomposites is summarized, focusing on their synthetic methods and electrocatalytic applications. Furthermore, some personal insights on the challenges and possible future work in this research field are proposed.

One-pot solvothermal synthesis of reduced graphene oxide-supported uniform PtCo nanocrystals for efficient and robust electrocatalysis

Pt-based nanocomposites with low Pt utilization and high-activity by incorporating with other transition metals have received significant interest in catalysis. Meanwhile, loading Pt-based catalysts on graphene has great research value for improved stability and dispersity of the catalysts. Herein, a facile l-proline-mediated solvothermal strategy was reported to construct reduced graphene oxide (rGO) supported sheet-like PtCo nanocrystals (Pt₇₈Co₂₂ NCs/rGO) in ethylene glycol (EG). The as-synthesized nanocomposite manifested remarkably improved catalytic properties and chemical stability for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), surpassing home-made Pt₂₉Co₇₁ nanoparticles (NPs)/rGO, Pt₈₃Co₁₇ NPs/rGO, Pt₅₂Co₄₈ NPs, commercial Pt/C and Pt black catalysts. These scenarios demonstrated an improved catalytic performances by tailoring the feeding ratio of Pt:Co and introducing rGO as a support. This work provides some new insights to design rGO-supported Pt-based catalysts by engineering the shapes and compositions in practical fuel cells.

Surface-modified Pt1Ni1–Ni(OH)2 nanoparticles with abundant Pt–Ni(OH)2 interfaces enhance electrocatalytic properties

Pt₁Ni₁–Ni(OH)₂ NPs with abundant Pt–Ni(OH)₂ interfaces exhibit a rather high activity and stability for the MOR in alkaline electrolytes.

Atomic Platinum Skin under Synergy of Cobalt for Enhanced Methanol Oxidation Electrocatalysis

To reduce the cost of the catalyst and the consumption of Pt, a facile electrochemical displacement preparation method is proposed, and the nanostructures can be easily controlled by a strong reducing agent and a surfactant. Two distinct Pt-Co spheres, Pt-Co core-shell spheres (CSSs), and Pt-Co hollow alloy spheres (HASs) were successfully synthesized by changing the introduction of N₂. Interestingly, Pt-Co CSSs possess a Pt-rich shell with 7 atomic layer thickness, which promotes the efficient utilization of Pt atoms. Pt-Co HASs have a highly open structure and a single alloy phase. For the methanol oxidation reaction, Pt-Co CSSs and Pt-Co HASs exhibit enhanced catalytic performances. Compared with the commercial Pt/C catalyst, the mass activity of the Pt-Co CSS catalyst is increased by 4 times, and it has better stability. More importantly, the current work opens a door to the batch preparation of Pt-based catalysts and synthesis of shell nanostructures.

Porous platinum-silver bimetallic alloys: surface composition and strain tunability toward enhanced electrocatalysis

Promoting surface strains in heterogeneous catalysts and heteroatomic interactions in alloying offer an effective strategy for the development of electrocatalysts with greatly enhanced activity. In this work, we design platinum-silver nanotubes (PtAg NTs) with tunable surface compositions by a controlled galvanic replacement reaction of well-defined Ag nanowires (NWs). The optimized and porous PtAg NTs (PtAg-4 NTs), with the Pt5Ag3 surface composition and (111) facet-dominant surface features, exhibit an extraordinary oxygen reduction reaction (ORR) activity that reaches a specific activity of 1.13 mA cm-2 and a mass activity of 0.688 A mg-1Pt at 0.9 V versus a reversible hydrogen electrode (RHE), which are 4.5 times and 4.3 times those of commercial Pt/C catalysts (0.25 mA cm-2 and 0.16 A mg-1Pt). Moreover, PtAg-4 NTs/C can endure under the ORR conditions over the course of 10 000 cycles with negligible activity decay. Remarkably, density functional theory simulations reveal that the porous PtAg-4 NTs exhibit enhanced adsorption interaction with adsorbates, attributed to the catalytically active sites on high-density (111) facets and modulation of the surface strain, further boosting the ORR activity and durability.

The in situ growth of ultrathin Fcc-NiPt nanocrystals on graphene for methanol and formic acid oxidation

Due to the increasing demand for energy, improving the current density of fuel cells is an urgent issue. Here we report a bifunctional electrocatalyst for fuel cells involving methanol or formic acid oxidation. A nanocomposite consisting of 7.2 nm NiPt nanocrystals, which are grown in situ on graphene nanosheets (NiPt/GN), has been prepared via a solution thermal decomposition method. The NiPt/GN nanocatalyst presents specific activities as high as 41.1 mA cm-2 and 42.9 mA cm-2 for methanol oxidation and formic acid oxidation, respectively, outperforming most reported catalysts. Moreover, it retains 76.3% of this activity after 900 cycles of methanol oxidation. Additionally, in comparison with general NiPt nanoparticles, the NiPt/GN nanocatalyst shows higher electrocatalytic activity in methanol and formic acid oxidation. All these results indicate that ultrathin NiPt nanocrystals grown in situ on graphene nanosheet substrates can significantly improve performance as a bifunctional electrocatalyst.

Synthesis of germanium-platinum nanoparticles as high-performance catalysts for spray-deposited large-area dye-sensitized solar cells (DSSC) and the hydrogen evolution reaction (HER)

GePt3 and Ge2Pt nanoparticles were synthesized via a solution colloidal method as catalysts for dye-sensitized solar cells (DSSC) and the hydrogen evolution reaction (HER). The shape, size, arrangement, phases and crystalline structures of Ge-Pt nanoparticles were determined, and the ability to be dispersed in nonpolar solvents enabled them to form a catalyst ink with a stable ejection for the spray coating technique. A series of electrochemical analyses confirmed the catalytic properties of Ge-Pt nanoparticles toward the I-/I3- redox reaction system. The DSSC using GePt3 nanoparticles as the counter electrode exhibited excellent power conversion efficiency (PCE) of 8.04% at 0.16 cm2, which was comparable to that of a DSSC using Pt as the counter electrode (8.0%); it also exhibited an average PCE of 7.26% even at a large working area (2 cm2). In addition, the GePt3 catalyst exhibited excellent HER electrocatalytic performance with a large current density and a low Tafel slope, and it could stably operate at a working area of up to 5 cm2 with a low over potential (<0.06 V) to achieve 10 mA cm-2 cathodic current. This study provides fundamental insights into the preparation of germanium-platinum intermetallic compound catalysts at the nanoscale, which can be beneficial for the design and development of clean energy devices.

One-step fabrication of bimetallic PtNi mesoporous nanospheres as an efficient catalyst for the oxygen reduction reaction

The controlled synthesis of Pt-based bimetallic porous nanostructures is highly important for the design of electrocatalysts with high performance. Herein, we report a one-step method for the direct synthesis of well-dispersed bimetallic PtNi mesoporous nanospheres (PtNi MNs) at high yield. Benefitting from the synergistic effect of composition (bimetallic PtNi) and structure (mesoporous and highly open structure), the as-obtained PtNi MNs exhibit superior catalytic activity and stability for the oxygen reduction reaction.

Random Alloyed versus Intermetallic Nanoparticles: A Comparison of Electrocatalytic Performance

As synthetic methods advance for metal nanoparticles, more rigorous studies of structure-function relationships can be made. Many electrocatalytic processes depend on the size, shape, and composition of the nanocatalysts. Here, the properties and electrocatalytic behavior of random alloyed and intermetallic nanoparticles are compared. Beginning with an introduction of metallic nanoparticles for catalysis and the unique features of bimetallic compositions, the discussion transitions to case studies of nanoscale electrocatalysts where direct comparisons of alloy and intermetallic compositions are undertaken for methanol electrooxidation, formic acid electrooxidation, the oxygen reduction reaction, and the electroreduction of carbon dioxide (CO2 ). Design and synthesis strategies for random alloyed and intermetallic nanoparticles are discussed, with an emphasis on Pt-M and Cu-M compositions as model systems. The differences in catalytic performance between alloys and intermetallic nanoparticles are highlighted in order to provide an outlook for future electrocatalyst design.

Hierarchical concave layered triangular PtCu alloy nanostructures: rational integration of dendritic nanostructures for efficient formic acid electrooxidation

The rational construction of multi-dimensional layered noble metal nanostructures is a great challenge since noble metals are not layer-structured materials. Herein, we report a one-pot hydrothermal synthetic method for PtCu hierarchical concave layered triangular (HCLT) nanostructures using dl-carnitine, KI, poly(vinylpyrrolidone), CuCl2, and H2PtCl6. The PtCu HCLT nanostructure is comprised of multilayered triangular dendrites. Its layer number is tunable by changing dl-carnitine concentrations, and the concavity/convexity of the PtCu triangle nanostructures is tunable by changing the H2PtCl6/CuCl2 ratio or KI concentrations. Hierarchical trigonal bipyramid nanoframes are also obtained under certain conditions. Because of its advantageous nanostructure and bimetallic synergetic effect, the obtained PtCu HCLT nanostructure exhibits enhanced electrocatalytic activity and prolonged stability to formic acid oxidation compared to commercial Pt black, Pd/C and some other nanostructures.

Amperometric myeloperoxidase immunoassay based on the use of CuPdPt nanowire networks

This research describes a nanowire network-based method for detecting the activity of myeloperoxidase (MPO), a biomarker of acute coronary syndromes (ACS). Trimetallic CuPdPt nanowire networks (CuPdPt NWNWs) were prepared by a one-step chemical reduction method. The metallic precursors quickly form nanowire network structures without the need for additional capping agents or surfactants. This process creates a product with a clean surface. The NWNWs were dropped onto a glassy carbon electrode (GCE) to obtain a sensor with good catalytic activity towards the reduction of hydrogen peroxide (H₂O₂), which was used as an electrochemical probe working at -0.4 V (vs. SCE). It also provided a large surface for further modification. Next, an antibody against MPO was immobilized on the modified GCE via the stable conjunction between Cu, Pt, Pd and amino groups. Upon binding of MPO to the antibody on the GCE, the current response to H₂O₂ was reduced by 35 μA·cm^-2. The immunosensor had a linear response within the 100 fg·mL^-1 to 50 ng·mL^-1 MPO concentration range and a 33 fg·mL^-1 detection limit (at an S/N ratio of 3). The recovery of spiked serum samples ranged from 99.8 to 103.6%. This result suggests that the method can be applied to the quantitation of MPO in human serum samples. Graphical abstract A trimetallic CuPdPt nanowire networks was placed on a glassy cabon electrode (GCE) to design an immunosensor for myeloperoxidase (MPO), a biomarker for the acute coronary syndrome (ACS). Antibody against MPO was immobilized on the network via conjugation between Cu, Pt, Pd and amino groups. Amperometric i-t measurements were conducted to quantify the amount of MPO that binds to the antibody on the surface of the modified GCE.

Facile Synthesis of Composition-Controlled Graphene-Supported PtPd Alloy Nanocatalysts and Their Applications in Methanol Electro-Oxidation and Lithium-Oxygen Batteries

A new and simple approach is reported for the synthesis of uniformly dispersed PtPd alloy nanocatalysts supported on graphene nanoplatelets (GNPs) (PtPd-GNPs) through the introduction of bifunctional materials, which can modify the GNP surface and simultaneously reduce metal ions. With the use of poly(4-styrenesulfonic acid), poly(vinyl pyrrolidone), poly(diallyldimethylammonium chloride), and poly(vinyl alcohol) as bifunctional materials, PtPd-GNPs can be produced through a procedure that is far simpler than previously reported methods. The as-prepared nanocrystals on GNPs clearly exhibit uniform PtPd alloy structures of around 2 nm in size, which are strongly anchored and well distributed on the GNP sheets. The Pt/Pd atomic ratio and loading density of the nanocrystals on the GNPs are controlled easily by changing the metal precursor feed ratio and the mass ratio of GNP to the metal precursor, respectively. As a result of the synergism between Pt and Pd, the as-prepared PtPd-GNPs exhibit markedly enhanced electrocatalytic performance during methanol electro-oxidation compared with monometallic Pt-GNP or commercially available Pt/C. Furthermore, the PtPd-GNP nanocatalysts also show greatly enhanced catalytic activity toward the oxygen reduction/evolution reaction in a lithium-oxygen (Li-O₂ ) process, resulting in greatly improved cycling stability of a Li-O₂ battery.

One-Pot Synthesis of Concave Platinum-Cobalt Nanocrystals and Their Superior Catalytic Performances for Methanol Electrochemical Oxidation and Oxygen Electrochemical Reduction

Exploring highly efficient electro-catalysts is of significant urgency for the widespread uptake of the direct methanol fuel cells (DMFCs). Pt-Co nanocrystals have attracted considerable attentions because of their superior catalytic performance toward both methanol oxidation and oxygen reduction in the preliminary assessments. This Research Article presents a Pt-Co bimetal catalyst that is synthesized through a facile coreduction strategy. The Pt-Co nanocrystals have concave cubic shape with a high uniform size of 7-9 nm and Pt-rich surfaces. The catalysis of the concave cubic Pt-Co nanoparticles toward both methanol electrochemical oxidation reaction (MOR) and oxygen electrochemical reduction reaction (ORR) is evaluated. In comparison with the commercial Pt/C catalyst (Johnson Matthey), the present concave cubic Pt-Co catalyst displays superior performances in not only catalytic activity but also durability. The concave Pt-Co catalyst also shows higher activities than spherical and cubic Pt-Co nanoparticles. The dramatic enhancement is mainly attributed to its alloyed composition, Pt-rich surface and the concave nanostructure. The results of our research indicate that the concave Pt-Co nanocrystal could be a promising catalyst for both MOR and ORR. The present work might also raise more concerns on exploiting morphology and composition of nanocrystal catalysts, which are expected to provide high catalytic performance in electrochemical reactions.

High-Indexed Pt3Ni Alloy Tetrahexahedral Nanoframes Evolved through Preferential CO Etching

Chemically controlling crystal structures in nanoscale is challenging, yet provides an effective way to improve catalytic performances. Pt-based nanoframes are a new class of nanomaterials that have great potential as high-performance catalysts. To date, these nanoframes are formed through acid etching in aqueous solutions, which demands long reaction time and often yields ill-defined surface structures. Herein we demonstrate a robust and unprecedented protocol for facile development of high-performance nanoframe catalysts using size and crystallographic facet-controlled PtNi₄ tetrahexahedral nanocrystals prepared through a colloidal synthesis approach as precursors. This new protocol employs the Mond process to preferentially dealloy nickel component in the ⟨100⟩ direction through carbon monoxide etching of carbon-supported PtNi₄ tetrahexahedral nanocrystals at an elevated temperature. The resultant Pt₃Ni alloy tetrahexahedral nanoframes possess an open, stable, and high-indexed microstructure, containing a segregated Pt thin layer strained to the Pt-Ni alloy surfaces and featuring a down-shift d-band center as revealed by the density functional theory calculations. These nanoframes exhibit much improved catalytic performance, such as high stability under prolonged electrochemical potential cycles, promoting direct electro-oxidation of formic acid to carbon dioxide and enhancing oxygen reduction reaction activities. Because carbon monoxide can be generated from the carbon support through thermal annealing in air, a common process for pretreating supported catalysts, the developed approach can be easily adopted for preparing industrial scale catalysts that are made of Pt-Ni and other alloy nanoframes.

Entropy-Driven Pt3Co Nanocube Assembles and Thermally Mediated Electrical Conductivity with Anisotropic Variation of the Rhombohedral Superlattice

Understanding the shape-dependent superlattices and resultant anisotropies of both structure and property allows for rational design of materials processing and engineering to fabricate transformative materials with useful properties for applications. This work shows the structural evolution from square lattice of two-dimensional (2D) thin film to rhombic lattice of large three-dimensional (3D) assembles of Pt₃Co nanocubes (NCs). Synchrotron-based X-ray supercrystallography determines the superlattice of large 3D supercrystal into an obtuse rhombohedral (Rh) symmetry, which holds a long-range coherence of both NC translation and atomic crystallographic orientation. The Rh superlattice has a trigonal cell angle of 104°, and the constitute NCs orient their atomic Pt₃Co(111) planes to the superlattice Rh[111] direction. The temperature-dependent in situ small and wide-angle X-ray scattering (SAXS/WAXS) measurements reveal a thermally induced superlattice contraction of supercrystal, which maintains translational ordering but slightly develops orientational disordering. The observed increases of both the packing density and the rotation magnitude of NCs indicate a rational compromise between configurational and rotational entropies of NCs. The resultant minimization of the total free energy is responsible for the formation and stability of the obtuse Rh superlattice. The temperature-dependent in situ measurements of SAXS and electrical resistance reveal that, in conjunction with the thermally induced sharp contraction of superlattice at 160 °C, the supercrystal becomes measurable of electrical resistance, which was followed by a temperature-dependent linear increase. Upon rapid annealing from 250 °C, the supercrystal remains almost constant in both structure and electrical resistance. The heating-enabled electrical conductivity of the supercrystal at high temperature implies the formation of a NC-interconnected architecture. The experiments and overall analysis provide solid evidence and essential information for the use of shape-dependent structural anisotropies of supercrystal to create nanobased novel architecture with desired properties.

Stable CO anti-poisoning and high durability of a Pt electrocatalyst supported on carbon nanotubes

Stable CO anti-poisoning and high durability of an anodic electrocatalyst are very important for direct methanol fuel cells (DMFCs).

Scalable synthesis of Cu-based ultrathin nanowire networks and their electrocatalytic properties

In this research, we developed an easy way to generate CuM (M = Pd, Pt and PdPt) ultrathin nanowire networks by simply injecting the metallic precursors into an aqueous solution which contained sodium borohydride under vigorous stirring. The reaction can be finished quickly without needing any other reagents, thus leaving the products with a clean surface. The prepared materials show an ultrathin diameter of less than 5 nanometers. The reaction can be easily amplified, resulting in scalable products. These properties combined with the superior catalytic performance of the prepared CuM nanowire networks underpin their potential use in glycerol electrooxidation reaction.