One-step synthesis of ultrathin PtxPb nerve-like nanowires as robust catalysts for enhanced methanol electrooxidation

Pt-Ru atomic alloys confined in mesoporous carbon hollow spheres for accelerating methanol oxidation

Active and durable electrocatalysts are essential for commercializing direct methanol fuel cells. However, Pt-based catalysts, extensively utilized in the methanol oxidation reaction (MOR), are suffered from resource scarcity and CO poisoning, which degrade MOR activity severely. Herein, Pt1Rux bimetallic catalysts were synthesized by confining Pt1Rux alloys within the shells of mesoporous carbon hollow spheres (MCHS) via a vacuum-assisted impregnation method (Pt1Rux@MCHS). The confinement effect induced by mesoporous carbon hollow spheres resulted in a robust structure of Pt1Ru3@MCHS with an ultrafine dispersion of alloy nanoparticles. The experimental and theoretical results confirmed that the boosting electrocatalytic activity and stability of the MOR over Pt1Ru3@MCHS were contributed to the regulated electronic structure as well as the superior CO tolerance of atomic Pt site caused by the electronic interaction between single Pt atoms and Ru nanoparticles. This strategy is versatile for the rational design of Pt-based bimetallic catalysts and has a positive impact on MOR performance.

High-efficient electrooxidation of ethylene glycol and ethanol on PdSn alloy loaded by versatile poly(3,4-ethylenedioxythiophene)

Developing a novel catalyst with lower noble-metal loading and higher catalytic efficiency is significant for promoting the widespread application of direct alcohol fuel cells (DAFCs). In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) supported the PdSn alloy (PdSn/PEDOT) were simply synthesized and their electrocatalytic performance toward the oxidation of ethylene glycol and ethanol (EGOR and EOR) were investigated in alkaline media, respectively. In comparison with other control catalysts, the optimized Pd4Sn6/PEDOT catalyst exhibits the highest mass activity (7125/4166 mA mgPd-1) and specific activity (26/15 mA cm-2) towards EGOR/EOR. The mass activity of Pd4Sn6/PEDOT for EGOR and EOR are 11.9 and 10.9 times higher than commercial Pd/C, respectively. Moreover, chronoamperometry (CA) and successive cyclic voltammetry (CV) tests show that the CO resistance ability and durability of the Pd4Sn6/PEDOT catalyst were superior to Pd4Sn6, Pd/PEDOT and commercial Pd/C catalysts, which can be attributed to the d-band center of Pd can be effectively downshifted and the interface strain effect between electrons caused by the conjugated structure between PEDOT groups. This work provides an effective strategy for the development of highly efficient anode catalysts of DAFCs.

Ag+-Induced Assembly of Pt Clusters for Photocatalytic Hydrogen Production

Cluster-assembled nanowires provide a unique strategy for the preparation of high-performance nanostructures. However, existing preparations are limited by complex processes and harsh reaction conditions. Here, Ag+ ions were utilized as a novel structure-directing agent to generate the self-assembly of Pt clusters to form ultrafine nanowires with a diameter of less than 5 nm. Electrospray ionization mass spectrometry (ESI-MS) and extended X-ray absorption fine structure (EXAFS) characterizations demonstrated that every Ag+ bridged two [Pt3(CO)3(μ2-CO)3]n2- clusters through coordination and formed a sandwich-like structure of [Pt3(CO)3(μ2-CO)3]nAg[Pt3(CO)3(μ2-CO)3]m3-. As a result, multiple sandwich-like structures of [Pt3(CO)3(μ2-CO)3]nAg[Pt3(CO)3(μ2-CO)3]m3- were established by Ag+ to form Pt nanowire superstructures {[Pt3(CO)6]nAg[Pt3(CO)6]mAg[Pt3(CO)6]x}∞ (abbreviated as Ag-Pt NWS). Our results demonstrate that the Pt nanowire superstructures showed promising cocatalytic performance for photocatalytic H2 production with the involvement of Ag+, which promises a desirable way to develop advanced functional nanomaterials.

Mixed-Dimensional Partial Dealloyed PtCuBi/C as High-Performance Electrocatalysts for Methanol Oxidation with Enhanced CO Tolerance

Developing efficient electrocatalysts for methanol oxidation reaction (MOR) is crucial in advancing the commercialization of direct methanol fuel cells (DMFCs). Herein, carbon-supported 0D/2D PtCuBi/C (0D/2D PtCuBi/C) catalysts are fabricated through a solvothermal method, followed by a partial electrochemical dealloying process to form a novel mixed-dimensional electrochemically dealloyed PtCuBi/C (0D/2D D-PtCuBi/C) catalysts. Benefiting from distinctive mixed-dimensional structure and composition, the as-obtained 0D/2D D-PtCuBi/C catalysts possess abundant accessible active sites. The introduction of Cu as a water-activating element weakens the COads, and oxophilic metal Bi facilitates the OHads, thereby enhancing its tolerance to CO poisoning and promoting MOR activity. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS) collectively reveal the electron transfer from Cu and Bi to Pt, the electron-enrichment effect induced by dealloying, and the strong interactions among Pt-M (Cu, Pt, and Bi) multi-active sites, which improve the tuning of the electronic structure and enhancement of electron transfer ability. Impressively, the optimized 0D/2D D-PtCuBi/C catalysts exhibit the superior mass activity (MA) of 17.68 A mgPt -1 for MOR, which is 14.86 times higher than that of commercial Pt/C. This study offers a proposed strategy for Pt-based alloy catalysts, enabling their use as efficient anodic materials in fuel cell applications.

Chemical-Dealloying-Derived PtPdPb-Based Multimetallic Nanoparticles: Dimethyl Ether Electrocatalysis and Fuel Cell Application

In this work, we report a novel multimetallic nanoparticle catalyst composed of Pt, Pd, and Pb and its electrochemical activity toward dimethyl ether (DME) oxidation in liquid electrolyte and polymer electrolyte fuel cells. Chemical dealloying of the catalyst with the lowest platinum-group metal (PGM) content, Pt2PdPb2/C, was conducted using HNO3 to tune the catalyst activity. Comprehensive characterization of the chemical-dealloying-derived catalyst nanoparticles unambiguously showed that the acid treatment removed 50% Pb from the nanoparticles with an insignificant effect on the PGM metals and led to the formation of smaller-sized nanoparticles. Electrochemical studies showed that Pb dissolution led to structural changes in the original catalysts. Chemical-dealloying-derived catalyst nanoparticles made of multiple phases (Pt, Pt3Pb, PtPb) provided one of the highest PGM-normalized power densities of 118 mW mgPGM-1 in a single direct DME fuel cell operated at low anode catalyst loading (1 mgPGM cm-2) at 70 °C. A possible DME oxidation pathway for these multimetallic catalysts was proposed based on an online mass spectrometry study and the analysis of the reaction products.

Recent progress on the synthesis of metal alloy nanowires as electrocatalysts

Benefiting from both one-dimensional (1D) morphology and alloy composition, metal alloy nanowires have been exploited as advanced electrocatalysts in various electrochemical processes. In this review, the synthesis approaches for metal alloy nanowires are classified into two categories: direct syntheses and syntheses based on preformed 1D nanostructures. Ligand systems that are of critical importance to the formation of alloy nanowires are summarized and reviewed, together with the strategies imposed to achieve the co-reduction of different metals. Meanwhile, different scenarios that form alloy nanowires from pre-synthesized 1D nanostructures are compared and contrasted. In addition, the characterization and electrocatalytic applications of metal alloy nanowires are briefly discussed.

T porous PtIr bimetallic nanotubes with core shell structure for enhanced electrocatalysis on methanol oxidation

Sluggish methanol oxidation brings challenges to the commercialization of the direct methanol fuel cells (DMFCs). Herein, porous PtIr bimetallic nanotubes were prepared via galvanic replacement using Ag nanowires as template. These PtIr catalysts show a core-shell nanostructure with a tunable Pt-rich surface. The mass activity of methanol oxidation reaction (MOR) at these porous PtIr nanotubes can reach up to 1.42 A mg^-1based on Pt loading, which is better than the commercial Pt/C catalysts and can be comparable with most of one-dimensional Pt-based MOR catalysts reported recently. In addition, these PtIr catalysts can maintain structural integrity after long-term durability test. The superior catalytic performance of the novel porous PtIr nanotubes will make it possible used in the commercial DMFCs as advanced MOR catalysts at industrial scale.

Surfactant-free synthesis of carbon-supported silver (Ag/C) nanobars as an efficient electrocatalyst for alcohol tolerance and oxidation of sodium borohydride in alkaline medium

We have synthesized carbon-supported silver (Ag/C) nanobars by a simple surfactant-free hydrothermal method using glucose as the reducing reagent as well as the source of carbon in Ag/C nanobars. Physicochemical characterization of the materials was performed by X-ray Diffraction (XRD), field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The XRD pattern confirmed the presence of a pure metallic silver phase. No carbon phase was detected, which indicates that the carbon exists mainly in the amorphous form. The electrocatalytic activity of Ag/C in different electrolyte solutions such as 0.5 M NaOH, 0.5 M NaOH + 1 M ethanol (EtOH), 0.5 M NaOH + 1 M ethylene glycol (EG), and 0.5 M NaOH + 0.01 M NaBH4 (sodium borohydride) was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) study. Alcohol tolerance of the catalysts was also established in the presence of ethanol and ethylene glycol. The forward-to-backward current ratio from cyclic voltammetry (CV) study of Ag/C-20 (20 h) in 0.5 M NaOH + 1 M ethanol solution at 100 mV s−1 scan rate is 4.13 times higher compared to that of Ag/C-5 (5 h). Hence, Ag/C-20 is a better candidate for the tolerance of ethanol. In the presence of ethylene glycol (1 M) in 0.5 M NaOH solution, it is obtained that the forward-to-backward current ratio at the same scan rate for Ag/C-20 is lower than that in the presence of ethanol. The durability of the catalyst was studied by chronoamperometry measurement. We studied the electrochemical kinetics of Ag/C catalysts for borohydride oxidation in an alkaline medium. The basic electrochemical results for borohydride oxidation show that Ag/C has very well strength and activity for direct borohydride oxidation in an alkaline medium. The reaction of borohydride oxidation with the contemporaneous BH4−. hydrolysis was noticed at the oxidized silver surface. Among all the synthesized Ag/C catalysts, Ag/C-20 exhibited the best electrocatalytic performance for borohydride oxidation in an alkaline medium. The activation energy and the number of exchange electrons at Ag/C-20 electrode surface for borohydride electro-oxidation were estimated as 57.2 kJ mol−1 and 2.27, respectively.

Reconciling structure prediction of alloyed, ultrathin nanowires with spectroscopy

A number of complementary, synergistic advances are reported herein. First, we describe the 'first-time' synthesis of ultrathin Ru2Co1 nanowires (NWs) possessing average diameters of 2.3 ± 0.5 nm using a modified surfactant-mediated protocol. Second, we utilize a combination of quantitative EDS, EDS mapping (along with accompanying line-scan profiles), and EXAFS spectroscopy results to probe the local atomic structure of not only novel Ru2Co1 NWs but also 'control' samples of analogous ultrathin Ru1Pt1, Au1Ag1, Pd1Pt1, and Pd1Pt9 NWs. We demonstrate that ultrathin NWs possess an atomic-level geometry that is fundamentally dependent upon their intrinsic chemical composition. In the case of the PdPt NW series, EDS mapping data are consistent with the formation of a homogeneous alloy, a finding further corroborated by EXAFS analysis. By contrast, EXAFS analysis results for both Ru1Pt1 and Ru2Co1 imply the generation of homophilic structures in which there is a strong tendency for the clustering of 'like' atoms; associated EDS results for Ru1Pt1 convey the same conclusion, namely the production of a heterogeneous structure. Conversely, EDS mapping data for Ru2Co1 suggests a uniform distribution of both elements. In the singular case of Au1Ag1, EDS mapping results are suggestive of a homogeneous alloy, whereas EXAFS analysis pointed to Ag segregation at the surface and an Au-rich core, within the context of a core-shell structure. These cumulative outcomes indicate that only a combined consideration of both EDS and EXAFS results can provide for an accurate representation of the local atomic structure of ultrathin NW motifs.

Tuning Surface Structure of Pd3Pb/Pt n Pb Nanocrystals for Boosting the Methanol Oxidation Reaction

Developing an efficient Pt-based electrocatalyst with well-defined structures for the methanol oxidation reaction (MOR) is critical, however, still remains a challenge. Here, a one-pot approach is reported for the synthesis of Pd3Pb/Pt n Pb nanocubes with tunable Pt composition varying from 3.50 to 2.37 and 2.07, serving as electrocatalysts toward MOR. Their MOR activities increase in a sequence of Pd3Pb/Pt3.50Pb << Pd3Pb/Pt2.07Pb < Pd3Pb/Pt2.37Pb, which are substantially higher than that of commercial Pt/C. Specifically, Pd3Pb/Pt2.37Pb electrocatalysts achieve the highest specific (13.68 mA cm-2) and mass (8.40 A mgPt -1) activities, which are ≈8.8 and 6.8 times higher than those of commercial Pt/C, respectively. Structure characterizations show that Pd3Pb/Pt2.37Pb and Pd3Pb/Pt2.07Pb are dominated by hexagonal-structured PtPb intermetallic phase on the surface, while the surface of Pd3Pb/Pt3.50Pb is mainly composed of face-centered cubic (fcc)-structured Pt x Pb phase. As such, hexagonal-structured PtPb phase is much more active than the fcc-structured Pt x Pb one toward MOR. This demonstration is supported by density functional theory calculations, where the hexagonal-structured PtPb phase shows the lowest adsorption energy of CO. The decrease in CO adsorption energy and structural stability also endows Pd3Pb/Pt n Pb electrocatalysts with superior durability relative to commercial Pt/C.

From bimetallic PdCu nanowires to ternary PdCu-SnO2 nanowires: Interface control for efficient ethanol electrooxidation

At present, although a large number of palladium-based nanowire electrocatalysts have been prepared, there are few reports on nanowires containing rich metal oxides. Herein, porous PdCu alloy nanowires and PdCu-SnO₂ nanowires were prepared by using a galvanic displacement synthesis method. Due to their one-dimensional structure, rough surfaces with non-homogeneous edges, electronic effect, and the advanced PdCu/SnO₂ interface of the as-synthesized PdCu-SnO₂ nanowire catalysts, they exhibited a mass activity of 7770.0 mA mg^-1 towards ethanol oxidation, which was 7.6-fold higher than that of Pd/C catalysts (1025.0 mA mg^-1). In addition, they behaved strong durability upon chronoamperometry and continuous cyclic voltammetry tests. The electrochemical measurements demonstrated that SnO₂ was introduced into the PdCu/SnO₂ interface, which promoted the oxidation of ethanol at a lower potential and accelerated the oxidation of Pd-CO_ads via SnO₂-OH_ads to regenerate the active sites. This research highlights the significance of introducing metal oxides into the nanostructure interface, and the performance of Pd-containing catalysts towards ethanol oxidation reaction was greatly improved.

High-density surface protuberances endow ternary PtFeSn nanowires with high catalytic performance for efficient alcohol electro-oxidation

Developing cost-effective catalysts with superb activity and stability to alcohol electro-oxidation is a decisive factor towards the progress of direct alcohol fuel cells (DAFCs). Rationally utilizing the architectural and surface microstructural sensitivity of nanocatalysts can significantly increase their electrocatalytic properties. Here, we report an appropriate route that allows the fabrication of ultrafine PtFeSn nanowires (NWs) with tunable compositions. Interestingly, the addition of Sn reconstructed the surface microstructures, making ultrafine 1D NWs rich in a large number of surface protuberances, which may facilitate the oxidation of ethanol and methanol. Impressively, further catalytic studies demonstrate that all the PtFeSn NWs exhibit excellent catalytic capabilities for ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR), and display composition-related electrocatalytic activity with Pt1Fe0.20Sn0.46 NWs, possessing the highest activity for EOR and MOR. In addition, the trimetallic PtFeSn NWs exhibit significant meliorative durability relative to PtFe NWs and commercial Pt/C. The superb electrocatalytic performance is ascribed to its one-dimensional (1D) structure, atomic-level fine diameter, synergistic effect among Pt, Fe, and Sn components and abundant protuberances on the surface. Thus, this study highlights the significance of accurate structure- and surface-controlled Pt-based NWs for electrocatalysis and provides a universal approach for designing multi-component catalysts.

Shape- and size-dependences of gold nanostructures on the electrooxidation of methanol under visible light irradiation

Plasmonic metal nanocatalysts have excellent light trapping properties and high chemical reactivity. Impressively, Au nanostructures can absorb a wide array of visible light by tuning their morphology. In this work, spherical gold nanoparticles (Au NSs), multi-branched gold nanoparticles (Au NMs) and gold nanorods (Au NRs) were successfully synthesized; the shape- and size-dependences of these gold nanocatalysts on the methanol oxidation reaction (MOR) under light irradiation were studied. It is worth mentioning that Au NRs have the highest anode peak current density under dark conditions due to the exposure of highly active facets. A similar enhancement effect was obtained for Au NSs and Au NMs under visible light irradiation, which is due to the generation of a high concentration of energetic charge carriers on these Au nanostructures. The size dependences of Au NSs on the MOR showed that a larger electrochemically active surface area (ECSA) was obtained for small nanoparticles, which is due to the surface effect. In addition, the catalytic performance, durability and anti-CO stripping of these Au nanocatalysts under visible light irradiation, as well as the effect of light intensity and wavelength were described in detail. This work provides an insight into the mechanism of plasmon enhanced electrocatalysis by Au nanostructures with different sizes and shapes.

Pt and RhPt dendritic nanowires and their potential application as anodic catalysts for fuel cells

Fuel cells have a number of benefits over conventional combustion-based technologies and can be used in a range of important applications, including transportation, as well as stationary, portable and emergency backup power systems. One of the major challenges in this field, however lies in controlling catalyst design which is critical for developing efficient and cost-effective fuel cell technology. Herein, for the first time, we report a facile controlled synthesis of Pt and RhPt dendritic nanowires using ultrathin AuAg nanowires as sacrificial templates. These dendritic nanowires exhibit remarkable catalytic performance in the elecrochemical oxidation of methanol and formic acid. In particular, the RhPt dendritic nanostructures show very high resistance to catalyst poisoning in methanol oxidation. This research demonstrates the advantages of using bimetallic dendritic nanostructures and we believe that these materials and electrocatalytic studies are important for further advancement of fuel cell research and technology.

Locally-ordered PtNiPb ternary nano-pompons as efficient bifunctional oxygen reduction and methanol oxidation catalysts

To accurately control the composition and structure of Pt-based alloys is essential for engineering highly active and stable catalysts, yet challenging. Here, ternary PtNiPb nano pompons (NPs) combining the features of a highly open structure, local-ordering and the introduction of Pb have been synthesized via a seed-mediated growth method. Taking advantage of the reduction potential differences, gradient distribution of Pb and Ni throughout the NPs is realized, and both the elemental composition and distribution can be facilely regulated by reaction time. The PtNiPb NPs exhibit much enhanced catalytic performance for both the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR), of which the ORR specific activity is 7.4- and 2.3-fold larger than those of the commercial Pt/C catalyst and binary PtNi NPs. Density functional theory (DFT) calculations reveal that the weak coupling between Pb-p and Pt-d orbitals together with the regulation of the over-compressed Pt surface by the local-ordering structure and embedded Pb atoms optimize the surface oxygen adsorption character and eventually boost the ORR.

H2-Induced coalescence of Pt nanoparticles for the preparation of ultrathin Pt nanowires with high-density planar defects

Construction of planar defects within a metallic catalyst can significantly improve its catalytic performance. However, it remains a huge challenge to introduce planar defects during the synthesis of metallic catalysts. In this work, we have reported an effective approach for the preparation of Pt nanowires with high-density planar defects. The success of the approach mainly relies on the attaching and merging of small Pt nanoparticles at low temperatures with the assistance of H2. By comparing the catalytic activities of Pt nanowires with high-density planar defects and commercial Pt/C catalysts toward methanol oxidation reactions, we show that the existence of planar defects can markedly enhance the electrocatalytic performance of the Pt nanowires. The Pt nanowires of 2.0 nm in diameter show a factor of 6.1 enhancement in specific activity and a factor of 5.4 enhancement in mass activity, respectively, for this reaction, compared to the commercial Pt/C catalyst. The method developed in this work could be an effective route to introduce planar defects within Pt catalysts, endowing them with much enhanced catalytic properties.

Ternary PtRuCu aerogels for enhanced methanol electrooxidation

Ternary PtRuCu aerogels are facilely synthesized by one-step in situ reduction. The formation of ternary PtRuCu aerogels can be completed within 2 hours owing to the accelerated gelation kinetics. Because of the unique porous architectures and synergistic effect, the optimized Pt4Ru1Cu5 aerogels exhibited good electrochemical performance for methanol oxidation reaction.

Shape-control of one-dimensional PtNi nanostructures as efficient electrocatalysts for alcohol electrooxidation

Bimetallic one-dimensional (1D) nanostructures such as nanowires (NWs) and nanorods (NRs), serving as high-efficiency anode electrocatalysts, have attracted extensive attention in the past decade. However, the precise design and synthesis of 1D Pt-based nanocrystals with tunable morphology and size still remain an arduous challenge. Driven by this, we report a facile yet efficient strategy for the first time to prepare PtNi ultrafine NWs (UNWs), sinuous NWs (SNWs) and ultrashort NRs (UNRs) by adjusting the amount of citric acid, ascorbic acid and glucose. Detailed analysis of their electrocatalytic properties has indicated that the as-obtained PtNi SNWs exhibit the most outstanding electrocatalytic activity toward ethylene glycol oxidation reaction (EGOR) and glycerol oxidation (GOR), 4.5 and 4.3 times higher in mass activity as well as 4.3 and 3.9 times higher in specific activity compared with the commercial Pt/C catalyst. The as-prepared PtNi SNWs are also more stable than the commercial Pt/C catalyst after successive durability tests. The proposed method provides insight into more rational designs of bimetallic nanocatalysts with 1D architectures and the as-synthesized PtNi catalysts with improved electrocatalytic performance assist in promoting the further development of direct alcohol fuel cells (DAFCs).

One-pot fabrication of Nitrogen-doped graphene supported binary palladium-sliver nanocapsules enable efficient ethylene glycol electrocatalysis

Fuel cells hold great potential of replacing traditional fossil fuel to alleviate the energy crisis and increasing environmental concerns. Although great progresses have been achieved over decades, the sluggish reaction kinetics and poor durability of electrocatalysts in fuel cells have been the decisive bottleneck that limited their practical applications. Herein, we focus on the design and development of cost-efficient anode electrocatalysts for fuel cells and report the successful creation of an advanced class of N-doped graphene (NG) supported binary PdAg nanocapsules (PdAg NCPs). The well-defined nanocatalysts with highly open structure exhibit greatly improved electrocatalytic performances for ethylene glycol oxidation reaction (EGOR). In particular, the optimized PdAg NCPs/NG show the mass and specific activities of 6118.3 mA mg^-1 and 13.8 mA cm^-2, which are 5.8 and 6.9 times larger than those of the commercial Pd/C catalysts, respectively. More importantly, such PdAg NCPs/NG can also maintain at least 500 potential cycles with limited catalytic activity attenuation, showing an advanced class of electrocatalysts for fuel cells.

3D-2D heterostructure of PdRu/NiZn oxyphosphides with improved durability for electrocatalytic methanol and ethanol oxidation

The rational design and engineering of bimetallic Pd-based nanocatalysts with both high activity and durability are of paramount significance for the practical applications of fuel cells. Herein, a new class of well-defined 2D NiZn oxyphosphide nanosheets (NiZnP NSs) have been successfully engineered to support unique 3D PdRu nanoflowers (PdRu NFs) via a facile strategy. Such nanohybrids with abundant surface active areas and modified electronic structure exhibit a great enhancement in electrocatalytic activity for the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR), whose mass/specific activities are 1739.5 mA mg-1/4.5 mA cm-2 and 4719.8 mA mg-1/12.3 mA cm-2, which are 8.3/9.0 and 8.3/9.5 times higher than those of commercial Pd/C catalysts, respectively. More interestingly, with the remarkable promotional effect of NiZnP NSs, such 3D-2D PdRu/NiZn oxyphosphide nanohybrids can even retain 72.4% and 70.1% of initial catalytic activity toward MOR and EOR for 1000 potential cycles with negligible morphological or compositional variations. The successful construction of this new class of electrocatalysts opens up a new way for designing 3D-2D nanohybrids with high performance for electrochemical reactions and beyond.

Ultrathin Metallic Nanowire-Based Architectures as High-Performing Electrocatalysts

Fuel cells (FCs) convert chemical energy into electricity through electrochemical reactions. They maintain desirable functional advantages that render them as attractive candidates for renewable energy alternatives. However, the high cost and general scarcity of conventional FC catalysts largely limit the ubiquitous application of this device configuration. For example, under current consumption requirements, there is an insufficient global reserve of Pt to provide for the needs of an effective FC for every car produced. Therefore, it is absolutely necessary in the future to replace Pt either completely or in part with far more plentiful, abundant, cheaper, and potentially less toxic first row transition metals, because the high cost-to-benefit ratio of conventional catalysts is and will continue to be a major limiting factor preventing mass commercialization. We and other groups have explored a number of nanowire-based catalytic architectures, which are either Pt-free or with reduced Pt content, as an energy efficient solution with improved performance metrics versus conventional, currently commercially available Pt nanoparticles that are already well established in the community. Specifically, in this Perspective, we highlight strategies aimed at the rational modification of not only the physical structure but also the chemical composition as a means of developing superior electrocatalysts for a number of small-molecule-based anodic oxidation and cathodic reduction reactions, which underlie the overall FC behavior. In particular, we focus on efforts to precisely, synergistically, and simultaneously tune not only the size, morphology, architectural motif, surface chemistry, and chemical composition of the as-generated catalysts but also the nature of the underlying support so as to controllably improve performance metrics of the hydrogen oxidation reaction, the methanol oxidation reaction, the ethanol oxidation reaction, and the formic acid oxidation reaction, in addition to the oxygen reduction reaction.

Hollow AuxAg/Au core/shell nanospheres as efficient catalysts for electrooxidation of liquid fuels

One plausible approach to endow nanocrystals with both enhanced catalytic activity and stability for the electrooxidation of liquid fuels is to chemically control the crystal structures of nanoparticles. To date, core-shell and alloy structures have been demonstrated to offer generally two precious opportunities to design highly efficient nanocatalysts for the electrooxidation reaction of organic molecules. We herein combine these two advantages and develop a general method to successfully synthesize hollow Au_xAg/Au core/shell nanospheres with a high yield approaching 100% via a combined seed mediated and galvanic replacement method. The results from the electrochemical measurements have revealed that this as-obtained hollow Au_xAg/Au core/shell nanosphere exhibited considerably high electrocatalytic performance towards ethylene glycol and glycerol oxidation with mass activity of 4585 and 3486 mA mg_Au^-1, which were 5.3- and 5.8-fold higher than that of pure Au. We trust this strategy may be extended to the syntheses of other multimetallic nanocatalysts with such fascinating nanostructures and the as-obtained hollow Au_xAg/Au core/shell nanospheres can be well applied to serve as highly desirable anode catalysts for the electrooxidation of ethylene glycol and glycerol.