Elucidating Cathodic Corrosion Mechanisms with Operando Electrochemical Transmission Electron Microscopy.

Cathodic corrosion represents an enigmatic electrochemical process in which metallic electrodes corrode under sufficiently reducing potentials. Although discovered by Fritz Haber in the 19th century, only recently has progress been made in beginning to understand the atomistic mechanisms of corroding bulk electrodes. The creation of nanoparticles as the end-product of the corrosion process suggests an additional length scale of complexity. Here, we studied the dynamic evolution of morphology, composition, and crystallographic structural information of nanocrystal corrosion products by analytical and four-dimensional electrochemical liquid-cell scanning transmission electron microscopy (EC-STEM). Our operando/in situ electron microscopy revealed, in real-time, at the nanometer scale, that cathodic corrosion yields significantly higher levels of structural degradation for heterogeneous nanocrystals than bulk electrodes. In particular, the cathodic corrosion of Au nanocubes on bulk Pt electrodes led to the unexpected formation of thermodynamically immiscible Au-Pt alloy nanoparticles. The highly kinetically driven corrosion process is evidenced by the successive anisotropic transition from stable Pt(111) bulk single-crystal surfaces evolving to energetically less-stable (100) and (110) steps. The motifs identified in this microscopy study of cathodic corrosion of nanocrystals are likely to underlie the structural evolution of nanoscale electrocatalysts during many electrochemical reactions under highly reducing potentials, such as CO2 and N2 reduction.

A completely precious metal-free alkaline fuel cell with enhanced performance using a carbon-coated nickel anode.

SignificanceWe present a groundbreaking advance in completely nonprecious hydrogen fuel cell technologies achieving a record power density of 200 mW/cm2 with Ni@CNx anode and Co-Mn cathode. The 2-nm CNx coating weakens the O-binding energy, which effectively mitigates the undesirable surface oxidation during hydrogen oxidation reaction (HOR) polarization, leading to a stable fuel cell operation for Ni@CNx over 100 h at 200 mA/cm2, superior to a Ni nanoparticle counterpart. Ni@CNx exhibited a dramatically enhanced tolerance to CO relative to Pt/C, enabling the use of hydrogen gas with trace amounts of CO, critical for practical applications. The complete removal of precious metals in fuel cells lowers the catalyst cost to virtually negligible levels and marks a milestone for practical alkaline fuel cells.

Electrocatalysis in Alkaline Media and Alkaline Membrane-Based Energy Technologies.

Hydrogen energy-based electrochemical energy conversion technologies offer the promise of enabling a transition of the global energy landscape from fossil fuels to renewable energy. Here, we present a comprehensive review of the fundamentals of electrocatalysis in alkaline media and applications in alkaline-based energy technologies, particularly alkaline fuel cells and water electrolyzers. Anion exchange (alkaline) membrane fuel cells (AEMFCs) enable the use of nonprecious electrocatalysts for the sluggish oxygen reduction reaction (ORR), relative to proton exchange membrane fuel cells (PEMFCs), which require Pt-based electrocatalysts. However, the hydrogen oxidation reaction (HOR) kinetics is significantly slower in alkaline media than in acidic media. Understanding these phenomena requires applying theoretical and experimental methods to unravel molecular-level thermodynamics and kinetics of hydrogen and oxygen electrocatalysis and, particularly, the proton-coupled electron transfer (PCET) process that takes place in a proton-deficient alkaline media. Extensive electrochemical and spectroscopic studies, on single-crystal Pt and metal oxides, have contributed to the development of activity descriptors, as well as the identification of the nature of active sites, and the rate-determining steps of the HOR and ORR. Among these, the structure and reactivity of interfacial water serve as key potential and pH-dependent kinetic factors that are helping elucidate the origins of the HOR and ORR activity differences in acids and bases. Additionally, deliberately modulating and controlling catalyst-support interactions have provided valuable insights for enhancing catalyst accessibility and durability during operation. The design and synthesis of highly conductive and durable alkaline membranes/ionomers have enabled AEMFCs to reach initial performance metrics equal to or higher than those of PEMFCs. We emphasize the importance of using membrane electrode assemblies (MEAs) to integrate the often separately pursued/optimized electrocatalyst/support and membranes/ionomer components. Operando/in situ methods, at multiscales, and ab initio simulations provide a mechanistic understanding of electron, ion, and mass transport at catalyst/ionomer/membrane interfaces and the necessary guidance to achieve fuel cell operation in air over thousands of hours. We hope that this Review will serve as a roadmap for advancing the scientific understanding of the fundamental factors governing electrochemical energy conversion in alkaline media with the ultimate goal of achieving ultralow Pt or precious-metal-free high-performance and durable alkaline fuel cells and related technologies.

Nonprecious transition metal nitrides as efficient oxygen reduction electrocatalysts for alkaline fuel cells.

Hydrogen fuel cells have attracted growing attention for high-performance automotive power but are hindered by the scarcity of platinum (and other precious metals) used to catalyze the sluggish oxygen reduction reaction (ORR). We report on a family of nonprecious transition metal nitrides (TMNs) as ORR electrocatalysts in alkaline medium. The air-exposed nitrides spontaneously form a several-nanometer-thick oxide shell on the conductive nitride core, serving as a highly active catalyst architecture. The most active catalyst, carbon-supported cobalt nitride (Co3N/C), exhibited a half-wave potential of 0.862 V and achieved a record-high peak power density among reported nitride cathode catalysts of 700 mW cm-2 in alkaline membrane electrode assemblies. Operando x-ray absorption spectroscopy studies revealed that Co3N/C remains stable below 1.0 V but experiences irreversible oxidation at higher potentials. This work provides a comprehensive analysis of nonprecious TMNs as ORR electrocatalysts and will help inform future design of TMNs for alkaline fuel cells and other energy applications.

Co3Mo3N-An efficient multifunctional electrocatalyst.

Efficient catalysts are required for both oxidative and reductive reactions of hydrogen and oxygen in sustainable energy conversion devices. However, current precious metal-based electrocatalysts do not perform well across the full range of reactions and reported multifunctional catalysts are all complex hybrids. Here, we show that single-phase porous Co3Mo3N prepared via a facile method is an efficient and reliable electrocatalyst for three essential energy conversion reactions; oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) in alkaline solutions. Co3Mo3N presents outstanding OER, ORR, and HER activity with high durability, comparable with the commercial catalysts RuO2 for OER and Pt/C for ORR and HER. In practical demonstrations, Co3Mo3N gives high specific capacity (850 mA h gZn -1 at 10 mA cm-2) as the cathode in a zinc-air battery, and a low potential (1.63 V at 10 mA cm-2) used in a water-splitting electrolyzer. Availability of Co and Mo d-states appear to result in high ORR and HER performance, while the OER properties result from a cobalt oxide-rich activation surface layer. Our findings will inspire further development of bimetallic nitrides as cost-effective and versatile multifunctional catalysts that will enable scalable usage of electrochemical energy devices.

Superconducting Quantum Metamaterials from Convergence of Soft and Hard Condensed Matter Science.

Superconducting quantum metamaterials are expected to exhibit a variety of novel properties, but have been a major challenge to prepare as a result of the lack of appropriate synthetic routes to high-quality materials. Here, the discovery of synthesis routes to block copolymer (BCP) self-assembly-directed niobium nitrides and carbonitrides is described. The resulting materials exhibit unusual structure retention even at temperatures as high as 1000 °C and resulting critical temperature, Tc , values comparable to their bulk analogues. Applying the concepts of soft matter self-assembly, it is demonstrated that a series of four different BCP-directed mesostructured superconductors are accessible from a single triblock terpolymer. Resulting materials display a mesostructure-dependent Tc without substantial variation of the XRD-measured lattice parameters. Finally, field-dependent magnetization measurements of a sample with double-gyroid morphology show abrupt jumps comparable in overall behavior to flux avalanches. Results suggest a fruitful convergence of soft and hard condensed matter science.

Materials Combining Asymmetric Pore Structures with Well-Defined Mesoporosity for Energy Storage and Conversion.

Porous materials design often faces a trade-off between the requirements of high internal surface area and high reagent flux. Inorganic materials with asymmetric/hierarchical pore structures or well-defined mesopores have been tested to overcome this trade-off, but success has remained limited when the strategies are employed individually. Here, the attributes of both strategies are combined and a scalable path to porous titanium nitride (TiN) and carbon membranes that are conducting (TiN, carbon) or superconducting (TiN) is demonstrated. These materials exhibit a combination of asymmetric, hierarchical pore structures and well-defined mesoporosity throughout the material. Fast transport through such TiN materials as an electrochemical double-layer capacitor provides a substantial improvement in capacity retention at high scan rates, resulting in state-of-the-art power density (28.2 kW kg-1) at competitive energy density (7.3 W-h kg-1). In the case of carbon membranes, a record-setting power density (287.9 kW kg-1) at 14.5 W-h kg-1 is reported. Results suggest distinct advantages of such pore architectures for energy storage and conversion applications and provide an advanced avenue for addressing the trade-off between high-surface-area and high-flux requirements.

Synergistic Bimetallic Metallic Organic Framework-Derived Pt-Co Oxygen Reduction Electrocatalysts.

The rational design of Pt-based electrocatalysts is of paramount importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt-Co alloys and nitrogen-doped carbons have been shown to be effective in enhancing the kinetics of the oxygen reduction reaction (ORR). Herein, we reported on two kinds of Pt-Co electrocatalysts, PtCo ordered intermetallic and PtCo2 disordered alloys, supported on bimetallic MOF-derived N-doped carbon. The synergistic interaction between Pt-Co nanoparticles and Co-N-C enhanced the overall ORR activity and maintained the integrity of both structures and their electrochemical properties during long-term stability testing. The optimal activity for both PtCo and PtCo2 occurred after 20 000 potential cycles. The enhanced performance of PtCo was ascribed to the formation of a two-atomic-layer Pt-rich shell and the lattice strain caused by the core-shell PtCo@Pt structure. The increased activity of PtCo2 was ascribed to the formation of large, spongy, and small solid nanoparticles during electrochemical dealloying and thus the exposure of more Pt sites on the surface. The strategy described herein advances our understanding of the structure-activity relationship in electrocatalysis and sheds light on the future development of more active and durable ORR electrocatalysts.

Combinatorial Studies of Palladium-Based Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells.

Hydrogen fuel cells have emerged as promising, potentially renewable energy-based, energy conversion technologies for powering electric vehicles. However, the sluggish oxygen reduction reaction (ORR) at the cathode has remained a longstanding challenge and requires the design of nonplatinum electrocatalysts with high activity and, ideally, low cost. Here, we present a combinatorial study of Pd-Cu thin-film electrodes with well-defined composition and structures, prepared by magnetron sputtering, as a fast method for assessing the ORR activity of binary alloys. This represents a facile catalyst screening method, using replaceable glassy carbon disk electrodes, which enables the rapid and reliable evaluation of ORR activity using standard rotating disk electrode (RDE) measurements. Among nine Pd-Cu alloys, Pd50Cu50 was identified as the most promising composition for the ORR and employed as a target for nanoparticle synthesis. The PdCu nanoparticles, supported on carbon, achieved a mass-specific and surface-specific activity, 3 and 2.5 times, respectively, as high as Pd/C in 1 M KOH. PdCu/C further exhibited an impressive durability with only 3 and 13 mV negative shifts in the half-wave potential after 20000 and 100000 potential cycles, respectively. The combinatorial approach guiding the nanoparticle synthesis, described herein, provides an optimized high-throughput screening method for other binary or ternary alloys as fuel cell electrocatalysts.

Cobalt-Based Nitride-Core Oxide-Shell Oxygen Reduction Electrocatalysts.

Developing high-performance, low-cost, and conductive nonprecious electrocatalysts for the oxygen reduction reaction (ORR) has been a key challenge for advancing fuel cell technologies. Here, we report on a novel family of cobalt nitrides (CoxN/C, x = 2, 3, 4) as ORR electrocatalysts in alkaline fuel cells. Co4N/C exhibited the highest ORR activity among the three types of cobalt nitrides studied, with a half-wave potential (E1/2) of 0.875 V vs RHE in 1 M KOH, rivaling that of commercial Pt/C (0.89 V). Moreover, Co4N/C showed an 8-fold improvement in mass activity at 0.85 V, when compared to cobalt oxide, Co3O4/C, and a negligible degradation (ΔE1/2 = 14 mV) after 10 000 potential cycles. The superior performance was ascribed to the formation of a conductive nitride core surrounded by a naturally formed thin oxide shell (about 2 nm). The conductive nitride core effectively mitigated the low conductivity of the metal oxide, and the thin oxide shell on the surface provided the active sites for the ORR. Strategies developed herein represent a promising approach for the design of other novel metal nitrides as electrocatalysts for fuel cells.

Octahedral spinel electrocatalysts for alkaline fuel cells.

Designing high-performance nonprecious electrocatalysts to replace Pt for the oxygen reduction reaction (ORR) has been a key challenge for advancing fuel cell technologies. Here, we report a systematic study of 15 different AB2O4/C spinel nanoparticles with well-controlled octahedral morphology. The 3 most active ORR electrocatalysts were MnCo2O4/C, CoMn2O4/C, and CoFe2O4/C. CoMn2O4/C exhibited a half-wave potential of 0.89 V in 1 M KOH, equal to the benchmark activity of Pt/C, which was ascribed to charge transfer between Co and Mn, as evidenced by X-ray absorption spectroscopy. Scanning transmission electron microscopy (STEM) provided atomic-scale, spatially resolved images, and high-energy-resolution electron-loss near-edge structure (ELNES) enabled fingerprinting the local chemical environment around the active sites. The most active MnCo2O4/C was shown to have a unique Co-Mn core-shell structure. ELNES spectra indicate that the Co in the core is predominantly Co2.7+ while in the shell, it is mainly Co2+ Broader Mn ELNES spectra indicate less-ordered nearest oxygen neighbors. Co in the shell occupies mainly tetrahedral sites, which are likely candidates as the active sites for the ORR. Such microscopic-level investigation probes the heterogeneous electronic structure at the single-nanoparticle level, and may provide a more rational basis for the design of electrocatalysts for alkaline fuel cells.

Ultrahigh Rate Performance of a Robust Lithium Nickel Manganese Cobalt Oxide Cathode with Preferentially Orientated Li-Diffusing Channels.

Lithium nickel manganese cobalt oxide (NMC) materials, with low cost and high energy density, are considered to be among the most promising cathode materials for Li-ion batteries (LIBs). However, several issues have hindered their further deployment, particularly for high-powered applications, including limited rate capability, capacity loss during cycling (especially at high temperatures and high voltages), and difficulty in reproducibly preparing the desired particle morphology. In this work, we have developed a robust LiNi0.33Mn0.33Co0.33O2 cathode material (NMC-111) capable of high-rate performance for LIBs. Our high power NMC-111 (HP-NMC) cathode materials showed significantly enhanced electrochemical performance, relative to a commercial NMC-111 (c-NMC), with discharge capacities of 138 and 131 mAh/g at high current rates of 20 and 30 C, respectively. The material also exhibited enhanced cycling stability under both room temperature and at 50 °C. We ascribe the high performance of our material to a unique crystalline microstructure observed by electron microscopy characterization, which showed preferential orientation of the Li-diffusing channels radially outward. This HP-NMC material achieved one of the highest performance metrics among NMC materials reported to date, especially for high-powered electric vehicles.

Metal-Organic-Framework-Derived Co-Fe Bimetallic Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells.

The oxygen reduction reaction (ORR) is considered the cornerstone for regenerative energy conversion devices involving fuel cells and electrolyzers. The development of non-precious-metal electrocatalysts is of paramount importance for their large-scale commercialization. Here, Co-Fe binary alloy embedded bimetallic organic frameworks (BMOF)s based on carbon nanocomposites have been designed with a compositionally optimized template, by a facile host-guest strategy, for ORR in alkaline media. The electrocatalyst exhibits promising electrocatalytic activity for ORR with a half-wave potential of 0.89 V in 0.1 M NaOH, comparable to state-of-the-art Pt/C electrocatalysts. More importantly, it exhibits robust durability after 30 000 potential cycles. Scanning transmission electron microscopy (STEM) and quantitative energy-dispersive X-ray (EDX) spectroscopy suggest that the Co-Fe alloy nanoparticles have a homogeneous elemental distribution of Co and Fe at the atomic-scale optimized BMOF and Co/Fe ratio of 9:1. The long-term durability is attributed to its ability to maintain its structural and compositional integrity after the cycling process, as evidenced by STEM-EDX analysis. This work provides valuable insights into the design and fabrication of novel platinum-group-metals-free highly active ORR electrocatalysts in alkaline media.

A Strategy for Increasing the Efficiency of the Oxygen Reduction Reaction in Mn-Doped Cobalt Ferrites.

Alkaline fuel cells have drawn increasing attention as next-generation energy-conversion devices for electrical vehicles, since high pH enables the use of non-precious-metal catalysts. Herein, we report on a family of rationally designed Mn-doped cobalt ferrite (MCF) spinel nanocrystals, with an optimal composition Mn0.8(CoFe2)0.73O4 (MCF-0.8), that are effective electrocatalysts for the oxygen reduction reaction. MCF-0.8 exhibits a half-wave potential ( E1/2) of 0.89 V vs RHE in 1 M NaOH, only 0.02 V less than that of commercial Pt/C under identical testing conditions and, to the best of our knowledge, one of the highest recorded values in the literature. Moreover, MCF-0.8 exhibits remarkable durability (Δ E1/2 = 0.014 V) after 10 000 electrochemical cycles. In situ X-ray absorption spectroscopy (XAS) reveals that the superior performance of the trimetallic MCF-0.8 originates from the synergistic catalytic effect of Mn and Co, while Fe helps preserve the spinel structure during cycling. We employed in situ XAS to track the evolution of the oxidation states and the metal-oxygen distances not only under constant applied potentials (steady state) but also during dynamic cyclic voltammetry (CV) (nonsteady state). The periodic conversion between Mn(III, IV)/Co(III) and Mn(II, III)/Co(II) as well as the essentially constant oxidation state of Fe during the CV suggests collaboration efforts among Mn, Co, and Fe. Mn and Co serve as the synergistic coactive sites to catalyze the oxygen reduction, apparently resulting in the observed high activity, while Fe works to maintain the integrity of the spinel structure, likely contributing to the remarkable durability of the catalyst. These findings provide a mechanistic understanding of the electrocatalytic processes of trimetallic oxides under real-time fuel cell operating conditions. This approach provides a new strategy to design high-performance non-precious-metal electrocatalysts for alkaline fuel cells.

Revealing the atomic ordering of binary intermetallics using in situ heating techniques at multilength scales.

Ordered intermetallic nanoparticles are promising electrocatalysts with enhanced activity and durability for the oxygen-reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). The ordered phase is generally identified based on the existence of superlattice ordering peaks in powder X-ray diffraction (PXRD). However, after employing a widely used postsynthesis annealing treatment, we have found that claims of "ordered" catalysts were possibly/likely mixed phases of ordered intermetallics and disordered solid solutions. Here, we employed in situ heating, synchrotron-based, X-ray diffraction to quantitatively investigate the impact of a variety of annealing conditions on the degree of ordering of large ensembles of Pt3Co nanoparticles. Monte Carlo simulations suggest that Pt3Co nanoparticles have a lower order-disorder phase transition (ODPT) temperature relative to the bulk counterpart. Furthermore, we employed microscopic-level in situ heating electron microscopy to directly visualize the morphological changes and the formation of both fully and partially ordered nanoparticles at the atomic scale. In general, a higher degree of ordering leads to more active and durable electrocatalysts. The annealed Pt3Co/C with an optimal degree of ordering exhibited significantly enhanced durability, relative to the disordered counterpart, in practical membrane electrode assembly (MEA) measurements. The results highlight the importance of understanding the annealing process to maximize the degree of ordering in intermetallics to optimize electrocatalytic activity.

The Color of the Elements: A Combined Experimental and Theoretical Electron Density Study of ScB2 C2.

The chemical or physical control parameters for the onset of superconductivity in MB2 C2 hetero-graphene materials are unclear. This is mainly due to the almost ubiquitous positional B/C disorder, rendering the description of real structures of borocarbides into one of the most challenging problems in materials science. We will show that high-resolution X-ray diffraction data provides all the essential information to decode even complex coloring problems due to B/C disorder. Electron density studies and subsequent analyses of the fine structure of the Laplacian of the electron density resolves the local electronic structure of ScB2 C2 at sub-atomic resolution and allows for an unequivocal identification of all atoms involved in the coloring scenario. This information could finally be used to identify the electron deficient character of the B/C layers in ScB2 C2 and to synthesize the first bimetallic hetero-metallocene with lithium and scandium atoms embedded in the pentagonal and heptagonal voids, respectively.

Pt-Decorated Composition-Tunable Pd-Fe@Pd/C Core-Shell Nanoparticles with Enhanced Electrocatalytic Activity toward the Oxygen Reduction Reaction.

Design of electrocatalysts with both a high-Pt-utilization efficiency and enhanced electrochemical activity is still the key challenge in the development of proton exchange membrane fuel cells. In the present work, Pd-Fe/C bimetallic nanoparticles (NPs) with an optimal Fe composition and decorated with Pt are introduced as promising catalysts toward the oxygen reduction reaction. These bimetallic nanoparticles have a Pd-Fe@Pd core-shell structure with a surface Pt decoration as established through the use of electron energy loss spectroscopy (EELS) and energy-dispersive X-ray (EDX) spectroscopy. These catalysts exhibit excellent electrocatalytic activity ( E1/2 = 0.866 V vs RHE), increasing the mass activity by more than 70% over that of Pt/C in terms of the total mass of Pt and Pd and by 14 times if only Pt is considered. Simple geometrical calculations, based on spherical core-shell models, indicate that Pd-Fe@Pt has a surface Pt decoration rather than a complete Pt monolayer. Such calculations applied to other examples in the literature point out the need for careful and rigorous arguments about claimed "Pt monolayer/multilayers". Such calculations must be based on not only elemental mapping data but also on the Pt/Pd and other metal atomic ratios in the precursors. Our analysis predicts a minimal Pt/Pd atomic ratio in order to achieve a complete Pt monolayer on the surface of the core materials.

Crucial Role of Donor Density in the Performance of Oxynitride Perovskite LaTiO2 N for Photocatalytic Water Oxidation.

LaTiO2 N photocatalysts were prepared by thermal ammonolysis of flux-synthesized La2 Ti2 O7 and La2 TiO5 , and were investigated for water oxidation. Though LaTiO2 N derived from La2 TiO5 appears defect-free by UV/Vis/near-IR and electron paramagnetic resonance (EPR) spectroscopy, its performance is much lower than that of conventional La2 Ti2 O7 -derived LaTiO2 N with defects. It is shown by Mott-Schottky analysis that La2 TiO5 -derived LaTiO2 N has significantly lower donor density; this can result in insufficient built-in electric field for the separation of photogenerated electrons and holes. The lower donor density is also consistent with the smaller difference between the Fermi level and the valence-band maximum, which accounts for a lower oxidative power of the holes. In light of this discovery, the donor density was increased substantially by introducing anion vacancies through annealing in Ar. This resulted in improved performance. The CoOx -assisted La2 TiO5 -derived LaTiO2 N annealed at 713 °C has a higher quantum efficiency (25 %) at 450 nm than high-performance conventional CoOx /LaTiO2 N (21 %).

Block copolymer self-assembly-directed synthesis of mesoporous gyroidal superconductors.

Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) superconductors from chiral ABC triblock terpolymer self-assembly-directed sol-gel-derived niobium oxide with subsequent thermal processing in air and ammonia gas. Superconducting materials exhibit a critical temperature (T c) of about 7 to 8 K, a flux exclusion of about 5% compared to a dense NbN solid, and an estimated critical current density (J c) of 440 A cm(-2) at 100 Oe and 2.5 K. We expect block copolymer self-assembly-directed mesoporous superconductors to provide interesting subjects for mesostructure-superconductivity correlation studies.

High-Performance Pd3Pb Intermetallic Catalyst for Electrochemical Oxygen Reduction.

Extensive efforts to develop highly active and strongly durable electrocatalyst for oxygen reduction are motivated by a need for metal-air batteries and fuel cells. Here, we report a very promising catalyst prototype of structurally ordered Pd-based alloys, Pd3Pb intermetallic compound. Such structurally ordered Pd3Pb/C exhibits a significant increase in mass activity. More importantly, compared to the conventional Pt/C catalysts, ordered Pd3Pb/C is highly durable and exhibits a much longer cycle life and higher cell efficiency in Zn-air batteries. Interestingly, ordered Pd3Pb/C possesses very high methanol tolerance during electrochemical oxygen reduction, which make it an excellent methanol-tolerant cathode catalyst for alkaline polymer electrolyte membrane fuel cells. This study provides a promising route to optimize the synthesis of ordered Pd-based intermetallic catalysts for fuel cells and metal-air batteries.