The Quasi‐Pt‐Allotrope Catalyst: Hollow PtCo@single‐Atom Pt1 on Nitrogen‐Doped Carbon toward Superior Oxygen Reduction

Single‐atom Pt and bimetallic Pt₃Co are considered the most promising oxygen reduction reaction (ORR) catalysts, with a much lower price than pure Pt. The combination of single‐atom Pt and bimetallic Pt₃Co in a highly active nanomaterial, however, is challenging and vulnerable to agglomeration under realistic reaction conditions, leading to a rapid fall in the ORR. Here, a sustainable quasi‐Pt‐allotrope catalyst, composed of hollow Pt₃Co (H‐PtCo) alloy cores and N‐doped carbon anchoring single atom Pt shells (Pt₁N‐C), is constructed. This unique nanoarchitecture enables the inner and exterior spaces to be easily accessible, exposing an extra‐high active surface area and active sites for the penetration of both aqueous and organic electrolytes. Moreover, the novel Pt₁N‐C shells not only effectively protect the H‐PtCo cores from agglomeration but also increase the efficiency of the ORR in virtue of the isolated Pt atoms. Thus, the H‐PtCo@Pt₁N‐C catalyst exhibits stable ORR without any fade over a prolonged 10 000 cycle test at 0.9 V in HClO₄ solution. Furthermore, this material can offer efficient and stable ORR activities in various organic electrolytes, indicating its great potential for next‐generation lithium–air batteries as well.     

Polyformamidine‐Derived Non‐Noble Metal Electrocatalysts for Efficient Oxygen Reduction Reaction

A facile approach for the template‐free synthesis of highly active non‐noble metal based oxygen reduction reaction (ORR) electrocatalysts is presented. Porous Fe?N?C/Fe/Fe₃C composite materials are obtained by pyrolysis of defined precursor mixtures of polyformamidine (PFA) and FeCl₃ as nitrogen‐rich carbon and iron sources, respectively. Selection of pyrolysis temperature (700–1100 °C) and FeCl₃ loading (5–30 wt%) yields materials with differing surface areas, porosity, graphitization degree, nitrogen and iron content, as well as ORR activity. While the ORR activity of Fe‐free materials is limited (i.e., synthesized from pure PFA), a huge increase in activity is observed for catalysts containing Fe, revealing the participation of the metal dopant in the construction of active electrocatalytic sites. Further activity improvement is achieved via acid‐leaching and repeated pyrolysis, a result which is attributed to the creation of new active sites located at the surface of the porous nitrogen‐doped carbon by dissolution of the Fe and Fe₃C nanophases. The best performing catalyst, which was synthesized with a low Fe loading (i.e., 5 wt%) and at a pyrolysis temperature of 900 °C, exhibits high activity, excellent H₂O selectivity, extended stability, in both basic and acidic media as well as a remarkable tolerance toward methanol.     

Structurally Ordered Low‐Pt Intermetallic Electrocatalysts toward Durably High Oxygen Reduction Reaction Activity

Carbon‐supported low‐Pt ordered intermetallic nanoparticulate catalysts (PtM₃, M = Fe, Co, and Ni) are explored in order to enhance the oxygen reduction reaction (ORR) activity while achieving a high stability compared to previously reported Pt‐richer ordered intermetallics (Pt₃M and PtM) and low‐Pt disordered alloy catalysts. Upon high‐temperature thermal annealing, ordered PtCo₃ intermetallic nanoparticles are successfully prepared with minimum particle sintering. In contrast, the PtFe₃ catalyst, despite the formation of ordered structure, suffers from obvious particle sintering and detrimental metal–support interaction, while the PtNi₃ catalyst shows no structural ordering transition at all but significant particle sintering. The ordered PtCo₃ catalyst exhibits durably thin Pt shells with a uniform thickness below 0.6 nm (corresponding to 2–3 Pt atomic layers) and a high Co content inside the nanoparticles after 10 000 potential cycling, leading to a durably compressive Pt surface and thereby both high activity (fivefold vs a commercial Pt catalyst and 1.7‐fold vs an ordered PtCo intermetallic catalyst) and high durability (5 mV loss in half‐wave potential and 9% drop in mass activity). These results provide a new strategy toward highly active and durable ORR electrocatalysts by rational development of low‐Pt ordered intermetallics.     

Fe,Cu‐Coordinated ZIF‐Derived Carbon Framework for Efficient Oxygen Reduction Reaction and Zinc–Air Batteries

Zeolitic imidazole frameworks (ZIFs) offer rich platforms for rational design and construction of high‐performance nonprecious‐metal oxygen reduction reaction (ORR) catalysts owing to their flexibility, hierarchical porous structures, and high surface area. Herein, an Fe, Cu‐coordinated ZIF‐derived carbon framework (Cu@Fe‐N‐C) with a well‐defined morphology of truncated rhombic dodecahedron is facilely prepared by introducing Fe²⁺ and Cu²⁺ during the growth of ZIF‐8, followed by pyrolysis. The obtained Cu@Fe‐N‐C, with bimetallic active sites, large surface area, high nitrogen doping level, and conductive carbon frameworks, exhibits excellent ORR performance. It displays 50 mV higher half‐wave potential (0.892 V) than that of Pt catalysts in an alkaline medium and comparable performance to Pt catalysts in an acidic medium. In addition, it also has excellent durability and methanol resistance ability in both acidic and alkaline solutions, which makes it one of the best Pt‐free catalysts reported to date for ORR. Impressively, when being employed as a cathode catalyst in zinc–air batteries, Cu@Fe‐N‐C presents a higher peak power density of 92 mW cm^?2 than that of Pt/C (74 mW cm^?2) as well as excellent durability.     

MO‐Co@N‐Doped Carbon (M = Zn or Co): Vital Roles of Inactive Zn and Highly Efficient Activity toward Oxygen Reduction/Evolution Reactions for Rechargeable Zn–Air Battery

A highly efficient bifunctional oxygen catalyst is required for practical applications of fuel cells and metal–air batteries, as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are their core electrode reactions. Here, the MO‐Co@N‐doped carbon (NC, M = Zn or Co) is developed as a highly active ORR/OER bifunctional catalyst via pyrolysis of a bimetal metal–organic framework containing Zn and Co, i.e., precursor (CoZn). The vital roles of inactive Zn in developing highly active bifunctional oxygen catalysts are unraveled. When the precursors include Zn, the surface contents of pyridinic N for ORR and the surface contents of Co–N_x and Co³⁺/Co²⁺ ratios for OER are enhanced, while the high specific surface areas, high porosity, and high electrochemical active surface areas are also achieved. Furthermore, the synergistic effects between Zn‐based and Co‐based species can promote the well growth of multiwalled carbon nanotubes (MWCNTs) at high pyrolysis temperatures (≥700 °C), which is favorable for charge transfer. The optimized CoZn‐NC‐700 shows the highly bifunctional ORR/OER activity and the excellent durability during the ORR/OER processes, even better than 20 wt% Pt/C (for ORR) and IrO₂ (for OER). CoZn‐NC‐700 also exhibits the prominent Zn–air battery performance and even outperforms the mixture of 20 wt% Pt/C and IrO₂.     

Structure Design Reveals the Role of Au for ORR Catalytic Performance Optimization in PtCo‐Based Catalysts

Au‐incorporation is a promising strategy to retard composition‐loss in Pt‐based catalyst. However, the unclear mechanism limits guided catalyst design and the performance optimization. Here, direct evidence is provided to validate the outward diffusion of Au atoms in Au‐core/Pt‐based‐shell structures. A Co interlayer is built between the Au‐core and PtCo‐based shell to exclude the possibility of atomic diffusion caused by interfacial alloying. In conjunction with the improved catalytic durability of the Au‐core@Pt‐based‐shell structure, it is reasonable to conclude that it is the subsurface segregated Au atoms rather than interfacial interaction that boosts the catalytic durability of Au‐core/Pt‐based‐shell structured catalysts towards oxygen reduction reaction. More importantly, by constructing Au‐core@Co‐interlayer@PtCoAu‐shell multilayer structure, the specific (1.730 mA cm^?2) and mass (0.692 A mg^?1_Pt) activities are enhanced 7‐ and 4‐ fold relative to the commercial Pt/C. After 10 000 cycles of accelerated durability test, the mass activity loss for the multilayered catalyst is as low as 6.14% while the loss exceeds 35% for the commercial Pt/C catalyst. The improved catalytic performance of the Au@Co@PtCoAu multilayer structure can be ascribed to the finely modulated electronic structure and the compensated composition loss owing to the delicate structure and composition profile design.     

N‐, O‐, and S‐Tridoped Carbon‐Encapsulated Co9S8 Nanomaterials: Efficient Bifunctional Electrocatalysts for Overall Water Splitting

The development of highly active and stable earth‐abundant catalysts to reduce or eliminate the reliance on noble‐metal based ones in green and sustainable (electro)chemical processes is nowadays of great interest. Here, N‐, O‐, and S‐tridoped carbon‐encapsulated Co₉S₈ (Co₉S₈@NOSC) nanomaterials are synthesized via simple pyrolysis of S‐ and Co(II)‐containing polypyrrole solid precursors, and the materials are proven to serve as noble metal‐free bifunctional electrocatalysts for water splitting in alkaline medium. The nanomaterials exhibit remarkable catalytic performances for oxygen evolution reaction in basic electrolyte, with small overpotentials, high anodic current densities, low Tafel slopes as well as very high (nearly 100%) Faradic efficiencies. Moreover, the materials are found to efficiently electrocatalyze hydrogen evolution reaction in acidic as well as basic solutions, showing high activity in both cases and maintaining good stability in alkaline medium. A two‐electrode electrolyzer assembled using the material synthesized at 900 °C (Co₉S₈@NOSC‐900) as an electrocatalyst at both electrodes gives current densities of 10 and 20 mA cm^?2 at potentials of 1.60 and 1.74 V, respectively. The excellent electrocatalytic activity exhibited by the materials is proposed to be mainly due to the synergistic effects between the Co₉S₈ nanoparticles cores and the heteroatom‐doped carbon shells in the materials.     

2D Dual‐Metal Zeolitic‐Imidazolate‐Framework‐(ZIF)‐Derived Bifunctional Air Electrodes with Ultrahigh Electrochemical Properties for Rechargeable Zinc–Air Batteries

Here first a 2D dual‐metal (Co/Zn) and leaf‐like zeolitic imidazolate framework (ZIF‐L)‐pyrolysis approach is reported for the low‐cost and facile preparation of Co nanoparticles encapsulated into nitrogen‐doped carbon nanotubes (Co‐N‐CNTs). Importantly, the reasonable Co/Zn molar ratio in the ZIF‐L is the key to the emergence of the encapsulated microstructure. Specifically, high‐dispersed cobalt nanoparticles are fully encapsulated in the tips of N‐CNTs, leading to the full formation of highly active Co–N–C moieties for oxygen reduction and evolution reactions (ORR and OER). As a result, the obtained Co‐N‐CNTs present superior electrocatalytic activity and stability toward ORR and OER over the commercial Pt/C and IrO₂ as well as most reported metal‐organic‐framework‐derived catalysts, respectively. Remarkably, as bifunctional air electrodes of the Zn–air battery, it also shows extraordinary charge–discharge performance. The present concept will provide a guideline for screening novel 2D metal‐organic frameworks as precursors to synthesize advanced multifunctional nanomaterials for cross‐cutting applications.     

Micro Solid Oxide Fuel Cells on Glass Ceramic Substrates

Miniaturized solid oxide fuel cells are fabricated on a photostructurable glass ceramic substrate (Foturan) by thin film and micromachining techniques. The anode is a sputtered platinum film and the cathode is made of a spray pyrolysis (SP)‐deposited lanthanum strontium cobalt iron oxide (LSCF), a sputtered platinum film and platinum paste. A single‐layer of yttria‐stabilized zirconia (YSZ) made by pulsed laser deposition (PLD) and a bilayer of PLD–YSZ and SP–YSZ are used as electrolytes. The total thickness of all layers is less than 1 µm and the cell is a free‐standing membrane with a diameter up to 200 µm. The electrolyte resistance and the sum of polarization resistances of the anode and cathode are measured between 400 and 600 °C by impedance spectroscopy and direct current (DC) techniques. The contribution of the electrolyte resistance to the total cell resistance is negligible for all cells. The area‐specific polarization resistance of the electrodes decreases for different cathode materials in the order of Pt paste > sputtered Pt > LSCF. The open circuit voltages (OCVs) of the single‐layer electrolyte cells ranges from 0.91 to 0.56 V at 550 °C. No electronic leakage in the PLD–YSZ electrolyte is found by in‐plane and cross‐plane electrical conductivity measurements and the low OCV is attributed to gas leakage through pinholes in the columnar microstructure of the electrolyte. By using a bilayer electrolyte of PLD–YSZ and SP–YSZ, an OCV of 1.06 V is obtained and the maximum power density reaches 152 mW cm⁻² at 550 °C.     

Anti-CO Poisoning FePtRh Nanoflowers with Rh-Rich Core and Fe-Rich Shell Boost Methanol Oxidation Electrocatalysis

Introducing oxophilic metals into Pt-based alloy catalysts can effectively alleviate the poisoning by CO intermediates (CO*) during methanol oxidation reactions (MOR). However, excessive oxophilic metals on the surface of catalysts tend to form thermodynamically stable carbonyl compound-like structures, occupying electrocatalytically active sites, which is not conducive to the enhancement of catalytic activity. Herein, a kind of surface segregated FePtRh nanoflowers for effectively eliminating the CO* poisoning during MOR electrocatalysis is presented. The FePtRh nanoflowers are constituted by the Rh-rich core and Fe-rich shell. The optimized Fe₂₁Pt₆₆Rh₁₃/C shows a high mass activity of 3.90 A mg_Pt⁻¹ and a specific activity of 4.85 mA cm⁻². It is confirmed that the electron transfer from Pt to Rh or Fe atoms is beneficial for the higher anti-CO poisoning ability, which mainly originate from the alloying of Rh atoms and surface-segregated structures. Density functional theory calculations reveal the decreased electrons adsorbed by CO* on both Pt–Pt bridge sites and top sites weakens the strong adsorption energy between Pt atoms and CO* intermediates. The optimal nanoflowers also show excellent performance toward ethanol oxidation reaction (EOR) with a high mass activity of 2.76 A mg_Pt⁻¹ and the enhanced anti-CO poisoning ability, as well as the improved stability.     

Zn‐MOF‐74 Derived N‐Doped Mesoporous Carbon as pH‐Universal Electrocatalyst for Oxygen Reduction Reaction

It is of increasing importance to explore new low‐cost and high‐activity electrocatalysts for oxygen reduction reaction (ORR), which have had a substantial impact across a diverse range of energy conversion system, including various fuel cell and metal–air batteries. Although engineering carbon nanostructures have been widely explored as a candidate class of Pt‐based ORR electrocatalysts owing to their proved high activity, outstanding stability, and ease of use, there still remains a daunting challenge to develop high activity metal‐free electrocatalysts in pH‐universal electrolyte system. Here, a reliable and controllable route amenable to prepare nitrogen‐doped porous carbon (NPC) with high yields and exceptional quality is described. The as‐prepared NPC shows advantages of high activity, high durability, and methanol‐tolerant as an efficient pH‐universal electrocatalyst for ORR, showing comparable or even better activity as compared with the commercial Pt/C catalysts not only in alkaline media but also in acidic and neutral electrolyte. Systematic electrochemical studies, combining with density functional theory calculation, demonstrate the unique nitrogen‐doping species and favorable pores in the as‐designed NPC synergistically contribute to the significantly improved catalytic activity in pH‐universal medium. The present work potentially presents an important breakthrough in developing ORR electrocatalysts for various fuel cells.     

Novel Platinum–Cobalt Alloy Nanoparticles Dispersed on Nitrogen‐Doped Graphene as a Cathode Electrocatalyst for PEMFC Applications

A novel synthesis procedure is devised to obtain nitrogen‐doping in hydrogen‐exfoliated graphene (HEG) sheets. An anionic polyelectrolyte–conducting polymer duo is used to form a uniform coating of the polymer over graphene sheets. Pyrolysis of graphene coated with polypyrrole, a nitrogen‐containing polymer, in an inert environment leads to the incorporation of nitrogen atoms in the graphene network with simultaneous removal of the polymer. These nitrogen‐doped graphene (N‐HEG) sheets are used as catalyst support for dispersing platinum and platinum–cobalt alloy nanoparticles synthesized by the modified‐polyol reduction method, yielding a uniform dispersion of the catalyst nanoparticles. Compared to commercial Pt/C electrocatalyst, Pt–Co/N‐HEG cathode electrocatalyst exhibits four times higher power density in proton exchange membrane fuel cells, which is attributed to the excellent dispersion of Pt–Co alloy nanoparticles on the N‐HEG support, the alloying effect of Pt–Co, and the high electrocatalytic activity of the N‐HEG support. A stability study shows that Pt/N‐HEG and Pt–Co/N‐HEG cathode electrocatalysts are highly stable in acidic media. The study shows two promising electrocatalysts for proton exchange membrane fuel cells, which on the basis of performance and stability present the possibility of replacing contemporary electrocatalysts.     

Pyrolyzed Cobalt Corrole as a Potential Non‐Precious Catalyst for Fuel Cells

Non‐precious metal catalysts of the oxygen reduction reaction are highly favored for use in polymer electrolyte fuel cells (PEFC) because of their relatively low cost. Here, a new carbon‐black‐supported pyrolyzed Co‐corrole (py‐Co‐corrole/C) catalyst of the oxygen reduction reaction (ORR) in a PEFC cathode is demonstrated to have high catalytic performance. The py‐Co‐corrole/C at 700 °C exhibits optimized ORR activity and participates in a direct four‐electron reduction pathway for the reduction of O₂ to H₂O. The H₂‐O₂ PEFC test of py‐Co‐corrole/C in the cathode reveals a maximum power density of 275 mW cm^?2, which yields a higher performance and a lower Co loading than previous studies of Co‐based catalysts for PEFCs. The enhancement of the ORR activity of py‐Co‐corrole/C is attributable to the four‐coordinated Co‐corrole structure and the oxidation state of the central cobalt.     

Atomic‐Scale Insights into the Low‐Temperature Oxidation of Methanol over a Single‐Atom Pt1‐Co3O4 Catalyst

Heterogeneous catalysts with single‐atom active sites offer a means of expanding the industrial application of noble metal catalysts. Herein, an atomically dispersed Pt₁‐Co₃O₄ catalyst is presented, which exhibits an exceptionally high efficiency for the total oxidation of methanol. Experimental and theoretical investigations indicate that this catalyst consists of Pt sites with a large proportion of occupied high electronic states. These sites possess a strong affinity for inactive Co²⁺ sites and anchor over the surface of (111) crystal plane, which increases the metal–support interaction of the Pt₁‐Co₃O₄ material and accelerates the rate of oxygen vacancies regeneration. In turn, this is determined to promote the coadsorption of the probe methanol molecule and O₂. Density functional theory calculations confirm that the electron transfer over the oxygen vacancies reduces both the methanol adsorption energy and activation barriers for methanol oxidation, which is proposed to significantly enhance the dissociation of the C? H bond in the methanol decomposition reaction. This investigation serves as a solid foundation for characterizing and understanding single‐atom catalysts for heterogeneous oxidation reactions.     

Metallic Cobalt Nanoparticles Encapsulated in Nitrogen‐Enriched Graphene Shells: Its Bifunctional Electrocatalysis and Application in Zinc–Air Batteries

There has been a continuous call for active, durable, and low‐cost electrocatalysts for a range of energy applications. Among many different nonprecious metal based candidates, transition metal nanoparticles encapsulated in graphene layers have gained increasing attention over recent years. In this study, it is demonstrated that metallic cobalt nanoparticles sheathed by multilayered nitrogen‐enriched graphene shells can be facilely prepared using cobalt‐containing Prussian blue colloids as the single precursor. These metallic cobalt cores can be readily leached out by HCl treatment, resulting in hollow graphene spheres. Products with or without acid leaching exhibit great bifunctional activities for electrocatalytic oxygen reduction and hydrogen evolution in both alkaline and acidic electrolytes. Most importantly, it is found that the removal of the metallic cores does not deteriorate but rather enhances the electrocatalytic performance. Based on this and other experimental observations, Co‐N‐C moieties are proposed as the catalytically active sites. At last, it is shown that these catalysts can be employed as the air catalyst of primary zinc–air batteries with excellent current density, power density, and operation durability.     

Nitrogen‐Doped Nanoporous Carbon/Graphene Nano‐Sandwiches: Synthesis and Application for Efficient Oxygen Reduction

A zeolitic‐imidazolate‐framework (ZIF) nanocrystal layer‐protected carbonization route is developed to prepare N‐doped nanoporous carbon/graphene nano‐sandwiches. The ZIF/graphene oxide/ZIF sandwich‐like structure with ultrasmall ZIF nanocrystals (i.e., ≈20 nm) fully covering the graphene oxide (GO) is prepared via a homogenous nucleation followed by a uniform deposition and confined growth process. The uniform coating of ZIF nanocrystals on the GO layer can effectively inhibit the agglomeration of GO during high‐temperature treatment (800 °C). After carbonization and acid etching, N‐doped nanoporous carbon/graphene nanosheets are formed, with a high specific surface area (1170 m² g^?1). These N‐doped nanoporous carbon/graphene nanosheets are used as the nonprecious metal electrocatalysts for oxygen reduction and exhibit a high onset potential (0.92 V vs reversible hydrogen electrode; RHE) and a large limiting current density (5.2 mA cm^?2 at 0.60 V). To further increase the oxygen reduction performance, nanoporous Co‐N_x/carbon nanosheets are also prepared by using cobalt nitrate and zinc nitrate as cometal sources, which reveal higher onset potential (0.96 V) than both commercial Pt/C (0.94 V) and N‐doped nanoporous carbon/graphene nanosheets. Such nanoporous Co‐N_x/carbon nanosheets also exhibit good performance such as high activity, stability, and methanol tolerance in acidic media.     

Multisegment PtRu Nanorods: Electrocatalysts with Adjustable Bimetallic Pair Sites

Multisegment PtRu nanorods (Pt–Ru, Pt–Ru–Pt, Pt–Ru–Pt–Ru, Pt–Ru–Pt–Ru–Pt, Pt–Ru–Pt–Ru–Pt–Ru) with customizable lengths of the individual metals are obtained by the sequential electrodeposition of the metals into the pores of anodic aluminum oxide (AAO) membranes. Field‐emission scanning electron microscopy (FESEM) shows that the nanorods are about 200 nm in diameter and 1.2 μm long, with 900 nm of total platinum‐segment length. The alternating platinum and ruthenium segments can be easily differentiated using FESEM. X‐ray diffractometry reveals that the platinum and ruthenium in the bimetallic nanorods are polycrystalline with face‐centered cubic and hexagonal close‐packed crystal lattice structures, respectively. The presence of Pt⁰, Pt^II, Pt^IV, Ru⁰, and Ru^VI on the surface of the bimetallic nanorods is demonstrated via X‐ray photoelectron spectroscopy. The nanorods are catalytically active in the room‐temperature electro‐oxidation of methanol. The relative rates of reaction, recorded using chronoamperometry, show a linear relationship between the long‐time (near‐steady‐state) current density and the number of Pt–Ru interfaces. The use of segmented nanorods with a controlled number of Pt–Ru interfaces removes many of the ambiguities in the interpretation of experimental data from conventional alloy catalysts and has provided a direct demonstration of the role of pair sites in bifunctional catalysis.     

Nanophase ZnCo2O4 as a High Performance Anode Material for Li‐Ion Batteries

ZnCo₂O₄ has been synthesized by the low‐temperature and cost‐effective urea combustion method. X‐ray diffraction (XRD), HR‐TEM and selected area electron diffraction (SAED) studies confirmed its formation in pure and nano‐phase form with particle size ～ 15–20 nm. Galvanostatic cycling of nano‐ZnCo₂O₄ in the voltage range 0.005–3.0 V versus Li at 60 mA g^–1 gave reversible capacities of 900 and 960 mA h g^–1, when cycled at 25 °C and 55 °C, respectively. These values correspond to ～ 8.3 and ～ 8.8 mol of recyclable Li per mole of ZnCo₂O₄. Almost stable cycling performance was exhibited in the range 5–60 cycles at 60 mA g^–1 and at 25 °C with ～ 98 % coulombic efficiency. A similar cycling stability at 55 °C, and good rate‐capability both at 25 and 55 °C were found. The average discharge‐ and charge‐potentials were ～ 1.2 V and ～ 1.9 V, respectively. The ex‐situ‐XRD, ‐HRTEM, ‐SAED and galvanostatic cycling data are consistent with a reaction mechanism for Li‐recyclability involving both de‐alloying‐alloying of Zn and displacement reactions, viz., LiZn ? Zn ? ZnO and Co ? CoO ? Co₃O₄. For the first time we have shown that both Zn‐ and Co‐ions act as mutual beneficial matrices and reversible capacity contribution of Zn through both alloy formation and displacement reaction takes place to yield stable and high capacities. Thus, nano‐ZnCo₂O₄ ranks among the best oxide materials with regard to Li‐recyclability.     

Vertex‐Reinforced PtCuCo Ternary Nanoframes as Efficient and Stable Electrocatalysts for the Oxygen Reduction Reaction and the Methanol Oxidation Reaction

Noble metal binary alloy nanoframes have emerged as a new class of fuel cell electrocatalysts because of their intrinsic high catalytic surface area and accompanied high catalytic activity. However, their inferior structural and compositional stability during catalysis pose as formidable huddles to their practical applications. Herein, it is reported that introduction of an additional component to the binary catalytic system may serve as a simple and effective means of enhancing the structural and compositional stability of nanoframe‐based electrocatalysts. It is demonstrated that in situ doping of Co to the PtCu alloy nanoframe yields a ternary PtCuCo rhombic dodecahedral nanoframe (Co‐PtCu RNF) with a reinforced vertex structure. Co‐PtCu RNF exhibits superior electrocatalytic activity and durability for the oxygen reduction reaction to those of PtCu rhombic dodecahedral nanoframe (PtCu RNF) and Pt/C catalysts, due to its ternary composition and vertex‐strengthened frame structure. Furthermore, Co‐PtCu RNF shows enhanced activity for the methanol oxidation reaction as compared to PtCu RNF and Pt/C.     

Synthesis of High‐Surface‐Area Platinum Nanotubes Using a Viral Template

A novel method for the synthesis of high‐active‐surface‐area, platinum–tobacco mosaic virus (Pt–TMV) nanotubes is presented. A platinum salt is reduced to its metallic form on the external surface of a rod‐shaped TMV by methanol, which serves as a solvent and reductant simultaneously. It was found that for the same Pt loading the Pt–TMV nanotubes had an electrochemically active surface area between 4 to 8 times larger than similarly sized Pt nanoparticles. A Pt–TMV catalyst displays greater stability in acidic conditions than those based on nanoparticles. When used as a catalyst for methanol oxidation, these Pt nanotubes display a 65% increase in catalytic mass activity compared to that based on Pt nanoparticles.