Ni Strongly Coupled with Mo2C Encapsulated in Nitrogen‐Doped Carbon Nanofibers as Robust Bifunctional Catalyst for Overall Water Splitting

It is urgently required to develop highly efficient and stable bifunctional non‐noble metal electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for water splitting. In this study, a facile electrospinning followed by a post‐carbonization treatment to synthesize nitrogen‐doped carbon nanofibers (NCNFs) integrated with Ni and Mo₂C nanoparticles (Ni/Mo₂C‐NCNFs) as water splitting electrocatalysts is developed. Owing to the strong hydrogen binding energy on Mo₂C and high electrical conductivity of Ni, synergetic effect between Ni and Mo₂C nanoparticles significantly promote both HER and OER activities. The optimized hybrid (Ni/Mo₂C(1:2)‐NCNFs) delivers low overpotentials of 143 mV for HER and 288 mV for OER at a current density of 10 mA cm^?2. An alkaline electrolyzer with Ni/Mo₂C(1:2)‐NCNFs as catalysts for both anode and cathode exhibits a current density of 10 mA cm^?2 at a voltage of 1.64 V, which is only 0.07 V larger than the benchmark of Pt/C‐RuO₂ electrodes. In addition, an outstanding long‐term durability during 100 h testing without obvious degradation is achieved, which is superior to most of the noble‐metal‐free electrocatalysts reported to date. This work provides a simple and effective approach for the preparation of low‐cost and high‐performance bifunctional electrocatalysts for efficient overall water splitting.     

Active MnOx Electrocatalysts Prepared by Atomic Layer Deposition for Oxygen Evolution and Oxygen Reduction Reactions

The ability to deposit conformal catalytic thin films enables opportunities to achieve complex nanostructured designs for catalysis. Atomic layer deposition (ALD) is capable of creating conformal thin films over complex substrates. Here, ALD‐MnO_x on glassy carbon is investigated as a catalyst for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), two reactions that are of growing interest due to their many applications in alternative energy technologies. The films are characterized by X‐ray photoelectron spectroscopy, X‐ray diffraction, scanning electron microscopy, ellipsometry, and cyclic voltammetry. The as‐deposited films consist of Mn(II)O, which is shown to be a poor catalyst for the ORR, but highly active for the OER. By controllably annealing the samples, Mn₂O₃ catalysts with good activity for both the ORR and OER are synthesized. Hypotheses are presented to explain the large difference in the activity between the MnO and Mn₂O₃ catalysts for the ORR, but similar activity for the OER, including the effects of surface oxidation under experimental conditions. These catalysts synthesized though ALD compare favorably to the best MnO_x catalysts in the literature, demonstrating a viable way to produce highly active, conformal thin films from earth‐abundant materials for the ORR and the OER.     

Ultrathin High Surface Area Nickel Boride (NixB) Nanosheets as Highly Efficient Electrocatalyst for Oxygen Evolution

The overriding obstacle to mass production of hydrogen from water as the premium fuel for powering our planet is the frustratingly slow kinetics of the oxygen evolution reaction (OER). Additionally, inadequate understanding of the key barriers of the OER is a hindrance to insightful design of advanced OER catalysts. This study presents ultrathin amorphous high‐surface area nickel boride (Ni_x B) nanosheets as a low‐cost, very efficient and stable catalyst for the OER for electrochemical water splitting. The catalyst affords 10 mA cm^?2 at 0.38 V overpotential during OER in 1.0 m KOH, reducing to only 0.28 V at 20 mA cm^?2 when supported on nickel foam, which ranks it among the best reported nonprecious catalysts for oxygen evolution. Operando X‐ray absorption fine‐structure spectroscopy measurements reveal prevalence of NiOOH, as well as Ni‐B under OER conditions, owing to a Ni‐B core@nickel oxyhydroxide shell (Ni‐B@NiO_x H) structure, and increase in disorder of the NiO_x H layer, thus revealing important insight into the transient states of the catalyst during oxygen evolution.     

Earth‐Abundant Iron Diboride (FeB2) Nanoparticles as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting

Developing efficient, durable, and earth‐abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing large‐scale water splitting. The authors report that FeB₂ nanoparticles, prepared by a facile chemical reduction of Fe²⁺ using LiBH₄ in an organic solvent, are a superb bifunctional electrocatalyst for overall water splitting. The FeB₂ electrode delivers a current density of 10 mA cm^?2 at overpotentials of 61 mV for hydrogen evolution reaction (HER) and 296 mV for oxygen evolution reaction (OER) in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV dec^?1, respectively. The electrode can sustain the HER at an overpotential of 100 mV for 24 h and OER for 1000 cyclic voltammetry cycles with negligible degradation. Density function theory calculations demonstrate that the boron‐rich surface possesses appropriate binding energy for chemisorption and desorption of hydrogen‐containing intermediates, thus favoring the HER process. The excellent OER activity of FeB₂ is ascribed to the formation of a FeOOH/FeB₂ heterojunction during water oxidation. An alkaline electrolyzer is constructed using two identical FeB₂‐NF electrodes as both anode and cathode, which can achieve a current density of 10 mA cm^?2 at 1.57 V for overall water splitting with a faradaic efficiency of nearly 100%, rivalling the integrated state‐of‐the‐art Pt/C and RuO₂/C.     

Selectively Etching Vanadium Oxide to Modulate Surface Vacancies of Unary Metal–Based Electrocatalysts for High‐Performance Water Oxidation

Electrocatalytic water splitting for hydrogen generation is hindered by the sluggish kinetics of water oxidation, and highly efficient electrocatalysts for the oxygen evolution reaction (OER) are urgently required. Numerous bi‐ and multimetal‐based, low‐cost, high‐performance OER electrocatalysts have been developed. However, unary metal–based high‐performance electrocatalysts are seldom reported. In the present study, Co₂(OH)₃Cl/vanadium oxide (VO_y) composites are synthesized, from which VO_y is completely etched out by a simple cyclic voltammetry treatment, which simultaneously transforms Co₂(OH)₃Cl in situ to ultrafine CoOOH. The selective removal of VO_y modulates the nature of the surface in the obtained CoOOH by creating surface oxygen vacancies (V_o), along with disordered grain boundaries. The best‐performing CoOOH with optimum V_o is found to be associated with a low overpotential of 282 mV at 10 mA cm^?2 catalytic current density on a simple glassy carbon electrode for OER. This facile protocol of selectively etching VO_y to modulate the nature of the surface is successfully applied to synthesize another Fe‐based electrocatalyst with high OER performance, thus establishing its utility for unary metal–based electrocatalyst synthesis.     

Realizing Ultrafast Oxygen Evolution by Introducing Proton Acceptor into Perovskites

The oxygen evolution reaction (OER) is of prime importance in multiple energy storage devices. Perovskite oxides involving lattice‐oxygen oxidation are generally regarded as highly active OER catalysts, but the deprotonation of surface‐bound intermediates limit the further activity improvement. Here, it is shown that this kinetic limitation can be removed by introducing Sr₃B₂O₆ (SB) which activates a proton‐acceptor functionality to boost OER activity. As a proof‐of‐concept example, an experimental validation is conducted on the extraordinary OER performance of a Sr(Co_0.8Fe_0.2)_0.7B_0.3O_3?δ (SCFB‐0.3) hybrid catalyst, made using Sr_0.8Co_0.8Fe_0.2O_3?δ as active component and SB as a proton acceptor. This smart hybrid exhibits an exceptionally ultrahigh OER activity with an extremely low overpotential of 340 mV in 0.1 m KOH and 240 mV in 1 m KOH required for 10 mA cm^?2 which is the top‐level catalytic activity among metal oxides reported so far, while maintaining excellent durability. The correlation of pH and activity study reveals that this enhanced activity mainly originates from the improved interfacial proton transfer. Such a strategy further demonstrated to be universal, which can be applied to enhance the OER activity of other high covalent oxides with close O 2p‐band centers relative to Fermi energy.     

Single‐Crystalline Ultrathin Co3O4 Nanosheets with Massive Vacancy Defects for Enhanced Electrocatalysis

The role of vacancy defects is demonstrated to be positive in various energy‐related processes. However, introducing vacancy defects into single‐crystalline nanostructures with given facets and studying their defect effect on electrocatalytic properties remains a great challenge. Here this study deliberately introduces oxygen defects into single‐crystalline ultrathin Co₃O₄ nanosheets with O‐terminated {111} facets by mild solvothermal reduction using ethylene glycol under alkaline condition. As‐prepared defect‐rich Co₃O₄ nanosheets show a low overpotential of 220 mV with a small Tafel slope of 49.1 mV dec^?1 for the oxygen evolution reaction (OER), which is among the best Co‐based OER catalysts to date and even more active than the state‐of‐the‐art IrO₂ catalyst. Such vacancy defects are formed by balancing with reducing environments under solvothermal conditions, but are surprisingly stable even after 1000 cycles of scanning under OER working conditions. Density functional theory plus U calculation attributes the enhanced performance to the oxygen vacancies and consequently exposed second‐layered Co metal sites, which leads to the lowered OER activation energy of 2.26 eV and improved electrical conductivity. This mild solvothermal reduction concept opens a new door for the understanding and future designing of advanced defect‐based electrocatalysts.     

All‐In‐One Perovskite Catalyst: Smart Controls of Architecture and Composition toward Enhanced Oxygen/Hydrogen Evolution Reactions

A conventional water electrolyzer consists of two electrodes, each of which is embedded with a costly and rare electrocatalyst, typically IrO₂/C for oxygen evolution reaction (OER) and Pt/C for hydrogen evolution reaction (HER), respectively. HER and OER electrocatalysts usually require very different pH values to keep them stable and active. Thus, the development of earth‐abundant nonprecious metal catalysts for both HER and OER is of great importance to practical applications. This work reports the results of integrated water electrolysis using the hybrids of electrospun La_0.5(Ba_0.4Sr_0.4Ca_0.2)_0.5Co_0.8Fe_0.2O_3–δ (L‐0.5) perovskite nanorods attached to reduced graphene oxide (rGO) nanosheets as bifunctional electrodes. Via rationalizing the composition and morphology of L‐0.5/rGO nanohybrids, excellent catalytic performance and stability toward OER and HER are achieved in alkaline media. The operating voltage of integrated L‐0.5/rGO electrolyzer is tested to be 1.76 V at 50 mA cm^–2, which is close to that of the commercially available IrO₂/C‐Pt/C couple (1.76 V @ 50 mA cm^–2). Such a bifunctional electrocatalyst could be extended toward practical electrolysis use with low expanse and high efficiency. More generally, the protocol described here broadens our horizons in terms of the designs and the diverse functionalities of catalysts for use in various applications.     

Copper–Nickel Nitride Nanosheets as Efficient Bifunctional Catalysts for Hydrazine‐Assisted Electrolytic Hydrogen Production

Electrocatalytic water splitting is one of the sustainable and promising strategies to generate hydrogen fuel but still remains a great challenge because of the sluggish anodic oxygen evolution reaction (OER). A very effective approach to dramatically decrease the input cell voltage of water electrolysis is to replace the anodic OER with hydrazine oxidation reaction (HzOR) due to its lower thermodynamic oxidation potential. Therefore, developing the low‐cost and efficient HzOR catalysts, coupled with the cathodic hydrogen evolution reaction (HER), is tremendously important for energy‐saving electrolytic hydrogen production. Herein, a new‐type of copper–nickel nitride (Cu₁Ni₂‐N) with rich Cu₄N/Ni₃N interface is rationally constructed on carbon fiber cloth. The 3D electrode exhibits extraordinary HER performance with an overpotential of 71.4 mV at 10 mA cm^?2 in 1.0 m KOH, simultaneously delivering an ultralow potential of 0.5 mV at 10 mA cm^?2 for HzOR in a 1.0 m KOH/0.5 m hydrazine electrolyte. Moreover, the electrolytic cell utilizing the synthesized Cu₁Ni₂‐N electrode as both the cathode and anode display a cell voltage of 0.24 V at 10 mA cm^?2 with an excellent stability over 75 h. The present work develops the promising copper–nickel‐based nitride as a bifunctional electrocatalyst through hydrazine‐assistance for energy‐saving electrolytic hydrogen production.     

Low flow extracorporeal CO<Subscript>2</Subscript> removal in ARDS patients: a prospective short-term crossover pilot study

Background

Lung protective mechanical ventilation (MV) is the corner stone of therapy for ARDS. However, its use may be limited by respiratory acidosis.This study explored feasibility of, effectiveness and safety of low flow extracorporeal CO₂ removal (ECCO₂R).

Methods

This was a prospective pilot study, using the Abylcap® (Bellco) ECCO₂R, with crossover off-on-off design (2-h blocks) under stable MV settings, and follow up till end of ECCO₂R. Primary endpoint for effectiveness was a 20% reduction of PaCO₂ after the first 2-h. Adverse events (AE) were recorded prospectively.We included 10 ARDS patients on MV, with PaO₂/FiO₂?<?150 mmHg, tidal volume?≤?8 mL/kg with positive end-expiratory pressure ≥?5 cmH₂O, FiO₂ titrated to SaO₂ 88–95%, plateau pressure ≥?28 cmH₂O, and respiratory acidosis (pH <7.25).

Results

After 2-h of ECCO₂R, 6 patients had a ≥?20% decrease in PaCO₂ (60%); PaCO₂ decreased 28.4% (from 58.4 to 48.7 mmHg, p?=?0.005), and pH increased (1.59%, p?=?0.005). ECCO₂R was hemodynamically well tolerated. During the whole period of ECCO₂R, 6 patients had an AE (60%); bleeding occurred in 5 patients (50%) and circuit thrombosis in 3 patients (30%), these were judged not to be life threatening.

Conclusions

In ARDS patients, low flow ECCO₂R significantly reduced PaCO₂ after 2 h, Follow up during the entire ECCO₂R period revealed a high incidence of bleeding and circuit thrombosis.

Trial registration

https://clinicaltrials.gov identifier: NCT01911533, registered 23 July 2013.

     

Ultralow Ru Loading Transition Metal Phosphides as High‐Efficient Bifunctional Electrocatalyst for a Solar‐to‐Hydrogen Generation System

Water splitting is a promising technology for sustainable conversion of hydrogen energy. The rational design of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) bifunctional electrocatalysts with superior activity and stability in the same electrolyte is the key to promoting their large‐scale applications. Herein, an ultralow Ru (1.08 wt%) transition metal phosphide on nickel foam (Ru–MnFeP/NF) derived from Prussian blue analogue, that effectively drivies both the OER and the HER in 1 m KOH, is reported. To reach 20 mA cm^?2 for OER and 10 mA cm^?2 for HER, the Ru–MnFeP/NF electrode only requires overpotentials of 191 and 35 mV, respectively. Such high electrocatalytic activity exceeds most transition metal phosphides for the OER and the HER, and even reaches Pt‐like HER electrocatalytic levels. Accordingly, it significantly accelerates full water splitting at 10 mA cm^?2 with 1.470 V, which outperforms that of the integrated RuO₂ and Pt/C couple electrode (1.560 V). In addition, the extremely long operational stability (50 h) and the successful demonstration of a solar‐to‐hydrogen generation system through full water splitting provide more flexibility for large‐scale applications of Ru–MnFeP/NF catalysts.     

Ultrafine Defective RuO2 Electrocatayst Integrated on Carbon Cloth for Robust Water Oxidation in Acidic Media

Developing efficient and durable electrocatalysts for the oxygen evolution reaction (OER) in acidic media is attractive but still challenging. In this study, ultrafine defective RuO₂ nanoparticles are successfully prepared on carbon cloth by means of dip‐coating, annealing, and acid etching. As a self‐supported electrocatalyst, it exhibits an ultralow overpotential of 179 mV in 0.5 m H₂SO₄. More importantly, the high activity can be well maintained for 20 h. The density functional calculations revealed that the defect can not only increase the number of active sites but also improve the intrinsic OER activity.     

Ni‐Metalloid (B,Si, P,As, and Te) Alloys as Water Oxidation Electrocatalysts

Breakthroughs toward effective water‐splitting electrocatalysts for mass hydrogen production will necessitate material design strategies based on unexplored material chemistries. Herein, Ni‐metalloid (B, Si, P, As, Te) alloys are reported as an emergent class of highly promising electrocatalysts for the oxygen evolution reaction (OER) and insight is offered into the origin of activity enhancement on the premise of the surface electronic structure, the OER activation energy, influence of the guest metalloid elements on the lattice structure of the host metal (Ni), and surface‐oxidized metalloid oxoanions. The metalloids modify the lattice structure of Ni, causing changes in the nearest Ni–Ni interatomic distance (d_Ni–Ni). The activation energy E_a scales with d_Ni–Ni indicating an apparent dependence of the OER activity on lattice properties. During the OER, surface Ni atoms are oxidized to nickel oxyhydroxide, which is the active state of the catalyst, meanwhile, the surface metalloids are oxidized to the corresponding oxoanions that affect the interfacial electrode/electrolyte properties and hence the adsorption/desorption interaction energies of the reacting species.     

High‐Performance Trifunctional Electrocatalysts Based on FeCo/Co2P Hybrid Nanoparticles for Zinc–Air Battery and Self‐Powered Overall Water Splitting

Currently, it is still a significant challenge to simultaneously boost various reactions by one electrocatalyst with high activity, excellent durability, as well as low cost. Herein, hybrid trifunctional electrocatalysts are explored via a facile one‐pot strategy toward an efficient oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The catalysts are rationally designed to be composed by FeCo nanoparticles encapsuled in graphitic carbon films, Co₂P nanoparticles, and N,P‐codoped carbon nanofiber networks. The FeCo nanoparticles and the synergistic effect from Co₂P and FeCo nanoparticles make the dominant contributions to the ORR, OER, and HER activities, respectively. Their bifunctional activity parameter (?E) for ORR and OER is low to 0.77 V, which is much smaller than those of most nonprecious metal catalysts ever reported, and comparable with state‐of‐the‐art Pt/C and RuO₂ (0.78 V). Accordingly, the as‐assembled Zn–air battery exhibits a high power density of 154 mW cm^?2 with a low charge–discharge voltage gap of 0.83 V (at 10 mA cm^?2) and excellent stability. The as‐constructed overall water‐splitting cell achieves a current density of 10 mA cm^?2 (at 1.68 V), which is comparable to the best reported trifunctional catalysts.     

Carbon Nanodot Surface Modifications Initiate Highly Efficient,Stable Catalysts for Both Oxygen Evolution and Reduction Reactions

Efficient, stable, and low‐cost electrocatalysts for the oxygen evolution and reduction reactions (OER and ORR) are essential components of energy conversion. Although much progress has been achieved in the development of platinum‐based electrocatalysts for ORR and iridium‐based electrocatalysts for OER, they are still not yet viable for large‐scale commercialization because of the high cost and scanty supply of the noble metals. Here, it is demonstrated that carbon nanodots surface‐modified with either phosphorus or amidogen can respectively achieve electrocatalytic activity approaching that of the benchmark Pt/C and IrO₂ /C catalysts for ORR and OER. Furthermore, phosphorus (amidogen)‐modified carbon nanodots with attached Au nanoparticles exhibit superior ORR (OER) activity better than commercial Pt/C (IrO₂/C) catalysts as well as excellent electrochemical stability under visible light.     

Single‐Atom to Single‐Atom Grafting of Pt1 onto Fe?N4 Center: Pt1@Fe?N?C Multifunctional Electrocatalyst with Significantly Enhanced Properties

Nonprecious metal catalysts (NPMCs) Fe? N? C are promising alternatives to noble metal Pt as the oxygen reduction reaction (ORR) catalysts for proton‐exchange‐membrane fuel cells. Herein, a new modulation strategy is reported to the active moiety Fe? N₄ via a precise “single‐atom to single‐atom” grafting of a Pt atom onto the Fe center through a bridging oxygen molecule, creating a new active moiety of Pt₁? O₂? Fe₁? N₄. The modulated Fe? N? C exhibits remarkably improved ORR stabilities in acidic media. Moreover, it shows unexpectedly high catalytic activities toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), with overpotentials of 310 mV for OER in alkaline solution and 60 mV for HER in acidic media at a current density of 10 mA cm^?2, outperforming the benchmark RuO₂ and comparable with Pt/C(20%), respectively. The enhanced multifunctional electrocatalytic properties are associated with the newly constructed active moiety Pt₁? O₂? Fe₁? N₄, which protects Fe sites from harmful species. Density functional theory calculations reveal the synergy in the new active moiety, which promotes the proton adsorption and reduction kinetics. In addition, the grafted Pt₁? O₂? dangling bonds may boost the OER activity. This study paves a new way to improve and extend NPMCs electrocatalytic properties through a precisely single‐atom to single‐atom grafting strategy.     

Polydopamine‐Inspired,Dual Heteroatom‐Doped Carbon Nanotubes for Highly Efficient Overall Water Splitting

Overall water splitting involved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for renewable energy conversion and storage. Heteroatom‐doped carbon materials have been extensively employed as efficient electrocatalysts for independent HER or OER processes, while those as the bifunctional catalysts for simultaneously generating H₂ and O₂ by splitting water have been seldom reported. Inspired by the unparalleled virtues of polydopamine, the authors devise the facile synthesis of nitrogen and sulfur dual‐doped carbon nanotubes with in situ, homogenous and high concentration sulfur doping. The newly developed dual‐doped electrocatalysts display superb bifunctional catalytic activities for both HER and OER in alkaline solutions, outperforming all other reported carbon counterparts. Experimental characterizations confirm that the excellent performance is attributed to the multiple doping together with efficient mass and charge transfer, while theoretical computations reveal the promotion effect of secondary sulfur dopant to enhance the spin density of dual‐doped samples and consequently to form highly electroactive sites for both HER and OER.     

Electrocatalytic Oxygen Evolution Reaction in Acidic Environments – Reaction Mechanisms and Catalysts

The low efficiency of the electrocatalytic oxidation of water to O₂ (oxygen evolution reaction‐OER) is considered as one of the major roadblocks for the storage of electricity from renewable sources in form of molecular fuels like H₂ or hydrocarbons. Especially in acidic environments, compatible with the powerful proton exchange membrane (PEM), an earth‐abundant OER catalyst that combines high activity and high stability is still unknown. Current PEM‐compatible OER catalysts still rely mostly on Ir and/or Ru as active components, which are both very scarce elements of the platinum group. Hence, the Ir and/or Ru amount in OER catalysts has to be strictly minimized. Unfortunately, the OER mechanism, which is the most powerful tool for OER catalyst optimization, still remains unclear. In this review, we first summarize the current state of our understanding of the OER mechanism on PEM‐compatible heterogeneous electrocatalysts, before we compare and contrast that to the OER mechanism on homogenous catalysts. Thereafter, an overview over monometallic OER catalysts is provided to obtain insights into structure‐function relations followed by a review of current material optimization concepts and support materials. Moreover, missing links required to complete the mechanistic picture as well as the most promising material optimization concepts are pointed out.     

Enabling Iron‐Based Highly Effective Electrochemical Water‐Splitting and Selective Oxygenation of Organic Substrates through In Situ Surface Modification of Intermetallic Iron Stannide Precatalyst

A strategy to overcome the unsatisfying catalytic performance and the durability of monometallic iron‐based materials for the electrochemical oxygen evolution reaction (OER) is provided by heterobimetallic iron–metal systems. Monometallic Fe catalysts show limited performance mostly due to poor conductivity and stability. Here, by taking advantage of the structurally ordered and highly conducting FeSn₂ nanostructure, for the first time, an intermetallic iron material is employed as an efficient anode for the alkaline OER, overall water‐splitting, and also for selective oxygenation of organic substrates. The electrophoretically deposited FeSn₂ on nickel foam (NF) and fluorine‐doped tin oxide (FTO) electrodes displays remarkable OER activity and durability with substantially low overpotentials of 197 and 273 mV at 10 mA cm^?2, respectively, which outperform most of the benchmarking NiFe‐based catalysts. The resulting superior activity is attributed to the in situ generation of α‐FeO(OH)@FeSn₂ where α‐FeO(OH) acts as the active site while FeSn₂ remains the conductive core. When the FeSn₂ anode is coupled with a Pt cathode for overall alkaline water‐splitting, a reduced cell potential (1.53 V) is attained outperforming that of noble metal‐based catalysts. FeSn₂ is further applied as an anode to produce value‐added products through selective oxygenation reactions of organic substrates.     

Metal–Organic Framework Templated Pd@PdO–Co3O4 Nanocubes as an Efficient Bifunctional Oxygen Electrocatalyst

The development of high‐efficiency bifunctional electrocatalyst for oxygen reduction and evolution reactions (ORR/OER) is critical for rechargeable metal–air batteries, a typical electrochemical energy storage and conversion technology. This work reports a general approach for the synthesis of Pd@PdO–Co₃O₄ nanocubes using the zeolite‐type metal–organic framework (MOF) as a template. The as‐synthesized materials exhibit a high electrocatalytic activity toward OER and ORR, which is comparable to those of commercial RuO₂ and Pt/C electrocatalysts, while its cycle performance and stability are much higher than those of commercial RuO₂ and Pt/C electrocatalysts. Various physicochemical characterizations and density functional theory calculations indicate that the favorable electrochemical performance of the Pd@PdO–Co₃O₄ nanocubes is mainly attributed to the synergistic effect between PdO and the robust hollow structure composed of interconnected crystalline Co₃O₄ nanocubes. This work establishes an efficient approach for the controlled design and synthesis of MOF‐templated hybrid nanomaterials, and provides a great potential for developing high‐performance electrocatalysts in energy storage and conversion.