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Reversible proton‐conducting solid oxide cells (R‐PSOCs) are considered to be one of the most promising devices for efficient power generation and hydrogen production. However, the requirement of high catalytic activity for fast oxygen reduction/evolution reaction (ORR/OER) and durability under high steam concentration of air electrode materials remains the major challenge for the practical application of R‐PSOCs. Here, a series of cobalt‐free Ruddlesden–Popper perovskite of Nd0.8Sr1.2Ni1‐xFexO4±δ are reported with mixed conductivity for enhanced ORR/OER kinetics. The R‐PSOCs with an optimal Nd0.8Sr1.2Ni0.7Fe0.3O4±δ air electrode show a high peak power density of 1.28 W cm−2 in the fuel cell mode and a promising current density of 3.24 A cm−2 at 1.3 V in the electrolysis cell mode at 700 °C. In addition, the R‐PSOCs show favorable stability under the fuel cell, electrolysis, and reversible modes for hundreds of hours. This work demonstrates that the Ruddlesden–Popper materials can be utilized as suitable air electrodes for R‐PSOCs. [ABSTRACT FROM AUTHOR]

Highly active Pt‐based intermetallic nanoparticles (i‐NPs) loaded on stable supports have garnered considerable interest as promising oxygen reduction reaction (ORR) catalysts for proton‐exchange‐membrane fuel cells (PEMFCs). Herein, thermostable tellurium (Te) is vapor‐deposited onto commercial conductive carbon to anchor high‐temperature‐synthesized Pt3Co i‐NPs. Advanced characterization and density functional theory (DFT) calculations demonstrate that the binding energy of Pt 4f and Co 2p shift positively by 0.12 and 0.95 eV after the introduction of Te in carbon support, promoting the formation of Pt─Te bonds, which enhances the metal–support interactions (MSIs) in Pt3Co/Te‐C (with a more negative binding energy of −10.28 eV). The average size of well‐dispersed Pt3Co i‐NPs (≈3.9 nm) on Te─C is considerably smaller than that of Pt3Co i‐NPs (≈9.1 nm) on commercial carbon. The specific activity of Pt3Co/Te‐C decreases by only 1.5% after 100,000 ultra‐long voltage‐accelerated cycles, while the morphology remains almost unchanged. The membrane electrode assembly using Pt3Co/Te‐C as a cathode demonstrates impressive activity (power density of 2.32 W cm−2@4 A cm−2 and mass activity of 0.50 A mgPt−1@0.9 V) and robust durability (mass activity@0.9 V loss of 26% after 30,000 cycles with intact L12 ordered structure) in H2–O2 operation, significantly exceeding the DOE 2025 requirements. [ABSTRACT FROM AUTHOR]

Hydrogen fuel cells represent a leading technology in developing green energy targeting net‐zero emissions goals by mid‐century. However, the sluggish kinetics of the oxygen reduction reaction (ORR) have hitherto demanded substantial quantities of expensive platinum (Pt) group metals. Advances in catalyst design, including the controllable fabrication of highly branched morphologies to increase the surface area‐to‐volume ratio, intermixing Pt with more affordable transition metals, and controlling composition, offer solutions that can further enhance activity and reduce expense. In this context, Pt/M (M = Fe, Ni, Co) nanopods and nanodendrites with precise composition control using more affordable starting materials are designed and crafted. The method is highly efficient, taking only 30 min and avoiding the need for high‐pressure equipment, making it highly scalable. These catalysts show superior ORR performance at an electrode loading as low as 0.0022 mgPt cm−2. One, nanodendritic Pt/Ni, achieves a mass activity of 0.55AmgPt−1$ \rm {0.55}\, {A\, mg}_{Pt}^{-1} $ at 0.9 V versus RHE, making it 87 times more efficient in terms of Pt‐content than a commercial 10 wt% Pt/C nanoparticle standard. These findings provide new opportunities for developing next‐generation, cost‐efficient Pt‐based catalysts, by potentially advancing hydrogen fuel cell technology through performance enhancement and addressing cost challenges through catalyst design. [ABSTRACT FROM AUTHOR]

Fabricating efficient non‐platinum‐group‐metal catalysts for the oxygen reduction reaction (ORR) in proton‐exchange membrane fuel cells still remains a big challenge. This study creates a unique bamboo‐like architecture of Mn and Fe single atomic sites (SASs) anchored on core‐shell structure of nanopaticles@carbon nanotubes (MnFe SASs/NPs@CNTs) via a precursor route, where the Fe nanoparticles (NPs) (identified as γ‐Fe and Austenite) are confined into CNTs, such an architecture exhibits compelling ORR activity and durability in 0.1 m HClO4. Experiments and calculations both reveal that the electron donor–acceptor paradigm between Mn SASs and Fe NPs launches a lattice‐electron coupling mechanism not only increasing occupation of π‐antibonding orbital in Mn−*O intermediates but also rising Jahn–Teller effect, thereby destabilize the Mn−*O intermediate and eventually facilitate the potential‐limiting step from *O to *OH. Such a coupling activation of the ORR‐inert Mn SASs greatly improves ORR performances of MnFe SASs/NPs@CNTs. [ABSTRACT FROM AUTHOR]

The insufficient durability of Pt‐based catalysts and the sluggish kinetics of oxygen reduction reaction (ORR) is hampering the development of proton exchange membrane fuel cells (PEMFCs) for commercialization. Herein, a single atom Ti‐modified activated nitrogen‐doped porous carbon (Ti‐a‐NPC) is designed to equalize O2‐activation/*OH‐removal through regulating the charge rearrangement of ultra‐small L12‐Pt3Co for efficient and durable oxygen reduction. The Ti single‐atom modified in the surface/pore of Ti‐a‐NPC can anchor the Pt‐based intermetallic nanoparticles (NPs) not only guarantees Pt‐based intermetallics’ ultra‐fine size (≈2.62 nm) but also maintains Pt‐based intermetallics during ORR process. The enhanced catalyst (L12‐Pt3Co/Ti‐a‐NPC) achieves 11‐fold mass activity (1.765 A mgPt−1) compared to commercial Pt/C. Notably, after 30 000 cycles of accelerated durability tests, the mass activity of the L12‐Pt3Co/Ti‐a‐NPC only decreased by 3.7%, while that of commercial Pt/C decreased by 37.1%. Rationalized by theoretical simulation, the introduction of Ti atoms can form charge channels between L12‐Pt3Co NPs and Ti‐a‐NPC, accelerating the charge transfer in the ORR process. Furthermore, the charge of L12‐Pt3Co will accumulate to Ti atoms and buffer the electron transfer of L12‐Pt3Co to the N atoms, thus optimizing the adsorption performance of the active site to the oxygen‐containing intermediate and improving the intrinsic activity of the catalyst. [ABSTRACT FROM AUTHOR]

Atomically dispersed iron–nitrogen–carbon catalysts are promised, low‐cost, and high‐performance electrocatalysts for the Oxygen Reduction Reaction (ORR) in fuel cells. However, most Fe–N–C materials are produced via pyrolysis at a high temperature and it is difficult to characterise the precise Fe–N configurations. This can lead to confusion surrounding the best chemical and coordination environment for Fe and understanding the subsequent ORR mechanisms. In this work, Fe porphyrin is used to produce a specific Fe–N environment, therefore allowing the role and activity of this environment to be studied. Carbon nanotubes (CNTs) are covalently functionalized with iron 5,10,15,20‐triphenylporphyrin (FeTPP) motifs via aryl diazonium methodology, enabling the exact role of only the Fe‐Pyrrolic N4 configuration of FeTPP in ORR to be studied and better understood. Upon covalent functionalization, a high electrochemical active site density of 1.12 × 1015 sites cm−2, approximately six‐fold more than that of noncovalently functionalized samples with 12.7% electrochemical active site. The heightened active site density and superior electrochemical active site utilization (12.7%) lead to the more favorable 4‐electron pathway for the ORR. Furthermore, a preliminary discussion regarding the selectivity of the ORR pathway is initiated. [ABSTRACT FROM AUTHOR]

Engineering the electronic configuration and intermediates adsorption behaviors of high‐performance non‐noble‐metal‐based catalysts for the sluggish oxygen reduction reaction (ORR) kinetics at the cathode is highly imperative for the development of anion exchange membrane fuel cells (AEMFCs), yet remains an enormous challenge. Herein, a rare‐earth metal oxide engineering tactic through the formation of Fe3O4/La2O3 heterostructures in N,O‐doped carbon nanospheres (Fe3O4/La2O3@N,O‐CNSs) for efficient oxygen reduction electrocatalysis is reported. The theoretical calculations reveal that the interfacial bonds formed by the La─O─Fe heterogeneous interface effectively optimize the electronic structure of the Fe d‐band center relative to the Fermi level, which results in a significant reduction of the reaction barriers of rate‐limiting steps during the ORR. The modulation in intermediates chemisorption enables Fe3O4/La2O3@N,O‐CNSs an outstanding ORR performance and improved stability, with a significantly higher half‐wave potential value (0.88 V). More impressively, this integrated catalyst delivers a remarkable power density of 148.7 mW cm−2 in practical AEMFC operating conditions, along with negligible performance degradation over 100 h using an H2‐air atmosphere, which is higher than commercial Pt/C‐coupled electrodes. The results presented here are believed to provide guidelines for fabricating high‐performance AEMFCs electrocatalysts in terms of heterointerface engineering and strong electronic coupling effect induced by rare‐earth oxides. [ABSTRACT FROM AUTHOR]

Pt‐based intermetallics are recognized as effective catalysts for oxygen reduction reaction (ORR) in fuel cells. However, the synthesis of intermetallics often requires prolonged annealing and the effect of different crystal structures on ORR still need to be investigated. Herein, L12‐Pt3Mn and L10‐PtMn intermetallics with Pt‐skin are rapidly synthesized through an emerging periodic carbothermal shock method to investigate their ORR‐activity difference. The formation of L12‐Pt3Mn and L10‐PtMn can be well‐controlled by the Pt/Mn feeding ratio, pulse cycles, and temperature. Electrocatalytic investigations show that L12‐Pt3Mn presents a more positive half‐wave potential (0.91 V vs RHE) and onset potential (1.02 V vs RHE) than those of L10‐PtMn. The mass activity and specific activity of L12‐Pt3Mn are respectively fourfold and threefold greater than those of L10‐PtMn. Theoretical calculations indicate that the L12‐Pt3Mn has a more substantial work function than L10‐PtMn, thereby conferring L12‐Pt3Mn with an increased electron density allocation for catalytic involvement. This electron confinement imparts L12‐Pt3Mn with a Pt d‐band center lower than that of L10‐PtMn, consequently attenuating the adsorption of strongly bonded *O intermediates during the rate‐determining step. This study not only employs a straightforward method for intermetallic preparation but also elucidates the discrepancies in ORR activity across intermetallics with distinct structures. [ABSTRACT FROM AUTHOR]

Transition metal single atoms anchored on nitrogen‐doped carbon (M‐N‐C) matrix with M‐N‐C active sites have shown to be promising catalysts for both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, a hybrid catalyst with low‐level loading of atomic Pt and Co species encapsulated in nitrogen‐doped graphene (Pt@CoN4‐G) is developed. The Pt@CoN4‐G shows low overpotential for HER in wide‐pH electrolyte and manifests improved mass activity with almost eight times greater than that of Pt/C at an overpotential of 50 mV. The Pt@CoN4‐G also exhibits a top‐level ORR activity (half‐wave potential, E1/2 = 0.893 V) and robust stability (>200 h) in alkaline medium. Using theoretical calculations and comprehensive characterizations , the strong metal–support interactions between Pt species and CoN4‐G support and synergistical cooperation of multiple active sites are clarified. A flow alkali‐Al/acid hybrid fuel cell using Pt@CoN4‐G as cathode catalyst delivers a large power density of 222 mW cm−2 with excellent stability to achieve simultaneously hydrogen evolution and electricity generation. In addition, Pt@CoN4‐G endows a flow Zn‐air battery with high power density (316 mW cm−2), good stability under large current density (>100 h at 100 mA cm−2), and long cycle life (over 600 h at 5 mA cm−2). [ABSTRACT FROM AUTHOR]

The anion‐exchange membrane direct ammonia fuel cell, as a carbon‐free fuel cell type, has recently received increasing attention albeit suffering from high cost of using the platinum‐group metal oxygen reduction reaction (ORR) catalysts. To pave the development of this promising power source, the atomically dispersed transition metal‐nitrogen‐carbon (M‐N‐C) materials with low cost and high ORR performance have allured to investigate their ammonia tolerance during the ORR. Herein, it is initially deconvoluted how compositional and structural elements of FeN4 sites modulate catalyst's performance. Furthermore, ORR catalytic activities of the M‐N‐C (M = Fe, Co or Mn) and Pt/C catalysts are investigated in ammonia‐containing electrolytes, showing that M‐N‐C catalysts have better ammonia tolerance than Pt/C. Among others, the Fe‐N‐C exhibits the best ammonia tolerance with only 4 mV negative shifts of half‐wave potential, 2.7% decrease of current, and negligibly irreversible activity loss. The superior ammonia tolerance of MN4 sites to Pt (111) surface is further confirmed by density functional theory calculations. The adsorption capacity of MN4 for O2 is higher than NH3 and the bonding force between MN4 and O2 is stronger than NH3, whereas opposite adsorption capacity and bonding force trends are observed on Pt (111) surface. [ABSTRACT FROM AUTHOR]

The two‐electron pathway to form hydrogen peroxide (H2O2) is undesirable for the oxygen reduction reaction (ORR) in iron and nitrogen doped carbon (Fe–N–C) material as it not only lowers the catalytic efficiency but also impairs the catalyst durability. In this study, a relay catalysis pathway is designed to minimize the two‐electron selectivity of Fe–N–C catalyst. Such a design is achieved by introducing two other sites, that is, MnN4 site and α‐Fe(110) face. A combination of transmission electron microscopy image and X‐ray absorption spectra verify the three site formation. Electrochemical test coupled with post‐treatment confirm the improvement of MnN4 site and α‐Fe(110) face on catalyst performance. Theoretical calculation proposes a relay catalysis pathway of three sites, that is, H2O2 released from the FeN4 site migrates to the MnN4 site or α‐Fe(110) face, on which the captive H2O2 is further reduced to H2O. The relay catalysis pathway positioned the as‐prepared catalyst among the best ORR catalysts in both aqueous electrode and alkaline direct methanol fuel cell test. This study examples an interesting relay catalysis pathway of multi‐sites for the ORR, which offers insights into the design of efficient electrocatalysts for fuel cells or beyond. [ABSTRACT FROM AUTHOR]

Developing efficient Pt‐based alloy as oxygen reduction reaction (ORR) electrocatalysts is critical for practical applications of fuel cells. High‐temperature reduction technology can improve the alloy atoms ordering but inevitably accelerate metal sintering. Here, Pt–Ni nanoparticles (<5 nm) embedded into ordered mesoporous carbon (OMC) matrix are developed, and its confinement effect suppresses nanoparticles sintering up to 900 °C. After an elaborative dealloying process, the surface structure of Pt–Ni nanoparticles changes from a Ni‐rich to Pt‐rich layer (the thickness is about 0.15 nm). The optimized sample (PtNi3@OMC‐A) displays outstanding mass and specific activities of 2.11 A mgPt–1 and 3.23 mA cmPt–2, more than one order of magnitude higher than commercial Pt/C (20 wt%). PtNi3@OMC‐A also exhibits long‐term stability with a negligible activity loss after 10 000 potential cycles. Both experimental results and density functional theory calculations reveal that alloying effect as well as strain effect weaken Pt–O binding strength, thus resulting in an outstanding ORR activity. Furthermore, the high long‐term stability can be attributed to the confinement of OMC, inhibiting the detachment or agglomeration of the embedded alloy nanoparticles. [ABSTRACT FROM AUTHOR]

Atomically dispersed transition metal‐nitrogen‐carbon catalysts are emerging as low‐cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost‐effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co‐doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high‐temperature post carbonization. It is determined that FeN4 is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe2+ and Fe3+ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe2+ and Fe3+ precursors. Fe2+@NCS‐A (starting with Fe2+ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open‐circuit voltage demonstrates the potential approach for developing high‐performance, low‐cost fuel cell catalysts. [ABSTRACT FROM AUTHOR]

Lowering the operating temperature (ideally below 400 °C) for solid oxide fuel cell (SOFC) technology deployment has been an important transition that introduces the benefit of reduced operational costs and system durability. However, the key technical issue limiting the transition is the sluggish cathodic performance, namely the oxygen reduction reaction (ORR) rate of the conventional sponge‐like cathode dramatically drops as the temperature reduces. In this paper, 3D engineering of a cathode is conducted on a protonic ceramic fuel cell to obtain an enhanced ORR between 400 and 600 °C. Compared with a cell using a conventional sponge‐like cathode, 3D engineering improves the cathode ORR by 41% at 400 °C with a peak power density of 0.410 W cm−2. A phase field simulation is applied to assist the engineering by understanding the competition between the cathode mass and charge transfer with different cathode porosities. The results show that structural engineering of existing well‐developed cathodes is a simple and effective method to promote cathode ORR for low temperature SOFC by regulating the mass and charge transfer. [ABSTRACT FROM AUTHOR]

An Fe/N/C catalyst derived from the pyrolysis of metal–organic frameworks, for example, a zeolitic‐imidazolate‐framework‐8 (ZIF‐8), has been regarded as one of the most promising non‐precious metal catalysts toward oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, its ORR mass activity is still much inferior to that of Pt, partly because of the lack of general and efficient synthetic strategies. Herein, a general carboxylate‐assisted strategy that dramatically enhances the ORR mass activity of ZIF‐derived Fe/N/C catalysts is reported. The carboxylate is found to promote the formation of Fe/N/C catalysts with denser accessible active sites and entangled carbon nanotubes, as well as a higher mesoporosity. These structural advantages make the carboxylate‐assisted Fe/N/C catalysts show a 2–10 fold higher ORR mass activity than the common carboxylate‐free one in various cases. When applied in H2–O2 PEMFCs, the active acetate‐assisted Fe/N/C catalyst generates a peak power density of 1.33 W cm−2, a new record of peak power density for a H2–O2 PEMFC with non‐Pt ORR catalysts. [ABSTRACT FROM AUTHOR]

The recent advances in electrocatalysis for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR) are thoroughly reviewed. This comprehensive review focuses on the single‐atom catalysts (SACs) including Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sn, W, Bi, Ru, Rh, Pd, Ag, Ir, Pt, and Au with single‐metal sites or dual‐metal sites. The recent development of single‐atom electrocatalysts with novel configurations and compositions is documented. The understanding of the process–structure–property relationships is highlighted. For the SACs, their electrocatalytic performance and stability in fuel cells, zinc–air batteries, electrolyzers, CO2RR, and NRR are summarized. The challenges and perspectives in the emerging field of single‐atom electrocatalysis are discussed. [ABSTRACT FROM AUTHOR]

The electrocatalytic value of nanoparticles has attracted substantial attention in relation to energy conversion devices, including solid oxide fuel cells. Among various forms of analogs, ex‐solved metal nanoparticles originating from their parent oxides display strong particle‐substrate interactions and thus have the benefits of extended durability and of course enhanced catalytic activity. Inspired by recent advances, here, novel air‐electrode materials based on BaCoO3–δ perovskites decorated with socketed Ag nanoparticles are presented. Doping with niobium (Nb5+) and tantalum (Ta5+) can significantly promote the stability of the cubic perovskite phase. The developed oxides exhibit promising performance outcomes in the highly prized low‐to‐intermediate temperature regimes (450–650 °C). Moreover, the exclusion of Ag particles further activates the parent scaffold, thereby conveying record‐level area‐specific resistance (e.g., ≈0.02 Ω cm2 at 650 °C). Coupled with the unique nanoarchitecture, the newly designed cathode showcases in this study hold great promise for future air‐electrodes in fuel cells. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial reactions in energy conversion and storage systems including fuel cells, metal–air batteries, and electrolyzers. Developing low‐cost, high‐efficiency, and durable non‐noble bifunctional oxygen electrocatalysts is the key to the commercialization of these devices. Here, based on an in‐depth understanding of ORR/OER reaction mechanisms, recent advances in the development of non‐noble electrocatalysts for ORR/OER are reviewed. In particular, rational design for enhancing the activity and stability and scalable synthesis toward the large‐scale production of bifunctional electrocatalysts are highlighted. Prospects and future challenges in the field of oxygen electrocatalysis are presented. [ABSTRACT FROM AUTHOR]

Direct carbon fuel cells (DCFCs) are an efficient energy‐conversion technology capable of generating electricity with carbon‐dioxide‐capture chemistry with solid carbon as fuels. The efficiency and performance of DCFCs depend on the kinetics of the carbon oxidation reactions (COR) and the oxygen reduction reactions (ORR), each occurring at anode and cathode, respectively. The limited active sites paired with reduced temperatures greatly decrease the efficiency of the electrochemical reactions. Ultraporous dual‐3D ceramic textiles (dual‐3DCT) are integrated into electrolyte‐supported DCFCs to enhance charge and mass transfer at the electrodes. Improved COR at the anode is achieved by the synergy between the 3DCT NiO–Ce0.8Gd0.2O1.95 (GDC) structure and optimal carbon fuel choice. In a comparative study, DCFCs using graphitic carbon (GC) as fuel show the best COR performance when compared to DCFCs utilizing alternative fuels such as carbon black (CB) and activated carbon (AC). The 3DCT Sm0.5Sr0.5CoO3‐δ–GDC (SSC–GDC) composite cathode shows electrochemical performance superior to that of the conventional screen‐printed SSC–GDC. A peak power density of 392 mW cm−2 at 600 °C is obtained in a DCFC using the 3DCT‐anode/electrolyte/3DCT‐cathode configuration, an unprecedented value for any reported DCFC as of yet. This points toward promising applications of dual‐3DCT electrodes for reduced‐temperature DCFCs. [ABSTRACT FROM AUTHOR]

Developing high-active, good-stable, and cost-effective electrocatalyst for oxygen reduction reaction (ORR) in all-pH medium is highly desired for the application of various fuel cell systems. Here, a network architecture hybrid with porous nitrogen-doped graphene encapsulated β-FeOOH nanoparticals (β-FeOOH/PNGNs) as ORR electrocatalyst, which exhibits remarkable enhancement ORR performance in terms of activity and stability in pHuniversal medium is reported. Systematic characterization combining with X-ray absorption fine structure analysis and the first principles simulations reveal that the as-formed surface FeO6 active sites that induced by a mass of Fe vacancies in β-FeOOH/PNGNs can significantly lower the thermodynamic barrier of the total reaction, and hence contribute to a remarkable enhancement in ORR activity. [ABSTRACT FROM AUTHOR]

Abstract: Currently, developing nonprecious‐metal catalysts to replace Pt‐based electrocatalysts in fuel cells has become a hot topic because the oxygen reduction reaction (ORR) in fuel cells often requires platinum, a precious metal, as a catalyst, which is one of the major hurdles for commercialization of the fuel cells. Recently, the newly emerging metal‐organic frameworks (MOFs) have been widely used as self‐sacrificed precursors/templates to fabricate heteroatom‐doped porous carbons. Here, the recent progress of MOF‐derived, heteroatom‐doped porous carbon catalysts for ORR in fuel cells is systematically reviewed, and the synthesis strategies for using different MOF precursors to prepare heteroatom‐doped porous carbon catalysts, including the direct carbonization of MOFs, MOF and heteroatom source mixture carbonization, and MOF‐based composite carbonization are summarized. The emphasis is placed on the precursor design of MOF‐derived metal‐free catalysts and transition‐metal‐doped carbon catalysts because the MOF precursors often determine the microstructures of the derived porous carbon catalysts. The discussion provides a useful strategy for in situ synthesis of heteroatom‐doped carbon ORR electrocatalysts by rationally designing MOF precursors. Due to the versatility of MOF structures, MOF‐derived porous carbons not only provide chances to develop highly efficient ORR electrocatalysts, but also broaden the family of nanoporous carbons for applications in supercapacitors and batteries. [ABSTRACT FROM AUTHOR]

The authors report first a new type of nitrogen-triggered Zn single atom catalyst, demonstrating high catalytic activity and remarkable durability for the oxygen reduction reaction process. Both X-ray absorption fine structure spectra and theoretical calculations suggest that the atomically dispersed Zn-N4 site is the main, as well as the most active, component with O adsorption as the rate-limiting step at a low overpotential of 1.70 V. This work opens a new field for the exploration of high-performance Pt-free electrochemical oxygen reduction catalysts for fuel cells. [ABSTRACT FROM AUTHOR]

Here, pyridinic nitrogen dominated graphene aerogels with/without iron incorporation (Fe-NG and NG) are prepared via a facile and effective process including freeze-drying of chemically reduced graphene oxide with/without iron precursor and thermal treatment in NH3. A high doping level of nitrogen has been achieved (up to 12.2 at% for NG and 11.3 at% for Fe-NG) with striking enrichment of pyridinic nitrogen (up to 90.4% of the total nitrogen content for NG, and 82.4% for Fe-NG). It is found that the Fe-NG catalysts display a more positive onset potential, higher current density, and better four-electron selectivity for ORR than their counterpart without iron incorporation. The most active Fe-NG exhibits outstanding ORR catalytic activity, high durability, and methanol tolerance ability that are comparable to or even superior to those of the commercial Pt/C catalyst at the same catalyst loading in alkaline environment. The excellent ORR performance can be ascribed to the synergistic effect of pyridinic N and Fe-N x sites (where iron probably coordinates with pyridinic N) that serve as active centers for ORR. Our Fe-NG can be developed into cost-effective and durable catalysts as viable replacements of the expensive Pt-based catalysts in practical fuel cell applications. [ABSTRACT FROM AUTHOR]

Here, a simple but efficient way is demonstrated for the preparation of nanoporous graphene enriched with Fe/Co-nitrogen-doped active sites (Fe/Co-NpGr) as a potential electrocatalyst for the electrochemical oxygen reduction reaction (ORR) applications. Once graphene is converted into porous graphene (pGr) by a controlled oxidative etching process, pGr can be converted into a potential electrocatalyst for ORR by utilizing the created edge sites of pGr for doping nitrogen and subsequently to utilize the doped nitrogens to build Fe/Co coordinated centers (Fe/Co-NpGr). The structural information elucidated using both XPS and TOF-SIMS study indicates the presence of coordination of the M-N (M = Fe and Co)-doped carbon active sites. Creation of this bimetallic coordination assisted by the nitrogen locked at the pore openings is found to be helping the system to substantially reduce the overpotential for ORR. A 30 mV difference in the overpotential ( η) with respect to the standard Pt/C catalyst and high retention in half wave potential after 10 000 cycles in ORR can be attained. A single cell of an anion exchange membrane fuel cell (AEMFC) by using Fe/Co-NpGr as the cathode delivers a maximum power density of ≈35 mWcm−2 compared to 60 mWcm−2 displayed by the Pt-based system. [ABSTRACT FROM AUTHOR]

Alloying techniques show genuine potential to develop more effective catalysts than Pt for oxygen reduction reaction (ORR), which is the key challenge in many important electrochemical energy conversion and storage devices, such as fuel cells and metal-air batteries. Tremendous efforts have been made to improve ORR activity by designing bimetallic nanocatalysts, which have been limited to only alloys of platinum and transition metals (TMs). The Pt-TM alloys suffer from critical durability in acid-media fuel cells. Here a new class of mesostructured Pt-Al catalysts is reported, consisting of atomic-layer-thick Pt skin and Pt3Al or Pt5Al intermetallic compound skeletons for the enhanced ORR performance. As a result of strong Pt-Al bonds that inhibit the evolution of Pt skin and produce ligand and compressive strain effects, the Pt3Al and Pt5Al mesoporous catalysts are exceptionally durable and ≈6.3- and ≈5.0-fold more active than the state-of-the-art Pt/C catalyst at 0.90 V, respectively. The high performance makes them promising candidates as cathode nanocatalysts in next-generation fuel cells. [ABSTRACT FROM AUTHOR]

Due to the high costs, slow reaction kinetics, and methanol poisoning of platinum-based cathode catalysts, designing and exploring non-Pt or low-Pt cathode electrocatalysts with a low cost, high catalytic performance, and high methanol-tolerance are crucial for the commercialization of fuel cells. Here, a facile method to fabricate a system of PdAg nanorings supported by graphene nanosheets is demonstrated; the fabrication is based on the galvanic displacement reaction between pre-synthesized Ag nanoparticles and palladium ions. X-ray diffraction and high-resolution transmission electron microscopy show that the synthesized PdAg nanocrystals exhibit a ring-shaped hollow structure with an average size of 27.49 nm and a wall thickness of 5.5 nm. Compared to the commercial Pd-C catalyst, the PdAg nanorings exhibit superior properties as a cathode electrocatalyst for oxygen reduction. Based on structural and electrochemical studies, these advantageous properties include efficient usage of noble metals and a high surface area because of the effective utilization of both the exterior and interior surfaces, high electrocatalytic performance for oxygen reduction from the synergistic effect of the alloyed PdAg crystalline phase, and most importantly, excellent tolerance of methanol crossover at high concentrations. It is anticipated that this synthesis of graphene-based PdAg nanorings will open up a new avenue for designing advanced electrocatalysts that are low in cost and that exhibit high catalytic performance for alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Direct Carbon Fuel Cells: Dual 3D Ceramic Textile Electrodes: Fast Kinetics for Carbon Oxidation Reaction and Oxygen Reduction Reaction in Direct Carbon Fuel Cells at Reduced Temperatures (Adv. Funct. Keywords: 3D ceramic textiles; carbon oxidation reaction; direct carbon fuel cells; oxygen reduction reaction; self-architecture EN 3D ceramic textiles carbon oxidation reaction direct carbon fuel cells oxygen reduction reaction self-architecture 1 1 1 05/13/20 20200511 NES 200511 In article number 1910096, Wei Wu, Meng Zhou, Dong Ding, and co-workers report a direct carbon fuel cell (DCFC) with dual-3D ceramic textile (3DCT) electrodes operating at 600 °C and below. 3D ceramic textiles, carbon oxidation reaction, direct carbon fuel cells, oxygen reduction reaction, self-architecture. [Extracted from the article]

Highly efficient non‐noble metal electrocatalysts are vital for metal–air batteries and fuel cells. Herein, a noble‐metal–free single‐atom Fe‐Nx‐C electrocatalyst is synthesized by incorporating Fe‐Phen complexes into the nanocages in situ during the growth of ZIF‐8, followed by pyrolysis at 900 °C under inert atmosphere. Fe‐Phen species provide both Fe2+ and the organic ligand (Phen) simultaneously, which play significant roles in preparing single‐atom catalysts. The obtained Fe‐Nx‐C exhibits a half‐wave potential of 0.91 V for the oxygen reduction reaction, higher than that of commercial Pt/C (0.82 V). As a cathode catalyst for primary zinc–air batteries (ZABs), the battery shows excellent electrochemical performances in terms of the high open‐circuit voltage (OCV) of 1.51 V and a high power density of 96.4 mW cm−2. The rechargeable ZAB with Fe‐Nx‐C catalyst and the alkaline electrolyte shows a remarkable cycling performance for 300 h with an initial round‐trip efficiency of 59.6%. Furthermore, the rechargeable all‐solid‐state ZABs with the Fe‐Nx‐C catalyst show high OCV of 1.49 V, long cycle life for 120 h, and foldability. The single‐atom Fe‐Nx‐C electrocatalyst may function as a promising catalyst for various metal–air batteries and fuel cells. [ABSTRACT FROM AUTHOR]

Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe3C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe3C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm−2 in peak power density) and an aprotic Li–O2 battery (8749 mAh g−1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe3C contribution to the catalyst performance, suggesting Fe3C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications. [ABSTRACT FROM AUTHOR]

On page 1289, Wei Chen and co‐workers report a method to fabricate graphene‐supported PdAg nanorings. As a potential fuel cell electrocatalyst, the hybrid nanomaterial exhibits excellent catalytic performance for oxygen reduction with the clean product of water. The unique nanostructure of the material with large active surface area, low noble metal loading, and high methanol tolerance is highlighted. [ABSTRACT FROM AUTHOR]