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Highlights: Oxygen-coordinated single-atom Mn catalyst was fabricated via introducing oxygen functional groups rich bacterial cellulose as the adsorption regulator through a combined impregnation–pyrolysis–etching synthetic route. Mn–O–C as the electrocatalyst exhibits superior electrocatalytic activity toward ammonia synthesis with a maximum NH3 yield rate of 1476.9 ± 62.6 μg h−1 cm−2 at − 0.7 V (vs. RHE) and a faradaic efficiency of 89.0 ± 3.8% at − 0.5 V (vs. RHE) under ambient conditions. Electrocatalytic mechanism of Mn–(O–C2)4 site for nitrate reduction reaction is unveiled by a combination of in situ spectroscopy characterization and computational study. Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection. Here, we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen (O) coordination on bacterial cellulose-converted graphitic carbon (Mn–O–C). Evidence of the atomically dispersed Mn–(O–C2)4 moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy. As a result, the as-synthesized Mn–O–C catalyst exhibits superior NitRR activity with an NH3 yield rate (RNH3) of 1476.9 ± 62.6 μg h−1 cm−2 at − 0.7 V (vs. reversible hydrogen electrode, RHE) and a faradaic efficiency (FE) of 89.0 ± 3.8% at − 0.5 V (vs. RHE) under ambient conditions. Further, when evaluated with a practical flow cell, Mn–O–C shows a high RNH3 of 3706.7 ± 552.0 μg h−1 cm−2 at a current density of 100 mA cm−2, 2.5 times of that in the H cell. The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn–(O–C2)4 sites not only effectively inhibit the competitive hydrogen evolution reaction, but also greatly promote the adsorption and activation of nitrate (NO3−), thus boosting both the FE and selectivity of NH3 over Mn–(O–C2)4 sites. [ABSTRACT FROM AUTHOR]

A general electrocatalyst design for water splitting through generating oxygen vacancies in bimetallic layered double hydroxides by using carbon nitride is proposed. The excellent OER activity of the achieved bimetallic layered double hydroxides is attributed to oxygen vacancies, which reduce the energy barrier of the rate-determining step. [ABSTRACT FROM AUTHOR]

To achieve practical application of fuel cell, it is vital to develop highly efficient and durable Pt‐free catalysts. Herein, we prepare atomically dispersed ZnNC catalysts with Zn‐Pyrrolic‐N4 moieties and abundant mesoporous structure. The ZnNC‐based anion‐exchange membrane fuel cell (AEMFC) presents an ultrahigh peak power density of 1.63 and 0.83 W cm−2 in H2‐O2 and H2‐air (CO2‐free), and also exhibits long‐term stability with more than 120 and 100 h for H2‐air (CO2‐free) and H2‐O2, respectively. Density functional calculations further unveil that the Zn‐Pyrrolic‐N4 structure is the origin of high activity of as‐synthesized ZnNC catalyst, while the Zn‐Pyridinic‐N4 moiety is inactive for oxygen reduction reaction (ORR), which successfully explain the puzzle why most Zn‐metal‐organic framework ‐derived ZnNC catalysts in previous reports did not present good ORR activity because of their Zn‐Pyridinic‐N4 moieties. This work offers a new route for speeding up development of AEMFCs. [ABSTRACT FROM AUTHOR]

In this study, dual-metal atomic pairs of manganese (Mn)-iron (Fe) binuclear sites (BNSs) with two conjoint MnN4 and FeN4 moieties (MnFeN8) anchored onto a graphite-like structure (GLS) (Mn-Fe BNSs/GLS) were constructed. The binuclear MnFeN8 structure was verified experimentally and theoretically. Magnetic measurements and Gaussian calculations reveal that this unique Mn-Fe BNSs exhibit strong short-range electronic interaction between Mn and Fe sites, which decouples two paired d electrons in Fe sites, thereby transforming Fe sites from an intermediate to a high spin state. The optimal electronic configuration of Fe sites and their binuclear structure facilitate an oxygen reduction reaction (ORR) thermodynamically and dynamically, respectively, endowing Mn-Fe BNSs with improved ORR performance. [ABSTRACT FROM AUTHOR]

Fine‐tuning single‐atom catalysts (SACs) to surpass their activity limit remains challenging at their atomic scale. Herein, we exploit p‐type semiconducting character of SACs having a metal center coordinated to nitrogen donors (MeNx) and rectify their local charge density by an n‐type semiconductor support. With iron phthalocyanine (FePc) as a model SAC, introducing an n‐type gallium monosulfide that features a low work function generates a space‐charged region across the junction interface, and causes distortion of the FeN4 moiety and spin‐state transition in the FeII center. This catalyst shows an over two‐fold higher specific oxygen‐reduction activity than that of pristine FePc. We further employ three other n‐type metal chalcogenides of varying work function as supports, and discover a linear correlation between the activities of the supported FeN4 and the rectification degrees, which clearly indicates that SACs can be continuously tuned by this rectification strategy. [ABSTRACT FROM AUTHOR]

As an emerging frontier, dual‐atom catalysts (DACs) have sparked broad interest in energy catalysis, however the undesired thermal atomic migration during synthesis process pose significant challenge in enabling further applications. Herein, an interfacial cladding strategy is reported to construct monodispersed dual‐atom metal sites (metal = Fe, Cu, or Ir), derived from metal dimer molecule functionalized metal‐organic frameworks. First, metal dimer molecule is immobilized at the surface of cubic ZIF‐8 by the interfacial cladding of polydopamine, thus preventing the potentially thermal migration of metal atoms during pyrolysis. Then, the paired metal atoms are anchored onto a hollow carbon nanocage and achieve nitrogen coordinated dual‐atom metal sites after annealing at 900 °C. Representatively, the resultant dual Fe catalysts exhibit remarkable activity for electrocatalytic oxygen reduction reaction with half‐wave potential of 0.951 and 0.816 V in alkaline and acidic media, respectively. The findings open up an avenue for the rational design of dual‐atom catalysts. [ABSTRACT FROM AUTHOR]

Combining isolated atomic active sites with those in nanoparticles for synergizing complex multistep catalysis is being actively pursued in the design of new electrocatalyst systems. However, these novel systems have been rarely studied due to the challenges with synthesis and analysis. Herein, a synergistically catalytic performance is demonstrated with a 0.89 V (vs reversible hydrogen electrode) onset potential in the four‐step oxygen reduction reaction (ORR) by localizing tungsten single atoms around tungsten nitride nanoparticles confined into nitrogen‐doped carbon (W SAs/WNNC). Through density functional theory calculations, it is shown that each of the active centers in the synergistic entity feature a specific potential‐determining step in their respective reaction pathway that can be merged to optimize the intermediate steps involving scaling relations on individual active centers. Impressively, the W SAs/WNNC as the air cathode in all‐solid‐state Zn‐air and Al‐air batteries demonstrate competitive durability and reversibility, despite the acknowledged low activity of W‐based catalyst toward the ORR. [ABSTRACT FROM AUTHOR]

Metal phthalocyanines (MPcs) have highly conjugated π electron systems and metal atoms acting as active centers, and so exhibit excellent electrocatalytic performance during the oxygen reduction reaction (ORR). However, these complexes also tend to undergo aggregation and exhibit poor electrical conductivity and minimal durability, all of which hinder their large‐scale industrial applications. In the present study, iron phthalocyanine (FePc) is applied to hollow carbon shells (HCSs) to generate an ORR catalyst containing single Fe atoms(HCS‐O‐FePc). The HCSs have numerous N/O‐based surface functional groups that promote the formation of Fe−O bonds with the FePc held in an axial coordination position. These axial Fe−O bonds disrupt the electron symmetry in the plane of the FePc molecules, which facilitate electron transfer. 1100HCS‐O‐FePc exhibits an onset potential of 0.98 V (vs RHE), a half‐wave potential of 0.91 V (vs RHE), an electron transfer number of 3.90, and durability better than that of a 20 % commercial Pt/C catalyst. Electrochemical impedance spectroscopy demonstrates that the ORR process over this material likely proceeds via a rapid 2+2 electron mechanism. This composite displays excellent oxygen reduction properties and is a promising alternative to Pt‐based ORR catalysts. [ABSTRACT FROM AUTHOR]

Simultaneously increasing the activity and stability of the single-atom active sites of M–N–C catalysts is critical but remains a great challenge. Here, we report an Fe–N–C catalyst with nitrogen-coordinated iron clusters and closely surrounding Fe–N4 active sites for oxygen reduction reaction in acidic fuel cells. A strong electronic interaction is built between iron clusters and satellite Fe–N4 due to unblocked electron transfer pathways and very short interacting distances. The iron clusters optimize the adsorption strength of oxygen reduction intermediates on Fe–N4 and also shorten the bond amplitude of Fe–N4 with incoherent vibrations. As a result, both the activity and stability of Fe–N4 sites are increased by about 60% in terms of turnover frequency and demetalation resistance. This work shows the great potential of strong electronic interactions between multiphase metal species for improvements of single-atom catalysts. It is challenging to break the activity–stability trade-off in Fe–N–C fuel cell catalysts. Here, the authors show that interactions between iron atoms and clusters accelerate reaction kinetics and suppress demetalation to improve fuel cell stability. [ABSTRACT FROM AUTHOR]

Rational design of efficient non‐precious materials for oxygen redox electrocatalysis is currently a critical obstacle for rechargeable zinc‐air batteries. Herein, this work presents a strategy to modulate the activity and mass transfer performance for advanced bifunctional electrocatalysts. This is achieved via a prior vacuum heat treatment‐assisted pyrolysis approach, obtaining atomically disperse Fe/Co sites and alloy nanoparticle composites rooted in the unique well‐aligned nanotubes hierarchical architecture. The design of multiple metal active species and hierarchically porous structure facilitates the bifunctional activity and accessibility of the active sites, respectively, which affords the catalyst enhanced performance in rechargeable zinc‐air batteries, outperforming the commercial Pt/C‐Ir/C benchmarks. This work provides a new avenue to improve activity and accessibility together with single atomic catalysts as advanced bifunctional air cathodes for efficient oxygen redox electrocatalysis. [ABSTRACT FROM AUTHOR]

Developing highly stable and efficient catalysts for the oxygen reduction reaction is important for the long-term operation of proton exchange membrane fuel cells. Herein, combined with the impregnation method, chains of N-doped carbon spheres with abundant pores synthesized by a simple and versatile nanoemulsion assembly strategy have been used to prepare platinum catalysts (Pt-PC-300) via pore confinement and anchoring effect, which enhances the interaction between the metal and the carbon support and thus hinders the metal agglomeration and fall off during the catalytic process. The structure and composition of the materials were characterized by HRTEM, XRD, BET, TEM, SEM, XAS and XPS. Under acidic conditions, Pt-PC-300 showed better catalytic performance in oxygen reduction reaction (ORR) than Pt supported by carbon (XC-72) and commercial Pt/C. Specifically, the Pt-PC-300 catalyst exhibited a similar half-wave potential but much better stability in comparison with the commercial Pt/C because of the pore-confined structure and anchoring effect, the synergy of which provides a new way to develop stable ORR catalysts. [ABSTRACT FROM AUTHOR]

Developing single‐atom electrocatalysts with high activity and superior selectivity at a wide potential window for CO2 reduction reaction (CO2RR) still remains a great challenge. Herein, a porous NiNC catalyst containing atomically dispersed NiN4 sites and nanostructured zirconium oxide (ZrO2@Ni‐NC) synthesized via a post‐synthetic coordination coupling carbonization strategy is reported. The as‐prepared ZrO2@Ni‐NC exhibits an initial potential of −0.3 V, maximum CO Faradaic efficiency (F.E.) of 98.6% ± 1.3, and a low Tafel slope of 71.7 mV dec−1 in electrochemical CO2RR. In particular, a wide potential window from −0.7 to −1.4 V with CO F.E. of above 90% on ZrO2@Ni‐NC far exceeds those of recently developed state‐of‐the‐art CO2RR electrocatalysts based on NiN moieties anchored carbon. In a flow cell, ZrO2@Ni‐NC delivers a current density of 200 mA cm−2 with a superior CO selectivity of 96.8% at −1.58 V in a practical scale. A series of designed experiments and structural analyses identify that the isolated NiN4 species act as real active sites to drive the CO2RR reaction and that the nanostructured ZrO2 largely accelerates the protonation process of *CO2− to *COOH intermediate, thus significantly reducing the energy barrier of this rate‐determining step and boosting whole catalytic performance. [ABSTRACT FROM AUTHOR]

Atomically dispersed Pt species are advocated as a promising electrocatalyst for the oxygen reduction reaction (ORR) to boost noble metal utilization efficiency. However, when assembled on various substrates, isolated Pt single atoms are often demonstrated to proceed through the two‐electron ORR pathway due to the unfavorable O─O bond cleavage thermodynamics in the absence of catalytic ensemble sites. In addition, although their distinct local coordination environments at the exact single active sites are intensively explored, the interactions and synergy between closely neighboring single atom sites remain elusive. Herein, atomically dispersed Pt monomers strongly interacting on a Mo2C support is demonstrated as a model catalyst in the four‐electron ORR, and the beneficial interactions between two closely neighboring and yet non‐contiguous Pt single atom sites (named as quasi‐paired Pt single atoms) are shown. Compared to isolated Pt single atom sites, the quasi‐paired Pt single atoms deliver a superior mass activity of 0.224 A mg−1Pt and near‐100% selectivity toward four‐electron ORR due to the synergistic interaction from the two quasi‐paired Pt atom sites in modulating the binding mode of reaction intermediates. Our first‐principles calculations reveal a unique mechanism of such quasi‐paired configuration for promoting four‐electron ORR. [ABSTRACT FROM AUTHOR]

The modulation effect has been widely investigated to tune the electronic state of single‐atomic M‐N‐C catalysts to enhance the activity of oxygen reduction reaction (ORR). However, the in‐depth study of modulation effect is rarely reported for the isolated dual‐atomic metal sites. Now, the catalytic activities of Fe‐N4 moiety can be enhanced by the adjacent Pt‐N4 moiety through the modulation effect, in which the Pt‐N4 acts as the modulator to tune the 3d electronic orbitals of Fe‐N4 active site and optimize ORR activity. Inspired by this principle, we design and synthesize the electrocatalyst that comprises isolated Fe‐N4/Pt‐N4 moieties dispersed in the nitrogen‐doped carbon matrix (Fe‐N4/Pt‐N4@NC) and exhibits a half‐wave potential of 0.93 V vs. RHE and negligible activity degradation (ΔE1/2=8 mV) after 10000 cycles in 0.1 M KOH. We also demonstrate that the modulation effect is not effective for optimizing the ORR performances of Co‐N4/Pt‐N4 and Mn‐N4/Pt‐N4 systems. [ABSTRACT FROM AUTHOR]

Correction to: I Nature Communications i https://doi.org/10.1038/s41467-018-07850-2, published online 21 December 2018. These authors contributed equally: Yuanjun Chen, Shufang Ji, Shu Zhao. [Extracted from the article]

[Display omitted] • The unique Pt-O-Cu structure is constructed on the 2.5Pt-2Cu/Fe 2 O 3 catalyst. • The Pt-O-Cu site shows the best reactivity for EWGS reaction. • The Pt-O-Cu site balances the binding ability of CO and the activation of OH–. • The Pt-O-Cu structure greatly boots the capability in antioxidation of Pt. Electrochemical water–gas shift (EWGS) reaction is an emerging technology with energy-saving and environmental-friendly advantages to produce high-purity hydrogen form the waste gas containing CO. However, it remains a significant challenge to design superior activity and highly durable EWGS electrocatalysts, particularly with low content of noble metals. Herein, a series of Pt-xCu/Fe 2 O 3 (x = 0, 2, 5) catalysts are synthesized by the complexation precipitation method to construct coupling sites between Pt and CuOx, aiming to optimize the adsorption of CO and the activation of OH–. The obtained 2.5Pt-2Cu/Fe 2 O 3 catalyst presents a unique Pt-O-Cu structure, delivering a much lowest onset potential, high specific activity, and excellent mass activity (1.5 A·mg Pt -1) at 0.73 V (vs. RHE), which is over 15 and 3 times that of commercial Pt/C (20%) and unmodified Pt/Fe 2 O 3 catalyst, respectively. Meanwhile, the in-situ X-ray absorption results demonstrate that the facilitated interaction among the Pt-O-Cu structure promotes the high durability of the 2.5Pt-2Cu/Fe 2 O 3 catalyst and the operability at high potential. More importantly, the moderate binding of CO and moderate activation of OH* are suggested for boosting the reactivity in the CO electro-oxidation reaction. In particular, the fabricated Pt||2.5Pt-2Cu/Fe 2 O 3 , employed in coupling the HER and CO electro-oxide reaction, shows a remarkable hydrogen production of about 98 mmol H2 ·h−1·mg Pt −1 at 0.8 V (vs. RHE). This work also definitely confirms the possibility of the catalyst being applied to produce hydrogen under practical conditions with different concentrations of CO, even being applied in the purification of trace CO in a hydrogen-rich atmosphere. [ABSTRACT FROM AUTHOR]

The reasonable design and construction of single-atom electrocatalysts with low-cost and excellent intrinsic activity for oxygen reduction reaction (ORR) is indispensable in metal-air batteries. Herein, a facile isolation anchoring strategy was reported for in situ formation of porous N-doped carbon catalysts (Fe 1 /NC) rich in Fe single atoms. The d -glucose, zinc gluconate and N-rich histidine were deployed as spatial isolation agents and anchoring agents to inhibit iron atom aggregation during the high-temperature pyrolysis. The as-synthesized Fe 1 /NC catalyst shows remarkable stability and superior ORR electrocatalytic activity under both alkaline and acidic conditions owing to highly dispersed Fe–N 4 sites, especially with a half-wave potential up to 0.91 V in 0.1 M KOH, exceeding 60 mV compared with Pt/C. Notably, the Fe 1 /NC-based Zn-air battery exhibits maximal power density of 164 mW cm−2, large specific capacities of 769 mA h g Zn −1, excellent cycle stability over 300 h, and great potential in renewable energy conversion electronics. A facile isolation anchoring strategy was reported to synthesize the Fe single-atom electrocatalyst that exhibits excellent ORR catalytic efficiency and long-term stability in both three electrodes system and zinc-air battery due to the abundant Fe–N 4 active sites. [Display omitted] • A facile isolation anchoring strategy was reported to prepare Fe single-atom electrocatalyst. • d -glucose, zinc gluconate and N-rich histidine were deployed as spatial isolation and anchoring agents. • The electrocatalysts exhibit superior ORR performance due to the abundant Fe–N 4 active sites. • The Zn-air battery assembled with Fe 1 /NC displays a high discharge specific capacity and excellent cyclic stability. [ABSTRACT FROM AUTHOR]

A template-engaged multistep synthesis process is developed to fabricate ultrathin carbon nanosheets assembled hierarchical nanoboxes embedded with dense Mo-N 4 active sites, which exhibited excellent activity and superb stability for oxygen reduction reaction. [Display omitted] • Unique hierarchical SA-Mo-C nanoboxes were fabricated via a template-engaged multistep synthesis process. • Comprehensive characterizations including EXAFS reveal Mo-N 4 atomic sites were formed and densely dispersed in the SA-Mo-C nanoboxes. • SA-Mo-C nanoboxes exhibited better ORR performance compared to commercial Pt/C catalysts. Construction of single-atom catalysts (SACs) with maximally exposed active sites remains a challenging task mainly because of the lack of suitable host matrices. In this study, hierarchical N -doped carbon nanoboxes composed of ultrathin nanosheets with dispersed atomic Mo (denoted as hierarchical SA-Mo-C nanoboxes) were fabricated via a template-engaged multistep synthesis process. Comprehensive characterizations, including X-ray absorption fine structure analysis, reveal the formation of Mo-N 4 atomic sites uniformly anchored on the hierarchical carbon nanoboxes. The prepared catalysts offer structural and morphological advantages, including ultrathin nanosheet units, unique hollow structures and abundant active Mo-N 4 species, that result in excellent activity with a half-wave potential of 0.86 V vs. RHE and superb stability for the oxygen reduction reaction in 0.1 M KOH; thus, the catalysts are promising air–cathode catalysts for Zn-air batteries with a high peak power density of 157.6 mW cm−2. [ABSTRACT FROM AUTHOR]

Atomically distributed iron electrocatalyst is valid for oxygen reduction reaction (ORR). However, accurate regulation of the structure improving its intrinsic activity is a challenge. Herein, a dual-atom catalyst FeCu-NC with atomically distributed Fe and Cu co-anchored on porous N-doped carbon is obtained. The FeN 4 and CuN 3 couple sites bridged by two nitrogen atoms, exist as Fe(II,III)N 2 (µ 2 -N) 2 Cu(I,II)N moieties with the metal distance of ∼2.5 Å in the structure of FeCu-NC. The synergistic effect of Fe and Cu dual-atom reducing the dissociation energy of *OOH intermediate, allows an optimized 4e- ORR reaction pathway. The FeCu-NC exhibits high-efficiency ORR activity with the half-wave potential (E 1/2) of 0.889 V (vs RHE) and outstanding stability without obvious decay for the E 1/2 after 10,000 cycles. The FeCu-NC based Zn-air battery presents large specific capacity of 795 mAh g−1 and energy density of 998 Wh kg−1 as well as high charge-discharge cycling stability superior to the Pt/C. [Display omitted] • A dual-atom catalyst FeCu-NC with Fe(II,III)N 2 (µ 2 -N) 2 Cu(I,II)N moieties is prepared. • The synergistic effect of Fe and Cu clearly reduces the dissociation energy of *OOH. • The FeCu-NC has a high ORR activity in an optimized 4e- reaction pathway. • The FeCu-NC based Zn-air battery exhibits a large stable energy density. [ABSTRACT FROM AUTHOR]

Single-atom Fe–N–C electrocatalysts are attracting more attentions as one most promising transition metal based single-atom catalyst towards the oxygen reduction reaction (ORR). However, the inaccessibility of internal Fe-N x active sites and insufficient stability hinder their large-scale application. Herein, a facile benzoate-assisted self-template strategy which could dramatically enhance the oxygen reduction reaction catalytic performance and stability of ZIF-8 derived atomically dispersed Fe–N–C catalysts (Fe-SA/Meso-C) is developed. The sodium benzoate used in the present work is effective for promoting the formation of Fe–N–C catalysts with denser accessible active sites as well as mesopores with diameters ranging from 2.5 to 5 nm. These structural advantages make the synthesized Fe-SA/Meso-C catalysts afford excellent electrocatalytic performance for the ORR in 0.1 M KOH with a positive half-wave potential (E 1/2) of 0.926 V vs. RHE and exceptionally high kinetic current density (J k) of 92.5 mA cm−2 at 0.85 V. Beyond that, Fe-SA/Meso-C shows outstanding long-term stability with over 90% activity retain after 90 h chronoamperometry i-t test as well as superior tolerance to methanol crossover. More importantly, the assembled zinc-air battery with Fe-SA/Meso-C as the cathode material achieves a high peak power density of 166.2 mW cm−2 and a high specific capacity of 776.1 mA h g−1. Our results reveal that small mesopores in atomically dispersed Fe–N–C electrocatalysts could facilitate mass transport, increase the accessibility of active sites and optimize the interface between electrolyte and carbon matrix, thus optimizing their electrocatalytic performance for the ORR. This work paves a way to the design and synthesis of stable single-atom electrocatalysts with optimized structure, electrochemical performance and promising applications. Ultrastable and highly catalytically active single-atom iron electrocatalysts (Fe-SA/Meso-C) with exclusively Fe–N 4 sites dispersed on ZIF-8 derived mesoporous N-doped carbon frameworks have been synthesized by a novel benzoate-assisted self-template strategy without acid leaching assistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrochemical production of hydrogen peroxide (H 2 O 2) is a sustainable and environmentally benign process. The electrochemical oxygen reduction process (ORR) via a two electron pathway (2e- ORR) offers a practical method for on-site H 2 O 2 generation. As an earth-abundant catalyst, the cobalt-nitrogen coordinated systems integrated into the carbon matrix (Co-NC) has caused wide attention for its high activity in 2e- ORR. Even though most of the reported Co-NC catalysts have classical planar Co-N 4 coordination, axial coordination engineering has recently emerged as an effective way to control the active sites in the axial direction by using different coordination ligands. The structure-function link between the Co-N configuration of non-planar coordination and 2e- ORR activity is, however, not fully understood. An axial-N coordinated Co-N 5 motif embedded in hierarchically porous graphite-3R carbon (Co-N 5 C) was effectively synthesized using a template-sacrificing method. The Co-N 5 C has a high selectivity for 2e- ORR and a high H 2 O 2 molar production rate of up to 6.78 mol peroxide/g catalyst /h in acidic media, both of which are better than its Co-N 4 counterpart. DFT analyses demonstrate that axial-N ligands regulated the d -band center of the Co atom in the Co-N 5 C catalyst, inducing a shift in Δ G *OOH near the Sabatier volcano plot's peak (Δ G *OOH = 4.22 eV). This optimized the binding of the *OOH intermediate and then enhanced the protonation of *OOH to produce H 2 O 2 more efficiently. [Display omitted] • A Co-N 5 C catalyst containing an axial-N ligand was synthesized for the effective ORR. • Co-N 5 C, with graphite-3R phase, showed a specific BET surface area of 801.6 m2/g. • Co-N 5 C exhibited a high selectivity for 2e- ORR and H 2 O 2 molar production rate. • Co-N 5 C possessed a high active SD and high intrinsic kinetic TOF. [ABSTRACT FROM AUTHOR]

[Display omitted] • FeSb-NC diatomic catalysts with a new local structure were synthesized. • The FeSb-NC shows excellent ORR performance in both acid and alkaline media. • The FeSb-NC-based PEMFC and ultralow temperature (−40 °C) Zn-air batter exhibit high peak power densities. • DFT calculation reveals the synergistic catalytic mechanism of SbN 4 and FeN 4 OH species. Dual atom catalysts (DAC) have attracted extensive concerns due to the combinatorial diversity of two central sites and their synergistic effects for boosting oxygen reduction reaction (ORR). However, how the synergistic effect modulates the local electronic structure and thus enhances the ORR activity is still ambiguity. Here, we successfully synthesize FeSb-NC diatomic catalysts with a new local structure of FeN 4 OH-SbN 4 , which is identified by synchrotron X-ray adsorption fine spectroscopy. The FeSb-NC shows excellent ORR activity with half-wave potentials of 0.795 V in 0.1 M HClO 4 and 0.905 V in 0.1 M KOH. Importantly, the FeSb-NC-based proton exchange membrane fuel cell exhibits a peak power density (PPD) of 0.4 W cm−2 at 1 bar H 2 /air condition, and the current density at 0.6 V iR-free reaches 0.673 A cm−2. Furthermore, the FeSb-NC-based solid-state Zn-air battery exhibits an ultrahigh PPD of 57.5 mW cm−2 at −40 °C ultralow temperature, apparently superior to Fe-NC and Pt/C – based ones. DFT calculations further reveal the synergistic catalytic mechanism of SbN 4 and FeN 4 OH species, i.e. SbN 4 could act as a lateral coordination site to enhance reaction kinetics and adsorption ability of FeN 4 OH species, and thus significantly boosts ORR performance. This work provides a new route of lateral coordination for the design of diatomic catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three-dimensional ordered macroporous frameworks with NiN 4 sites were obtained. • 3DOM Ni N C was highly efficiency for ORR and OER performances in neutral condition. • The neutral zinc-air batteries exhibited outstanding long term stability of 580 cycles at 1.0 mA cm−2. • The failure mechanism of air electrode in neutral condition was revealed. Neutral zinc-air batteries prevent the carbon based catalysts from being oxidized during cycling, which show excellent potential for long-term energy storage. Three-dimensional ordered macroporous nitrogen doped carbon frameworks with NiN 4 (3DOM Ni N C) were constructed by in situ reaction of Ni nanoparticles and dicyandiamide. The 3DOM Ni N C bifunctional catalysts exhibit comparable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) efficiency and stablity. The 3D interconnected structure of 3DOM Ni N C provides sufficient channel for mass transfer, resulting in high power density (35 mW cm−2) and long cycle life (580 cycles) of neutral zinc-air batteries. Meanwhile the failure mechanism in neutral electrolyte was discussed. [ABSTRACT FROM AUTHOR]

Reducing the usage of noble metals, such as platinum-based catalysts for oxygen reduction reaction (ORR) is pressingly demanded towards the practical applications of proton-exchange membrane fuel cells. One promising way is to develop Pt single atom catalysts (SACs), which, however, are plagued by their preference toward two-electron ORR pathway as well as stability issue. Herein, a single-atom alloy (SAA) catalyst with platinum-cobalt (Pt-Co) dual sites encapsulated in nitrogen-doped graphitized carbon nanotubes (Pt 1 Co 100 /N-GCNT) consisting of isolated Pt atoms decorated on the surface of Co nanoparticles was reported. Based on complementary spectroscopic characterizations and first-principle calculations, we propose that the unique Pt-Co dual sites in SAA facilitates the adsorption and dissociation of oxygen, particularly for the immobilization of OOH* intermediate and the dissociation of OH* intermediate, and thus result in high-efficiency four-electron ORR pathway. Consequently, the Pt 1 Co 100 /N-GCNT SAA catalyst achieves a mass activity of 0.81 A mg–1 Pt at 0.90 V (versus the reversible hydrogen electrode) in 0.1 M HClO 4 electrolyte, outperform commercial Pt/C catalyst for 5.4 times. The superior stability of the SAA catalyst was reflected by the results from the 30,000 potential-scanning cycles combined with the post characterization of the catalyst. [Display omitted] • A single atom alloy (SAA) catalyst with well-defined platinum-cobalt (Pt-Co) dual sites was reported. • The unique Pt-Co dual sites in SAA facilitates the immobilization of OOH* intermediate and the dissociation of OH* intermediate. • The rationally designed PtCo SAA was found to have 4e- ORR activity in acidic media and exhibited high activity and durability. [ABSTRACT FROM AUTHOR]