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Although porphyry systems like metallo-phthalocynine are recognized as promising molecular models for electrocatalytic oxygen reduction reaction (ORR), their poor durability and methanol tolerance are still challenges and need improvement before being considered for practical applications. Herein, we successfully designed and constructed a Fe-phthalocyanine-derived highly conjugated 2D covalent organic framework (2D FePc-COF), using octa-amino-Fe-phthalocyanine (OA-FePc) and cyclohexanone as precursors. The prepared 2D FePc-COF was characterized via multiple analytic techniques. The electrochemical studies indicated that prepared 2D FePc-COF was far more superior to OA-FePc and 20% Pt/C, displaying anodic shift of 100 and 50 mV (vs RHE) in formal potential, respectively. Moreover, this catalyst also demonstrated excellent methanol tolerance and durability (over 10,000 CV cycles). Theoretical investigations revealed that due to extended conjugation and elimination of electron donating groups (-NH2), the shifting of dz2-orbital (Fe) energy took nearer to π*-orbital (O2), allowing optimum coupling of both the orbitals, thereby enhancing 4e− ORR. This work demonstrates the art of molecular design, aiming at improving catalytic activity of macrocyclic molecular systems towards ORR. [ABSTRACT FROM AUTHOR]

Atomic cobalt–nitrogen–carbon (Co–NC) material was synthesized using spent LiCoO2, and contained a heavy Co–N4 loading (1.42 at%). The synthesized Co–NC exhibited high oxygen reduction reaction activity (with onset and half-wave potentials of 0.97 V and 0.87 V, respectively) and robust Al–air battery performance, delivering a specific power of 121.3 mW cm−2. [ABSTRACT FROM AUTHOR]

The fabrication of flexible catalytic films with isolated single/dual‐atomic sites and their integration in wearable electronics is challenging. Herein, an efficient method to prepare atomically dispersed binary Ni/Co‐decorated flexible carbon nanofiber (NiCo‐CNF) film using formamide‐derived cyano‐specific NiCo‐NC as nanofillers was developed. The optimized Ni1Co1‐CNF catalytic film, having large‐area, high density of adjacent Ni‐N4 and Co‐N4 active sites, and good mechanical properties under repeated bending and release conditions, possessed high catalytic activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The ORR/OER potential difference (ΔE10) for Ni1Co1‐CNF at 10.0 mA cm−2 was highly comparable with the Pt/C+RuO2 mixture. In addition, flexible Ni1Co1‐CNF‐assembled Zn‐air battery displayed very good mechanical robustness and cycling stability. Our work may inspire the fabrication of other atomic metal‐decorated films for membrane electrocatalysis. [ABSTRACT FROM AUTHOR]

Highlights: Precisely located S doping of atomic Fe-N4 in Fe(N3)(N–C–S) motif was realized. This S doping renders weakened *OH binding and faster charge transfer on Fe-N4. Fe-NSC showed excellent oxygen reduction reaction performance with onset potential ~ 1.09 V and half-wave potential ~ 0.92 V.Immobilizing metal atoms by multiple nitrogen atoms has triggered exceptional catalytic activity toward many critical electrochemical reactions due to their merits of highly unsaturated coordination and strong metal-substrate interaction. Herein, atomically dispersed Fe-NC material with precise sulfur modification to Fe periphery (termed as Fe-NSC) was synthesized, X-ray absorption near edge structure analysis confirmed the central Fe atom being stabilized in a specific configuration of Fe(N3)(N–C–S). By enabling precisely localized S doping, the electronic structure of Fe-N4 moiety could be mediated, leading to the beneficial adjustment of absorption/desorption properties of reactant/intermediate on Fe center. Density functional theory simulation suggested that more negative charge density would be localized over Fe-N4 moiety after S doping, allowing weakened binding capability to *OH intermediates and faster charge transfer from Fe center to O species. Electrochemical measurements revealed that the Fe-NSC sample exhibited significantly enhanced oxygen reduction reaction performance compared to the S-free Fe-NC material (termed as Fe-NC), showing an excellent onset potential of 1.09 V and half-wave potential of 0.92 V in 0.1 M KOH. Our work may enlighten relevant studies regarding to accessing improvement on the catalytic performance of atomically dispersed M-NC materials by managing precisely tuned local environments of M-Nx moiety. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were employed to investigate the electrochemical oxygen reduction reaction on the (111) and (100) surfaces of cobalt(II) oxide. Different mechanisms were applied to evaluate the oxygen reduction reaction performance of cobalt(II) oxide structures in terms of the Gibbs free energy and density of states. A variety of intermediate structures based on associative and dissociative mechanisms were constructed and optimized. As a result, we estimated the catalytic activity by calculating the free energy of the intermediates and constructing free energy diagrams, which suggested that the oxygen reduction reaction Gibbs free energy on cobalt(II) oxide (111) and (100) surfaces based on the associative mechanism is smaller than that based on the dissociative mechanism, demonstrating that the associative mechanism should be more likely to be the oxygen reduction reaction pathway. Moreover, the theoretical oxygen reduction reaction activity on the cobalt(II) oxide (111) surface was found to be higher than that on the cobalt(II) oxide (100) surface. These results shed light on the rational design of high-performance cobalt(II) oxide oxygen reduction reaction catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Herein, defect‐rich graphene oxide with a crumpled form was fabricated through the fast thermal expansion of H2SO4‐intercalated graphite oxide. The fast removal of intercalated H2SO4 molecules and by‐product gases result in the formation of crumpled edges, whereas the partial reduction of H2SO4 leads to a large amount of defects and minor S doping (ca. 0.55 at%). The expanded graphene oxide with a crumpled form and rich defects was used as electrode materials for the oxygen reduction reaction (ORR), and a very high ORR performance was observed in 0.1 mol L−1 KOH, exhibiting an onset potential of 0.92 V, a half‐wave potential of 0.83 V, and a roughly 5.68 mA cm−2 limiting current density with catalyst loading of 0.1274 mg cm−2. Our work provides reliable GO‐based catalyst materials for the ORR; moreover, it will expand the knowledge one type of high‐activity site for the ORR: defects on crumpled edges. [ABSTRACT FROM AUTHOR]

Highlights: [•] Very small CoOx particles were incorporated into Ag/rGO composite. [•] CoOx could promote the ORR activity of the resulted nanocomposites. [•] Underlying mechanism was given to explain the high-performance of CoOx-Ag/rGO. [•] Our strategy provides the possiblity to form better Ag-based ORR catalysts. [ABSTRACT FROM AUTHOR]

To date, “metal-free” catalysts originating from graphene and CNTs have been revealed to contain metal impurities. Many types of such “metal-free” carbons have been synthesized by metal-involving methods, and it is urgent to confirm the origin of the catalytic performance. Herein, we verified that residual metals were inevitably present in these N-doped carbons and the catalytic performance for the hydrogen evolution reaction (HER) was due to the remaining metals, present at only a ppm level. [ABSTRACT FROM AUTHOR]

Solid-phase templates are commonly used for building hollow-structured carbon materials (CMs) but often demand post treatments to remove templates. Herein, we develop an efficient and general method to construct hollow carbonaceous structure via the templating of sacrificial carbon nitride (termed as f-NC) without post treatment. The f-NC template can be decomposed under high-temperature annealing, additionally, it can serve as N source to enrich the N content. Applying f-NC template, we manage the synthesis of hollow-structured highly dispersed binary FeCo-nitrogen-carbon material (termed as f-NC@FeCo-NC). Its hollow feature is confirmed by direct observation using HRTEM. Meanwhile, Fe/Co in oxidation states have been verified uniformly distributing in heavily N-doped CMs (N content ∼ 13.2 at.%). The resulted f-NC@FeCo-NC, as examined by electrochemical measurements, exhibits highly efficient performance toward oxygen reduction reaction (ORR) in alkaline medium. It respectively shows much enhanced onset and half-wave potentials of 1.01 and 0.89 V relative to the FeCo-NC that is obtained without f-NC, in contrast, 20 wt% Pt/C shows 0.95 V onset potential and 0.83 V half-wave potential. The f-NC@FeCo-NC catalyst also shows excellent Al-air battery performance when applied as cathode, which possesses a high open circuit voltage of 1.91 V and a high peak power density of 241 mW cm−2. We believe this sacrificial f-NC can be applied as general template for the fabrication of other hollow-structured carbon-based materials for broad electrochemical applications. [ABSTRACT FROM AUTHOR]

Supportive atomic Zn electrocatalysts exhibit excellent stability for oxygen reduction reaction (ORR) due to their fully occupied d orbitals of Zn, but their catalytic activity is not satisfactory. Whereas heteroatom doping can anchor the Zn atoms to achieve higher Zn loading; and additionally serve as auxiliary sites to enhance the catalytic activity of Zn sites. Herein, we present a method for the synthesis of N, S co-doped carbon with highly dispersed Zn (named Zn-NSC). The ORR activity of the Zn-NSC catalysts is optimized by adjusting the pyrolysis temperature and the atomic structure of the dopant molecules. The optimized Zn-NSC demonstrates significantly enhanced ORR electrocatalytic activity, this is attributable to its highly co-doping of N and S heteroatoms that are adjacent to Zn atoms. Specifically, the Zn-NSC 3 catalyst exhibits remarkable ORR characteristics with excellent onset voltage (0.97 V vs RHE) and half-wave potential (0.87 V vs RHE), surpassing those of Pt/C (0.97 V and 0.85 V, respectively). Additionally, the Zn-NSC 3 can be utilized as efficient cathode for Al-air batteries, achieving a high power density of 119.4 mW cm−2 and satisfactory discharge stability. This work proposes an approach for synthesizing low-cost and efficient ORR electrocatalysts for Al-air battery applications. • The Zn-NSC were synthesized through hydrothermal reaction and pyrolysis process. • The Zn-NSC 3 has a high doping level of N and Zn, with 32.4 and 2.6 at%, respectively. • The Zn-NSC 3 exhibits onset voltage (0.97 V) and half-wave potential (0.87 V), superior to Pt/C. • The Zn-NSC 3 assembled Al-air battery delivers high cell voltages and large powers. [ABSTRACT FROM AUTHOR]

Atomic cobalt–nitrogen–carbon (Co–NC) material was synthesized using spent LiCoO2, and contained a heavy Co–N4 loading (1.42 at%). The synthesized Co–NC exhibited high oxygen reduction reaction activity (with onset and half-wave potentials of 0.97 V and 0.87 V, respectively) and robust Al–air battery performance, delivering a specific power of 121.3 mW cm−2. [ABSTRACT FROM AUTHOR]

Developing metal-free carbon electrocatalysts with atomically precise structures of hetero-doping is crucial for inventing reliable alternatives to precious metal-based catalysts. Our study reveals that the optimal active site is the edge-exposed N-neighbored carbon site in a chained N- C -C-S structure. Carbon material with N- C -C-S functional doping is controllably synthesized through polymer dehalogenation and heteroatom doping with thiomorpholine at room temperature. The resulting N/S-co-doped carbon with N- C -C-S functionalization, named N-C 2 -S, exhibits excellent ORR performance compared to other types of N, S-co-doped carbon, and commercial Pt/C. Typically, the N-C 2 -S sample shows the earliest onset potential of 0.96 V and a high half-wave potential of 0.85 V for promoting ORR. Assembled into an Al-air battery, The N-C 2 -S delivers an exceptional open-circuit voltage of 1.95 V and a large specific power of 128.1 mW cm 2. The synthesis strategy developed in this work can potentially open up precise functionalization of synthetic carbons with heteroatoms. [Display omitted] • The C site near the N in N-C-C-S is identified as highly active for oxygen reduction. • Different types of N, S-co-doped carbon are obtained via dehalogenation of PVDC. • N-C-C-S doping is realized via dehalogenation coupling reaction with thiomorpholine. • The N-C 2 -S sample exhibits exceptionally good oxygen reduction reaction performance. • The N-C 2 -S-assembled Al-air battery delivers high cell voltages and large powers. [ABSTRACT FROM AUTHOR]

• CeO 2 nanocubes efficiently catalyze 2e− ORR at the cathode and 2e− WOR at the anode. • CeO 2 NCs deliver high selectivity of 83% and faradic efficiency of 95.3% for 2e− ORR. • CeO 2 NCs also achieve high efficiency of 66% for 2e- WOR. • CeO 2 NCs obtain a high H 2 O 2 yield of 4.6 mol g cat. −1 h−1 (FE>85%) in a flow cell. Synthesis of H 2 O 2 via 2e− O 2 reduction or 2e− H 2 O oxidation has been widely acknowledged as promising alteratives to the energy-intensive anthraquinone processes. Herein, we report that the 2e− O 2 reduction and 2e− H 2 O oxidation reactions, for the first time, can be efficiently promoted on CeO 2 (100) facets, while majority of previous CeO 2 materials are utilized overwhelmingly as catalyst substrates. Electrochemical measurements indicate that CeO 2 nanocubes (NCs) deliver very high H 2 O 2 selectivity of 83% and faradic efficiency of 95.3% for 2e− O 2 reduction. Its H 2 O 2 yield rate at 0.5 V (vs. RHE) reaches 632 mmol g cat −1 h−1, which exceeds the performance of facet-unspecified CeO 2 nanodots (NDs) in this work and many noble metal- or carbon-based electrocatalysts in previous literatures. Furthermore, it also shows a high efficiency of 66% for 2e− H 2 O oxidation. When assembled into flow cell reactor, the CeO 2 NCs can obtain a total H 2 O 2 yield of 4.6 mol g cat. −1 h−1, and manage stable faradic efficiency (> 85%) in wide voltage range. Our work may inspire further investigation of rare earth metal oxide-based materials for 2e− oxygen electrocatalysis. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The fundamental understanding of electrocatalyst interactions at interfacial level for ORR is provided. • The chemistry and recent development in electrocatalytic ORR are explored. • The strategies for benchmarking electrocatalysts' performance are highlighted. • Future aspects of electrocatalyst interactions at interfacial level are discussed. The cathode process, oxygen reduction reaction (ORR), is crucial for producing green and reliable energy from the reorganization of chemical bonds in fuel cells. However, the application of ORR is limited due to its inefficiency, which can not only be attributed to the linearity of ORR intermediates binding energies (E b *OOH, E b *O, E b *OH) on the catalyst's active site (represented as *) but also to the serious influences of the watery environment on active sites. In an aqueous environment, catalyst interactions, including covalent, ionic, and van der Waals forces, at the interfacial level are critical in determining the catalytic activity and can considerably alter the kinetics and selectivity of ORR. Therefore, the interfacial confinement's unique properties can provide exciting new possibilities for designing molecular as well as material-based catalysts for ORR. Although several published reviews have focused on developments in interfacial engineering for electrocatalysis, not specifically for ORR, this domain still lacks an inclusive debate on the mechanism of interface structures during ORR. We highlighted the most recent employed strategies for interface structure construction and the role of interfacial interactions during ORR. Finally, the barriers and prospects for the construction of electrocatalysts based on such concepts as control of interfacial interactions, engineering, and technologies are also discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A catalyst-free approach was adopted to prepare a large conjugated poly-FePc. • Spectroscopic investigations confirmed the existence of FePc moieties in the prepared poly-FePc catalyst. • Poly-FePc displayed superior ORR performance in terms of activity, durability, and methanol tolarance. • DFT calculations indicated the down-shift in eg-orbital energy of FePc to facilitate ORR. Although Fe-phthalocyanine (FePc) has undergone extensive chemical modifications to realize improved oxygen reduction reaction (ORR), its superior performance has yet to be demonstrated at a practical level. Herein, a conjugated poly-FePc was prepared via microwave-assisted polymerization of 1,2,4,5-tetracyanobenzene in presence of FeCl 2. The characterization results of multiple spectroscopic techniques indicated that poly-FePc and monomeric FePc possessed similar structural features, proving that the polymerization process was successful. Further, the prepared poly-FePc was tested for ORR in 0.1 M KOH electrolyte and compared with the traditional 20% Pt/C and monomeric FePc catalysts. Poly-FePc was found to be the best ORR catalyst among studied electrocatalysts, displaying 258 and 40 mV positive shifts in half-wave potential compared with FePc and 20% Pt/C, respectively. The theoretical studies suggested that the large conjugation in poly-FePc down-shifted the energy of the dz2-orbital of Fe closer to the π*-orbital of O 2 (as also supported by the anodic shift in Fe3+/Fe2+ redox potential after polymerization), which allowed for an optimal coupling between these orbitals and therefore followed the 4e- ORR pathway. This study found that adjusting the electronic structures of the active sites of electrocatalysts might have improved their performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomically dispersed Fe-N 4 sites supported by flower-like N-doped carbon is synthesized. • The as-obtained Fe-NC exhibits improved density (6.84 wt%) and accessibility of Fe sites. • In alkaline, Fe-NC shows onset and half-wave potentials of 1.02 and 0.94 V, respectively. • In acid, Fe-NC shows high ORR onset potential of 0.89 V and low H 2 O 2 %<0.5%. Simultaneously improving the loading and accessibility of atomically dispersed metal sites to achieve high-activity and high-throughput electrocatalysis is important yet challenging. Herein, a simple method based on formamide chemistry was developed for the efficient synthesis of 3D flower-like N-doped carbons decorated with highly loaded atomic Fe-N 4 motifs. Approximately twice as much atomic Fe (6.84 wt%) was loaded due to the introduction of 2,1,3-benzothiadiazole (Bz) as additional ligands in the preparation of formamide-derived binary ZnFe-NC (f-ZnFe-NC). Meanwhile, with the promotion of Bz, the f-ZnFe-NC precursor also showed improved 3D flower structure that could be robustly inherited into the formation of flower-like Fe-NC product after high-temperature treatment, leading to the obtainment of rich open pores for exposing more atomic Fe sites (site density of 26.6 umol g−1 and turnover of frequency of 1.73 s−1) for oxygen reduction electrocatalysis. Electrochemical measurements showed that the Bz-promoted synthesized Fe-NC (referred to as Bz-Fe 1 -NC) possessed superior onset potential (1.04 V) and half-wave potential (0.94 V), and its assembled Al-air battery provided a very large specific power of 238.2 mW cm−2 along with high-rate capability and good long-term stability. [ABSTRACT FROM AUTHOR]

• Atomically dispersed binary NiFe-NC with tunable Ni/Fe ratios were fabricated. • The NiFe-NC with an optimal Ni/Fe ratio of 66:34 contained rich Ni-Fe dual-site. • Dual-site mode of Ni-Fe was beneficial for more charge localized over Ni/Fe sites. • Ni 66 Fe 34 -NC showed excellent ORR, OER, and rechargeable Zn-air battery performance. • DFT and in-situ Raman studies suggested Fe in Ni-Fe dimer responded for ORR/OER. Atomically dispersed metal-nitrogen-carbon complexes on carbon supports have drawn tremendous attention in the electrocatalysis fields. Herein, we managed the synthesis of atomically dispersed binary Ni x Fe 100-x -NC (x = 0–100) materials with tunable Ni/Fe ratios and investigated their underneath synergy effects for the enhancement of oxygen reduction (ORR) and oxygen evolution reactions (OER). EXAFS revealed the abundant presence of Ni(N 3)-Fe(N 3)-C n moieties in Ni 66 Fe 34 -NC sample. XPS fine scans indicated deep synergy of dual-site Ni/Fe that favored more charge localized over Ni/Fe sites. Electrochemical measurments showed that the Ni 66 Fe 34 -NC delivered a very high ORR half-wave potential (E 1/2) of 0.85 V and a low OER overpotential of 467 mV at ∼10 mA cm−2 (E j=10). The Fe site with Ni neighboring, as suggested by DFT simulations and in-situ Raman, was the responsible site for both ORR and OER. Furthermore, the Ni 66 Fe 34 -NC-assembled Zn-air battery afforded large specific power density and extraordinary cycling stability. [ABSTRACT FROM AUTHOR]

Aluminum-air batteries (AAB) have been expected as one promising energy technology for next-generation electrical vehicles owing to their low costs, light weights, high specific energy, environmental benignity and mechanical rechargeability. Yet currently, efficient catalytic materials for air cathodes are mostly based on expensive and scarce precious metal Pt, which have severely impeded the implantation of AAB. Herein, a series of non-precious binary FeCo-nitrogen-doped carbon (FeCo-NC) materials with heavily loaded Fe/Co species and in-situ generated interconnected carbon nanotube (CNT) were synthesized from cost-effective materials. With merits of dense active sites, largely exposed surface area, and good electron/ionic conductivity, the as-made binary FeCo-NC with optimal synthetic parameters exhibit excellent oxygen reduction reaction performance in alkaline electrolyte, rendering high onset potential of 1.05 V and half-wave potential of 0.91 V, which surpass those of Pt/C by 50 and 40 mV, respectively. Remarkably, the FeCo-NC-assembled AAB delivers an exceptional open-circuit voltage of 1.88 V and a large specific power of 188 mW cm−2, and additionally maintains high discharge voltage of 1.70 V at the current density of 10.0 mA cm−2. Our work renders a new type of high-performance air cathode material for AAB implantation. Image 1 • In-situ formed CNT network was designed to thread highly dispersed FeCo-NC. • The binary FeCo-NC/CNT composite exhibited excellent ORR performance. • The FeCo-NC/CNT rendered a 1.05-V onset and 0.91-V half-wave potential. • The FeCo-NC/CNT composite showed remarkable Al-air battery performance. [ABSTRACT FROM AUTHOR]