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In this paper, a novel soft template assisted strategy has been constructed to the size-tunable preparation of porous Cu−N−C/Surfactant catalysts successfully. The synergistic effects between the adjacent Cu ACs and atomically dispersed Cu-N 4 are favorable for manipulating the binding energy of O 2 adsorption and intermediates desorption at the atomic interface of catalysts, resulting in an excellent electrocatalytic oxygen reduction reaction (ORR) performance with a faster kinetics for Cu−N−C/F127 comparable to the commercially available Pt/C catalyst. [Display omitted] In this paper, a novel, simple and mild soft template assisted strategy and further carbonization approach has been constructed to the size-tunable preparation of porous Cu−N−C/Surfactant catalysts successfully. Note that the pluronic F127 has a significant influence on the synthesis of porous Cu−N−C/F127 with the atomically dispersed Cu-N 4 and adjacent Cu atomic clusters (ACs) than other surfactants owing to their particular non-ionic structure. By combining a series of experimental analysis and density functional theory (DFT) calculations, the synergistic effects between the adjacent Cu ACs and atomically dispersed Cu-N 4 are favorable for manipulating the binding energy of O 2 adsorption and intermediates desorption at the atomic interface of catalysts, resulting in an excellent electrocatalytic ORR performance with a faster kinetics for Cu−N−C/F127 than those of the Cu−N−C, Cu−N−C/CTAB, Cu−N−C/SDS, and comparable with the commercial Pt/C catalyst. This method not only provides a novel approach for synthesizing highly effective copper based single atom catalysts toward ORR, but also offers an in-depth understanding of the synergisms of adjacent ACs on the Cu single atoms (SAs) for highly effective electrocatalytic ORR and Zn-air Battery. [ABSTRACT FROM AUTHOR]

Electrocatalytic oxygen reduction to hydrogen peroxide (H2O2) is one of the most promising methods to replace the conventional anthraquinone route for the green and facile synthesis of H2O2. Owing to the outstanding electrochemical active surface area and fast charge transfer capability of carbon nanomaterials or nanostructures with different dimensions, such as 1D, 2D, and 3D, various strategies including nanostructure engineering, defect engineering, and interface engineering have been proposed to promote the catalytic activity of carbon‐based catalysts toward two‐electron (2e−) oxygen reduction reaction (ORR) for H2O2 generation over the past decade. In this review, the latest progress, major achievements, and prospects of the transition metal‐supported carbon with different dimensions for highly efficient electrochemical H2O2 preparation via the 2e− ORR process are summarized. The rational design principles and synthetic strategies of transition metal‐supported carbon are systematically introduced while the representative advances, the identification of active sites, and their possible catalytic mechanisms toward the H2O2 production are discussed. Finally, according to the current development stage and existing shortcomings of 2e– ORR catalysts for H2O2 production, the challenges and prospects of transition metal‐supported carbon with different dimensions are also summarized. [ABSTRACT FROM AUTHOR]

[Display omitted] Herein, a soft-template strategy involving the cationic surfactants has been successfully applied to size-controlled synthesis of hierarchical porous Fe-N/C for the first time. Specifically, a small amount of Fe and cationic surfactants can be uniformly doped into the zinc-based zeolite imidazole framework (ZIF-8) crystal particles and the cationic surfactants play a critical role in the formation of hierarchically porous Fe-ZIF-8@surfactant precursors. When the Fe-ZIF-8@surfactant is subsequently pyrolyzed, atomically dispersed Fe-N x coordination structures can be in-situ converted to Fe-N/C, while the cationic surfactants decompose to form a carbon matrix to encapsulate the active sites, thereby preventing the aggregation of nanoparticles to a certain extent. As a result, the combined Fe nanocrystals and atomically dispersed Fe-N x in the graphitic carbon matrix generate a synergistic effect to boost the electrocatalytic behaviors with a more positive half-wave potential (0.92 V) for oxygen reduction reaction (ORR) and a lower overpotential (420 mV at 10 mA cm−2) for oxygen evolution reaction (OER). As a proof of concept, the Fe-N/C@TTAB based zinc-air batteries (ZABs) present an outstanding peak power density (107.9 mW cm−2) and a superior specific capacity (706.3 mAh g−1) with robust cycling stability over 900 cycles for 150 h, which are better than the commercial Pt/C + IrO 2 based ZABs. [ABSTRACT FROM AUTHOR]

In this paper, for the first time, a rationally designed strategy for synthesis of Co nanoparticles encapsulated by boron and nitrogen co‐doped carbon nanosheets (CNs), namely B, N‐Co/CNs, as highly efficient electrocatalyst for oxygen reduction reaction (ORR) is demonstrated. The generated Co nanoparticles not only create well‐defined heterointerfaces with high conductivity to overcome the poor ORR activity but also promote the formation of robust graphitic carbon. The co‐existence of boron and nitrogen atoms can increase the highest occupied molecular orbital energy of sp2 hybridization, activating π electrons in graphitic CNs, thereby enhancing the activity of the catalyst. The B, N‐Co/CNs exhibit a comparable half‐wave potential (E1/2 = 0.83 V) to that of commercial Pt/C catalyst (E1/2 = 0.85 V) with a larger current density for ORR. Importantly, the homemade disposable Zn‐air battery (ZAB) is able to deliver excellent performance, including a peak power density of 93.93 mW cm−2 and a specific capacity of 727.5 mAh g−1, outperforming the Pt/C catalyst. The findings highlight a new guideline for constructing B, N‐Co/CNs catalyst with a rationally designed structure toward superior property for advanced metal‐air cathode materials. [ABSTRACT FROM AUTHOR]

Transition metal single‐atom catalysts (SACs) are currently a hot area of research in the field of electrocatalytic oxygen reduction reaction (ORR). In this review, the recent advances in transition metal single‐atom supported by 2D materials as catalysts for ORR with high performance are reported. Due to their large surface area, uniformly exposed lattice plane, and adjustable electronic state, 2D materials are ideal supporting materials for exploring ORR active sites and surface reactions. The rational design principles and synthetic strategies of transition metal SACs supported by 2D materials are systematically introduced while the identification of active sites, their possible catalytic mechanisms as well as the perspectives on the future of transition metal SACs supported by 2D materials for ORR applications are discussed. Finally, according to the current development trend of ORR catalysts, the future opportunities and challenges of transition metal SACs supported by 2D materials are summarized. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly efficient Fe SAs/NPs@NC catalyst for boosting the ORR is developed. • A synergistic effect stemming from the isolated Fe-N x and metallic Fe is uncovered. • The catalyst showed high ORR activity and stability superior to the commercial Pt/C. • The Zn-air battery exhibits high power density and excellent cycling stability. Herein, a proof-of-concept study on the evaluation of Fe nanoparticles (Fe NPs) encapsulated by nitrogen-doped carbon to Fe single atoms (Fe SAs) for boosting the oxygen reduction reaction (ORR) catalytic activity toward Zn-air batteries was reported. Specifically, unlike Fe SAs encapsulated by nitrogen-doped carbon (Fe SAs@NC), the Fe SAs and Fe NPs co-embedded in nitrogen-doped carbon (Fe SAs/NPs@NC) derived from a pyrolysis and acid dissolution protocols exhibits excellent ORR performance with good stability and remarkable methanol tolerance in alkaline solutions. Combining a series of experimental analyses, the strong interaction between the atomically dispersed Fe-N x and adjacent Fe NPs in altering the electronic structure of isolated Fe-N x sites could weaken the binding energies of the ORR intermediates on Fe SAs/NPs@NC, resulting in an enhanced electrocatalytic kinetics than Fe SAs@NC and Pt/C catalysts. This strategy not only offers a new way for synthesis highly efficient Fe-N/C catalysts toward ORR, but also provides the new insights into the understanding of the mechanism of adjacent Fe NPs encapsulated by nitrogen-doped carbon to Fe SAs sites. [ABSTRACT FROM AUTHOR]

In this work, an in-situ synthetic, pyrolytic and carbonized method is elaborately demonstrated to prepare the nickel cobalt sulphide (NiCo 2 S 4) nanoparticles (NPs)/carbon nitrogen nanosheets (CNNs) composites as a highly efficient bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries (ZABs). Specifically, the in-situ synthesized NiCo 2 S 4 NPs confined in cages of CNNs create a well-defined electron transfer hetero-interface with more exposed active sites. The combined NiCo 2 S 4 NPs with the CNNs generate a synergistic effect, which provides effective electron transfer pathways to enhance the electrocatalytic behaviors, yielding a more positive half-wave potential (0.83 V) for oxygen reduction reaction (ORR) and a lower overpotential (360 mV at 10 mA cm−2) for oxygen evolution reaction (OER). As a proof of concept, the equipped ZABs exhibit a high peak power density of 92 mW cm−2 and a superior energy density of 1025 Wh kg−1 with robust cycling stability over 1000 cycles for 180 h, which are better than that of a commercially available Pt/C-RuO 2 catalyst. The findings highlight the practical viability of the NiCo 2 S 4 /CNNs composites in rechargeable ZABs and provide a new approach for the efficient synthesis of bifunctional oxygen electrocatalyst in the future. Image, graphical abstract An in-situ synthetic, pyrolytic and carbonized method was elaborately developed to prepare the nickel cobalt sulfide/carbon nitrogen nanosheets (NiCo 2 S 4 /CNNs) composites as highly efficient bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries (ZABs). The equipped ZABs display a high peak power density (92 mW cm−2), yielding superior energy density of 1025 Wh kg−1 with robust cycling stability over 1000 cycles for 180 h, which are better than that of a commercial available Pt/C-RuO 2 catalyst. [ABSTRACT FROM AUTHOR]

A highly efficient nitrogen-doped carbon nanotubes (N-CNTs) electrocatalyst derived from nitrogen-doped carbon dots (N- C dots) and metal-organic frameworks (MOFs) for oxygen reduction reaction (ORR) was demonstrated successfully for the first time. The N- C dots with plenty of hydroxyl and amine groups can favor the formation of N-CNTs through the catalytic decomposition of MOFs in a lower temperature. On the other hand, the N- C dots serve as inducers of the graphitic structure and supply extra nitrogen, extending a potential electrocatalytic activity of N-CNTs. Results show that the N-CNTs provided an excellent ORR electrocatalytic performance, yielding a positive onset potential of 0.88 V vs. RHE and a high kinetic current density of up to 5.58 mA cm−2 at 0.2 V. In addition, the slope of N-CNTs being ∼81 mV/dec can be found to be much lower than that of the Pt/C catalyst (∼132 mV/dec). These superior performances are attributed to defects in the graphitic crystal structure and the synergistic coupling effects of N- C dots and N-CNTs. In addition, a slight loss in activity for the N-CNTs catalyst can be found whereas the Pt/C catalyst decreases nearly 45% of its initial activity, which exhibit highly catalytic durability and tolerance to methanol in an alkaline media. Nitrogen-doped carbon nanotubes (N-CNTs) electrocatalyst derived from nitrogen-doped carbon dots (N- C dots) and metal-organic frameworks (MOFs) was demonstrated for the oxygen reduction reaction (ORR), yielding a positive onset potential of 0.88 V vs. RHE and a high kinetic current density of up to 5.58 mA cm−2 at 0.2 V, a highly catalytic durability, and tolerance to methanol in an alkaline media. Image 1 • Nitrogen-doped carbon nanotubes (N-CNTs) were synthesized by a direct pyrolysis of ZIF-67 and N-Cdots mixture simultaneously in a lower temperature for the first time. • N-Cdots not only serve as the inducer of the graphitic structure and the extra nitrogen supplier, but also favor the N-CNTs formation through catalytic decomposition of ZIF-67. • The defects of graphitic crystal structure and synergic effect of N-Cdots greatly outperforms the ORR electrocatalytic performance. • An efficient 4e-dominated ORR process and an outstanding cyclic stability were paramount for N-CNTs exhibiting an excellent electrocatalytic performance than N-Cdots and Co–N–C nanohybrids. [ABSTRACT FROM AUTHOR]