Electrochemical H2O2 production through the 2‐electron oxygen reduction reaction (ORR) is a promising alternative to the energy‐intensive anthraquinone process. Herein, by simultaneously regulating the coordination number of the atomically dispersed cobalt sites and the nearby oxygen functional groups via a one‐step microwave thermal shock, a highly selective and active CoNC electrocatalyst for H2O2 electrosynthesis that exhibits a high H2O2 selectivity (91.3%), outstanding mass activity (44.4 A g−1 at 0.65 V), and large kinetic current density (11.3 mA cm−2 at 0.65 V) in 0.1 m KOH is obtained. In strong contrast to the typical CoN4 moieties for the 4‐electron ORR, the present CoNC catalyst possesses a low‐coordinated CoN2 configuration and abundant epoxide groups, which work in synergy for promoting the 2‐electron ORR, as demonstrated by a series of control experiments and theoretical simulations. This study may provide an effective avenue to modulating the composition and structure of electrocatalysts at the atomic scale, leading to the development of new electrocatalysts with unprecedented reactivity.

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this approach benefits from generating highly concentrated H 2 O 2 at the largescale level, it suffers from high cost and insecurity that hinder its practical application and thus prompt the search for alternative strategy to produce H 2 O 2 .Recently, the production of H 2 O 2 via the 2-electron oxygen reduction reaction (ORR) method has emerged as a promising alternative approach. Compared with the conventional anthraquinone reaction, this electrochemical strategy has several advantageous features such as sustainability without carbon emissions, operation at mild condition, and on-demand generation of H 2 O 2 with no further transportation. Typically, the ORR process consists of multielectron transfer steps and it can proceed either through the 4-electron pathway to generate H 2 O or through the 2-electron pathway to produce H 2 O 2 . It is noted that all the potentials in this review are relative to the reversible hydrogen electrode (RHE). The elementary steps involved in the 4-electron and 2-electron ORR processes in acidic media are presented as follows [7] The pathway of the 4-electron ORR processThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202103824.

Selective two-electron (2e−) oxygen reduction reaction (ORR) offers great opportunities for hydrogen peroxide (H2O2) electrosynthesis and its widespread employment depends on identifying cost-effective catalysts with high activity and selectivity. Main-group metal and nitrogen coordinated carbons (M-N-Cs) are promising but remain largely underexplored due to the low metal-atom density and the lack of understanding in the structure-property correlation. Here, we report using a nanoarchitectured Sb2S3 template to synthesize high-density (10.32 wt%) antimony (Sb) single atoms on nitrogen- and sulfur-codoped carbon nanofibers (Sb-NSCF), which exhibits both high selectivity (97.2%) and mass activity (114.9 A g−1 at 0.65 V) toward the 2e− ORR in alkaline electrolyte. Further, when evaluated with a practical flow cell, Sb-NSCF shows a high production rate of 7.46 mol gcatalyst−1 h−1 with negligible loss in activity and selectivity in a 75-h continuous electrolysis. Density functional theory calculations demonstrate that the coordination configuration and the S dopants synergistically contribute to the enhanced 2e− ORR activity and selectivity of the Sb-N4 moieties.

Graphene‐supported single‐atom catalysts (SACs) are promising alternatives to precious metals for catalyzing the technologically important hydrogen evolution reaction (HER), but their performances are limited by the low intrinsic activity and insufficient mass transport. Herein, a highly HER‐active graphene‐supported Co‐N‐C SAC is reported with unique design features in the morphology of the substrate and the microenvironment of the single metal sites: i) the crumpled and scrolled morphology of the graphene substrate circumvents the issues encountered by stacked nanoplatelets, resulting in improved exposure of the electrode/electrolyte interfaces (≈10 times enhancement); ii) the in‐plane holes in graphene preferentially orientate the Co atoms at the edge sites with low‐coordinated Co‐N3 configuration that exhibits enhanced intrinsic activity (≈2.6 times enhancement compared to the conventional Co‐N4 moiety), as evidenced by detailed experiments and density functional theory calculations. As a result, this catalyst exhibits significantly improved HER activity with an overpotential (η) of merely 82 mV at 10 mA cm−2, a small Tafel slope of 59.0 mV dec−1 and a turnover frequency of 0.81 s−1 at η = 100 mV, ranking it among the best Co‐N‐C SACs.

The atomic dispersion of metal atoms on substrates provides an ideal method to maximize metal utilization efficiency, which is important for the production of cost-effective catalysts and the atomic-level control of the electronic structure. However, due to the high surface energy, individual single atoms tend to migrate and aggregate into nanoparticles during preparation and catalytic operation. In the past few years, various synthetic strategies based on ultrafast thermal activation toward the effective preparation of single-atom catalysts (SACs) have emerged, which could effectively solve the aggregation issue. Here, we highlight and summarize the latest developments in various ultrafast synthetic strategy with rapid energy input by heating shockwave and instant quenching for the synthesis of SACs, including Joule heating, microwave heating, solid-phase laser irradiation, flame-assisted method, arc-discharge method and so on, with special emphasis on how to achieve the uniform dispersion of single metal atoms at high metal loadings as well as the suitability for scalable production. Finally, we point out the advantages and disadvantages of the ultrafast heating strategies as well as the trends and challenges of future developments.

precious-metal-based ones. We envision that the generality of the NH 4 I-based method is not only limited to carbon-based SACs, but can also be extended to other types of supports. With the Pt-N-C HER catalyst as the example, we also demonstrated that the complete removal of the metal aggregates enabled the elucidation on the roles of the atomic PtN x sites and Pt NPs in contributing to the catalytic activity. Our strategy could be employed to assist the preparation of SACs with well-defined active sites and benefit the rational design of high-performance SACs.

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