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Iron single‐atom catalysts (SACs) have garnered increasing attention as highly efficient catalysts for the oxygen reduction reaction (ORR), yet their performance in practical devices remains suboptimal due to the low density of accessible active sites. Anchoring iron single atoms on 2D support is a promising way to increase the accessible active sites but remains difficult attributing to the high aggregation tendency of iron atoms on the 2D support. Herein, a vacuum vapor deposition strategy is presented to fabricate an iron SAC supported on ultrathin N‐doped carbon nanosheets with densely active sites (FeSAs‐UNCNS). Experimental analyses confirm that the FeSAs‐UNCNS achieves densely accessible active sites (1.11 × 1020 sites g−1) in the configuration of Fe─N4O. Consequently, the half‐wave potential of FeSAs‐UNCNS in 0.1 m KOH reaches a remarkable value of 0.951 V versus RHE. Moreover, when employed as the cathode of various kinds of Zn–air batteries, FeSAs‐UNCNS exhibits boosting performances by achieving a maximum power density of 306 mW cm−2 and long cycle life (>180 h) at room temperature, surpassing both Pt/C and reported SACs. Further investigations reveal that FeSAs‐UNCNS facilitates the mass and charge transfer during catalysis and the atomic configuration favors the desorption of *OH kinetically. [ABSTRACT FROM AUTHOR]

Incorporating atom‐nanocluster interactions into Fe─N─C single‐atom catalysts (Fe‐SACs) represents a viable strategy for enhancing their oxygen reduction reaction (ORR) activity, however, further investigation is necessary to elucidate the underlying mechanism. Herein, Cu nanoclusters are incorporated into Fe‐SACs to realize markedly enhanced pH‐universal ORR performance and investigate the underlying mechanism. The rate‐determining step (RDS) investigation reveals that the existence of Cu nanoclusters does not alter the RDS of Fe─N─C despite their differences in acidic, neutral, or alkaline media but instead optimizes the electronic configuration of Fe─N─C and significantly promotes the RDS. The synergistic effect between the Fe single atoms and Cu nanoclusters significantly enhances the half‐wave potential by 45, 90, and 18 mV in the HClO4, PBS, and KOH electrolytes, respectively. The catalysts further demonstrate remarkable maximum power densities of 971.4, 94.9, and 234.7 mW cm−2 in H2/O2 fuel cells, neutral Zn‐air batteries, and alkaline Zn‐air batteries, respectively. [ABSTRACT FROM AUTHOR]

Developing highly active, selective, and stable electrocatalysts for the CO2 reduction reaction (CO2RR) is essential to relieve the greenhouse effect and the energy crisis. Traditional catalytic electrodes require ionomer binders, which inevitably impose undesired high CO2 transport resistance and block the active sites. Herein, Ni single atoms anchored on nitrogen‐doped carbon nanoarrays (denoted as Ni‐SAC‐NA) were developed as the electrode without additional ionomers for efficient CO2RR. The unique nanoarray structure provided a higher specific surface area, more exposed active sites, and enhanced electron/mass transport due to its short diffusion pathway and ionomer‐free nature. As a result, the Ni‐SAC‐NA electrode exhibited enhanced activity of CO2RR and selectivity towards CO with Faradaic efficiency of 96.7%, turnover frequency of 27,504 h−1, and cathodic energy efficiencies of 54.9% at −0.88 V (vs. RHE). Our findings provide a rational design strategy for CO2RR electrocatalysts by constructing ionomer‐free electrodes. [ABSTRACT FROM AUTHOR]

Developing efficient nanozymes to mimic natural enzymes for scavenging reactive radicals remains a significant challenge owing to the insufficient activity of conventional nanozymes. Herein, we report a novel Ru single‐atom nanozyme (SAE), featuring atomically dispersed Ru atoms on a biocompatible MgAl‐layered double hydroxide (Ru1/LDH). The prepared Ru1/LDH SAE shows high intrinsic peroxidase (POD)‐like catalytic activity, which outperforms the Ru nanoclusters (NCs) nanozyme by a factor of 20 and surpasses most SAEs. The density functional theory calculations reveal that the high intrinsic POD‐like activity of Ru1/LDH can be attributed to a heterolytic path of H2O2 dissociation on the single Ru sites, which requires lower free energy (0.43 eV) compared to the homolytic path dissociation on Ru NC (0.63 eV). In addition, the Ru1/LDH SAE shows excellent multiple free radicals scavenging ability, including superoxide anion radical (O2⋅−), hydroxyl radical (⋅OH), nitric oxide radical (NO⋅) and 2, 2‐diphenyl‐1‐picrylhydrazyl radical (DPPH⋅). Given the advantages of Ru1/LDH with high enzymatic activities, biosafety, and ease to scale up, it paves the way for exploring SAEs in the practical biological immunity system. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) with rationally designed microenvironments (defined as coordination environments and electronic configurations) show superior catalytic activity, selectivity, and stability in a majority of reactions. However, the construction of isolated SACs with definite microenvironments to understand the microenvironment–activity relationship is still challenging. Herein, a facile strategy is developed to construct a series of Ru SACs with tunable geometric and electronic structures by employing NiFe‐layered double hydroxides (LDH) with different cation vacancies (MII or MIII) as supports. Detailed spectroscopic characterizations and theoretical calculations reveal that the Ru‐O coordination environments and electronic configurations of single‐atomic Ru can be easily tailored by the vacancy regulation. As a result, isolated Ru atoms anchored by MIII vacancies (denoted as Ru1/LDH‐VIII) with Ru‐O‐Ni coordination environments facilitate the desorption of benzaldehyde, thus leading to higher efficiency of benzyl alcohol oxidation with a superior turnover frequency of 1331 h−1. [ABSTRACT FROM AUTHOR]

The development of inexpensive and highly efficient nonprecious metal catalysts to substitute Pt in the alkaline oxygen reduction reaction is an appealing idea in the energy field. Herein, a Mn oxygen reduction electrocatalyst with a half‐wave potential (E1/2) as high as 0.910 V under an alkaline oxygen reduction reaction process is developed, and the dynamic atomic structure change of the highly efficient Mn single‐atomic site is investigated using operando X‐ray absorption spectroscopy. These results demonstrate that the low‐valence MnL+N4 is the active site during the oxygen reduction process. Density functional theory reveals that facile electron transfer from MnL+N4 to adsorbed *OH species plays a key role in the excellent electrocatalytic performance. Moreover, when assembled as the cathode in a zinc–air battery, this MnN4 material shows high power density and excellent durability, demonstrating its promising potential to substitute the Pt catalyst in practical devices. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) show great promise for electrochemical CO2 reduction reaction (CRR), but the low density of active sites and the poor electrical conduction and mass transport of the single‐atom electrode greatly limit their performance. Herein, we prepared a nickel single‐atom electrode consisting of isolated, high‐density and low‐valent nickel(I) sites anchored on a self‐standing N‐doped carbon nanotube array with nickel–copper alloy encapsulation on a carbon‐fiber paper. The combination of single‐atom nickel(I) sites and self‐standing array structure gives rise to an excellent electrocatalytic CO2 reduction performance. The introduction of copper tunes the d‐band electron configuration and enhances the adsorption of hydrogen, which impedes the hydrogen evolution reaction. The single‐nickel‐atom electrode exhibits a specific current density of −32.87 mA cm−2 and turnover frequency of 1962 h−1 at a mild overpotential of 620 mV for CO formation with 97 % Faradic efficiency. [ABSTRACT FROM AUTHOR]

Surface modification with a photosensitizer is an efficient way to improve visible light activity of wide band gap semiconductors, but is rarely applied in photocatalytic organic synthesis. Herein, we report that 2‐aminoterephthalic acid (ATA) sensitized {110}‐facetted BiOCl nanosheets, prepared by a solvothermal method, exhibit outstanding photocatalytic activity for the selective oxidative coupling of benzylamine to N‐benzylidenebenzylamine under visible light. UV‐vis diffuse reflectance spectra confirmed that the introduction of ATA extends the light absorption of wide band gap BiOCl into the visible light region. Characterization by HRTEM and SAED indicated that the samples were predominantly terminated by {110} facets. BiOCl incorporating 0.18 % ATA exhibited superior activity for the photocatalytic oxidation of benzylamine under visible light, with 100 % conversion and 100 % selectivity towards N‐benzylidenebenzylamine. The catalyst exhibited excellent recyclability and works well with other substituted benzylamines, suggesting its robust and universal nature. This work provides an example for the application of a low‐cost and highly efficient visible‐light‐responsive photocatalyst in organic synthesis. [ABSTRACT FROM AUTHOR]

Abstract: Developing an efficient single‐atom material (SAM) synthesis and exploring the energy‐related catalytic reaction are important but still challenging. A polymerization–pyrolysis–evaporation (PPE) strategy was developed to synthesize N‐doped porous carbon (NPC) with anchored atomically dispersed Fe‐N4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe‐N4 site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn–air battery devices containing the Fe‐N4 SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application. [ABSTRACT FROM AUTHOR]

An extensive array of 4 H-pyrido[1,2- a]pyrimidin-4-ones have been synthesized from commercially available 2-aminopyridines and β-oxo esters with excellent yields under solvent-free conditions. The reaction, catalyzed by cheap and nontoxic BiCl3, proceeds with short reaction times under mild conditions and normal atmosphere. Only water and alcohol are formed as co-products in this green reaction. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts have drawn considerable attention because of their unique catalytic properties. However, the high surface energy of single atoms restricts their fabrication and creates significant challenges for further developments. In order to overcome this problem, metal organic framework (MOF)‐derived carbon materials can be served as ideal supports to anchor atomically dispersed metal atoms, due to their tunable particle size and shape features, by providing high surface area, porosity, thermal, and chemical stability. This review highlights the recent advances in i) different types of construction strategies for MOF‐derived carbon‐supported single‐atom catalysts, and ii) the catalytic applications of these MOF‐derived carbon‐supported single‐atom catalysts. Further, this review offers a valuable insight into the current challenges and future opportunities for MOF‐derived carbon‐supported single‐atom catalysts. [ABSTRACT FROM AUTHOR]