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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 × 10 20  sites g -1 ) in the configuration of Fe─N 4 O. 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., (© 2023 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Modulating the electronic metal-support interaction (EMSI) of the single-atomic sites against leaching via microenvironment regulation is critical to achieving high activity and stability but remains challenging. Herein, this work selectively confines Pt single atoms on CoFe layered double hydroxide (LDH) by three oxygen atoms around cation vacancy (Pt 1 /LDH V ) or one oxygen atom at the regular surface (Pt 1 /LDH) via cation vacancy engineering. By characterizing the structural evolution of the obtained catalysts before and after vacancy construction and single-atom anchoring, this work demonstrates how the microenvironments modulate the EMSI and the catalytic performance. Theoretical simulations further reveal a significantly enhanced EMSI effect by the three-coordinated Pt 1 atoms on cation vacancies in Pt 1 /LDH V , which endows a more prominent anti-leaching feature than the one-coordinated ones on the regular surface. As a result, the Pt 1 /LDH V catalyst shows exceptional performance in anti-Markovnikov alkene hydrosilylation, with a turnover frequency of 1.3 × 10 5 h -1 . More importantly, the enhanced EMSI of Pt 1 /LDH V effectively prevented the leaching of Pt atom from the catalyst surface and can be recycled at least ten times with only a 3.4% loss of catalytic efficiency with minimal Pt leaching, and reach a high turnover number of 1.0 × 10 6 ., (© 2023 Wiley-VCH GmbH.)

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 (Ru 1 /LDH). The prepared Ru 1 /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 Ru 1 /LDH can be attributed to a heterolytic path of H 2 O 2 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 Ru 1 /LDH SAE shows excellent multiple free radicals scavenging ability, including superoxide anion radical (O 2 ⋅ - ), hydroxyl radical (⋅OH), nitric oxide radical (NO⋅) and 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH⋅). Given the advantages of Ru 1 /LDH with high enzymatic activities, biosafety, and ease to scale up, it paves the way for exploring SAEs in the practical biological immunity system., (© 2023 Wiley-VCH GmbH.)

Single-atom catalysts (SACs) show great promise for electrochemical CO 2 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 CO 2 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., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Strain regulation has become an important strategy to tune the surface chemistry and optimize the catalytic performance of nanocatalysts. Herein, the construction of atomic-layer IrO x on IrCo nanodendrites with tunable IrO bond length by compressive strain effect for oxygen evolution reaction (OER) in acidic environment is demonstrated. Evidenced from in situ extended X-ray absorption fine structure, it is shown that the compressive strain of the IrO x layer on the IrCo nanodendrites decreases gradually from 2.51% to the unstrained state with atomic layer growth (from ≈2 to ≈9 atomic layers of IrO x ), resulting in the variation of the IrO bond length from shortened 1.94 Å to normal 1.99 Å. The ≈3 atomic-layer IrO x on IrCo nanodendrites with an IrO bond length of 1.96 Å (1.51% strain) exhibits the optimal OER activity compared to the higher-strained (2.51%, ≈2 atomic-layer IrO x ) and unstrained (>6 atomic-layer IrO x ) counterparts, with an overpotential of only 247 mV to achieve a current density of 10 mA cm -2 . Density functional theory calculations reveal that the precisely tuned compressive strain effect balances the adsorbate-substrate interaction and facilitates the rate-determining step to form HOO*, thus assuring the best performance of the three atomic-layer IrO x for OER., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Structure engineering of ultrathin metal-organic framework (MOF) nanosheets to self-supporting and well-aligned MOF superstructures is highly desired for diverse applications, especially important for electrocatalysis. In this work, a facile layered double hydroxides in situ transformation strategy is developed to synthesize ultrathin bimetal-MOF nanosheets (BMNSs) arrays on conductive substrates. This approach is versatile, and applicable to obtain various BMNSs or even trimetal-MOF nanosheets arrays on different substrates. As a proof of concept application, the obtained ultrathin NiCo-BDC BMNSs array exhibits an excellent catalytic activity toward the oxygen evolution reaction with an overpotential of only 230 mV to reach a current density of 10 mA cm -2 in 1 m KOH. The present work demonstrates a strategy to prepare ultrathin bimetal-MOF nanosheets arrays, which might open an avenue for various promising applications of MOF materials., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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-N 4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe-N 4 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-N 4 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., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel polymer encapsulation strategy to synthesize metal isolated-single-atomic-site (ISAS) catalysts supported by porous nitrogen-doped carbon nanospheres is reported. First, metal precursors are encapsulated in situ by polymers through polymerization; then, metal ISASs are created within the polymer-derived p-CN nanospheres by controlled pyrolysis at high temperature (200-900 °C). Transmission electron microscopy and N 2 sorption results reveal this material to exhibit a nanospheric morphology, a high surface area (≈380 m 2 g -1 ), and a porous structure (with micropores and mesopores). Characterization by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure confirms the metal to be present as metal ISASs. This methodology is applicable to both noble and nonprecious metals (M-ISAS/p-CN, M = Co, Ni, Cu, Mn, Pd, etc.). In particular, the Co-ISAS/p-CN nanospheres obtained using this method show comparable (E 1/2 = 0.838 V) electrochemical oxygen reduction activity to commercial Pt/C with 20 wt% Pt loading (E 1/2 = 0.834 V) in alkaline media, superior methanol tolerance, and outstanding stability, even after 5000 cycles., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)