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Supported metal single atom catalysis is a dynamic research area in catalysis science combining the advantages of homogeneous and heterogeneous catalysis. Understanding the interactions between metal single atoms and the support constitutes a challenge facing the development of such catalysts, since these interactions are essential in optimizing the catalytic performance. For conventional carbon supports, two types of surfaces can contribute to single atom stabilization: the basal planes and the prismatic surface; both of which can be decorated by defects and surface oxygen groups. To date, most studies on carbon‐supported single atom catalysts focused on nitrogen‐doped carbons, which, unlike classic carbon materials, have a fairly well‐defined chemical environment. Herein we report the synthesis, characterization and modeling of rhodium single atom catalysts supported on carbon materials presenting distinct concentrations of surface oxygen groups and basal/prismatic surface area. The influence of these parameters on the speciation of the Rh species, their coordination and ultimately on their catalytic performance in hydrogenation and hydroformylation reactions is analyzed. The results obtained show that catalysis itself is an interesting tool for the fine characterization of these materials, for which the detection of small quantities of metal clusters remains a challenge, even when combining several cutting‐edge analytical methods. [ABSTRACT FROM AUTHOR]

Ordered porous carbon materials with regularly arranged pores and adjustable pore sizes have attracted significant attention due to their versatile applications across various fields. In this context, uniform carbon coating of anodic aluminum oxide (AAO) membranes is an effective approach to fabricating an ordered array of cylindrical carbonaceous nanopores with adjustable pore diameter and length. The resulting carbon-coated AAO (C/AAO) composite exhibits a meticulously ordered array of meso/macropores, devoid of inter-particle pores and resistance, setting it apart from conventional ordered porous carbons with powder forms. The pore dimensions of C/AAO can be precisely controlled over a wide range, and the carbon chemistry can be customized through heteroatom doping and chemical modifications, all without altering the pore structure. These inherent advantages position C/AAO as a highly promising material with broad application prospects. This review article provides a comprehensive overview of the synthesis and characterization of C/AAO and related materials, along with their diverse utilization in the fields of optics, field emission, gas sensing, energy storage, electrocatalyst support, and bionics. Furthermore, an outlook on the C/AAO materials is given at the end, highlighting their potential and associated challenges. [ABSTRACT FROM AUTHOR]

Single-atomic metal catalysts are attractive for green chemistry in terms of their outstanding catalytic performance and savings in precious metal usage owing to maximized metal utilization, including anode catalysts in polymer electrolyte fuel cells (PEFCs). Heteroatom-doped porous carbons are extensively used as supports, where the heteroatoms contribute to the immobilization of single-atomic metals. However, high-content doping of heteroatoms, especially sulphur (S), into carbon supports is still challenging because S species can be readily desorbed during heat treatment. Herein, we present a bottom-up fabrication approach for S-rich porous carbons from molecular precursors via a thermal polymerization process. A simple carbonization of molecules with thermally stable S-containing building blocks and polymerizable ethynyl moieties at 900 °C yields microporous carbon materials with record-high S content (over 15 wt%). The abundant S species function as an effective anchoring site for single-atomic platinum (Pt) species. Toward anode catalysts in PEFCs, the prepared single-atomic Pt catalysts efficiently promote the electrochemical hydrogen oxidation reaction, whose activity is comparable to that of commercial Pt/C, despite the significantly low Pt loading amount. [ABSTRACT FROM AUTHOR]

Template-assisted chemical vapor deposition (CVD) is a promising approach for fabricating nanoporous materials based on graphene walls. Among conventional metal oxide templates, CaO, produced through the thermal decomposition of CaCO3, offers improved environmental sustainability and lower production costs, thereby potentially making it a viable candidate for green template materials. Nevertheless, the underlying reaction mechanisms of the interaction on the CaO surface during the CVD process remain indeterminate, giving rise to challenges in regulating graphene formation and obtaining high-quality materials. In this work, a comprehensive experimental–theoretical investigation has unveiled the CVD mechanism on CaO. CaO exhibits efficient catalytic activity in the dissociation of CH4, thereby facilitating a thermodynamically favorable conversion of CH4 to graphene. These findings highlight the potential of using CaO as a substrate for graphene growth, combining both sustainability and cost-effectiveness. When the shell-like graphene layer deposited on CaO particles is released through the dissolution of CaO with HCl, the resulting nanoporous graphene-based materials can be readily compacted by the capillary force of the liquid upon drying. The folded surfaces, however, can become available for electric double-layer capacitance via electrochemical exfoliation under a low applied potential (<1.2 V vs. Ag/AgClO4). [ABSTRACT FROM AUTHOR]

The gelation of MXene promises to assemble a 3D conductive and catalytic monolith for various applications. However, controllable assembly and function customization are still challenging. Here, with a "killing two birds with one stone" initiator (metal halide, typically ZnI2), the controllable gelation of MXene is enabled, which produces a sulfur host that stabilizes not only the cathode but also the lithium metal anode for lithium‐sulfur batteries. Zn2+ cations trigger the gelation and act as linkers between MXene nanosheets (NSs), while the iodine anions as spacers avoid the NSs restacking, forming a monolith with a well‐tunable 3D structure. As a sulfur host, the formed 3D monolith with adsorptive Zn─O sites and highly accessible surface greatly enhances the sulfur redox kinetics, effectively suppressing the shuttling and sulfur loss. At the same time, iodine anions are released into the electrolyte as additives eliminating dead Li for the anode in cycling. Thus, the assembled battery shows high Coulombic efficiency (∼above 99%, even under high sulfur loading: 6.6 mg cm−2) and long cycling stability. Under the practical condition (E/S ratio: 5 µL mgs−1, sulfur loading: 5 mg cm−2), high capacity retention of >70% for 200 cycles is achieved. [ABSTRACT FROM AUTHOR]

Although lithium–oxygen batteries have attracted attention due to their extremely high energy densities, rational design, and critical evaluation of high‐energy‐density cathode for practical Li–O2 batteries is still urgently needed. Herein, the multiscale, angstrom‐to‐millimeter, precisely controllable synthesis of binder‐free cathodes with minimally stacked graphene free from edge sites is demonstrated. The proposed Li–O2 battery, based on a hierarchically porous cathode with a practical mass loading of >4.0 mg cm−2, simultaneously exhibits an unprecedented specific areal (>30.0 mAh cm−2), mass (>6300 mAh g−1), and volumetric (>480 mAh cm−3) capacities. The battery displays the optimal energy density of 793 Wh kg−1 critically normalized to the total mass of all active materials including electrolytes and even discharge products Li2O2. Comprehensive in situ characterizations demonstrate a unique discharge mechanism in hierarchical pores which contributes to competitive battery performance. Superior rate performance in a current density range of 0.1 to 0.8 mA cm−2 and long‐cycle stability (>260 cycles) at a current density of 0.4 mA cm−2, outperforming state‐of‐the‐art carbon cathodes. This study yields insight into next‐generation carbon cathodes, not only for use in practical Li–O2 batteries, but also in other metal–gas batteries with high energy densities. [ABSTRACT FROM AUTHOR]

This study proposes a next‐generation model membrane electrode for fundamental electrochemical research of amorphous‐based porous carbon materials. This novel electrode is fabricated by the uniform carbon coating of anodic aluminum oxide formed on an Al substrate and free from a barrier layer. The conformally carbon‐coated layer forms vertically aligned giant carbon nanotubes, and their walls comprise low‐crystalline stacked graphene sheets. The diameter and the length of the nanopores can be tuned over a broad range of between 10 to 200 nm and 2 to 90 µm, respectively. Moreover, unlike composite electrodes made from other ordered nanoporous carbons, this model electrode exhibits an absence of inter‐particle spacing and hence no contact resistance between particles. Thus, this model electrode provides representative nanopores of low‐crystalline carbon materials. An atomic‐scale structural model of the low‐crystalline carbon walls is built with the aid of an in‐house temperature‐programmed desorption system to enable theoretical simulations to be performed. Using this model electrode, the electrical conductivity of low‐crystalline carbon walls and mass transportation in an electric double‐layer system are elucidated. This representative model electrode is expected to help clarify the complex electrochemical processes in porous carbon electrodes. [ABSTRACT FROM AUTHOR]

Water‐dispersible carbon nano‐test tubes (CNTTs) with an inner and outer diameter of about 25 and 35 nm, respectively, were prepared by the template technique and then their inner carbon surface was selectively oxidized to introduce carboxy groups. The adsorption behavior of DNA molecules on the oxidized CNTTs (Ox‐CNTTs) was examined in the presence of Ca2+ cations. Many DNA molecules are attracted to the inner space of Ox‐CNTTs based on the Ca2+‐mediated electrostatic interaction between DNA phosphate groups and carboxylate anions on the inner carbon surface. Moreover, the total net charge of the DNA adsorbed was found to be equal to the total charge of the carboxylate anions. This selective adsorption into the interior of Ox‐CNTTs can be explained from the fact that the electrostatic interaction onto the inner concave surface is much stronger than that on the outer convex surface. On the other hand, the desorption of DNA easily occurs whenever Ca2+ cations are removed by washing with deionized water. Thus, each of Ox‐CNTTs works well as a nano‐container for a large amount of DNA molecules, thereby resulting in the occurrence of DNA enrichment in the nanospace. [ABSTRACT FROM AUTHOR]