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Carbon-supported nanocomposites are attracting particular attention as high-performance, low-cost electrocatalysts for electrochemical water splitting. These are mostly prepared by pyrolysis and hydrothermal procedures that are time-consuming (from hours to days) and typically difficult to produce a nonequilibrium phase. Herein, for the first time ever, we exploit magnetic induction heating-quenching for ultrafast production of carbon-FeNi spinel oxide nanocomposites (within seconds), which exhibit an unprecedentedly high performance towards oxygen evolution reaction (OER), with an ultralow overpotential of only +260 mV to reach the high current density of 100 mA cm-2. Experimental and theoretical studies show that the rapid heating and quenching process (ca. 103 K s-1) impedes the Ni and Fe phase segregation and produces a Cl-rich surface, both contributing to the remarkable catalytic activity. Results from this study highlight the unique advantage of ultrafast heating/quenching in the structural engineering of functional nanocomposites to achieve high electrocatalytic performance towards important electrochemical reactions.

Oxygen reduction reaction (ORR) plays an important role in dictating the performance of various electrochemical energy technologies. As platinum nanoparticles have served as the catalysts of choice towards ORR, minimizing the cost of the catalysts by diminishing the platinum nanoparticle size has become a critical route to advancing the technological development. Herein, first-principle calculations show that carbon-supported Pt9 clusters represent the threshold domain size, and the ORR activity can be significantly improved by doping of adjacent cobalt atoms. This is confirmed experimentally, where platinum and cobalt are dispersed in nitrogen-doped carbon nanowires in varied forms, single atoms, few-atom clusters, and nanoparticles, depending on the initial feeds. The sample consisting primarily of Pt2~7 clusters doped with atomic Co species exhibits the best mass activity among the series, with a current density of 4.16 A mgPt -1 at +0.85 V vs. RHE that is almost 50 times higher than that of commercial Pt/C.

Hydrogen evolution reaction is an important process in electrochemical energy technologies. Herein, ruthenium and nitrogen codoped carbon nanowires are prepared as effective hydrogen evolution catalysts. The catalytic performance is markedly better than that of commercial platinum catalyst, with an overpotential of only -12 mV to reach the current density of 10 mV cm-2 in 1 M KOH and -47 mV in 0.1 M KOH. Comparisons with control experiments suggest that the remarkable activity is mainly ascribed to individual ruthenium atoms embedded within the carbon matrix, with minimal contributions from ruthenium nanoparticles. Consistent results are obtained in first-principles calculations, where RuCxNy moieties are found to show a much lower hydrogen binding energy than ruthenium nanoparticles, and a lower kinetic barrier for water dissociation than platinum. Among these, RuC2N2 stands out as the most active catalytic center, where both ruthenium and adjacent carbon atoms are the possible active sites.

Rational design of single-metal atom sites in carbon substrates by a flexible strategy is highly desired for the preparation of high-performance catalysts for metal-air batteries. In this study, biomass hydrogel reactors are utilized as structural templates to prepare carbon aerogels embedded with single iron atoms by controlled pyrolysis. The tortuous and interlaced hydrogel chains lead to the formation of abundant nanowrinkles in the porous carbon aerogels, and single iron atoms are dispersed and stabilized within the defective carbon skeletons. X-ray absorption spectroscopy measurements indicate that the iron centers are mostly involved in the coordination structure of FeN4, with a minor fraction (ca. 1/5) in the form of FeN3C. First-principles calculations show that the FeN x sites in the Stone-Wales configurations induced by the nanowrinkles of the hierarchically porous carbon aerogels show a much lower free energy than the normal counterparts. The resulting iron and nitrogen-codoped carbon aerogels exhibit excellent and reversible oxygen electrocatalytic activity, and can be used as bifunctional cathode catalysts in rechargeable Zn-air batteries, with a performance even better than that based on commercial Pt/C and RuO2 catalysts. Results from this study highlight the significance of structural distortions of the metal sites in carbon matrices in the design and engineering of highly active single-atom catalysts.

Rational design of single-metal atom sites in carbon substrates by a flexible strategy is highly desired for the preparation of high-performance catalysts for metal-air batteries. In this study, biomass hydrogel reactors are utilized as structural templates to prepare carbon aerogels embedded with single iron atoms by controlled pyrolysis. The tortuous and interlaced hydrogel chains lead to the formation of abundant nanowrinkles in the porous carbon aerogels, and single iron atoms are dispersed and stabilized within the defective carbon skeletons. X-ray absorption spectroscopy measurements indicate that the iron centers are mostly involved in the coordination structure of FeN4, with a minor fraction (ca. 1/5) in the form of FeN3C. First-principles calculations show that the FeN x sites in the Stone-Wales configurations induced by the nanowrinkles of the hierarchically porous carbon aerogels show a much lower free energy than the normal counterparts. The resulting iron and nitrogen-codoped carbon aerogels exhibit excellent and reversible oxygen electrocatalytic activity, and can be used as bifunctional cathode catalysts in rechargeable Zn-air batteries, with a performance even better than that based on commercial Pt/C and RuO2 catalysts. Results from this study highlight the significance of structural distortions of the metal sites in carbon matrices in the design and engineering of highly active single-atom catalysts.

Limited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single‐side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti2C3Tx MXene quantum dots (MQDs) and α‐Fe2O3 nanodots (FO) are anchored on the surface of ZnIn2S4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as "electron extractor" and S−O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high‐performance composite electrodes. [ABSTRACT FROM AUTHOR]

Iron, nitrogen‐codoped carbon (Fe−N−C) nanocomposites have emerged as viable electrocatalysts for the oxygen reduction reaction (ORR) due to the formation of FeNxCy coordination moieties. In this study, results from first‐principles calculations show a nearly linear correlation of the energy barriers of key reaction steps with the Fe magnetic moment. Experimentally, when single Cu sites are incorporated into Fe−N−C aerogels (denoted as NCAG/Fe−Cu), the Fe centers exhibit a reduced magnetic moment and markedly enhanced ORR activity within a wide pH range of 0–14. With the NCAG/Fe−Cu nanocomposites used as the cathode catalyst in a neutral/quasi‐solid aluminum–air and alkaline/quasi‐solid zinc–air battery, both achieve a remarkable performance with an ultrahigh open‐circuit voltage of 2.00 and 1.51 V, large power density of 130 and 186 mW cm−2, and good mechanical flexibility, all markedly better than those with commercial Pt/C or Pt/C‐RuO2 catalysts at the cathode. [ABSTRACT FROM AUTHOR]

Heteroatom‐doped carbon materials are promising electrocatalysts towards the oxygen reduction reaction (ORR). In this study, dual metals (Fe an Co) and nitrogen‐codoped porous carbon cages (CHS−FeCo) were synthesized by controlled pyrolysis of silica nanoparticle‐supported melamine‐formaldehyde resin embedded with iron and cobalt precursors, followed by acid etching. Transmission electron microscopy measurements confirmed the formation of hollow carbon cages, and the absence of metal (oxide) nanoparticles suggested atomic dispersion of the metal species within the mesoporous carbon skeletons. X‐ray photoelectron spectroscopic analysis revealed a composition of mostly carbon, oxygen, and nitrogen, with ca. 1 % metals. Electrochemically, the dual‐metal ones showed a significant enhancement of the catalytic performance towards ORR in alkaline media, as compared to samples with single or no metal dopants. This was accounted for by the synergistic interaction between the Fe and Co centers in the carbon samples, as evidenced in X‐ray absorption spectroscopic studies. Remarkably, the CHS−FeCo sample exhibited apparent resistance against KSCN poisoning, where XPS analysis revealed oxidation of KSCN and no metal‐sulfur interaction, in sharp contrast to the Fe counterpart which was easily poisoned. Results from this study suggest that the synergistic interactions between dual metal centers may be exploited for enhanced ORR performance of carbon‐based nanocomposite catalysts. [ABSTRACT FROM AUTHOR]

Surface recombination at the photoanode/electrolyte junction seriously impedes photoelectrochemical (PEC) performance. Through coating of photoanodes with oxygen evolution catalysts, the photocurrent can be enhanced; however, current systems for water splitting still suffer from high recombination. We describe herein a novel charge transfer system designed with BiVO4 as a prototype. In this system, porphyrins act as an interfacial‐charge‐transfer mediator, like a volleyball setter, to efficiently suppress surface recombination through higher hole‐transfer kinetics rather than as a traditional photosensitizer. Furthermore, we found that the introduction of a "setter" can ensure a long lifetime of charge carriers at the photoanode/electrolyte interface. This simple interface charge‐modulation system exhibits increased photocurrent density from 0.68 to 4.75 mA cm−2 and provides a promising design strategy for efficient photogenerated charge separation to improve PEC performance. [ABSTRACT FROM AUTHOR]

The development of cost-effective, high-performance electrocatalysts for hydrogen evolution reaction (HER) is urgently needed. In the present study, a new type of HER catalyst was developed where ruthenium ions were embedded into the molecular skeletons of graphitic carbon nitride (C3N4) nanosheets of 2.0 ± 0.4 nm in thickness by refluxing C3N4 and RuCl3 in water. This took advantage of the strong affinity of ruthenium ions to pyridinic nitrogen of the tri-s-triazine units of C3N4. The formation of C3N4–Ru nanocomposites was confirmed by optical and X-ray photoelectron spectroscopic measurements, which suggested charge transfer from the C3N4 scaffold to the ruthenium centers. Significantly, the hybrid materials were readily dispersible in water and exhibited apparent electrocatalytic activity towards HER in acid and their activity increased with the loading of ruthenium metal centers in the C3N4 matrix. Within the present experimental context, the sample saturated with ruthenium ion complexation at a ruthenium to pyridinic nitrogen atomic ratio of ca. 1 : 2 displayed the best performance, with an overpotential of only 140 mV to achieve the current density of 10 mA cm−2, a low Tafel slope of 57 mV dec−1, and a large exchange current density of 0.072 mA cm−2. The activity was markedly lower when C3N4 was embedded with other metal ions such as Fe3+, Co3+, Ni3+ and Cu2+. This suggests minimal contributions from the C3N4 nanosheets to the HER activity, and the activity was most likely due to the formation of Ru–N moieties where the synergistic interactions between the carbon nitride and ruthenium metal centers facilitated the adsorption of hydrogen. This was strongly supported by results from density functional theory calculations. [ABSTRACT FROM AUTHOR]

Nanocomposites based on palladium nanoparticles deposited onto TiO2 nanobelts were prepared by chemical reduction of Pd(II) precursors and the catalytic activity towards ethanol oxidation reaction (EOR) was examined and compared within the context of TiO2 oxygen vacancies formed by thermal annealing at controlled temperatures (400-600 °C) in a hydrogen atmosphere. Transmission electron microscopic measurements showed that the Pd nanoparticles (about 5 nm in diameter) were clustered somewhat on the surfaces of hydrogen-treated TiO2 nanobelts (Pd/hTiO2), but distributed rather evenly on the untreated ones (Pd/TiO2). X-ray photoelectron spectroscopic studies suggested electron transfer from Ti to Pd in the Pd/hTiO2 samples, as compared to untreated Pd/TiO2, due to the formation of oxygen vacancies in TiO2 nanobelts where the concentration increased with increasing thermal annealing temperature, as evidenced in electron paramagnetic resonance measurements. Significantly, electrochemical measurements showed markedly enhanced EOR activity of both Pd/TiO2 and Pd/hTiO2 in alkaline media, as compared to commercial Pd/C, and the activity increased drastically with the concentration of oxygen vacancies, most likely because oxygen vacancies facilitated the formation of hydroxyl species on the TiO2 surface that played a critical role in the oxidation of ethanol to acetate. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane fuel cells represent a next-generation power supply technology that may be used in a diverse range of applications. Towards this end, the rational design and engineering of functional nanomaterials as low-cost, high-performance catalysts is of critical significance in the wide-spread commercialization of fuel cell technology. One major bottleneck is the oxygen reduction reaction (ORR) at the cathode. Whereas platinum-based nanoparticles have been used as the catalysts of choice, further engineering of the nanoparticles is urgently needed to enhance the catalytic performance and concurrently reduce the costs. Extensive research has also been extended to non-platinum metals or even metal-free nanocatalysts that may be viable alternatives to platinum. In this review article, we will summarize recent progress in these areas of research within the context of interfacial electron transfer: (a) interactions between metal elements in alloy nanoparticles, (b) metal–ligand interfacial bonding interactions, (c) metal–carbon substrate interactions, and (d) heteroatom doping of graphitic carbons. Results have shown that ready manipulation of the electronic interactions between the catalyst surface and oxygen species may serve as a fundamental mechanism for the optimization of the catalytic performance. [ABSTRACT FROM AUTHOR]

Graphene oxides with different surface charges were fabricated from carboxylated graphene oxide by chemical modification with amino- (–NH2), poly-m-aminobenzene sulfonic acid- (–NH2/–SO3H), or methoxyl- (–OCH3) terminated functional groups. The chemically functionalized graphene oxides and the carboxylated graphene oxide were characterized by infrared spectroscopy, X-ray photoelectron spectroscopy, UV-Vis spectrometry, ζ potential measurements, field emission scanning electron microscopy, and contact angle analyses. Subsequently, the resulting graphene oxides were used as substrates for culturing primary rat hippocampal neurons to investigate neurite outgrowth and branching. The morphological features of neurons that directly reflect their potential capability in synaptic transmission were characterized. The results demonstrate that the chemical properties of graphene oxide can be systematically modified by attaching different functional groups that confer known characteristics to the substrate. By manipulating the charge carried by the functionalized graphene oxides, the outgrowth and branching of neuronal processes can be controlled. Compared with neutral, zwitterionic, or negatively charged graphene oxides, positively charged graphene oxide was found to be more beneficial for neurite outgrowth and branching. The ability to chemically modify graphene oxide to control neurite outgrowth could be implemented clinically, especially in cases wherein long-term presence of outgrowth modulation is necessary. [ABSTRACT FROM AUTHOR]

The supramolecular interaction between the host molecule β-cyclodextrin (β-CD) and the guest molecule adamantane is extensively applied in several disciplines. However, recent studies on the applications of this molecular recognition mainly focused on glass, silicon, and gold substrates. Few studies have explored the field of poly(dimethylsiloxane) (PDMS), an optically transparent elastomer widely used in biological microfluidic devices. In the present study, various functional group-modified adamantyl-terminated dendronized molecules were synthesized via an efficient and facile route. The binding of adamantyl-terminated dendronized molecules onto β-CD-conjugated PDMS surfaces and their reversible dissociation from PDMS surfaces through the competitive mechanism of β-CD-N3 were studied. The results showed that the dissociation is relatively slow compared with the binding, and the former process can be accelerated through exchanging the original β-CD-N3 solution with a fresh one. Afterward, more complex multilayer assemblies were constructed on PDMS surfaces using the host–guest interaction between adamantane and β-CD as well as between biotin and streptavidin. A further study on the association and dissociation of the established multilayer assemblies showed that the assembly constructed with a biotinylated monoadamantyl-terminated molecule has a reversible property, whereas that with a biotinylated triadamantyl-terminated molecule has an irreversible property. These results demonstrated that the reversible properties of the fabricated assembly can be easily modulated on the PDMS surfaces by regulating the valence of the supramolecular interaction between adamantane and β-CD. [ABSTRACT FROM AUTHOR]

Correction for ‘Hydrogen evolution reaction catalyzed by ruthenium ion-complexed graphitic carbon nitride nanosheets’ by Yi Peng et al., J. Mater. Chem. A, 2017, DOI: 10.1039/c7ta03826g. [ABSTRACT FROM AUTHOR]

Perovskite oxynitrides, in addition to being promising electrocatalysts and photoabsorbers, present an interesting case study in crystal symmetry. Full or partial ordering of the O and N anions affects global symmetry and influences material performance and functionality; however, anion ordering is challenging to detect experimentally. In this work, we synthesize a novel perovskite oxynitride CaW(O,N) 3 and characterize its crystal structure using both X-ray and neutron diffraction. Through co-refinement of the diffraction patterns with a range of literature and theory-derived model structures, we demonstrate that CaW(O,N) 3 adopts an orthorhombic Pnma average structure and exhibits octahedral distortion with evidence for preferred anion site occupancy. However, through comparison with a large, low-symmetry unit cell, we identify the presence of disorder that is not fully accounted for by the high-symmetry model. We compare CaW(O,N) 3 with SrW(O,N) 3 to demonstrate the broader presence of such disorder and identify contrasting features in the electronic structures. This work signifies an updated perspective on the inherent crystal symmetry present in perovskite oxynitrides.

For conventional potential-resolved ratiometric electrochemiluminescence (ECL) systems, the introduction of multiplex coreactants is imperative. However, the undesirable interactions between different coreactants inevitably affect analytical accuracy and sensitivity. Herein, through the coordination of aggregation-induced emission ligands with gadolinium cations, the self-luminescent metal-organic framework (Gd-MOF) is prepared and serves as a novel coreactant-free anodic ECL emitter. By the intercalation of [Ru(bpy) 2 dppz] 2+ with light switch effect into DNA duplex, one high-efficiency cathodic ECL probe is obtained using K 2 S 2 O 8 as a coreactant. In the presence of acetamiprid, the strong affinity between the target and its aptamer induces the release of [Ru(bpy) 2 dppz] 2+ , resulting in a decreasing cathode signal and an increasing anode signal owing to the ECL resonance energy transfer from Gd-MOF to [Ru(bpy) 2 dppz] 2+ . In this way, an efficient dual-signal ECL aptasensor is constructed for the ratiometric analysis of acetamiprid, exhibiting a remarkably low detection limit of 0.033 pM. Strikingly, by using only one exogenous coreactant, the cross interference from multiple coreactants can be eliminated, thus improving the detection accuracy. The developed high-performance ECL sensing platform is successfully applied to monitor the residual level of acetamiprid in real samples, demonstrating its potential application in the field of food security.

Limited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single-side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti 2 C 3 T x MXene quantum dots (MQDs) and α-Fe 2 O 3 nanodots (FO) are anchored on the surface of ZnIn 2 S 4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as "electron extractor" and S-O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high-performance composite electrodes., (© 2023 Wiley-VCH GmbH.)

BiVO 4 is a promising photoanode for photoelectrochemical (PEC) water splitting but suffers from high charge carrier recombination and sluggish surface water oxidation kinetics that limit its efficiency. In this work, a model of sulfur-incorporated FeOOH cocatalyst-loaded BiVO 4 was constructed. The composite photoanode (BiVO 4 /S-FeOOH) demonstrates an enhanced photocurrent density of 3.58 mA cm -2 , which is 3.7 times higher than that of the pristine BiVO 4 photoanode. However, the current explanations for the generation of enhanced photocurrent signals through the incorporation of elements and cocatalyst loading remain unclear and require further in-depth research. In this work, the hole transfer kinetics were investigated by using a scanning photoelectrochemical microscope (SPECM). The results suggest that the incorporation of sulfur can effectively improve the charge transfer capacity of FeOOH. Moreover, the oxygen evolution reaction model provides evidence that S-doping can induce a "fast" surface catalytic reaction at the cocatalyst/solution interface. The work not only presents a promising approach for designing a highly efficient photoanode but also offers valuable insights into the role of element doping in the PEC water-splitting system.

Iron, nitrogen-codoped carbon (Fe-N-C) nanocomposites have emerged as viable electrocatalysts for the oxygen reduction reaction (ORR) due to the formation of FeN x C y coordination moieties. In this study, results from first-principles calculations show a nearly linear correlation of the energy barriers of key reaction steps with the Fe magnetic moment. Experimentally, when single Cu sites are incorporated into Fe-N-C aerogels (denoted as NCAG/Fe-Cu), the Fe centers exhibit a reduced magnetic moment and markedly enhanced ORR activity within a wide pH range of 0-14. With the NCAG/Fe-Cu nanocomposites used as the cathode catalyst in a neutral/quasi-solid aluminum-air and alkaline/quasi-solid zinc-air battery, both achieve a remarkable performance with an ultrahigh open-circuit voltage of 2.00 and 1.51 V, large power density of 130 and 186 mW cm -2 , and good mechanical flexibility, all markedly better than those with commercial Pt/C or Pt/C-RuO 2 catalysts at the cathode., (© 2022 Wiley-VCH GmbH.)

Carbon-supported nanocomposites are attracting particular attention as high-performance, low-cost electrocatalysts for electrochemical water splitting. These are mostly prepared by pyrolysis and hydrothermal procedures that are time-consuming (from hours to days) and typically difficult to produce a nonequilibrium phase. Herein, for the first time ever, we exploit magnetic induction heating-quenching for ultrafast production of carbon-FeNi spinel oxide nanocomposites (within seconds), which exhibit an unprecedentedly high performance towards oxygen evolution reaction (OER), with an ultralow overpotential of only +260 mV to reach the high current density of 100 mA cm -2 . Experimental and theoretical studies show that the rapid heating and quenching process (ca. 10 3 K s -1 ) impedes the Ni and Fe phase segregation and produces a Cl-rich surface, both contributing to the remarkable catalytic activity. Results from this study highlight the unique advantage of ultrafast heating/quenching in the structural engineering of functional nanocomposites to achieve high electrocatalytic performance towards important electrochemical reactions., Competing Interests: The authors declare that there is no conflict of interest regarding the publication of this article., (Copyright © 2022 Bingzhang Lu et al.)

Oxygen reduction reaction (ORR) plays an important role in dictating the performance of various electrochemical energy technologies. As platinum nanoparticles have served as the catalysts of choice towards ORR, minimizing the cost of the catalysts by diminishing the platinum nanoparticle size has become a critical route to advancing the technological development. Herein, first-principle calculations show that carbon-supported Pt 9 clusters represent the threshold domain size, and the ORR activity can be significantly improved by doping of adjacent cobalt atoms. This is confirmed experimentally, where platinum and cobalt are dispersed in nitrogen-doped carbon nanowires in varied forms, single atoms, few-atom clusters, and nanoparticles, depending on the initial feeds. The sample consisting primarily of Pt 2~7 clusters doped with atomic Co species exhibits the best mass activity among the series, with a current density of 4.16 A mg Pt -1 at +0.85 V vs. RHE that is almost 50 times higher than that of commercial Pt/C., Competing Interests: The authors declare that there is no conflict of interest regarding the publication of this article., (Copyright © 2020 Bingzhang Lu et al.)

Rational design of single-metal atom sites in carbon substrates by a flexible strategy is highly desired for the preparation of high-performance catalysts for metal-air batteries. In this study, biomass hydrogel reactors are utilized as structural templates to prepare carbon aerogels embedded with single iron atoms by controlled pyrolysis. The tortuous and interlaced hydrogel chains lead to the formation of abundant nanowrinkles in the porous carbon aerogels, and single iron atoms are dispersed and stabilized within the defective carbon skeletons. X-ray absorption spectroscopy measurements indicate that the iron centers are mostly involved in the coordination structure of FeN 4 , with a minor fraction (ca. 1/5) in the form of FeN 3 C. First-principles calculations show that the FeN x sites in the Stone-Wales configurations induced by the nanowrinkles of the hierarchically porous carbon aerogels show a much lower free energy than the normal counterparts. The resulting iron and nitrogen-codoped carbon aerogels exhibit excellent and reversible oxygen electrocatalytic activity, and can be used as bifunctional cathode catalysts in rechargeable Zn-air batteries, with a performance even better than that based on commercial Pt/C and RuO 2 catalysts. Results from this study highlight the significance of structural distortions of the metal sites in carbon matrices in the design and engineering of highly active single-atom catalysts., Competing Interests: The authors declare no competing financial interests., (Copyright © 2019 Ting He et al.)