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We report the first all-alkynyl-protected Au2Ag8Cu5 cluster, which adopts a M@M8@M6 core configuration similar with Au7Ag8/Ag9Cu6 clusters. The three clusters exhibited strong metal core effect toward CO2RR, which was understood by DFT calculations.

The rate performance of Li-S batteries still remains poor due to the limited redox kinetics of polysulfides (PSs). Herein, by selectively coating a set of 2-demensional (2D) organic molecules, chenodeoxycholic acid (CA), 4,4′,4′′,4′′′-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TTBA), berberine chloride hydrate (BCH) and poly(diallyl dimethyl ammonium chloride) (PDDA) on honey comb-like porous carbon (HC) interlayers, respectively, the redox kinetics of PSs are remarkably enhanced in the interspace between the 2D molecules and carbon matrix, in the order of CA

Hot carriers generated by localized surface plasmon resonance (LSPR) excitation of plasmonic metal nanoparticles are known to enhance electrocatalytic reactions. However, the participation of plasmonically generated carriers in interfacial electrochemical reactions is often limited by fast relaxation of these carriers. Herein, we address this challenge by tuning the electronic structure of a plasmonic electrocatalyst. Specifically, we design an electrocatalyst for alkaline hydrogen evolution reaction (HER) that consists of nanoparticles of a ternary Cu-Pt-Ni ternary alloy. The CuPt alloy has both plasmonic attributes and electrocatalytic HER activity. Ni doping contributes an electron-deficient 3d band and fully filled 4s band, which promotes water adsorption and prolongs the lifetimes of excited carriers generated by plasmonic excitation. As an outcome, the Cu-Pt-Ni nanoparticles exhibit boosted activity for electrochemical water dissociation and HER under LSPR excitation.

High entropy alloy (HEA) catalysts exhibit excellent multifunctional catalytic performance due to the synergistic effect of multi-metal components. However, shape-controlled synthesis of such kinds of HEA catalysts, especially those with high index facets, still faces great challenges, limiting further enhancement of their catalytic performance. Herein, one-pot synthesis of convex cube-shaped Pt

Design and engineering of low-cost, high-performance catalysts is a critical step in electrochemical CO2 reduction (CO2R) to value-added chemicals and fuels. Herein, SnO2 nanoparticles were grown onto carbon cloth (SnO2/CF) by a facile hydrothermal procedure and exhibited excellent electrocatalytic activity towards CO2R due to reconstruction into SnO2/Sn Mott-Schottky heterojunctions during CO2R electrolysis, as manifested in X-ray diffraction, X-ray photoelectron spectroscopy, and operando Raman spectroscopy measurements. The heterostructured SnO2/Sn electrode delivered a high faradaic efficiency of 93 ± 1% and a partial current density of 28.7 mA cm−2 for formate production at − 1.0 V vs. reversible hydrogen electrode in an H-type cell (which remained stable for 9 h), and 174.86 mA cm−2 at − 1.18 V on a gas-diffusion electrode in a flow cell. Density functional theory calculations show that the SnO2/Sn heterostructures in situ formed under CO2R conditions helped decrease the energy barrier to form formate as compared to pristine SnO2 and Sn, and were responsible for the high activity and selectivity of formate production. Results from this study unravels the evolution dynamics of SnO2 catalysts under CO2R condition and provides a further understanding of the active component of SnO2 catalyst in CO2R.

Transition metal phosphides (TMPs) are promising anode candidates for sodium-ion batteries, due to their high theoretical specific capacity and working potential. However, the low conductivity and excessive volume variation of TMPs during insertion/extraction of sodium ions results in a poor rate performance and long-term cycling stability, largely limiting their practical application. In this paper, the NiP 2 nanoparticles encapsulated in three-dimensional graphene (NiP 2 @rGO) were obtained from the flower-like sphericalα-Ni(OH) 2 by phosphating and carbon encapsulation processes. When used as a sodium-ion batteries anode material, NiP 2 @rGO composite shows excellent cycling performance (117 mA h g -1 at 10 A g -1 after 8000 cycles). The outstanding electrochemical performance of NiP 2 @rGO is ascribed to the synergistic effect of the rGO and NiP 2 core. The rGO wrapped on the NiP 2 nanoparticles build a conductive way, improving ionic and electronic conductivity. The effective combination of NiP 2 nanoparticles with graphene greatly reduces the NiP 2 nanoparticles aggregation and pulverization during the discharge/charge process. This paper may shed light on the construct of high-performance anode material for sodium ion batteries and to other electrode materials.

Doping metal nanoclusters (NCs) with another metal usually leads to superior catalytic performance toward CO

In this manuscript, ruthenium (Ru) nanoparticles functionalized with nitrene ligands through the ruthenium-nitrene (Ru N) π bonds are explored. By synthesizing the nitrene ligands with and without 15N-labelling, Ru N π bonds on Ru nanoparticles are evidenced by experimental and theoretically calculated FTIR spectra. The coordination of nitrene ligands on Ru nanoparticles surface, the interfacial charge delocalization and the impact of nitrene ligands on the catalytic performance of Ru nanoparticles are further characterized by magic-angle spinning solid-state carbon nuclear magnetic resonance spectroscopy (13C NMR) of 13CO-adsorbed Ru nanoparticles, photoluminescence and the hydrogenation of styrene.

Transition metal selenides have been widely studied as anode materials of sodium ion batteries (SIBs), however, the investigation of solid-electrolyte-interface (SEI) on these materials, which is critical to the electrochemical performance of SIBs, remains at its infancy. Here in this paper, ZnSe@C nanoparticles were prepared from ZIF-8 and the SEI layers on these electrodes with and without reduced graphene oxide (rGO) layers were examined in details by X-ray photoelectron spectroscopies at varied charged/discharged states. It is observed that fast and complicated electrolyte decomposition reactions on ZnSe@C leads to quite thick SEI film and intercalation of solvated sodium ions through such thick SEI film results in slow ion diffusion kinetics and unstable electrode structure. However, the presence of rGO could efficiently suppress the decomposition of electrolyte, thus thin and stable SEI film was formed. ZnSe@C electrodes wrapped by rGO demonstrates enhanced interfacial charge transfer kinetics and high electrochemical performance, a capacity retention of 96.4%, after 1000 cycles at 5 A/g. This study might offer a simple avenue for the designing high performance anode materials through manipulation of SEI film.

Since water dissociation and H desorption kinetics essentially determine the performance of the alkaline hydrogen evolution reaction (HER), rationally regulating surface adsorption behavior to achieve a superior catalytic surface is always challenging for catalysts. Herein, N-doped Pt–Ru single atom alloy electrocatalysts were constructed by dispersing diluted Pt single atoms onto Ru nanoparticles by thermal annealing in an ammonium atmosphere. The prepared (Ru–N)@Pt can substantially boost the alkaline HER catalysis of Ru nanoparticles and deliver an impressive overpotential of only 15 mV at 10 mA cm−2. X-ray-absorption fine structure characterization confirms that the doped N species have bonding interaction with both Ru and Pt sites. Theoretical calculations reveal that N incorporation helps strengthen the interfacial interaction between H2O and Ru sites by precise orbital engineering, while the Pt sites facilitate the H2 desorption kinetics. This work not only provides an effective strategy to construct single atom alloy electrocatalysts for a high-performance alkaline HER, but also sheds light on the understanding of the reaction mechanism at the atomic level.

The slow redox dynamics and dissolution of polysulfides in lithium–sulfur (Li–S) batteries result in poor rate performance and rapid decay of battery capacity, thus limiting their practical application. Ferroelectric barium titanate (BT) nanoparticles have been reported to effectively improve the electrochemical performance of Li–S batteries due to the inherent self-polarization and high adsorption capacity of the BT nanoparticles towards polysulfides. Here in this paper, BT nanoparticles, behave as highly efficient electrocatalyst and demonstrate much higher redox dynamics towards the conversion reaction of polysulfides and Li2S than TiO2, as shown by both electrochemical measurements and density functional theory calculation. The coupling of the sulfur host of the hollow and graphitic carbon flakes (HGCF) and the BT nanoparticles (HGCF/S-BT) enable excellent electrochemical performance of Li–S batteries, delivering a 0.047% capacity decay per cycle in 1000 cycles at 1 C, 788 mAh g–1 at 2 C and a reversible capacity of 613 mAh g−1 after 300 cycles at a current density of 0.5 C at a S loading of 3.4 mg cm–2. HGCF/S-BT also shows great promise for practical application in flexible devices as demonstrated on the soft-packaged Li–S batteries.

The photovoltaic performance of perovskite sloar cells (PSCs) is strongly dependent on the crystallinity, morphorlogy and defects of perovskite films. In the present work, a novel strategy was developed to fabricate the high quality CsPbI3 inorganic perovskite by tuning the growth dynamics of CsPbI3 by pretreatment of fresh CsPbI3 films with phenylethylamine iodide (PEAI). The PEAI can mediate the phase transformation from 1D (DMAPbI3) (DMA: dimethylammonium) to 3D CsPbI3 all-inorganic perovskite films via the PEA2CsPb2I7 of 2D perovskite intermediate phase, resulting in highly crystalline CsPbI3 perovskite films with remarkably enlarged grains and reduced defects. The as-achieved highly crystalline CsPbI3 inorganic perovskite not only exhibited improved phase stability but also significant reduced defects. The perovskite solar cells based on these CsPbI3 thin films exhibited a champion efficiency of 17.08%, much higher than those prepared through posttreatment or direct addition of PEAI into CsPbI3 precursor solution. This work not only developed an effective strategy to prepare high crystalline CsPbI3 film and highly efficient CsPbI3-based all-inorganic PSCs, but also unraveled the mediation mechanism of CsPbI3 by pre-treatment of PEAI, shedding light for further development of high perfomance perovskite-based optoelectronics.

Bi2S3 is a n-type (negative type) semiconductor that has a narrow band gap and an ideal band edge position for hydrogen generation. However, high charge recombination rate, low photoelectrochemical (PEC) efficiency and poor stability are of major concerns of Bi2S3 as a photoelectrode. Herein, we report an efficient Vanadium-rich Bi2S3 nanowires (atomic ratio of V to Bi is 1/22) that have been prepared on fluorine-doped tin oxide (FTO) substrate by an in-situ solution-processed reaction with BiVO4 film as precursor. The resulting V-rich photoelectrode demonstrates notably high charge separation efficiency and fast charge transport with respect to pristine Bi2S3 nanowires. As a result, the photocurrent density of ca. 10 mA·cm−2 at -0.2 V vs Ag/AgCl is obtained under visible light illumination. In addition, V-rich Bi2S3 generates IPCE (incident photocurrent-to-current conversion efficiency) of 50% at 460 nm and 45% at 760 nm, demonstrating a 2.0 and 2.8-fold increase, respectively, when compared with pristine Bi2S3. This enhancement is probably due to increased light absorption, less charge recombination, and faster charge transfer. More importantly, in contrast to pristine Bi2S3 sample that suffers detrimental photocorrosion in sulfide containing electrolyte, V-rich Bi2S3 nanowires retain 84.6% of its initial photocurrent over the course of 1 h. These findings are expected to shed light on engineering high-performance and robust metal sulfide materials for photoelectrochemical application.

Transition metal phosphides have received extensive attention as anode materials of sodium ion batteries due to their high theoretical specific capacity and low redox potentials. However, the large volume change during the insertion/extraction of sodium ions often leads to a poor electrochemical performance and thus limits their practical application. Herein, we rationally designed three-dimensional hierarchical Ni5P4 nanospheres wrapped by rGO nanostructures (Ni5P4@rGO) through a sequential hydrothermal synthesis and phosphidation of highly folded spherical α-Ni(OH)2. The graphene nanosheets can effectively prevent the collapse of spherical α-Ni(OH)2 and aggregation of Ni5P4 active materials during phosphidation. Besides, the strong coupling between the nickel phosphide and graphene layers leads to excellent electrochemical performance of Ni5P4@rGO composite as anode materials of SIBs, delivering a specific capacity of 304 mA h g–1 at 0.2 A g–1 after 200 cycles. The strategy developed in this paper may shed light on the morphology-controlled synthesis of transition metal phosphides with high performance for energy storage devices.

Binary transition metal selenides have been more promising than single transition metal selenides as anode materials for sodium-ion batteries (SIBs). However, the controlled synthesis of transition metal selenides, especially those derived from metal-organic-frameworks with well-controlled structure and morphology is still challenging. In this paper, highly porous NiCoSe4 @NC composite microspheres were synthesized by simultaneous carbonization and selenization of a Ni-Co-based metal-organic framework (NiCo-MOF) and characterized by scanning electron microscopy, transition electron microscopy, X-Ray diffraction, X-Ray photoelectron spectroscopy and electrochemical techniques. The rationally engineered NiCoSe4 @NC composite exhibits a capacity of 325 mAh g-1 at a current density of 1 A g-1 , and 277.8 mAh g-1 at 10 A g-1 . Most importantly, the NiCoSe4 @NC retains a capacity of 293 mAh g-1 at 1 A g-1 after 1500 cycles, with a capacity decay rate of 0.025 % per cycle.

Transition metal phosphides (TMPs) are promising anode candidates for sodium-ion batteries, due to their high theoretical specific capacity and working potential. However, the low conductivity and excessive volume variation of TMPs during insertion/extraction of sodium ions result in a poor rate performance and long-term cycling stability, largely limiting their practical application. In this paper, NiP

Metal oxides have been widely studied as promoter of catalytic performance of metal catalysts through the strong metal-support interactions. However, the mechanism behind it is still debating. Here a series of PdCu nanoparticles with size from 4.9 to 15.4 nm are prepared and loaded on CeO2 nanorods, which are further characterized by HRTEM, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical CO stripping. The coupling of PdCu nanoparticles and CeO2 nanorods induces compressive strain on PdCu nanoparticles, which is strongly dependent on the size of PdCu nanoparticles. The correlation among the compressive strain, down-shift of the d-band center, reduced CO binding energy and augmentation of PdO content for PdCu nanoparticles is further discussed in details. Based on comprehensive analyses, it is concluded that the reduced CO oxidation potential on PdCu nanoparticles upon CeO2 support is from enhanced PdO on PdCu, while the synergy of compressive strain, enhanced PdO and oxygen vacancy remarkably promotes the catalytic performance of PdCu towards electrooxidation of formic acid.

Localized surface plasmon resonance (LSPR) excitation of noble metal nanoparticles has been shown to accelerate and drive photochemical reactions. Here, LSPR excitation is shown to enhance the electrocatalysis of a fuel-cell-relevant reaction. The electrocatalyst consists of Pdx Ag alloy nanotubes (NTs), which combine the catalytic activity of Pd toward the methanol oxidation reaction (MOR) and the visible-light plasmonic response of Ag. The alloy electrocatalyst exhibits enhanced MOR activity under LSPR excitation with significantly higher current densities and a shift to more positive potentials. The modulation of MOR activity is ascribed primarily to hot holes generated by LSPR excitation of the Pdx Ag NTs.

Constructing core–shell nanostructures is demonstrated to be an effective strategy to improve catalytic activity of metal nanoparticles. However, the impact of the atomic ordering of the metal core...

Development of low-cost and high-efficiency electrocatalysts for hydrogen evolution reaction is a critical step toward sustainable water splitting. Herein, in situ growth of heterostructured MoC/Mo2C nanoribbons and nanoflowers on copper foam (MoxC/Cu), copper foil, and nickel foam (MoxC/Ni) are prepared via a two-step method: hydrothermal preparation of molybdenum precursors followed by pyrolysis at controlled temperatures. The MoxC/Cu hybrids are found to exhibit an excellent catalytic activity, as compared to the MoxC/Ni and Cu foil counterparts, and the sample prepared at 750 °C stands out as the best among the series with a low overpotential of 169 mV to reach the current density of 200 mA cm–2 in 1 M KOH, and 194 mV in 0.5 M H2SO4, and the corresponding Tafel slopes of 98 and 74 mV dec–1, respectively. The electrocatalytic activity is also found to vary with the Mo2+/Mo3+ and N contents in the samples that impact the electrical conductivity and electron-transfer kinetics of the hydrogen evolution re...

Electrochemical reduction of carbon dioxide has been attracting extensive interest due to its fundamental significance both in environmental protection and in energy storage. In this review, recent progress in the manipulation of the catalytic activity and selectivity of various transition metals towards CO2 reduction reaction (CO2RR) is summarized within the context of deliberate surface functionalization by select organic ligands. This is primarily manifested in three effects, interfacial charge transfer, suppression of hydrogen evolution, and stabilization of key reaction intermediates. The review is concluded with a perspective of the challenges and promises in the structural engineering of metal catalysts for enhanced CO2RR performance.

The recognition of the solid electrolyte interface (SEI) between the electrode materials and electrolyte is limiting the selection of electrode materials, electrolytes, and further the electrochemical performance of batteries. Herein, we report ZnSe@C core-shell nanocomposites derived from ZIF-8 as anode materials of lithium-ion batteries, the electrochemical performances, and SEI films formed on ZnSe@C in both ether and carbonate electrolytes. It is found that ZnSe@C delivers a reversible capacity of 617.1 mA h·g-1 after 800 cycles at 1 A·g-1 in the ether electrolyte, much higher than that in the carbonate electrolyte. Both ex situ X-ray diffraction and X-ray photoelectron spectroscopies reveal that stable SEI films are formed on ZnSe@C in the ether electrolyte while selenium is involved in the formation of SEI films and further dissolved into the carbonate electrolyte because of the concurrent decomposition of electrolytes and insertion of Li+ into ZnSe, which differentiates between the cycling performances of ZnSe@C composites in ether and carbonate electrolytes.

Electroreduction of carbon dioxide (CO2RR) into fuels and chemicals is an appealing approach to tackle CO2 emission challenges. To this end, it is critical to develop highly efficient and selective electrocatalysts for the CO2RR. Herein, we report a simple strategy for the preparation of heterostructured intermetallic CuSn electrocatalysts (Cu3Sn/Cu6Sn5) supported on porous copper foam through an electrodeposition–calcination process. The obtained CuSn intermetallic catalysts demonstrate a faradaic efficiency of 82% and a current density of 18.9 mA cm−2 at −1.0 V vs. the reversible hydrogen electrode for formate production in 0.1 M NaHCO3 electrolyte for as long as 42 h. By using a gas diffusion electrode and 1 M KOH electrolyte, the current density of this catalyst for formic acid production can reach values as high as 148 mA cm−2. Density functional theory calculations show that the moderate Gibbs free energy of hydrogen adsorption on the heterostructured Cu3Sn/Cu6Sn5 catalysts not only suppresses hydrogen evolution, but also favors the production of formic acid. This study demonstrates a straightforward approach to the preparation of high-performance electrocatalysts towards the selective electroreduction of CO2 to formate.

Transition metal phosphide (TMP) co-catalysts have been widely applied to modify graphitic carbon nitride (g-C3N4) for improving the photocatalytic activity, but it is still a great challenge to fabricate high performance and stable g-C3N4 based photocatalysts decorated with TMP co-catalysts by simple approaches. Herein, we report a facile and general strategy for the synthesis of TMP/g-C3N4 hybrid photocatalysts with high H2 production performance under visible light irradiation. Among the as-prepared TMP/g-C3N4 hybrids, the CoP/g-C3N4 sample with an optimum mass content of 2.5 wt% delivers the highest photocatalytic H2 evolution rate of 956.8 μmol g−1 h−1. DFT calculations and experimental results reveal that the superior catalytic activity could be predominantly attributed to the larger number of active sites and the enhanced photo-excited charge transfer dynamics benefitting from the synergistic effect of the ultrasmall particle size and the intimate contact interface between g-C3N4 and CoP. We anticipate that the protocol would provide a promising strategy for designing TMP co-catalyst based hybrid nanostructures aiming to optimize photocatalytic hydrogen generation efficiency.

In the present study, ruthenium nanoparticles functionalized with terminal and internal alkynes were prepared, and it was found that internal alkynes formed a η2 side-on configuration on the surfac...

Binary transition metal selenides have been more promising than single transition metal selenides as anode materials for sodium-ion batteries (SIBs). However, the controlled synthesis of transition metal selenides, especially those derived from metal-organic-frameworks with well-controlled structure and morphology is still challenging. In this paper, highly porous NiCoSe

It is desirable to unravel the correlation between the geometric and electronic structures and the activity and further prepare high-performance electrocatalysts. Here in this paper, trimetallic Ru@Au-Pt core-shell nanoparticles were prepared by sequential ethanol reduction method, and further subject to characterization of X-ray diffraction, high angle annular dark field transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical CO stripping. Further analysis based on Williamson-Hall method revealed that the Au/Pt atomic ratio and shell thickness result in apparent variation of micro-strain and CO binding energy of Ru@AuPt nanoparticles, where the CO oxidation peak potential showed an inverted volcano-shape dependence on the microstrain of the metal nanoparticles while the catalytic activity towards electrooxidation of formic acid is linearly dependent on the micro-strain. The best Ru@Au-Pt catalyst delivers a specific activity of 4.14 mA cm−2, which is 52 times that of Pt/C, respectively. This study indicated that the microstrain and stacking fault of metal nanoparticles might be a good descriptor for the catalytic activity and may shed light the rational design, synthesis and surface engineering towards the high-performance electrocatalyst.

The Se-based energy storage materials are promising candidates for the development of high-performance rechargeable battery systems due to its distinctive features, such as the high-energy density, high power density, high storage capacity, superior cycle performance, excellent rate capability, moderate charge/discharge voltage plateaus, and environmental friendliness. Specifically, the electrical conductivity of Se is significantly greater than that of S, though it is chemically and electrochemically analogous to S to a great extent. However, various Li–Se battery systems still suffer from the enormous challenges in achieving extensive practical application including low mass loading of active materials, significant volume change, severe electrode pulverization, and the dissolution of intermediate lithium polyselenides in the electrolyte, similar to that in Li-S batteries. Both the advances and challenges of Li–Se batteries in carbonate/ether-based electrolytes are critically reviewed and future design strategies and fabrication techniques of Se-based electrodes are also envisioned.

The catalytic activity of alloy nanomaterials can be well modulated through the electrochemical dissolution of the more active component from alloy nanomaterials. In this paper, PdAg alloy nanotubes of diverse Pd to Ag ratio are prepared by galvanic displacement electrochemical reaction. The Ag-leached PdAg nanotubes are characterized by cyclic voltammetric scans, high-angle annular dark-field scanning transmission electron spectroscopy, energy dispersive X-ray elemental mapping and X-ray photoelectron spectroscopy measurements and demonstrate the formation of PdAg@Pd core-shell nanotubes structure with roughed surface and largely enhanced electrochemical surface area. The PdAg@Pd core-shell nanotubes show significantly enhanced catalytic activities and durability towards electro-oxidation of formic acid and methanol than the as-prepared PdAg nanotubes, with the mass activity and specific activity of 1.93 A mg−1 and 2.67 mA cm−2 towards formic acid respectively, which are 7.8 and 4.8 times that of Pd/C. The increased catalytic performance is ascribed to the unique surface and electronic structure of PdAg@Pd core-shell nanotubes.

It has been challenging to synthesize palladium (Pd) and ruthenium (Ru) alloy nanoparticles of solid solution in atomic scale, thus preventing us to study the size effect on the catalytic activity. Here we reported the synthesis of PdRu alloy nanoparticles through polyol reduction method, with the size from 6.0 to 16.6 nm. Elemental mapping indicated that Pd and Ru with 1:1 ratio are evenly distributed over the alloy nanoparticles. XRD of PdRu alloy nanoparticles displayed the characteristic diffraction patterns of face centered cubic (fcc) of Pd and invariable inter plane distance of (1 1 1). The band width of valence state increased from 5.7 to 6.2 eV when the diameter of the nanoparticles increased from 6.0 to 16.6 nm. The size effect of PdRu alloys towards electrooxidation of formic acid was examined on the support of CNT. PdRu alloy nanoparticles with diameter of 15.6 nm performed best among all the samples, 5.7 times higher than that of commercial Pd/C with formic acid. PdRu alloy nanoparticles also demonstrated optimum catalytic activity towards methanol oxidation in alkaline medium solution and the best performance was achieved by PdRu alloy nanoparticles with diameter of 15.6 nm, which was 2.5 times that of Pd/C. A volcano shape dependence of catalytic activity towards both formic acid and methanol oxidation on the size of PdRu alloy nanoparticles was observed. This work provided a vial strategy for the size-controlled synthesis of alloy nanoparticles of solid solution in atomic scale, especially for those elements that are immiscible, unraveled the size effect on the electronic structure and catalytic activity on metal nanoparticles and may shed light on the optimization of alloy noble metal nanoparticles.

To date, controversies remain in the unambiguous identification of the active sites in N-doped carbons for oxygen reduction reaction (ORR). In the present study, prolonged potential cycling was conducted on three N-doped carbons in O2-saturated 0.1 M KOH aqueous solution, where apparent attenuation of the ORR activity was observed, within the context of limiting current and onset potential. The attenuation trend of the limiting current was closely correlated with the diminishing content of graphitic N, as manifested in X-ray photoelectron spectroscopy measurements and Mott–Schottky analysis. In addition, the specific activity per graphitic N was found to be almost invariant within a wide range of potentials during prolonged potential cycling for all three model catalysts, in good agreement with theoretical prediction, whereas no such a correlation was observed with pyrrolic or pyridinic N. Density functional theory calculations showed that the first-electron reduction, which is a rate-determining step for...