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The low‐voltage charging capacity and rate performance are two crucial but mutually restricted properties of K‐ion batteries. Herein, a sulfonamide and amide linkages‐triggered N doping high‐temperature removal strategy is proposed to obtain porous carbon with rich carbon vacancies, high sp2 hybridized C content (65.3%), and large interlayer spacing using coal tar pitch as carbon precursor. Carbon vacancies and sp2 hybridized C are proved to be not only active sites for low‐voltage potassium storage but also conducive to the fast transfer of ions and electrons, endowing reversible and fast potassium storage at low voltage. Moreover, abundant carbon vacancies and large carbon interlayer spacing alleviate volume variation, improving the cycling stability for 8500 cycles (about 3700 h). This work sheds new light on the design of low‐voltage, durable, and fast potassium storage carbon anodes, and promotes the development of practical carbon anodes for high energy density K‐ion batteries in the future. [ABSTRACT FROM AUTHOR]

An efficient chemical synthesis route, with an aim of reaching an ultrahigh nitrogen (N)‐doping level in carbon materials can provide a platform where the type and amount of N dopant can be tuned over a wide range. We propose a C‐S‐C linkage‐triggered confined‐pyrolysis strategy for the high‐efficiency in situ N‐doping into carbon matrix and an ultrahigh doping level up to 13.5 at %, which is close to the theoretical upper limit (15.2 at %) is realized at a high carbonization temperature of 1000 °C. The pyridinic N is dominant with a maximum percent of 48.7 %. By using I3− reduction as an example, the resultant NCM‐5 exhibits the best activity with a power conversion efficiency of 8.77 %. A pyridinic N site‐dependent activity is demonstrated in which the amount of active sites increases with the increase of pyridinic N, and the carbon atom adjacent to electron‐withdrawing pyridinic N at the armchair edge acts as the most favorable site for the adsorption of I2. [ABSTRACT FROM AUTHOR]

Carbon materials have rapidly grown as highly promising candidates to replace noble metal catalysts in energy storage/conversion technologies. In this work, a strategy of hydrogen‐bonding triggered assembly to configure hollow carbon nanosheets by applying Silicalite‐1 as a substrate in the aqueous solution of dopamine is reported. Remarkably, the combined density functional theory modelling and experimental verification present a molecule/nano‐scale insight into the nature of the bonding behavior during the fabrication process. It is demonstrated that the SiOH on the surface of Silicalite‐1 acts as an anchor and that it is energetically favorable to pre‐adsorb the building blocks of polydopamine by hydrogen‐bonding, which triggers the subsequent assembly. As an example, the as‐prepared hollow carbon nanosheets with unique structure can efficiently catalyze tri‐iodide reduction and a power conversion efficiency up to 8.58%. [ABSTRACT FROM AUTHOR]

The development of cost‐effective and durable oxygen electrocatalysts remains highly critical but challenging for energy conversion and storage devices. Herein, a novel FeNi alloy nanoparticle core encapsulated in carbon shells supported on a N‐enriched graphene‐like carbon matrix (denoted as FeNi@C/NG) was constructed by facile pyrolyzing the mixture of metal salts, glucose, and dicyandiamide. The in situ pyrolysis of dicyandiamide in the presence of glucose plays a significant effect on the fabrication of the porous FeNi@C/NG with a high content of doped N and large specific surface area. The optimized FeNi@C/NG catalyst displays not only a superior catalytic performance for the oxygen reduction reaction (ORR, with an onset potential of 1.0 V and half‐wave potential of 0.84 V) and oxygen evolution reaction (OER, the potential at 10 mA cm−2 is 1.66 V) simultaneously in alkaline, but also outstanding long‐term cycling durability. The excellent bifunctional ORR/OER electrocatalytic performance is ascribed to the synergism of the carbon shell and FeNi alloy core together with the high‐content of nitrogen doped on the large specific surface area graphene‐like carbon. [ABSTRACT FROM AUTHOR]

Nitrogen-doped hollow carbon spheres (NHCSs) derived from polystyrene@polypyrrole-polyaniline (PS@PPY-PANI) core-shell composite microspheres of large surface area with improved electrochemistry performances have been effectively prepared and characterized systematically. NHCSs exhibited exceptional electrochemical properties with a maximum specific capacitance of 294.9 F g − 1 at a 5 mVs − 1 with good cycling stability of 95% after 5000 cycles at 0.5 A g − 1. It also showed enhanced oxygen reduction reaction (ORR) activity with a high onset potential of 0.83 V vs. RHE at 1600 rpm via the more favorable four-electron pathway in an alkaline medium. Enhanced electrochemical and electrocatalytic performances could arise from the hollow porous spherical structure, high surface area, and considerable pyrrolic-pyridinic nitrogen contents. Pyrolysis commences the incorporation of nitrogen units together with the high degree of graphitization which contributes exceptionally to improve the ion/charge transfers. Significantly, the synergistic effect of pyrolysis and the proper concentration of PPY-PANI improve the overall electrochemistry performances of NHCSs. The excellent cyclic stability, high specific capacitance, and exceptional ORR activity indicate its perspective as an efficient electrode material for supercapacitors and fuel cells. Image 1 • Preparation of nitrogen-doped hollow carbon spheres (NHCSs). • Polystyrene@polypyrrole-polyaniline (PS@PPY-PANI) was pyrolyzed to obtain NHCSs. • Pyrolysis results in the incorporation of nitrogen units along with high degree of graphitization. • Improved electrochemistry performances indicate the perspective of NHCSs as an efficient electrode material. [ABSTRACT FROM AUTHOR]

• A Co nanoparticle encapsulated in porous Co,N dual-doped graphene-like carbon sample was prepared. • Co@NC sample exhibited a high catalytic activity and stability for oxygen reduction reaction. • Nitrogen species, Co@C, and Co-N x contributed to the outstanding catalytic performance. Rational design and construction of robust electrocatalysts towards oxygen reduction reaction (ORR) are vital for energy conversion devices. Here, we report a hierarchically engineered Co nanoparticle (NP) encapsulated in Co, N codoped graphene-like carbon sample (Co@NC) via direct pyrolyzing the mixture of glucose, dicyandiamide and cobalt salt. Benefiting from the Co-N 4 moiety and high content of doped N species (8.81 at.%) which highly dispersed on the large Co NP modified carbon surface, Co@NC sample delivers remarkable ORR catalytic performance with an onset potential of 0.98 V and a half-wave potential of 0.86 V together with robust durability, which outperforms the benchmark Pt/C catalyst and most of published Co-N x -C samples in alkali. This facile mass-producible strategy undoubtedly provides an avenue to achieve highly active and durable practical-oriented electrocatalytic catalysts for wide electrochemical energy devices. [ABSTRACT FROM AUTHOR]