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1. Recent advances in graphene‐based materials for fuel cell applications

   https://doi.org/10.1002/ese3.833  

   Su, Hanrui ; Hu, Yun Hang ( October 2020 , Energy Science & Engineering)

   The unique chemical and physical properties of graphene and its derivatives (graphene oxide, heteroatom‐doped graphene, and functionalized graphene) have stimulated tremendous efforts and made significant progress in fuel cell applications. This review focuses on the latest advances in the use of graphene‐based materials in electrodes, electrolytes, and bipolar plates for fuel cells. The understanding of structure‐activity relationships of metal‐free heteroatom‐doped graphene and graphene‐supported catalysts was highlighted. The performances and advantages of graphene‐based materials in membranes and bipolar plates were summarized. We also outlined the challenges and perspectives in using graphene‐based materials for fuel cell applications.

    

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2. Coexistence of Urbach‐Tail‐Like Localized States and Metallic Conduction Channels in Nitrogen‐Doped 3D Curved Graphene

   https://doi.org/10.1002/adma.202205986  

   Tanabe, Yoichi ; Ito, Yoshikazu ; Sugawara, Katsuaki ; Jeong, Samuel ; Ohto, Tatsuhiko ; Nishiuchi, Tomohiko ; Kawada, Naoaki ; Kimura, Shojiro ; Aleman, Christopher Florencio ; Takahashi, Takashi ; et al ( November 2022 , Advanced Materials)

   Nitrogen (N) doping is one of the most effective approaches to tailor the chemical and physical properties of graphene. By the interplay between N dopants and 3D curvature of graphene lattices, N‐doped 3D graphene displays superior performance in electrocatalysis and solar‐energy harvesting for energy and environmental applications. However, the electrical transport properties and the electronic states, which are the key factors to understand the origins of the N‐doping effect in 3D graphene, are still missing. The electronic properties of N‐doped 3D graphene are systematically investigated by an electric‐double‐layer transistor method. It is demonstrated that Urbach‐tail‐like localized states are located around the neutral point of N‐doped 3D graphene with the background metallic transport channels. The dual nature of electronic states, generated by the synergistic effect of N dopants and 3D curvature of graphene, can be the electronic origin of the high electrocatalysis, enhanced molecular adsorption, and light absorption of N‐doped 3D graphene.

    

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3. N-Doped graphene/C 60 covalent hybrid as a new material for energy harvesting applications

   https://doi.org/10.1039/C8SC02013B  

   Barrejón, Myriam ; Arellano, Luis M. ; Gobeze, Habtom B. ; Gómez-Escalonilla, María J. ; Fierro, Jose Luis ; D'Souza, Francis ; Langa, Fernando ( January 2018 , Chemical Science)

   N-Doped graphene (N-G) has been covalently functionalized on the nitrogen with a C₆₀derivative. Photophysical studies of the new hybrid and electron pooling experiments reveal the utility of this material in photocatalytic energy harvesting applications.

    

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4. Lateral Graphene p–n Junctions Realized by Nanoscale Bipolar Doping Using Surface Electric Dipoles and Self‐Organized Molecular Anions

   https://doi.org/10.1002/admi.201801380  

   Zhang, Yong ; Hu, Guangliang ; Gong, Maogang ; Alamri, Mohammed ; Ma, Chunrui ; Liu, Ming ; Wu, Judy Z. ( November 2018 , Advanced Materials Interfaces)

   Lateral p–n junctions take the unique advantages of 2D materials, such as graphene, to enable single‐atomic layer microelectronics. A major challenge in fabrication of the lateral p–n junctions is in the control of electronic properties on a 2D atomic sheet with nanometer precision. Herein, a facile approach that employs decoration of molecular anions of bis‐(trifluoromethylsulfonyl)‐imide (TFSI) to generate p‐doping on the otherwise n‐doped graphene by positively polarized surface electric dipoles (pointing toward the surface) formed on the surface oxygen‐deficient layer “intrinsic” to an oxide ferroelectric back gate is reported. The characteristic double conductance minimaV_Dirac−andV_Dirac+illustrated in the obtained lateral graphene p–n junctions can be tuned in the range of −1 to 0 V and 0 to +1 V, respectively, by controlling the TFSI anions and surface dipoles quantitatively. The unique advantage of this approach is in adoption of polarity‐controlled molecular ion attachment on graphene, which could be further developed for various lateral electronics on 2D materials.

    

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5. Precursor-mediated in situ growth of hierarchical N-doped graphene nanofibers confining nickel single atoms for CO 2 electroreduction

   https://doi.org/10.1073/pnas.2219043120  

   Wang, Huan ; Li, Youzeng ; Wang, Maoyu ; Chen, Shan ; Yao, Meng ; Chen, Jialei ; Liao, Xuelong ; Zhang, Yiwen ; Lu, Xuan ; Matios, Edward ; et al ( April 2023 , Proceedings of the National Academy of Sciences)

   Despite the various strategies for achieving metal–nitrogen–carbon (M–N–C) single-atom catalysts (SACs) with different microenvironments for electrochemical carbon dioxide reduction reaction (CO 2 RR), the synthesis–structure–performance correlation remains elusive due to the lack of well-controlled synthetic approaches. Here, we employed Ni nanoparticles as starting materials for the direct synthesis of nickel (Ni) SACs in one spot through harvesting the interaction between metallic Ni and N atoms in the precursor during the chemical vapor deposition growth of hierarchical N-doped graphene fibers. By combining with first-principle calculations, we found that the Ni-N configuration is closely correlated to the N contents in the precursor, in which the acetonitrile with a high N/C ratio favors the formation of Ni-N 3 , while the pyridine with a low N/C ratio is more likely to promote the evolution of Ni-N 2 . Moreover, we revealed that the presence of N favors the formation of H-terminated edge of sp 2 carbon and consequently leads to the formation of graphene fibers consisting of vertically stacked graphene flakes, instead of the traditional growth of carbon nanotubes on Ni nanoparticles. With a high capability in balancing the *COOH formation and *CO desorption, the as-prepared hierarchical N-doped graphene nanofibers with Ni-N 3 sites exhibit a superior CO 2 RR performance compared to that with Ni-N 2 and Ni-N 4 ones. 

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