The sluggish kinetics of Oxygen Reduction Reaction (ORR) at the cathode in proton exchange membrane fuel cells or metal-air batteries requires highly effective and stable electrocatalysts to boost the reaction. The low abundance and high price of Pt-based electrocatalysts hamper the widespread application of proton exchange membrane fuel cells and metal-air batteries. As promising alternatives, metal-free carbon materials, especially upon doping heteroatoms or creating defects demonstrated excellent ORR activity, which is as efficient as or even superior to commercial platinum on carbon. Significant progress on the development of advanced carbon materials as highly stable and durable catalysts has been achieved, but the catalytic mechanisms of these materials still remain undistinguished. In present review, we summarized the up-to-date progress in the studies of carbon materials, and emphasized on the combination of experiment and theory to clarify the underlying mechanisms of these materials. At last, we proposed the perspectives on the proper strategies of elucidating the mechanisms of carbon materials as electrocatalysts towards ORR.npj Computational Materials (2019) 5:78 ; https://doi.

Recently, this long-sought quantum anomalous Hall effect was realized in the magnetic topological insulator. However, the requirement of an extremely low temperature (approximately 30 mK) hinders realistic applications. Based on ab-initio band structure calculations, we propose a quantum anomalous Hall platform with a large energy gap of 0.34 and 0.06 eV on honeycomb lattices comprised of Sn and Ge, respectively. The ferromagnetic order forms in one sublattice of the honeycomb structure by controlling the surface functionalization rather than dilute magnetic doping, which is expected to be visualized by spin polarized STM in experiment. Strong coupling between the inherent quantum spin Hall state and ferromagnetism results in considerable exchange splitting and consequently an ferromagnetic insulator with a large energy gap. The estimated mean-field Curie temperature is 243 and 509 K for Sn and Ge lattices, respectively. The large energy gap and high Curie temperature indicate the feasibility of the quantum anomalous Hall effect in the near-room-temperature and even room-temperature regions.PACS numbers: 71.70. Ej,73.43.Cd, The quantum anomalous Hall (QAH) effect is a topologically nontrivial phase characterized by a finite Chern number and chiral edge states inside the bulk band gap, which leads to the quantized Hall effect without a magnetic field [1]. The chiral edge states carry dissipationless electric current owing to robustness against backscattering [2] and are therefore attractive for applications in low-power-consumption electronics. Recently, this long-sought QAH effect was realized chromium-doped (Bi,Sb) 2 Te 3 (ref.[3]), the magnetic topological insulator [4,5]. However, the requirement of an extremely low temperature (approximately 30 mK) hinders realistic applications, which is fundamentally limited by the bulk energy-gap and the ferromagnetic Curie temperature [3]. Thus, novel materials are in high demand for future applications of the QAH effect.In a quantum spin Hall (QSH) system [6][7][8], the topological band structure is identified by a band inversion in both spin channels that are time-reversal (TR) conjugates of each other. A pair of counter-propagating edge states with opposite spins exists, i.e., two copies of quantum anomalous Hall (QAH) edge states. If the ferromagnetic (FM) order suppresses one of the spin channels, it can lead to the QAH effect [9][10][11]. The band inversion in a single spin channel, which is characterized by a finite Chern number, originates from the gapless edge state inside the bulk energy-gap. Therefore, the following transition-metal-doped topological insulators were proposed to realize the QAH effects: the aforementioned chromium-doped Bi 2 Te 3 (ref.[11]), manganesedoped HgTe quantum wells (QWs) [10,12], and other magnetically doped QWs [13,14]. The bulk energy-gap of these 2D QSH insulators are usually of the order of 1 or 10 meV. It is believed that the ferromagnetism of a magnetic QSH insulator can be enhanced owing to the band edge singularity of such an ...

We have developed a kind of high-yield synthesis strategy for silver nanowires by a two-step injection polyol method. Silver nanowires and polyethylene oxide (PEO) (M(w) = 900,000) were prepared in a homogeneous-coating ink. Wet composite films with different thicknesses were fabricated on a PET substrate by drawn-down rod-coating technology. Silver nanowires on PET substrates present a homogeneous distribution under the assistance of PEO. Then PEO was thermally removed in situ at a relatively low temperature attributed to its special thermal behavior under atmospheric conditions. As-prepared metallic nanowire films on PET substrates show excellent stability and a good combination of conductivity and light transmission. A layer of transparent poly(ethersulfones) (PESs) was further coated on silver nanowire networks by the same coating method to prevent the shedding and corrosion of silver nanowires. Sandwich-structured flexible transparent films were obtained and displayed excellent electromagnetic interference (EMI) shielding effectiveness.

Topological insulators (TIs) are promising for achieving dissipationless transport devices due to the robust gapless states inside the insulating bulk gap. However, cur- *

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