Efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional electrocatalysts have been pursued for decades. Meanwhile, single metal atoms embedded in a two-dimensional material substrate (2D-substrate) have emerged as an outstanding catalyst. Herein, we report on computational ORR/OER efficiencies of a series of single atom catalyst systems, with a nitrogen-doped boron phosphide monolayer (N 3 -BP) as the 2D-substrate, and with Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rh, Pd, Ir, and Pt as the single-atom subject (M). In brief, our density functional theory results show that the overpotentials for ORR/OER are low for CoN 3 -BP, NiN 3 -BP, and PtN 3 -BP, with {η ORR ; η OER } of {0.36; 0.42 V}, {0.29; 0.44 V}, and {0.32; 0.25 V}, respectively. The relevant attributes such as the chemical stability of the 2D-substrate in the ORR/OER environments, immobilization of the single-atom subject on the 2D-substrate, and mechanisms of the ORR/OER activity and the catalyst recovery on the MN 3 -BP catalysts were carefully examined. The key to the comparative study is how the electronic states of the reaction center near the Fermi level of the catalytic system match the frontier orbitals of ORR/OER reaction intermediates. In short, our method predicts the ORR/OER catalytic efficiencies of novel catalysts via a single-atom/2D-substrate design strategy.

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Demand for high‐performance electromagnetic (EM) wave absorbing materials with high‐temperature resistance is always urgent for application in a harsh environment. In this contribution, two‐dimensional material, Ti3C2Tx MXene, was introduced into a hyperbranched polyborosilazane. After pyrolyzation, the as‐prepared TiC/SiBCN ceramics present excellent EM wave absorption in X‐band. The TiC nanograins appearing after annealing provide multilevel reflection and interface polarization. Dipole polarization formed at interface defects, in company with interfacial polarization, also makes a great contribution to enhanced EM wave absorption. The TiC/SiBCN nanocomplex prepared with 5 wt% Ti3C2Tx MXene possesses a minimum reflection coefficient of −45.44 dB at 10.93 GHz and abroad bandwidth 8.4 and 12.4 GHz, almost covering the entire X‐band. Tuning the thickness in the range of 2.35‐2.54 mm, the effective absorption band can achieve the entire X‐band. And the EM wave absorbing performance has been maintained to a large extent at 600°C with the minimum reflection coefficient of −26.12 dB at 12.13 GHz and the effective absorption bandwidth of 2 GHz. Last but not the least, TiC/SiBCN ceramics offer a good thermal stability in argon as well as in air atmosphere, making it possible to serve in high‐temperature detrimental environments. This study is expected to provide a new perspective for the design of high‐performance absorbing materials that are able to be used in harsh environments, especially in high temperatures.

Present conductive silicone rubber with carbon blacks has low compression recovery, and is difficult to make long-term electromagnetic shielding products. In order to solve the problem, special hollow-shell carbon blacks were used and then treated by coupling agent to prepare conductive silicone rubber. The compression set of conductive rubber at 1008C for 48 h was only 8.9%, displaying a extremely good recovery. Importantly, the special rubber can be extruded and then continuously vulcanized. Moreover, its electromagnetic shielding effectiveness reached beyond 20 dB at the frequency of 0.01 MHz-10 GHz. After the thermal oxidative aging at 90 and 1108C for 30 days, carbon blacks occurred to aggregate, which gives rise to a drop of tensile property and slight effects on the modulus and hardness. The compression set also increased, but it still maintained a low level after 30 days. There is only little change for the conductivity of silicone rubber and thus its electromagnetic shielding effectiveness still retained beyond 20 dB, showing a good aging resistance. It is believed that our findings may provide an effective solution to fabricate rubber products to sever the electromagnetic protection. POLYM. COMPOS., 00:000-000, 2018.

R F, et al. A sparse estimation algorithm for the radar target range-direction under strong mainlobe jamming conditions (in Chinese).