The exploitation of a high-activity and low-cost bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as the cathode catalyst is a research priority in metal−air batteries. Herein, a novel bifunctional hybrid catalyst of hortensia-like MnO 2 synergized with carbon nanotubes (CNTs) (MnO 2 /CNTs) is controllably synthesized by reasonably designing the crystal structure and morphology as well as electronic arrangement. On the basis of these strategies, the hybrid accelerates the reaction kinetics and avoids the change of structures. As expected, MnO 2 /CNTs exhibit a remarkable ORR and OER activity [low ORR Tafel slope: 71 mV dec −1 , low OER Tafel slope: 67 mV dec −1 , and small potential difference (ΔE): 0.85 V] and a long-term stability, which should be attributed to its unique morphology, K + ions in the 2 × 2 tunnels, and synergistic effect between MnO 2 and CNTs. Notably, in zinc−air batteries (ZABs), aluminum−air batteries (AABs), and magnesium−air batteries (MABs), the composite shows high power density (ZABs: 243 mW cm −2 , AABs: 530 mW cm −2 , and MABs: 614 mW cm −2 ) and large specific capacities (793 mA h g Zn −1 , 918 mA h g Al −1, and 878 mA h g Mg −1 ). Importantly, the rechargeable ZABs reveal small charge−discharge voltage drop (0.81 V) and strong cycle durability (500 h), which are better than the noble-metal Pt/C + IrO 2 mixture catalyst (the voltage drop: 1.15 V at first and 2 V after 100 h). These superior performances together with the simple synthetic method of the hybrid reveal great promise in large-power energy storage and conversion equipment.

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Carbon-doped silicon oxide (CDO) thin films as low dielectric constant materials were deposited on both n-type silicon (Si) (100) and indium tin oxide coated polyethylene naphthalate (ITO/PEN) substrates, using the plasma-enhanced chemical vapor deposition of tetrakis(trimethylsilyoxy)silane (TTMSS) precursor. Chemical structures of the CDO films were analyzed by using FTIR (Fourier transformation infrared) spectroscopy and XPS (X-ray photoelectron spectroscopy). The chemical bonds related with hydrocarbon and Si–O were the main characteristics of the CDO films. The prominent peaks from the FTIR spectra included Si–O–Si stretching, Si–CH3 bending, Si–(CH3)x stretching, and CHx stretching modes. XPS spectra composed of the O1s, C1s, and Si2p electron orbitals were used to quantitatively analyze the elemental composition of the CDO films. The growth mechanisms of CDO films were dependent on the substrate type. For the ITO/PEN substrate, the lack of Si atoms on the ITO surface made difficulty in forming initial Si–O bonds, resulting in insufficient Si–O–Si structure. In comparison, the CDO films could grow easily on Si substrates due to pre-existing Si–O bonds on the surface. The chemical structures of the CDO films are expected to affect electrical and mechanical performances.