中央研究院 原子與分子科學研究所

A 3D trenched-structure metal−insulator−metal (MIM) nanocapacitor array with an ultrahigh equivalent planar capacitance (EPC) of ∼300 μF cm−2 is demonstrated. Zinc oxide (ZnO) and aluminum oxide (Al2O3) bilayer dielectric is deposited on 1 μm high biomimetic silicon nanotip (SiNT) substrate using the atomic layer deposition method. The large EPC is achieved by utilizing the large surface area of the densely packed SiNT (∼5 × 1010 cm−2) coated conformally with an ultrahigh dielectric constant of ZnO. The EPC value is 30 times higher than those previously reported in metal−insulator−metal or metal−insulator−semiconductor nanocapacitors using similar porosity dimensions of the support materials.

Band gap opening and engineering is one of the high priority goals in the development of graphene electronics. Here, we report on the opening and scaling of band gap in BN doped graphene (BNG) films grown by low-pressure chemical vapor deposition method. HRTEM is employed to resolve the graphene and h-BN domain formation in great details. X-ray photoelectron, micro-Raman and UV-Vis spectroscopy studies revealed a distinct structural and phase evolution in BNG films at low BN concentration. Synchrotron radiation based XAS-XES measurements concluded a gap opening in BNG films, which is also confirmed by field effect transistor measurements. For the first time, a significant band gap as high as 600 meV is observed for low BN concentrations and is attributed to the opening of p-p^*band gap of graphene due to isoelectronic BN doping.

Photocatalytic conversion of carbon dioxide (CO₂) to hydrocarbons such as methanol makes possible simultaneous solar energy harvesting and CO₂ reduction, two birds with one stone for the energy and environmental issues. This work describes a high photocatalytic conversion of CO₂ to methanol using graphene oxides (GOs) as a promising photocatalyst. Modified Hummer’s method has been applied to synthesize the GO based photocatalyst for the enhanced catalytic activity. The photocatalytic CO₂ to methanol conversion rate on modified graphene oxide (GO-3) is 0.172 mmole g-cat^-1 h^-1 under visible light, which is six-fold higher than the pure TiO₂.

The limited natural abundance and high cost of Pt has been a major barrier in its applications for hydrogen fuel cells. In this work, based on the pyrolyzed vitamin B12 (py-B12/C), it is reported to produce superior catalytic activity in the oxygen reduction reaction (ORR) with an electron transfer number of 3.90, which is very close to the ideal case of 4. The H2–O2 fuel cell using py-B12/C provides a maximum power density of 370 mW/cm² and a current density of 0.720 A/cm² at 0.5 V at 70 ^oC. The long-term stability and high ORR activity of py-B12/C make it a viable candidate as a Pt-substitute in the ORR.