Graphene has attracted a lot of attention for ultracapacitor electrodes because of its high electrical conductivity, high surface area, and superb chemical stability. However, poor volumetric capacitive performance of typical graphene-based electrodes has hindered their practical applications because of the extremely low density. Herein we report a scalable synthesis method of holey graphene (h-Graphene) in a single step without using any catalysts or special chemicals. The film made of the as-synthesized h-Graphene exhibited relatively strong mechanical strength, 2D hole morphology, high density, and facile processability. This scalable one-step synthesis method for h-Graphene is time-efficient, cost-efficient, environmentally friendly, and generally applicable to other two-dimensional materials. The ultracapacitor electrodes based on the h-Graphene show a remarkably improved volumetric capacitance with about 700% increase compared to that of regular graphene electrodes. Modeling on individual h-Graphene was carried out to understand the excellent processability and improved ultracapacitor performance.

The design of new materials is an important subject in order to attain new properties and applications, and it is of particular interest when some peculiar topological properties such as reduced dimensionality and rule-breaking chemical bonding are involved. In this work, we designed a novel two-dimensional (2D) inorganic material, namely Be2 C monolayer, by comprehensive density functional theory (DFT) computations. In Be2 C monolayer, each carbon atom binds to six Be atoms in an almost planar fashion, forming a quasi-planar hexacoordinate carbon (phC) moiety. Be2 C monolayer has good stability and is the lowest-energy structure in 2D space confirmed by a global minima search based on the particle-swarm optimization (PSO) method. As a semiconductor with a direct medium band gap, Be2 C monolayer is promising for applications in electronics and optoelectronics.

Inspired by our theoretical finding that C₂Al₆(2-) has a planar D₂h minimum with two planar tetracoordinate carbons (ptCs), we computationally designed a new two-dimensional (2D) inorganic material, an Al₂C monolayer. All carbons in this monolayer are ptC's, stabilized inductively by binding to four electropositive Al atoms in the same plane. The Al₂C monolayer is semiconducting with an indirect minimum band gap and a slightly larger direct band gap. Good persistence of the Al₂C monolayer is indicated by its moderate cohesive energy, the absence of imaginary modes in its phonon spectrum, and the high melting point predicted by molecular dynamics (MD) simulations. Moreover, a particle-swarm optimization (PSO) global minimum search found the Al₂C monolayer to be the lowest-energy 2D structure compared to other Al₂C alternatives. Dividing the Al₂C monolayer results in one-dimensional (1D) Al₂C nanoribbons, which are computed to have quite rich characteristics such as direct or indirect band gaps with various values, depending on the direction of the division and the resulting edge configuration.

Boron nitride nanotubes (BNNTs), the one-dimensional member of the boron nitride nanostructure family, are generally accepted to be highly inert to oxidative treatments and can only be covalently modifi ed by highly reactive species. Conversely, it is discovered that the BNNTs can be chemically dispersed and their morphology modifi ed by a relatively mild method: simply sonicating the nanotubes in aqueous ammonia solution. The dispersed nanotubes are significantly corroded, with end-caps removed, tips sharpened, and walls thinned. The sonication treatment in aqueous ammonia solution also removes amorphous BN impurities and shortened BNNTs, resembling various oxidative treatments of carbon nanotubes. Importantly, the majority of BNNTs are at least partially longitudinally cut, or "unzipped". Entangled and freestanding BN nanoribbons (BNNRs), resulting from the unzipping, are found to be ∼5-20 nm in width and up to a few hundred nanometers in length. This is the fi rst chemical method to obtain BNNRs from BNNT unzipping. This method is not derived from known carbon nanotube unzipping strategies, but is unique to BNNTs because the use of aqueous ammonia solutions specifi cally targets the B-N bond network. This study may pave the way for convenient processing of BNNTs, previously thought to be highly inert, toward controlling their dispersion, purity, lengths, and electronic properties.