Although various carbon nanomaterials including activated carbon, carbon nanotubes, and graphene have been successfully demonstrated for high-performance ultracapacitors, their capacitances need to be improved further for wider and more challenging applications. Herein, using nitrogen-doped graphene produced by a simple plasma process, we developed ultracapacitors whose capacitances (∼280 F/g(electrode)) are about 4 times larger than those of pristine graphene based counterparts without sacrificing other essential and useful properties for ultracapacitor operations including excellent cycle life (>200,000), high power capability, and compatibility with flexible substrates. While we were trying to understand the improved capacitance using scanning photoemission microscopy with a capability of probing local nitrogen-carbon bonding configurations within a single sheet of graphene, we observed interesting microscopic features of N-configurations: N-doped sites even at basal planes, distinctive distributions of N-configurations between edges and basal planes, and their distinctive evolutions with plasma duration. The local N-configuration mappings during plasma treatment, alongside binding energy calculated by density functional theory, revealed that the origin of the improved capacitance is a certain N-configuration at basal planes.

The high porosity of metal-organic frameworks (MOFs) has been used to achieve exceptional gas adsorptive properties but as yet remains largely unexplored for electrochemical energy storage devices. This study shows that MOFs made as nanocrystals (nMOFs) can be doped with graphene and successfully incorporated into devices to function as supercapacitors. A series of 23 different nMOFs with multiple organic functionalities and metal ions, differing pore sizes and shapes, discrete and infinite metal oxide backbones, large and small nanocrystals, and a variety of structure types have been prepared and examined. Several members of this series give high capacitance; in particular, a zirconium MOF exhibits exceptionally high capacitance. It has the stack and areal capacitance of 0.64 and 5.09 mF cm(-2), about 6 times that of the supercapacitors made from the benchmark commercial activated carbon materials and a performance that is preserved over at least 10000 charge/discharge cycles.

The increasing demands on high performance energy storage systems have raised a new class of devices, so-called lithium ion capacitors (LICs). As its name says, LIC is an intermediate system between lithium ion batteries and supercapacitors, designed for taking advantages of both types of energy storage systems. Herein, as a quest to improve the Li storage capability compared to that of other existing carbon nanomaterials, we have developed extrinsically defective multiwall carbon nanotubes by nitrogen-doping. Nitrogen-doped carbon nanotubes contain wall defects through which lithium ions can diffuse so as to occupy a large portion of the interwall space as storage regions. Furthermore, when integrated with 3 nm nickel oxide nanoparticles for a further capacity boost, nitrogen doping enables unprecedented cell performance by engaging anomalous electrochemical phenomena such as nanoparticles division into even smaller ones, their agglomeration-free diffusion between nitrogen-doped sites as well as capacity rise with cycles. The final cells exhibit a capacity as high as 3500 mAh/g, a cycle life of greater than 10,000 times, and a discharge rate capability of 1.5 min while retaining a capacity of 350 mAh/g.

Postsynthetic exchange (PSE) of Ti(IV) into a Zr(IV)-based MOF enabled photocatalytic CO2 reduction to HCOOH under visible light irradiation with the aid of BNAH and TEOA. Use of a mixed-ligand strategy enhanced the photocatalytic activity of the MOF by introducing new energy levels in the band structure of the MOF.

We present a new hybrid density-functional method which predicts transition state barriers with the same accuracy as CBS-APNO, and transition state barriers and enthalpies of reaction with smaller errors than B3LYP, BHandHLYP, and G2. The accuracy of the new method is demonstrated on 132 energies, including 74 transition state barriers and 58 enthalpies of reaction. For 40 reactions with reliable experimental barriers, the absolute mean deviations of the transition state barriers are 0.9, 1.0, 3.1, 3.5, and 3.6 kcal/mol for the new method and the CBS-APNO, G2, B3LYP, and BHandHLYP methods, respectively. The absolute mean deviations of the enthalpies of reaction for 38 reactions with reliable experimental enthalpies are 1.2, 1.4, 3.0, and 5.9 kcal/mol for the new method and the G2, B3LYP, and BHandHLYP methods, respectively. For the new method the maximum absolute deviations for the barriers and enthalpies of reaction are 2.6 and 5.6 kcal/mol, respectively. In addition, we present a simple scheme for a high-level correction that allows accurate determination of atomization energies. The accuracy of this scheme is demonstrated on the 55 atomization energies of the G2 test set [J. Chem. Phys. 94, 7221 (1992)].