We examine the possibility of nitrogen-doped C60 fullerene (N-C60) as a cathode catalyst for hydrogen fuel cells. We use first-principles spin-polarized density functional theory calculations to simulate the electrocatalytic reactions on N-C60. The first-principles results show that an O2 molecule can be adsorbed and partially reduced on the N-C complex sites (Pauling sites) of N-C60 without any activation barrier. Through a direct pathway, the partially reduced O2 can further react with H(+) and additional electrons and complete the water formation reaction (WFR) with no activation energy barrier. In the indirect pathway, reduced O2 reacts with H(+) and additional electrons to form H2O molecules through a transition state (TS) with a small activation barrier (0.22-0.37 eV). From an intermediate state to a TS, H(+) can obtain a kinetic energy of ∼0.95-3.68 eV, due to the Coulomb electric interaction, and easily overcome the activation energy barrier during the WFR. The full catalytic reaction cycles can be completed energetically, and N-C60 fullerene recovers to its original structure for the next catalytic reaction cycle. N-C60 fullerene is a potential cathode catalyst for hydrogen fuel cells.

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We present calculated electronic properties of gallium nitride ͑GaN͒, silicon ͑Si͒, diamond ͑C͒, and ruthenium dioxide (RuO 2 ). We implemented a simple computational procedure that avoids a recently identified basis set and variational effect. This effect, inherent to the use of basis sets in variational calculations, is believed to have affected ab initio calculations of electronic properties of semiconductors since their inception. We employed ab initio, density-functional calculations using a local-density-approximation potential and the linear combination of atomic orbital formalism. There is an excellent agreement between our findings and experimental results. In particular, the calculated, direct, minimum band gap of GaN, for low temperatures, is 3.2 eV, while the practical band gap, as per the calculated density of states, is 3.40 eV. Band gaps and excitation energies for silicon and diamond compare favorably with experimental results.

The electronic structure, charge distribution, effective charge, and charge transfer in ferroelectric tetragonal BaTiO 3 are carefully studied using a local density functional potential and a self-consistent ab initio LCAO (linear combination of atomic orbitals) method. It is shown that the band gap and low-energy conduction band can be calculated with a reasonable accuracy when the ab initio LCAO method is used with an optimum basis set of atomic orbitals. The calculated optical spectrum, band gap, and effective mass of BaTiO 3 , obtained from the calculated electronic structure, are in good agreement with experimental results.

The growth mechanism of magnetic nanoparticles (NPs) in the presence of graphite oxide (GO) has been investigated by varying the iron precursor dosage and reaction time (product donated as MP/GO). The synthesized magnetic NPs were anchored on the GO sheets due to the abundant oxygen-containing functionalities on the GO sheets such as carboxyl, hydroxyl and epoxy functional groups. The introduced NPs changed the intrinsic functionalities and lattice structure of the basal GO as indicated by FT-IR, Raman and XRD analysis, and this effect was enhanced by increasing the amount of iron precursor. Uniform distribution of NPs within the basal GO sheets and an increased particle size from 19.5 to 25.4, 31.5 and 85.4 nm were observed using scanning electron microscope (SEM) and transmission electron microscope (TEM) when increasing the weight ratio of GO to iron precursor from 10 : 1, to 5 : 1, 1 : 1 and 1 : 5, respectively. An aggregation of NPs was observed when increasing the iron precursor dosage or prolonging the reaction time from 1 to 8 h. Most functionalities were removed and the magnetic NPs were partially converted to iron upon thermal treatment under a reducing condition. The GO and MP/GO nanocomposites reacted for one and two hours (denoted as MP/GO 1 -1 h and MP/GO 1 -2 h) were converted from insulator to semiconductor after the annealing treatment as annealed GO (A-GO, 8.86 S cm À1 ), annealed MP/GO 1 -1 h (A-MP/GO 1 -1 h, 7.48 Â 10 À2 S cm À1 ) and annealed MP/GO 1 -2 h (A-MP/GO 1 -2 h, 7.58 Â 10 À2 S cm À1 ). The saturation magnetization was also enhanced significantly after the annealing treatment, increased from almost 0 to 26.7 and 83.6 emu g À1 for A-MP/GO 1 -1 h and A-MP/GO 1 -2 h, respectively.