We report on the local atomic and electronic structures of a nitrogen-doped graphite surface by scanning tunneling microscopy, scanning tunneling spectroscopy, x-ray photoelectron spectroscopy, and first-principles calculations. The nitrogen-doped graphite was prepared by nitrogen ion bombardment followed by thermal annealing. Two types of nitrogen species were identified at the atomic level: pyridinic-N (N bonded to two C nearest neighbors) and graphitic-N (N bonded to three C nearest neighbors). Distinct electronic states of localized π states were found to appear in the occupied and unoccupied regions near the Fermi level at the carbon atoms around pyridinic-N and graphitic-N species, respectively. The origin of these states is discussed based on experimental results and theoretical simulations.

A sharp change in the N 2 emission channel from N 2 O(a)→N 2 (g) +O(a) to N(a)+N(a)→N 2 (g) has been found at around 500 K in a steady-state NO+D 2 reaction over stepped Pd(211)= [(S)3(111)×(100)] by means of angle-resolved desorption. The desorbing N 2 is highly collimated at around 30° off normal toward the step-down direction below about 500 K due to the intermediate N 2 O decomposition, whereas, above 500 K, the near normally directed desorption due to the recombination of N(a) is relatively enhanced. The N 2 O decomposition channel is promoted when the reaction is carried out with hydrogen (deuterium) and the channel change is accelerated by quick changes of the amounts of surface hydrogen and oxygen (or NO(a)) into the opposite directions, and enhanced nitrogen removal as ammonia on the resultant hydrogen-rich surface. In the steady-state NO+CO reaction, the N 2 emission channel gradually changes above 500 K toward recombination. A model for the off-normal N 2 emission is briefly described.

Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms.

The electronic structures of nitrogen species incorporated into highly oriented pyrolytic graphite (HOPG), prepared by low energy (200 eV) nitrogen ion sputtering and subsequent annealing at 1000 K, were investigated by X-ray photoelectron spectroscopy (XPS), angle-dependent X-ray absorption spectroscopy (XAS), and Raman spectroscopy. An additional peak was observed at higher binding energy of 401.9 eV than 400.9 eV for graphitic1 N (graphitic N in the basal plane) in N 1s XPS, where graphitic2 N (graphitic N in the zigzag edge and/or vacancy sites) has been theoretically expected to appear. N 1s XPS showed that graphitic1 N and graphitic2 N were preferably incorporated under low nitrogen content doping conditions (8 × 10(13) ions cm(-2)), while pyridinic N and graphitic1 N were dominantly observed under high nitrogen content doping conditions. In addition, angle-dependent N 1s XAS showed that the graphitic N and pyridinic N atoms were incorporated into the basal plane of HOPG and thus were highly oriented. Furthermore, Raman spectroscopy revealed that low energy sputtering resulted in almost no fraction of the disturbed graphite surface layers under the lowest nitrogen doping condition. The suitable nitrogen doping condition was discovered for realizing the well-controlled nitrogen doped HOPG. The electrochemical properties for the oxygen reduction reaction of these samples in acidic solution were examined and discussed.

The angle resolved intensity and velocity distributions of desorbing product N(2) were measured under a steady-state N(2)O+CO reaction on Rh(110) by cross-correlation time-of-flight techniques. Three-dimensional intensity distribution of N(2) has been constructed from the angle resolved intensity distributions in the planes along different crystal azimuths. N(2) desorption has been found to split into two lobes sharply collimated along 50-63 degrees off normal toward [001] and [001] directions, suggesting that N(2)O is decomposed through the transition state of N(2)O adsorbed with the molecular axis parallel to the [001] direction. From the velocity distribution analysis, each desorption lobe is found to consist of two components with different peak angles, ca. 50 degrees and 74 degrees off normal. In both lobe cases, desorption components have been interpreted by the model of two adsorption sites; N(2)O at on-top site emits N(2) to 50 degrees and that at bridge site emits to 74 degrees.