Beijing University of Technology

About: Beijing University of Technology is a education organization based out in Beijing, Beijing, China. It is known for research contribution in the topics: Microstructure & Computer science. The organization has 31929 authors who have published 31987 publications receiving 352112 citations. The organization is also known as: Běijīng Gōngyè Dàxué & Beijing Polytechnic University.

Enhanced photocatalytic N2 fixation via defective and fluoride modified TiO2 surface

Abstract: Photocatalytic N2 fixation (PNF) provides a low-cost route to generate ammonia. The poor conversion efficiency from photon to ammonia seriously hinders the step forward because of the low concentration of N2 molecules. Herein, we demonstrate a photocatalyst with surface oxygen vacancies (Vo) and a F modified surface to facilitate N2 adsorption and activation on the surface of catalysts. The Vo site promotes the chemical adsorption of N2, electron transfer from catalyst to N2. F modification switches the TiO2 surface properties from hydrophilic to aerophilic, thus facilitating the adsorption of N2. Meanwhile, the hydrogen reduction reaction (HER) is suppressed, as protons hard to adsorb on F capped surfaces. The optimal NH3 production rate can reach 206 μmolh−1g−1, which is ∼ 9 times higher than that of pure TiO2 nanoparticles (∼23 μmolh−1g−1). This report provides a potential strategy to overcome mass transfer limitation and achieve a high conversion efficiency in PNF.

Development of High Current-Density Cathodes With Scandia-Doped Tungsten Powders

Abstract: The development of high current-density cathodes employing scandia-doped tungsten powders is reviewed in this paper. A matrix with a submicrometer microstructure characterized by uniformly distributed nanometer particles of scandia is believed to play a dominant role in the improved emission capability of these cathodes. Space-charge-limited current densities of over 30 A/cm2 at 850 degCb have been repeatedly obtained for many runs of cathodes fabricated from the different batches of scandia-doped tungsten powders. A lifetime of over 10000 h at 950-degCb 2-A/cm2 dc loading in a test diode has been achieved. Periodic high current-density pulse testing was also carried out during the test. The performance for both the dc and pulsed current densities remained stable. When tested at Stanford Linear Accelerator Center in a cathode life test vehicle with a Pierce gun configuration, the cathode operated for 500 h at 1170 degC b, with a pulsed loading of 100 A/cm2 and with less than 5% degradation in current density. The outstanding performance of these cathodes is attributed to a surface multilayer of Ba-Sc-O of about 100-nm thickness that uniformly covers the W grains with nanometer-size particles distributed on the growth steps. The layer is formed after proper activation by diffusion of free or ionic Sc together with Ba and O from the interior of the cathode to its surface. This highly mobile, free, or ionic Sc is liberated from constituents produced during impregnation and activation by reactions between the matrix materials and impregnants

In situ poly(methyl methacrylate)-templating generation and excellent catalytic performance of MnOx/3DOM LaMnO3 for the combustion of toluene and methanol

Abstract: Rhombohedrally crystallized three-dimensionally ordered macroporous (3DOM) LaMnO3 supported MnOx (5, 8, 12, 16 wt% MnOx/3DOM LaMnO3) catalysts were prepared using the in situ tryptophan-assisted poly(methyl methacrylate)-templating strategy. Physicochemical properties of the materials were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the combustion of toluene and methanol. It is shown that the MnOx/3DOM LaMnO3 samples displayed a 3DOM architecture and a high surface area of 19–31 m2/g. The 12 wt% MnOx/3DOM LaMnO3 sample showed the highest oxygen adspecies concentration and the best low-temperature reducibility as well as the highly dispersed MnOx particles on the LaMnO3 surface, giving the highest TOF values of 7.9 x 10−6 s−1 for toluene combustion at 160 °C and 7.3 x 10−6 s−1 for methanol combustion at 80 °C. The apparent activation energies of the MnOx/3DOM LaMnO3 catalysts were 61–62 and 48–54 kJ/mol for toluene and methanol combustion, respectively. It is concluded that the excellent catalytic performance of 12 wt% MnOx/3DOM LaMnO3 was associated with its highest oxygen adspecies concentration, best low-temperature reducibility, and strong interaction between MnOx and 3DOM LaMnO3.