Atomic layer deposition of ultrathin layered TiO_2 on Pt/C cathode catalyst for extended durability in polymer electrolyte fuel cells

This study shows the preparation of a TiO2 coated Pt/C（TiO2/Pt/C） by atomic layer deposition（ALD）,and the examination of the possibility for TiO2/Pt/C to be used as a durable cathode catalyst in polymer electrolyte fuel cells（PEFCs）. Cyclic voltammetry results revealed that TiO2/Pt/C catalyst which has 2 nm protective layer showed similar activity for the oxygen reduction reaction compared to Pt/C catalysts and they also had good durability. TiO2/Pt/C prepared by 10 ALD cycles degraded 70% after 2000 Accelerated degradation test, while Pt/C corroded 92% in the same conditions. TiO2 ultrathin layer by ALD is able to achieve a good balance between the durability and activity, leading to TiO2/Pt/C as a promising cathode catalyst for PEFCs. The mechanism of the TiO2 protective layer used to prevent the degradation of Pt/C is discussed.

Controlling Mechanism and Resulting Spray Characteristics of Injection of Fuel Containing Dissolved Gas

This paper presents a recent advance in the study of injection of fuel containing dissolved gas (IFCDG).Using diesel fuel containing dissolved CO2, experiments were performed under atmospheric conditions on a diesel hole-type nozzle and simple nozzles. The effects of gas concentration in the fuel, injection pressure and the nozzle L/D ratio were examined. In order to reveal the controlling mechanism of IFCDG, the orifice flow pattern, pressure characteristics and their effects were also investigated. The result shows that IFCDG can produce a parabolic-shaped spray pattern with good atomization, which suggests the ekistence of a new atomisation mechanism. In terms of atomization, the beneficial effect of the IFCDG is obtained at the dissolved gas concentration above the transition and in the region of larger nozzle L/D ratio. However, under unfavorable conditions, IFCDG will lead to deterioration of atomization with coarse fuel droplets. It is found that the big difference of the oracle pressure characteristics caused by the variation of the nozzle L/D ratio has a dominant influence on the separation of the dissolved gas from the fuel inside the orifice and is verified to account for a dramatic change in the spray pattern and determine the effect of IFCDG. It is considered that the concept of IFCDG could be attractive in producing more efficient, clean engine and find use in a wide range of application.

Spray characteristics and controlling mechanism of fuel containing CO2

This paper presents studies of spray characteristics and controlling mechanism of fuel containing CO2. Using diesel fuel containing CO2 gas, experiments were conducted on diesel hole-type nozzles and simple nozzles. The steady spray and transient spray characteristics were observed and measured by instantaneous shadowgraphy, high-speed photography, phase Doppler anemometry （PDA） and LDSA respectively. The effects of CO2 concentration in the fuel, the injection pressure, the nozzle L/D ratio, surrounding gas pressure and temperature on the atomization behavior and spray pattern were evaluated. The results show that the injection of fuel containing CO2 can greatly improve the atomization and produce a parabolic-shaped spray; and the CO2 gas concentration, surrounding gas pressure, temperature and nozzle config- uration have dominant influences on spray characteristics of the fuel containing CO2. New insight into the controlling mechanism of atomization of the fuel containing CO2 was provided.