摘要: Direct methanol fuel cell (DMFC) is a potential commercial fuel cell technology that is presently hindered by the expensive noble metal materials of the anode. Developing a method to obtain a uniformly dispersed metal phosphide catalyst with narrow size distribution is still a challenge. In this work, cobalt oxide was deposited on carbon cloth (CC) through atomic layer deposition (ALD), then cobalt phosphide was obtained after the phosphorization process. By changing the number of ALD-based ozone pulses (ALD-O3) for CC, the nucleation and growth modes of cobalt oxide (ALD-CoOx) on the CC were regulated, and CoPx nanoparticles with small particle size and uniform distribution were obtained. The optimized CoPx-based catalyst with 40 cycles of ALD-O3 treatment (CoPx/40-CC) exhibits excellent activity (153 mA/cm2) toward methanol electrocatalytic oxidation reaction in the alkaline solution, which is higher than the catalyst prepared by impregnation (Imp-CoPx/CC), although the CoPx loading of CoPx/40-CC is lower than that of Imp-CoPx/CC. The results indicate that the enhanced activity benefits from the small particle size and the uniform CoPx distribution, which promote the electron-transfer and mass transport kinetics of the methanol electro-oxidation process.
摘要: Oxidation treated carbon materials for exploiting highly efficient and stable loaded catalysts have been proven to be valid. In this work, the surfaces of carbon aerogels (CA) were functionalized with different oxidizing agents, i.e., H2O2 and HNO3. A series of Ru-supported catalysts on carbon aerogels (CA) with/without functionalized were prepared by the impregnation strategy. The impact of oxidation treatment on the texture features of carbon aerogels, the types and contents of formed surface oxygen-containing functional groups, the metal-support interactions and the Fischer-Tropsch synthesis reaction performances of the catalysts were systematically investigated. Our results showed that Ru/CA catalyst without oxidation treatment displayed the highest initial activity but the poor stability, while the Ru/CA-H2O2 catalyst exhibited excellent activity and C5+ selectivity. The oxidation treatment increased the carbon aerogels defects, thereby broadening the specific surface area. The increased content of oxygen-containing functional groups on the surface enhanced the interaction between the support and Ru nanoparticles and improved the stability of the catalyst. Nevertheless, the excessive oxygen-containing functional groups on the surface decreased the activity and the C5+ selectivity of carbon aerogels-loaded Ru catalysts.
摘要: Herein, SiO2 supported metallic Ni (Ni/SiO2) and bimetallic Ni-Zn (NixZn/SiO2) (x represents the Ni/Zn atomic ratio) catalysts were prepared by the incipient wetness impregnation method and their activities were tested in vapor phase hydrodeoxygenation (HDO) of anisole under 0.1 MPa. The characterization results show that Ni-Zn alloy forms in NixZn/SiO2 after reduction at 550 °C, and a suitable Ni/Zn atomic ratio (30) leads to smaller alloy particle size and consequently more H2 adsorption amount than others. In the HDO reaction, the formation of Ni-Zn alloy facilitates the direct deoxygenation pathway and suppresses CO methanation and C−C bond hydrogenolysis, which is ascribed to the isolation effect of the Ni atoms by the oxophilic Zn ones. Ni30Zn/SiO2 gives not only higher anisole conversion but also higher selectivity to benzene than Ni/SiO2. Therefore, the introduction of a suitable amount of oxophilic Zn in Ni/SiO2 promotes the HDO of anisole to benzene. Finally, we propose that the Ni30Zn/SiO2 deactivation is related to the oxidation of Ni-Zn alloy and carbon deposition on the catalyst surface.
