用基于密度泛函理论的第一性原理,对Sc作为催化剂对氢气在Mg(0001)表面解离和扩散性能进行了研究。首先,对Sc原子在Mg(0001)表面的稳定吸附和替代位置进行了研究,结果表明,Sc原子将替代在表面的第二层稳定。接下来有对氢气在Sc替代在第...用基于密度泛函理论的第一性原理,对Sc作为催化剂对氢气在Mg(0001)表面解离和扩散性能进行了研究。首先,对Sc原子在Mg(0001)表面的稳定吸附和替代位置进行了研究,结果表明,Sc原子将替代在表面的第二层稳定。接下来有对氢气在Sc替代在第二层的Mg(0001)表面解离和扩散性能进行了研究。结果显示由于Sc的存在,氢气在其表面的解离势垒下降至0.57 e V,氢原子在其表面扩散的势垒降低至0.11 e V,利用分波态密度分析得出Sc原子d轨道上的电子对氢气在Mg表面解离起到了促进的作用;更重要的是,氢原子在Sc原子上方的hcp位向Mg内部扩散的势垒由0.69 e V下降至0.26 e V。大幅度降低氢原子向Mg内部扩散的阻力,也为氢原子向Mg内部扩散提供了更多的通道。Sc有效提高了镁基储氢材料的吸放氢动力学性能,是改善镁基储氢材料的动力学性能很好的催化剂。展开更多
Mg-3Ni-2MnO2 nanocomposite is fabricated by mechanical-milling under hydrogen atmosphere with the pressure of 0.5MPa, and heat and mass transfer of reaction bed was measured through the self-made apparatus. The result...Mg-3Ni-2MnO2 nanocomposite is fabricated by mechanical-milling under hydrogen atmosphere with the pressure of 0.5MPa, and heat and mass transfer of reaction bed was measured through the self-made apparatus. The results show that compared with the intrinsic absorption of Mg-3Ni-2MnO2 hydrogen storage material, the accumulated absorption kinetics of the reaction bed behaves so differently. At 150-300℃ during absorption process, the higher the temperature is, the better the intrinsic kinetics behaves. But during the same temperature range, the lower the initial temperature of the reaction bed is, the better the accumulated absorption kinetics is. During the absorption process, the temperature of reaction bed wall is lower than that of center, and the initial temperature has no influence on the highest temperature in the center of the reaction bed . When the reaction is finished, the reaction bed temperature turns to be homogeneous gradually.展开更多
文摘用基于密度泛函理论的第一性原理,对Sc作为催化剂对氢气在Mg(0001)表面解离和扩散性能进行了研究。首先,对Sc原子在Mg(0001)表面的稳定吸附和替代位置进行了研究,结果表明,Sc原子将替代在表面的第二层稳定。接下来有对氢气在Sc替代在第二层的Mg(0001)表面解离和扩散性能进行了研究。结果显示由于Sc的存在,氢气在其表面的解离势垒下降至0.57 e V,氢原子在其表面扩散的势垒降低至0.11 e V,利用分波态密度分析得出Sc原子d轨道上的电子对氢气在Mg表面解离起到了促进的作用;更重要的是,氢原子在Sc原子上方的hcp位向Mg内部扩散的势垒由0.69 e V下降至0.26 e V。大幅度降低氢原子向Mg内部扩散的阻力,也为氢原子向Mg内部扩散提供了更多的通道。Sc有效提高了镁基储氢材料的吸放氢动力学性能,是改善镁基储氢材料的动力学性能很好的催化剂。
文摘Mg-3Ni-2MnO2 nanocomposite is fabricated by mechanical-milling under hydrogen atmosphere with the pressure of 0.5MPa, and heat and mass transfer of reaction bed was measured through the self-made apparatus. The results show that compared with the intrinsic absorption of Mg-3Ni-2MnO2 hydrogen storage material, the accumulated absorption kinetics of the reaction bed behaves so differently. At 150-300℃ during absorption process, the higher the temperature is, the better the intrinsic kinetics behaves. But during the same temperature range, the lower the initial temperature of the reaction bed is, the better the accumulated absorption kinetics is. During the absorption process, the temperature of reaction bed wall is lower than that of center, and the initial temperature has no influence on the highest temperature in the center of the reaction bed . When the reaction is finished, the reaction bed temperature turns to be homogeneous gradually.
