Using two kinds of molybdenum （Mo） powders with different micro-morphologies as raw materials, the Mo wires with a diameter of 0.18 mm and Mo sheets with thickness of 0.5 and 0.2 mm were prepared at the same process...Using two kinds of molybdenum （Mo） powders with different micro-morphologies as raw materials, the Mo wires with a diameter of 0.18 mm and Mo sheets with thickness of 0.5 and 0.2 mm were prepared at the same process of pressing, sintering, drawing, or rolling, respectively. By comparative analysis on the microstructure and mechanical properties of Mo wires and Mo sheets, the effect of Mo powder micro-morphology on properties and quality of Mo products was studied. The results show that, compared with that prepared by traditional Mo powder with inhomogeneous particle size and aggregation, the Mo wires prepared by specific Mo powder with homogeneous particle sizes, less agglomeration, and better dispersion exhibit higher yield, higher tensile strength, and lower elongation at room temperature, and the Mo sheets also show excellent high-temperature performances and better isotropy. The essential reason for those is the difference of Mo powder micro-morphology. Inhomogeneous particle size and aggregation of Mo powder greatly influence the microstructure of Mo sintered compacts and mechanical properties of Mo products.展开更多
Effects of space velocity, reaction temperature and support acidity on product distribution and induction period in 1-butene isomerization and metathesis over Mo/mordenite-alumina were investigated. As revealed by the...Effects of space velocity, reaction temperature and support acidity on product distribution and induction period in 1-butene isomerization and metathesis over Mo/mordenite-alumina were investigated. As revealed by the catalytic performance results, induction period and objective product were closely related to the reaction conditions. Lower space velocity led to longer induction period and higher propene yield. The optimal reaction temperature for propene production is around 150 ~C and it shifted to 100 ~C for ethene production. 1-Butene auto-metathesis predominated in the reaction network if the support with lower degree of sodium exchanged. And propene gradually became the dominant product upon increasing the support sodium exchange degree. 6Mo/H100Na0M-30A1 catalyst with a support of full sodium exchange degree exhibited the highest propene yield.展开更多
94mTc was produced via natMo(p, xn)94mTc reaction. Deposition of MoO3 on Cu substrate was carried out via two special sedimentation methods for the production of 94mTc. The 533 mg of MoO3, 600 μL of collodium (nitroc...94mTc was produced via natMo(p, xn)94mTc reaction. Deposition of MoO3 on Cu substrate was carried out via two special sedimentation methods for the production of 94mTc. The 533 mg of MoO3, 600 μL of collodium (nitrocellulose) and 3 mL of acetone were used to prepare a MoO3 layer of 11.69 cm2 and 45.81 mg·cm-2. Also, a MoO3 layer was prepared by 533 mg of MoO3, 71.188 mg of methylcellulose and 4 mL of water. The targets were checked by SEM and thermal shock test.展开更多
化石燃料的大量消耗所带来的全球性挑战推动人们大力发展清洁和可持续的能源.氢能作为一种绿色、无污染的能源载体,是能源向绿色经济转换的关键,而利用可再生能源进行的电解水制氢被认为是实现绿色制氢的最佳选择.然而由于析氧反应(OER...化石燃料的大量消耗所带来的全球性挑战推动人们大力发展清洁和可持续的能源.氢能作为一种绿色、无污染的能源载体,是能源向绿色经济转换的关键,而利用可再生能源进行的电解水制氢被认为是实现绿色制氢的最佳选择.然而由于析氧反应(OER)的氧化电位(1.23 V)较高,动力学缓慢,实际水电解需要更多的能量输入.具有低氧化电位的甲醇辅助水电解(0.016 V)可以匹配可再生能源实现低能耗电解制氢,受到了广泛关注.开发高效的用于催化甲醇氧化(MOR)和析氢反应(HER)的双功能催化剂是实现这一愿景的前提.传统的Pt基催化剂容易受到阳极侧MOR过程中产生的CO中间体毒化,严重影响甲醇辅助水电解制氢的效率.为了提升Pt基催化剂的催化活性和稳定性,一种有效的策略是引入合适的功能组分来促进催化反应.例如,贵金属颗粒和亲氧化成分(如过渡金属氧化物和磷化物)之间的金属-载体相互作用可以有效提高Pt基催化剂的抗CO中毒能力.过渡金属硒化物由于其优良的金属性和亲氧性作为催化促进剂受到越来越多的关注.硒化钼(MoSe_(2))具有良好的稳定性和导电性并且其2H相中的不饱和边缘具有水活化和解离活性,同时其吸附H原子的吉布斯自由能(ΔGH^(*))接近于零.考虑到MoSe_(2)的高水活化/解离能力,本文成功制备了二维MoSe_(2)纳米片负载的Pt纳米粒子复合催化剂(Pt/MoSe_(2))用于高效甲醇电解制氢.密度泛函理论计算表明,亲氧组分MoSe_(2)显著优化了CO^(*)和H^(*)在Pt表面的吸附能,从而大大提高了甲醇辅助水电解的活性和稳定性.其中,Pt/MoSe_(2)的甲醇氧化峰值电流密度为67.8 m Acm^(-2),是商业Pt/C催化剂的2.5倍;在10 m A·cm^(-2)的电流密度下,HER的过电位低至32 m V.由Pt/MoSe_(2)|Pt/MoSe_(2)组装的两电极电解槽驱动10 m A·cm^(-2)的电流密度仅需要0.67 V的电压,与相同条件下的水电解相比节省了约1.09 V的电池电压,大大降低了能量输入.催化性能的提升可以归因于改善的电荷转移以及Pt与亲氧MoSe_(2)之间的金属-载体相互作用,该相互作用使得Pt从MoSe_(2)载体上得到了部分电子,增加了Pt周围的电子密度,使得邻近Pt的d带中心下移,从而通过削弱CO-Pt键进而增强了Pt位点的抗CO中毒能力.综上,本文对开发用于甲醇辅助水电解制氢的新型双功能催化剂具有借鉴意义.展开更多
基金financially supported by the National Science Technology Supporting Program of China(No.2012BAE06B02)
文摘Using two kinds of molybdenum （Mo） powders with different micro-morphologies as raw materials, the Mo wires with a diameter of 0.18 mm and Mo sheets with thickness of 0.5 and 0.2 mm were prepared at the same process of pressing, sintering, drawing, or rolling, respectively. By comparative analysis on the microstructure and mechanical properties of Mo wires and Mo sheets, the effect of Mo powder micro-morphology on properties and quality of Mo products was studied. The results show that, compared with that prepared by traditional Mo powder with inhomogeneous particle size and aggregation, the Mo wires prepared by specific Mo powder with homogeneous particle sizes, less agglomeration, and better dispersion exhibit higher yield, higher tensile strength, and lower elongation at room temperature, and the Mo sheets also show excellent high-temperature performances and better isotropy. The essential reason for those is the difference of Mo powder micro-morphology. Inhomogeneous particle size and aggregation of Mo powder greatly influence the microstructure of Mo sintered compacts and mechanical properties of Mo products.
基金the National Natural Science Foundation of China(Grant No.20903088 and 21006104)
文摘Effects of space velocity, reaction temperature and support acidity on product distribution and induction period in 1-butene isomerization and metathesis over Mo/mordenite-alumina were investigated. As revealed by the catalytic performance results, induction period and objective product were closely related to the reaction conditions. Lower space velocity led to longer induction period and higher propene yield. The optimal reaction temperature for propene production is around 150 ~C and it shifted to 100 ~C for ethene production. 1-Butene auto-metathesis predominated in the reaction network if the support with lower degree of sodium exchanged. And propene gradually became the dominant product upon increasing the support sodium exchange degree. 6Mo/H100Na0M-30A1 catalyst with a support of full sodium exchange degree exhibited the highest propene yield.
文摘94mTc was produced via natMo(p, xn)94mTc reaction. Deposition of MoO3 on Cu substrate was carried out via two special sedimentation methods for the production of 94mTc. The 533 mg of MoO3, 600 μL of collodium (nitrocellulose) and 3 mL of acetone were used to prepare a MoO3 layer of 11.69 cm2 and 45.81 mg·cm-2. Also, a MoO3 layer was prepared by 533 mg of MoO3, 71.188 mg of methylcellulose and 4 mL of water. The targets were checked by SEM and thermal shock test.
文摘化石燃料的大量消耗所带来的全球性挑战推动人们大力发展清洁和可持续的能源.氢能作为一种绿色、无污染的能源载体,是能源向绿色经济转换的关键,而利用可再生能源进行的电解水制氢被认为是实现绿色制氢的最佳选择.然而由于析氧反应(OER)的氧化电位(1.23 V)较高,动力学缓慢,实际水电解需要更多的能量输入.具有低氧化电位的甲醇辅助水电解(0.016 V)可以匹配可再生能源实现低能耗电解制氢,受到了广泛关注.开发高效的用于催化甲醇氧化(MOR)和析氢反应(HER)的双功能催化剂是实现这一愿景的前提.传统的Pt基催化剂容易受到阳极侧MOR过程中产生的CO中间体毒化,严重影响甲醇辅助水电解制氢的效率.为了提升Pt基催化剂的催化活性和稳定性,一种有效的策略是引入合适的功能组分来促进催化反应.例如,贵金属颗粒和亲氧化成分(如过渡金属氧化物和磷化物)之间的金属-载体相互作用可以有效提高Pt基催化剂的抗CO中毒能力.过渡金属硒化物由于其优良的金属性和亲氧性作为催化促进剂受到越来越多的关注.硒化钼(MoSe_(2))具有良好的稳定性和导电性并且其2H相中的不饱和边缘具有水活化和解离活性,同时其吸附H原子的吉布斯自由能(ΔGH^(*))接近于零.考虑到MoSe_(2)的高水活化/解离能力,本文成功制备了二维MoSe_(2)纳米片负载的Pt纳米粒子复合催化剂(Pt/MoSe_(2))用于高效甲醇电解制氢.密度泛函理论计算表明,亲氧组分MoSe_(2)显著优化了CO^(*)和H^(*)在Pt表面的吸附能,从而大大提高了甲醇辅助水电解的活性和稳定性.其中,Pt/MoSe_(2)的甲醇氧化峰值电流密度为67.8 m Acm^(-2),是商业Pt/C催化剂的2.5倍;在10 m A·cm^(-2)的电流密度下,HER的过电位低至32 m V.由Pt/MoSe_(2)|Pt/MoSe_(2)组装的两电极电解槽驱动10 m A·cm^(-2)的电流密度仅需要0.67 V的电压,与相同条件下的水电解相比节省了约1.09 V的电池电压,大大降低了能量输入.催化性能的提升可以归因于改善的电荷转移以及Pt与亲氧MoSe_(2)之间的金属-载体相互作用,该相互作用使得Pt从MoSe_(2)载体上得到了部分电子,增加了Pt周围的电子密度,使得邻近Pt的d带中心下移,从而通过削弱CO-Pt键进而增强了Pt位点的抗CO中毒能力.综上,本文对开发用于甲醇辅助水电解制氢的新型双功能催化剂具有借鉴意义.
