Molybdenum phosphide(MoP) catalyst has been widely applied in hydrogenation reactions, while the preparation of unsupported MoP catalysts with ultra-small size and large specific surface area(SBET) is still challengin...Molybdenum phosphide(MoP) catalyst has been widely applied in hydrogenation reactions, while the preparation of unsupported MoP catalysts with ultra-small size and large specific surface area(SBET) is still challenging. Herein, we have provided a facile method for preparing a series of MoP-x(x=P/Mo ratios ranging from 1 to 5) catalysts by pyrolyzing phytic acid(PA)-derived Mo complexes in a H2 atmosphere. The physicochemical properties and the catalytic activity of MoP catalysts were investigated. The results showed that the obtained MoP-5 catalyst had the largest SBETand exhibited ultra-small nanoparticle diameter of 3.6 nm, which ascribed to the chelation of PA and the confinement of deposited products.As the content of PA increased, the synthetic mechanism of MoP was also affected, which led to the difference in the valence of surface Mo species. The characterization results further confirmed that Moδ+ sites in MoP catalysts are active sites for methanation reaction and its content on the surface of MoP-x catalysts determines the catalytic activity.展开更多
化学复合镀RE Ni Mo P WC合金镀层具有良好的硬度、耐蚀、耐磨、抗氧化性能 ,但沉积速度对镀层性能有很大的影响。采用增重法研究了稀土元素、镀液温度、pH值、钼酸钠浓度对化学复合镀RE Ni Mo P WC合金镀层沉积速度的影响 ,并探讨了稀...化学复合镀RE Ni Mo P WC合金镀层具有良好的硬度、耐蚀、耐磨、抗氧化性能 ,但沉积速度对镀层性能有很大的影响。采用增重法研究了稀土元素、镀液温度、pH值、钼酸钠浓度对化学复合镀RE Ni Mo P WC合金镀层沉积速度的影响 ,并探讨了稀土元素的作用机理。结果表明 ,稀土元素的加入增大了复合镀层的沉积速度 ,其中混合稀土的作用最为明显 ;稀土元素的加入能促进反应离子在金属基体表面的吸附 ,增大阴极极化 ,改变界面双电层结构 ,从而使沉积速率加快。RE Ni Mo P WC最佳工艺条件为 :混合稀土浓度 4 g/L ,镀液温度 80℃ ,pH值 7.0～ 7 5 ,钼酸钠浓度≤ 0 .3g/L。展开更多
研究了非晶Ni Mo P沉积层的应力、成分及气孔率,它们对镀层在5%NaCl中的抗腐蚀性能的影响,同时研究了气孔、应力产生的原因。研究结果表明:在合适的Na2MoO4浓度及pH值下获得的非晶Ni Mo P沉积层具有最佳抗腐蚀性。随着镀液中Na2MoO4... 研究了非晶Ni Mo P沉积层的应力、成分及气孔率,它们对镀层在5%NaCl中的抗腐蚀性能的影响,同时研究了气孔、应力产生的原因。研究结果表明:在合适的Na2MoO4浓度及pH值下获得的非晶Ni Mo P沉积层具有最佳抗腐蚀性。随着镀液中Na2MoO4含量的增加,镀层应力很快从压应力向拉应力转变,镀层的气孔率增加。当Na2MoO4浓度大约为0.05g/L时,容易获得低孔隙率、低应力的非晶镀层。镀层气孔率、应力增加,镀层的耐蚀性显著降低。试样的长期腐蚀抵抗主要取决于镀层的应力,短期腐蚀抵抗则取决于镀层的气孔率。镀层具有低应力无气孔时,非晶镀层中Mo的含量越高,镀层在5%NaCl中的抗腐蚀性越好,而P含量的变化对镀层抗腐蚀性能无明显影响。镀层的应力采用X射线应力仪测定,并通过观察试样在5%HCl中浸泡25d后的外观进一步验证。采用浸泡腐蚀测试、硝酸变黑腐蚀测试、气孔率贴滤纸测试及电化学腐蚀测试技术对比研究了沉积层的腐蚀行为。展开更多
基金Financial supports from the National High Technology Research and Development Program of China (863 Project) (2015AA050504)。
文摘Molybdenum phosphide(MoP) catalyst has been widely applied in hydrogenation reactions, while the preparation of unsupported MoP catalysts with ultra-small size and large specific surface area(SBET) is still challenging. Herein, we have provided a facile method for preparing a series of MoP-x(x=P/Mo ratios ranging from 1 to 5) catalysts by pyrolyzing phytic acid(PA)-derived Mo complexes in a H2 atmosphere. The physicochemical properties and the catalytic activity of MoP catalysts were investigated. The results showed that the obtained MoP-5 catalyst had the largest SBETand exhibited ultra-small nanoparticle diameter of 3.6 nm, which ascribed to the chelation of PA and the confinement of deposited products.As the content of PA increased, the synthetic mechanism of MoP was also affected, which led to the difference in the valence of surface Mo species. The characterization results further confirmed that Moδ+ sites in MoP catalysts are active sites for methanation reaction and its content on the surface of MoP-x catalysts determines the catalytic activity.
文摘化学复合镀RE Ni Mo P WC合金镀层具有良好的硬度、耐蚀、耐磨、抗氧化性能 ,但沉积速度对镀层性能有很大的影响。采用增重法研究了稀土元素、镀液温度、pH值、钼酸钠浓度对化学复合镀RE Ni Mo P WC合金镀层沉积速度的影响 ,并探讨了稀土元素的作用机理。结果表明 ,稀土元素的加入增大了复合镀层的沉积速度 ,其中混合稀土的作用最为明显 ;稀土元素的加入能促进反应离子在金属基体表面的吸附 ,增大阴极极化 ,改变界面双电层结构 ,从而使沉积速率加快。RE Ni Mo P WC最佳工艺条件为 :混合稀土浓度 4 g/L ,镀液温度 80℃ ,pH值 7.0～ 7 5 ,钼酸钠浓度≤ 0 .3g/L。
文摘 研究了非晶Ni Mo P沉积层的应力、成分及气孔率,它们对镀层在5%NaCl中的抗腐蚀性能的影响,同时研究了气孔、应力产生的原因。研究结果表明:在合适的Na2MoO4浓度及pH值下获得的非晶Ni Mo P沉积层具有最佳抗腐蚀性。随着镀液中Na2MoO4含量的增加,镀层应力很快从压应力向拉应力转变,镀层的气孔率增加。当Na2MoO4浓度大约为0.05g/L时,容易获得低孔隙率、低应力的非晶镀层。镀层气孔率、应力增加,镀层的耐蚀性显著降低。试样的长期腐蚀抵抗主要取决于镀层的应力,短期腐蚀抵抗则取决于镀层的气孔率。镀层具有低应力无气孔时,非晶镀层中Mo的含量越高,镀层在5%NaCl中的抗腐蚀性越好,而P含量的变化对镀层抗腐蚀性能无明显影响。镀层的应力采用X射线应力仪测定,并通过观察试样在5%HCl中浸泡25d后的外观进一步验证。采用浸泡腐蚀测试、硝酸变黑腐蚀测试、气孔率贴滤纸测试及电化学腐蚀测试技术对比研究了沉积层的腐蚀行为。
