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When Cu(110), Ni(l 10), Ag(110) surfaces are exposed to O2 at room temperature, one dimensional metal-oxygen strings grow in the < 001 > direction of the (110) surfaces. A similar phenomenon occurs in the adsorption of H2 on Ni( 110) surface at room temperature, where the one dimensional strings grow along the < 110 > direction. These phenomena are undoubtedly different from the adsorption induced reconstruction but are explained by the chemical reconstruction involving the formation of quasi-compounds and their self-ordering on the metal surfaces. The chemical reconstruction is indispensablly important to understand the structure and catalysis of alloy and bimetallic surfaces. Pt0.25Rh0.75(100) alloy surface being active for the reaction of NO with H2 is an interesting example. When the Pt-Rh(100) alloy surface is exposed to NO or O2 at arround 500 K, a p(3 × 1) ordered Rh-O over-layer is obtained on a Pt-enriched 2nd layer by the chemical reconstruction. Ordering of Rh-0 in the p(3 × 1) structure on the Pt(100) surface was reproduced by heating a Rh/Pt(100) bimetallic surface in O2, and the chemical reconstruction making the p(3 × 1) Rh-O overlayer on a Pt enriched 2nd layer was also proved by heating a Pt/Rh(100) bimetallic surface in O2 or NO. The activation mechanism of the Pt-Rh alloy and the Pt/Rh bimetallic surfaces by the chemical reconstruction was evidently shown by using a Pt deposited Rh(100), Pt/Rh(100), surface. That is, the Pt/Rh(100) is not so active for the reaction of NO with H2, but the reconstructed p(3 × 1)Rh-O/Pt-layer/Rh(100) surface is very active for the reaction. Therefore, it was concluded that the chemical reconstruction of the Pt-Rh catalyst makes the active surface which is composed of Rh-O and a Pt layer. 相似文献
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提出了电感耦合等离子体原子发射光谱法测定铂铑合金中铑含量的方法。含铑(wRh≤40%)的铂铑合金称样0.1000 g,用盐酸-硝酸(3+1)溶液10 mL和氢氟酸(ρ=1.18 g·mL-1)0.5 mL于微波消解仪中消解完全。选择波长为343.489 nm的谱线作为测定铑的分析线。方法的检出限为0.029 mg·L-1。方法用于分析5个铂铑合金样品,测定值与国家标准方法测定值的相对误差在0.10%~0.40%之间,回收率在99.6%~101.0%之间。 相似文献
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低贵金属Pt-Rh型三效催化剂空燃比性能的研究 总被引:3,自引:0,他引:3
研究了以浸渍法制备的低贵金属Pt-Rh型三效催化剂对C3H8, CO, NO的催化活性. 主要考察了CeO2-ZrO2和BaO的添加对催化剂空燃比性能的影响, 通过氧化反应、水气变换和蒸汽重整的性能研究, 探讨了催化剂三效工作窗口扩大的原因. 结果表明, 催化剂中只添加CeO2-ZrO2时即具有优异的水气变换性能, 蒸汽重整在250 ℃左右发生, 并且在450 ℃以下时C3H8的转化率一直保持在20%左右; BaO添加到含有CeO2-ZrO2的催化剂中对水气变换和蒸汽重整则有明显的促进作用, 能进一步扩大催化剂的三效工作窗口; 催化剂中只添加CeO2-ZrO2时, 能明显提高催化剂对CO的氧化反应活性, 但对C3H8的氧化反应的影响则不明显; BaO和CeO2-ZrO2同时存在于催化剂中时, 能进一步提高CO的氧化反应活性, 对C3H8的氧化反应则没有明显的促进作用. 相似文献
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