Catalytic Activity of Supported Metal Particles for Sulfuric Acid Decomposition Reaction
Catalytic Activity of Supported Metal Particles for Sulfuric Acid Decomposition Reaction
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DOI：
10.1016/j.cattod.2008.03.029
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发表时间：
2007-08
期刊：
影响因子：
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通讯作者：
S. Rashkeev;D. Ginosar;L. Petkovic;H. Farrell
中科院分区：
文献类型：
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作者：
S. Rashkeev;D. Ginosar;L. Petkovic;H. Farrell
在热化学硫基循环中，利用硫酸催化分解为SO2和O2，通过分解水来生产氢气是相当令人感兴趣的。然而，迄今为止研究的所有已知的由氧化物基材上的金属颗粒组成的催化体系都随着运行时间而失活。为了了解影响催化剂活性的因素，我们研究了几种铂族金属（PGM）催化剂的新活性，包括Pd、Pt、Rh、Ir，在850°C和Ru负载在二氧化钛上，并进行了广泛的理论研究（基于密度泛函理论的第一性原理计算和计算机模拟）不同粒径和形状的PGM纳米颗粒在TiO_2（金红石型和金红石型）和Al_2 O_3（γ-和η-氧化铝）表面的活性。催化体系的活性和失活由（i）O原子从SOn（n=1，2，3）物种脱离的能垒和（ii）硫酸分解产物（原子O、S和SOn物种）从金属纳米颗粒的去除速率定义。我们表明，这两个纳米尺度的功能共同导致所观察到的实验行为。反应产物的去除速率总是低于SO_n的分解速率。这两个速率之间的关系解释了为什么“较软”的PGM纳米颗粒（Pd和Pt）表现出最高的初始催化活性。
Production of hydrogen by splitting of water in the thermochemical sulfur-based cycles that employs the catalytic decomposition of sulfuric acid into SO2and O2is of considerable interest. However, all of the known catalytic systems studied to date that consist of metal particles on oxide substrates deactivate with time on stream. To develop an understanding of the factors that are responsible for catalyst activity, we investigate the fresh activity of several platinum group metals (PGM) catalysts, including Pd, Pt, Rh, Ir, and Ru supported on titania at 850°C and perform an extensive theoretical study (density-functional-theory-based first-principles calculations and computer simulations) of the activity of the PGM nanoparticles of different size and shape positioned on TiO2(rutile and anatase) and Al2O3(γ- and η-alumina) surfaces. The activity and deactivation of the catalytic systems are defined by (i) the energy barrier for the detachment of O atoms from the SOn(n=1, 2, 3) species, and (ii) the removal rate of the products of the sulfuric acid decomposition (atomic O, S, and the SOnspecies) from metal nanoparticles. We show that these two nanoscale features collectively result in the observed experimental behavior. The removal rate of the reaction products is always lower than the SOndecomposition rates. The relation between these two rates explains why the “softer” PGM nanoparticles (Pd and Pt) exhibit the highest initial catalytic activity.