Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.
Dalton Trans. 2013 Oct 1;42(41):14653-67. doi: 10.1039/c3dt51818c.
The platinum group metals (PGMs) are widely employed as catalysts, especially for the mitigation of automotive exhaust pollutants. The low natural abundance of PGMs and increasing demand from the expanding automotive sector necessitates strategies to improve the efficiency of PGM use. Conventional catalysts typically consist of PGM nanoparticles dispersed on high surface area oxide supports. However, high PGM loadings must be used to counter sintering, ablation, and deactivation of the catalyst such that sufficient activity is maintained over the operating lifetime. An appealing strategy for reducing metal loading is the substitution of PGM ions into oxide hosts: the use of single atoms (ions) as catalytic active sites represents a highly atom-efficient alternative to the use of nanoparticles. This review addresses the crystal chemistry and reactivity of oxide compounds of precious metals that are, or could be relevant to developing an understanding of the role of precious metal ions in heterogeneous catalysis. We review the chemical conditions that facilitate stabilization of the notoriously oxophobic precious metals in oxide environments, and survey complex oxide hosts that have proven to be amenable to reversible redox cycling of PGMs.
铂族金属（PGMs）被广泛用作催化剂，尤其是用于减轻汽车尾气污染物。PGMs 的天然丰度低，而汽车行业的不断扩张导致需求不断增加，因此需要采取策略来提高 PGM 的使用效率。传统的催化剂通常由分散在高表面积氧化物载体上的 PGM 纳米颗粒组成。然而，为了防止催化剂的烧结、烧蚀和失活，必须使用高 PGM 负载量，以在整个工作寿命内保持足够的活性。一种降低金属负载的有吸引力的策略是将 PGM 离子取代到氧化物宿主中：将单原子（离子）用作催化活性位点代表了一种比使用纳米颗粒更高效的原子方法。本综述介绍了氧化物化合物的晶体化学和反应性，这些化合物是或可能与理解贵金属离子在多相催化中的作用有关。我们综述了促进贵金属在氧化物环境中稳定存在的化学条件，并调查了已被证明适用于 PGM 可逆氧化还原循环的复杂氧化物宿主。
