Towards efficient use of noble metals via exsolution exemplified for CO oxidation

Many catalysts and in particular automotive exhaust
catalysts usually consist of noble metal nanoparticles dispersed on metal oxide
supports. While highly active, such catalysts are expensive and prone to
deactivation by sintering and thus alternative methods for their production are
being sought to ensure more efficient use of noble metals. Exsolution has been
shown to be an approach to produce confined nanoparticles, which in turn are
more stable against agglomeration, and, at the same time strained, displaying
enhanced activity. While exsolution has been extensively investigated for
relatively high metal loadings, it has yet to be explored for dilute loadings
which is expected to be more challenging but more suitable for application of
noble metals. Here we explore the substitution of Rh into an A-site deficient
perovskite titante aiming to investigate the possibility of exsolving from
dilute amounts of noble metal substituted perovskites. We show that this is
possible and in spite of certain limitations, they still compete well against
conventionally prepared samples with higher apparent surface loading when
applied for CO oxidation.

众多催化剂，尤其是汽车尾气催化剂，通常由贵金属纳米颗粒分散在金属氧化物载体上构成。尽管这些催化剂具有高活性，但成本高昂且易于因烧结而失活，因此寻求其生产替代方法以确保贵金属的更高效利用。析出法已被证实为制备受限纳米颗粒的方法，这些纳米颗粒因抗团聚能力更强而更稳定，同时由于应变效应而展现出增强的活性。尽管析出法已在相对高金属负载量方面得到了广泛研究，但对于稀释负载量尚缺乏探索，而稀释负载量预计将更具挑战性但更适宜于贵金属的应用。在本研究中，我们探讨了将铑（Rh）取代尖晶石型钛酸锶的A位缺陷，旨在研究从稀释量的贵金属取代尖晶石中析出的可能性。我们证明了这是可行的，尽管存在某些局限性，但在应用于一氧化碳氧化时，它们仍能与常规制备的高表观表面负载样品相媲美。