Comparison of precious metal doped and impregnated perovskite oxides for TWC application

Soot oxidation in low-O2 and O2-free environment by lanthanum-based perovskites: structural changes and the effect of Ag doping

The use of La-based, Cu (LCO), Mn (LMO) and Fe (LFO) perovskites doped with Ag were studied for potential application as cGPF soot oxidation catalysts. Special emphasis was placed on...

Platinum incorporation into titanate perovskites to deliver emergent active and stable platinum nanoparticles

Platinum functions exceptionally well as a nanoparticulate catalyst in many important fields, such as in the removal of atmospheric pollutants, but it is scarce, expensive and not always sufficiently durable. Here, we report a perovskite system in which 0.5 wt% Pt is integrated into the support and its subsequent conversion through exsolution to achieve a resilient catalyst. Owing to the instability of most Pt oxides at high temperatures, a thermally stable platinum oxide precursor, barium platinate, was used to preserve the platinum as an oxide during the solid-state synthesis in an approach akin to the Trojan horse legend. By tailoring the procedure, it is possible to produce a uniform equilibrated structure with active emergent Pt nanoparticles strongly embedded in the perovskite surface that display better CO oxidation activity and stability than those of conventionally prepared Pt catalysts. This catalyst was further evaluated for a variety of reactions under realistic test environments-CO and NO oxidation, diesel oxidation catalysis and ammonia slip reactions were investigated.

Understanding the Impact of Defects on Catalytic CO Oxidation of LaFeO3-Supported Rh, Pd, and Pt Single-Atom Catalysts

Understanding the intrinsic catalytic properties of perovskite materials can accelerate the development of highly active and abundant complex oxide catalysts. Here, we performed a first-principles density functional theory study combined with a microkinetics analysis to comprehensively investigate the influence of defects on catalytic CO oxidation of LaFeO₃ catalysts containing single atoms of Rh, Pd, and Pt. La defects and subsurface O vacancies considerably affect the local electronic structure of these single atoms adsorbed at the surface or replacing Fe in the surface of the perovskite. As a consequence, not only the stability of the introduced single atoms is enhanced but also the CO and O₂ adsorption energies are modified. This also affects the barriers for CO oxidation. Uniquely, we find that the presence of La defects results in a much higher CO oxidation rate for the doped perovskite surface. A linear correlation between the activation barrier for CO oxidation and the surface O vacancy formation energy for these models is identified. Additionally, the presence of subsurface O vacancies only slightly promotes CO oxidation on the LaFeO₃ surface with an adsorbed Rh atom. Our findings suggest that the introduction of La defects in LaFeO₃-based environmental catalysts could be a promising strategy toward improved oxidation performance. The insights revealed herein guide the design of the perovskite-based three-way catalyst through compositional variation.

In situ synthesis of supported metal nanocatalysts through heterogeneous doping

Supported metal nanoparticles hold great promise for many fields, including catalysis and renewable energy. Here we report a novel methodology for the in situ growth of architecturally tailored, regenerative metal nanocatalysts that is applicable to a wide range of materials. The main idea underlying this strategy is to selectively diffuse catalytically active metals along the grain boundaries of host oxides and then to reduce the diffused metallic species to form nanoclusters. As a case study, we choose ceria and zirconia, the most recognized oxide supports, and spontaneously form various metal particles on their surface with controlled size and distribution. Metal atoms move back and forth between the interior (as cations) and the exterior (as clusters) of the host oxide lattice as the reductive and oxidative atmospheres repeat, even at temperatures below 700 °C. Furthermore, they exhibit excellent sintering/coking resistance and reactivity toward chemical/electrochemical reactions, demonstrating potential to be used in various applications.

Supported metal nanoparticles hold great promise for many fields, including catalysis and renewable energy. Here the authors report a novel methodology for the in-situ growth of architecturally tailored, regenerative metal nanocatalysts that is applicable to a wide range of materials.