Activation of subnanometric Pt on Cu-modified CeO2 via redox-coupled atomic layer deposition for CO oxidation

Abstract

Improving the low-temperature activity (below 100 °C) and noble-metal efficiency of automotive exhaust catalysts has been a continuous effort to eliminate cold-start emissions, yet great challenges remain. Here we report a strategy to activate the low-temperature performance of Pt catalysts on Cu-modified CeO2 supports based on redox-coupled atomic layer deposition. The interfacial reducibility and structure of composite catalysts have been precisely tuned by oxide doping and accurate control of Pt size. Cu-modified CeO2-supported Pt sub-nanoclusters demonstrate a remarkable performance with an onset of CO oxidation reactivity below room temperature, which is one order of magnitude more active than atomically-dispersed Pt catalysts. The Cu-O-Ce site with activated lattice oxygen anchors deposited Pt sub-nanoclusters, leading to a moderate CO adsorption strength at the interface that facilitates the low-temperature CO oxidation performance.

Dependence of inherent selective atomic layer deposition of FeOx on Pt nanoparticles on the coreactant and temperature

“…The intensity of the CO adsorption peak decreases with increasing FeO x cycles, which indicates that the Pt surface becomes covered by FeO x . The linear adsorption peak can be divided into three peaks, which can be assigned to CO adsorbed on the Pt (111) and Pt(100) facets and on Pt's low coordinated sites such as edges and corners. 27 Here, it is assumed that the low-coordinated sites are the edges, because the vertex sites only occupy a small part of the surface area of the nanoparticle.…”

“…The pristine surface of nanoparticles consists of different facets, where Pt atoms in these facets and edges are differently coordinated. Here, we considered the low-index facets (100) and (111) to mimic the regular surface of Pt nanoparticles, whereas the joint atomic chains of (100) and (111) facets were constructed to mimic the edge sites of nanoparticles. The 4 × 4 supercells with five atomic layers were used to simulate the TBF adsorption and decomposition on the Pt( 111) and (100) slabs, whereas a 13.75 × 14.04 Å 2 rectangular unit cell with eight atomic layers was used to model the growth of FeO x on the edge slab.…”

“…M(Cp) 2 precursor molecules exhibit robust decomposition on the surface of Pt nanoparticles. The reaction rates on different sites of Pt NPs follow the order of edge >(100) > (111), which indicates that low coordination edge sites were inherently selected to be covered and the (111) facets were covered after the first few ALD cycles. 21 Besides the metal precursor, the coreactant also has a significant impact on the ALD process.…”

“…When TBF and O 2 were used, it was found that the ALD process occurred only above 250°C, indicating that the organic ligands of the TBF precursor cannot be eliminated by O 2 below this temperature. However, by utilizing O 3 instead of O 2 , the edge site was preferentially covered at 150°C while exposing Pt (111) and Pt(100) facets. Furthermore, it was found that the selective deposition on edge sites was greatly suppressed at a higher temperature (200°C) when using TBF and O 3 .…”

Oxygen Defect Engineering of β‐MnO2 Catalysts via Phase Transformation for Selective Catalytic Reduction of NO

“…[5][6][7] In terms of vehicle exhausts, the new emission standard requires that catalysts should be active even below 100 °C for eliminating cold-start emission. [8] The inferior low-temperature activity and narrow operation window of ≈300-400 °C make the commercial vanadium-based catalysts impracticable for low-temperature SCR (below 200 °C). [9][10][11] Low-temperature NH 3 -SCR requires a catalyst with excellent redox property to activate reactants and oxidize partial NO to NO 2 (Equation (2)).…”