Atomically Thick Oxide Overcoating Stimulates Low-Temperature Reactive Metal–Support Interactions for Enhanced Catalysis

Abstract

Reactive metal−support interactions (RMSIs) induce the formation of bimetallic alloys and offer an effective way to tune the electronic and geometric properties of metal sites for advanced catalysis. However, RMSIs often require high-temperature reductions (>500 °C), which significantly limits the tuning of bimetallic compositional varieties. Here, we report that an atomically thick Ga 2 O 3 coating of Pd nanoparticles enables the initiation of RMSIs at a much lower temperature of ∼250 °C. State-of-the-art microscopic and in situ spectroscopic studies disclose that low-temperature RMSIs initiate the formation of rarely reported Ga-rich PdGa alloy phases, distinct from the Pd 2 Ga phase formed in traditional Pd/Ga 2 O 3 catalysts after hightemperature reduction. In the CO 2 hydrogenation reaction, the Ga-rich alloy phases impressively boost the formation of methanol and dimethyl ether ∼5 times higher than that of Pd/Ga 2 O 3 . In situ infrared spectroscopy reveals that the Ga-rich phases greatly favor formate formation as well as its subsequent hydrogenation, thus leading to high productivity.

Combining Atomic Layer Deposition with Surface Organometallic Chemistry to Enhance Atomic-Scale Interactions and Improve the Activity and Selectivity of Cu–Zn/SiO2 Catalysts for the Hydrogenation of CO2 to Methanol

“…It is essential to note that while the ex situ XANES spectrum of Cu–Zn(5)/SiO 2 , obtained after H 2 pretreatment at 500 °C, shows a mixture of Zn states, i.e., Zn 0 and Zn 2+ , the in situ XANES experiment shows clearly that under a H 2 atmosphere, Zn 2+ species are reduced fully to Zn 0 even at 300 °C (Figures f and c). This observation is consistent with the emergence of reactive metal support interactions (RMSI) in Cu–Zn(5)/SiO 2 under a H 2 atmosphere, likely due to an atomic-scale mixing, as was reported recently for an ALD-derived PdGa/Al 2 O 3 catalyst for CO 2 hydrogenation to methanol . The emergence of RMSI in a H 2 atmosphere is also consistent with the XPS results discussed above.…”

“…Further, a controlled engineering of the metal/support interface will benefit the elucidation of robust structure–activity relationships . In this context, atomic layer deposition (ALD) can be a method of choice and has been used in the preparation of heterogeneous catalysis, e.g., by forming an overcoat of controlled thickness (e.g., a metal oxide) onto a support or a catalyst. , In particular, ALD enables a high conformality of the grown films and their tunable composition and thickness down to the sub-nm scale. , In addition, ALD allows to manipulate in a controlled fashion the relative abundance and distribution of Brønsted and Lewis (strong and weak) acid sites. – Yet, the use of ALD to create heterogeneous catalysts with well-defined metal/support interfaces remains relatively underexplored. – …”

Atomic Cobalt–Silver Dual-Metal Sites Confined on Carbon Nitride with Synergistic Ag Nanoparticles for Enhanced CO2 Photoreduction

“…As displayed in HAADF-STEM elemental mapping, Ag and Co atoms were atomically dispersed on P-doped CN, the introduction of Co species could trigger the aggregation of adjacent Ag SA sites, leading to the deposition of Ag NPs which were surrounded by adjacent Co species (Figure g–i) . Previous studies in EMSIs have proved that the introduction of other metal sites could exert additional interactions on the original metal–support complex. − Furthermore, the strengthened EMSIs of NPs and SA sites could induce substantial charge transfers between the support and metal NPs to modulate the catalytic performance . In comparison, the metal species were found to be exclusively single atoms in both Ag 1 –CN (Figure S3) and Co 1 Ag 1 –PCN (Figure S4).…”

Insight into the Dynamic Evolution of Supported Metal Catalysts by In Situ/Operando Techniques and Theoretical Simulations

“…(e) Schematic illustration of RMSI in conventional A/BO x catalyst and atomically thick oxide overcoating catalyst. Reproduced from ref . Copyright 2023 American Chemical Society.…”