Our approach to architected catalysts relies on sol–gel-derived oxide aerogels that serve as an ultraporous mesoscale platform that innately wires in three dimensions the necessary transport functionality at play in heterogeneous catalysis: ion mobility, electron mobility, and mass transport [1]. We track performance using a model bifunctional catalytic reaction: gas-phase oxidation of carbon monoxide at metal nanoparticles (NPs) supported on such reducing oxides as titania and ceria. The covalently bonded network suppresses sintering and agglomeration of the ~10-nm oxide NPs, which allows the high surface area characteristic of aerogels to maintain co-continuity with the mesoporous network that provides a facile transport pathway for reactants and product. The size comparability of the networked oxide NPs and the ~3–5-nm supported catalytic Au, Cu, or Ni(OH)2 NPs permits a degree of interfacial intimacy that enables the reducing oxide to control the chemical state and size of the catalyst at low weight loadings (1–5 wt. %), including during temperature-programmed oxidation in the absence of CO. The resulting interplay between reducing oxide NP and metal NP yields high activity (mol of product per second per mol of catalyst), low values of T50 (temperature of 50% CO conversion), plasmonic response for Cu NPs under oxidizing conditions, and persistent activity in the presence of gas-phase water. With this combination of properties, ceria aerogel–supported Cu NPs preferentially oxidizes CO in H2-rich feedstreams, demonstrating a successful, durable COPROX system [2].

Architected heterogeneous catalysts influence operando resilience

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ACS Fall 2022

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