Develop High-Performance Cu-Based RWGS Catalysts by Controlling Oxide–Oxide Interface

Abstract

The high-temperature reverse water–gas shift (RWGS) is an industrially relevant reaction. Cu-based catalysts easily sinter and deactivate under these conditions. We demonstrate that it is possible to obtain high-performance and stable catalysts by modifying the mechanism of action. Cu/CeO x -MgO (denoted as Cu/Ce x Mg y ) catalysts were developed in which Cu nanoparticles mostly generate spillover H that migrates to support sites where CO 2 is selectively reduced, with the rate controlled by the oxide–oxide CeO x -MgO interface. An optimal Cu/Ce 0.05 Mg 0.95 catalyst (in terms of performance at the lowest possible Ce amount) exhibits a near-equilibrium CO 2 conversion with a reaction rate of 516.0 μmol·g cat –1 ·s –1, near-total selectivity to CO at 600 °C, and a high space-velocity of 300,000 mL·g cat –1 ·h –1 . These are among the top performances in the RWGS reaction. Extensive characterization data have proven that the surface-abundant Ce-[O v ]-Mg sites play a critical role in CO 2 adsorption/activation as well as the carrier for the spillover of hydrogen species. The mechanism is substantially different from those indicated for Cu-based catalysts for CO 2 hydrogenation. By decoupling H and CO 2 activation sites and realizing efficient surface mobility of H-spillover species via an enhanced oxide–oxide interface, it is possible to maintain the overall stability and activity of the catalyst when the Cu nanoparticles sinter at a high temperature (i.e., ≥600 °C).