Reduction‐induced metal/oxide interfacial sites for selective CO₂ hydrogenation

Abstract

The interfacial structures of bimetallic‐derived catalysts play an important role in promoting the activation of reactants such as CO2. In particular, both the physical property (e.g., local bonding environment) and the electronic property (e.g., oxidation state) can evolve from their native states under different environments, such as upon reduction and during the catalytic reaction. Hence, taking the CO2 hydrogenation reaction over Rh‐based catalysts as a case study, the present work compares the interfacial structures in tuning the selectivity toward CH4 or CO. The combination of ex situ and in situ characterization reveals two representative interfacial structures: the Rh/CeOx interface formed over Rh/CeO2 is active and selective to produce CH4 (~95%) by following a formate‐mediated pathway; in comparison, the InOx/Rh interface derived after reduction is active for CO2 activation and enables a redox mechanism for the exclusive formation of CO (~100%). This work provides insights into the environment‐induced structural evolution at the metal−oxide interfaces, as well as the role of distinct interfacial active sites in tuning the selectivity of CO2 hydrogenation.

Bimetallic-Derived Catalytic Structures for CO2-Assisted Ethane Activation

“…Thus, metal oxophilicity is a descriptor that can be employed to approximate or predict the segregation trend for a given bimetallic ensemble. Generally, as shown in Figure b, metals with low electronegativity, low work function, and/or high d-band center relative to the Fermi level tend to bind oxygen species more strongly, leading to the segregation of the specific metal to form an O*-adsorbed surface or oxide on the surface of the bimetallic ensemble, often referred to as the metal oxide/metal (M′O x /M) inverse interface. , …”

“…Generally, as shown in Figure 1b, metals with low electronegativity, 33 low work function, 34 and/or high d-band center relative to the Fermi level 32 tend to bind oxygen species more strongly, leading to the segregation of the specific metal to form an O*-adsorbed surface or oxide on the surface of the bimetallic ensemble, often referred to as the metal oxide/metal (M′O x /M) inverse interface. 35,36 Most oxide supports, except for a few early transition metal oxides (e.g., Cr 2 O 3 , Nb 2 O 5 , and V 2 O 5 ), generally exhibit lower activity in alkane activation compared to metal surfaces, while they play a crucial role in CO 2 activation. Both redox sites and acid/base centers can contribute to the CO 2 reduction pathway.…”