New migration strategy to boost CO2 reduction to CO

Classical strong metal–support interaction (SMSI) theory describes the way reducible oxide migrates to the surface of metal nanoparticles (NPs) to obtain metal@oxide encapsulation structure during high-temperature H₂ thermal treatment, resulting in high selectivity and stability.

However, the encapsulation structure inhibits the adsorption and dissociation of reactant molecules (e.g., H₂) over metal, leading to low activity, especially for the hydrogenation reaction.

Recently, a research group led by Prof. Liu Yuefeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has proposed a new migration strategy, in which the TiO₂ selectively migrates to second oxide support rather than the surface of metal NPs in Ru/(TiO_x)MnO catalysts, boosting the CO₂ reduction to CO via a reverse water–gas shift reaction.

The study was published in Nature Catalysis on Oct. 9.

The researchers achieved controlled migration by utilizing the strong interaction between TiO₂ and MnO in Ru/(TiO_x)MnO catalysts during H₂ thermal treatment, and TiO₂ spontaneously re-dispersed on the MnO surface, avoiding the formation of TiO_x shell on Ru NPs for the ternary catalyst (Ru/TiO_x/MnO).

Meanwhile, high-density TiO_x/MnO interfaces generated during the process and acted as a highly efficient H transportation channel with low barrier, and resulting in enhanced H-spillover for the migration of activated H species from metal Ru to support for consequent reaction.

The Ru/TiO_x/MnO catalyst showed 3.3-fold catalytic activity for CO₂ reduction to CO compared with a Ru/MnO catalyst. In addition, the Ti/Mn support preparation was not sensitive to the crystalline structure and grain size of TiO₂ NPs. Even the mechanical mixing of Ru/TiO₂ and Ru/MnO_x enhanced the activity.

Moreover, the researchers verified that the synergistic effect of TiO₂ and MnO didn't alter the catalytic intrinsic performance, and efficient H transport provided a large number of active sites (hydroxyl groups) for the reaction process.

"Our study provides references for the design of novel selective hydrogenation catalysts via the in-situ creation of oxide–oxide interfaces acting as hydrogen species transport channels," said Prof. Liu.