New strategy boosting carbon dioxide reduction to carbon monoxide

Classical strong metal-support interaction (SMSI) describes that reducible oxide migrates to the surface 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 molecular (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 reverse water-gas shift reaction. 

This 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, acting 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 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, they 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.