Avoiding Sabatier's conflict in bifunctional heterogeneous catalysts for the WGS reaction

The cardinal rule in heterogeneous catalysis is the Sabatier Principle, believed to be ubiquitous and unavoidable in catalyst design. This paper points out that it is possible to avoid the inherent contradiction embedded in the principle and find catalysts with much higher efficiencies. For illustration, we use the water-gas-shift (WGS) reaction to reach conclusions. A new mechanism called water-assisted pathway (WAP) is proposed on two-component catalysts (metal + oxygen-covered substrate), and its high efficiency for WGS reaction is observed for the as-designed catalyst, Au/TiC(111). In WAP, the weakly reactive oxygen-covered substrate avoids the Sabatier conflict of the rate-determining step, in stark contrast to much studied highly reactive substrates that follow the LH-associative or LH-redox process.