Abstract
<jats:p>The Mars–van Krevelen (MvK) mechanism, in which lattice oxygens and oxygen vacancies participate in the redox reactions of target molecules, has emerged as a novel catalytic strategy to replace conventional supported metal catalysis for the reverse water-gas shift (rWGS) reaction. Although loading Pd nanoparticles as a cocatalyst to promote the dissociation of H2 is crucial for the MvK-type rWGS, it also promotes the sequential hydrogenation of CO into CH4 because of the strong adsorption of CO on Pd. Here, we show that rWGS selectively proceeds over a Pd-Cu alloy loaded on SrTi0.8Mn0.2O3, which promotes rWGS through the MvK mechanism. We found that 5 wt% Pd-loaded SrTi0.8Mn0.2O3 (Pd/STMO) produced both CO and CH4 at 773 K with yields of 35.5% and 7.1%, respectively, whereas 5 wt% Pd-Cu-loaded SrTi0.8Mn0.2O3 (Pd-Cu(5.0)) selectively produced CO with a yield of 49.1%. High-angle annular dark-field scanning transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy confirmed the presence of a face-centered cubic alloy (PdCu3) and disordered alloy (Pd1−xCux) of Pd and Cu in Pd-Cu(5.0) with much larger particle sizes than the monometallic Pd particles in Pd/STMO. In situ Fourier-transform infrared spectra showed a strong absorption band of adsorbed CO species in Pd/STMO, while it became negligible in Pd-Cu(5.0). The formation of the alloy would offer isolated Pd species in the nanoparticles to suppress the adsorption of CO in a bridged configuration, which is amenable to the sequential hydrogenation to CH4, leading to selective rWGS over the alloy-loaded STMO. The present study demonstrates that employing an alloying strategy significantly enhances MvK-type rWGS.</jats:p>