Binary supports TiO2-CeO2 and TiO2-ZrO2 improved CH3OH formation and selectivity effectively, but with little effect on CO2 conversion. Pd-Cu/Ti0.8Ce0.2O2 enhanced CH3OH formation by ca. 46 % comparing to Pd-Cu/TiO2-C. Pd-Cu/Ti0.1Zr0.9O2 exhibited the highest catalytic performance: CH3OH formation rate was 0.62 μmol g-cat−1s−1, which was enhanced by 121 %, 51 %, and 51 % in comparison to Pd-Cu/TiO2-C, Pd-Cu/ZrO2-C, and Pd-Cu/Ti0.8Ce0.2O2, respectively. More interestingly, lowering temperature from 523 K to 493 K further enhanced CH3OH selectivity from 44.6%–58.8%. Binary supports significantly increased surface area. Unexpectedly, it did not improve H2 reduction for Pd-Cu/TixZr1-xO2 in H2-TPR, but decreased H2 uptake to stoichiometric level, implying SMSI was adjusted to moderate state. However, the excessive H2 uptake further increased for Pd-Cu/TixCe1-xO2, indicating unalleviated SMSI. Furthermore, Pd-Cu alloy formation was improved in Pd-Cu/TixZr1-xO2, which was favorable for CH3OH synthesis. Binary supports also improved CO2 adsorptive behavior towards weakly-bonded species, contributing to better performance.
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