Fracchia Martina, Ghigna Paolo, Pozzi Tommaso, Anselmi Tamburini Umberto, Colombo Valentina, Braglia Luca, Torelli Piero
Dipartimento di Chimica, Università di Pavia, V. le Taramelli 13, I-27100, Pavia, Italy.
INSTM, Consorzio Interuniversitario per la Scienza e Tecnologia dei Materiali, Via Giusti 9, I-50121 Firenze, Italy.
J Phys Chem Lett. 2020 May 7;11(9):3589-3593. doi: 10.1021/acs.jpclett.0c00602. Epub 2020 Apr 23.
The mechanisms of CO oxidation on the MgCoNiCuZnO high-entropy oxide were studied by means of operando soft X-ray absorption spectroscopy. We found that Cu is the active metal and that Cu(II) can be rapidly reduced to Cu(I) by CO when the temperature is higher than 130 °C. Co and Ni do not have any role in this respect. The Cu(II) oxidation state can be easily but slowly recovered by treatment of the sample with O at ca. 250 °C. However, it should be noted that CuO is readily and irreversibly reduced to Cu(I) when it is treated with CO at > 100 °C. Thus, the main conclusion of this work is that the high configurational entropy of MgCoNiCuZnO stabilizes the rock-salt structure and permits the oxidation/reduction of Cu to be reversible, thus permitting the catalytic cycle to take place.
通过原位软X射线吸收光谱法研究了MgCoNiCuZnO高熵氧化物上CO氧化的机理。我们发现Cu是活性金属，当温度高于130°C时，Cu(II)可被CO迅速还原为Cu(I)。在这方面，Co和Ni没有任何作用。通过在约250°C下用O处理样品，Cu(II)氧化态可以很容易但缓慢地恢复。然而，应该注意的是，当在>100°C下用CO处理时，CuO很容易且不可逆地还原为Cu(I)。因此，这项工作的主要结论是，MgCoNiCuZnO的高构型熵稳定了岩盐结构，并使Cu的氧化/还原可逆，从而使催化循环得以发生。
