3.1.5. Preparation of Mixed Oxides by High Energy Milling-HEM Using Commercial Samples

General Procedure: Mixed oxides were prepared by weighting defined quantities of commercial metal oxides powders and pouring them in cylindrical agate jars (46 mL), together with 3 agate spheres, 1 cm in diameter. Jars were sealed and placed in a planetary mill (Pulverisette 7-Fritsch, GmbH, Idar-Oberstein, Germany) and subjected to two cycles at 800 rpm, each with a duration of 90 min.


#### *3.2. Characterization*

Powder materials composition was determined by EDX measurements using an EDX-720 Shimadzu Spectrometer (Shimadzu Europe GmbH, Duisburg, Germany).

UV-Visible DRS spectra were recorded in the 200–800 nm region with a Cary-5000 spectrophotometer (Agilent Technologies, Santa Clara, CA, United States), equipped with an integration sphere covered by polymer internal coating, with a standard sample of the same material and with sample-holder for powder material.

X-ray Photoelectron Spectroscopy (XPS) analyses were run on a PHI 5000 Versa Probe II Scanning XPS Microprobe spectrometer (ULVAC-PHI Inc., Kanagawa, Japan). The measurements were done with a monochromatised Al Kα source (X-ray spot 200 μm), at a power of 50.3 W. Wide scans and detailed spectra were acquired in Fixed Analyzer Transmission (FAT) mode with a pass energy of 117.40 eV and 29.35 eV, respectively. An electron gun was used for charge compensation (1.0 V 20.0 μA). Data processing was performed by using the MultiPak software v. 9.9.0.8.

Gas mixtures were analyzed using a GC (Thermo Scientific Focus GC), equipped with a SUPELCO Carboxen™ 1010 PLOT (30 m × 0.32 mm) and with a TCD detector.

A 150 W Xe XBO lamp (Osram) was used as source of light for irradiation.
