X-ray diffraction (XRD) measurement was performed using a Bruker AXS-D8 Advance diffractometer using Cu Kα ( = 0.15418 nm) radiation at 30 kV and 40 mA. The 2θ diffractograms were recorded between 10 and 60° with a step size of 0.025° and a step time of 20 s•step -1 . H2-temperature programmed reduction (H2-TPR) and CO2-temperature programmed reduction (CO2-TPD) experiments were conducted on a Hiden instrument equipped with an online QGA mass spectrometer (MS). In H2-TPR measurement, about 30 mg of catalyst was first outgassed under Ar flow of 20 mL/min at 100 C to eliminate physisorbed water and impurities. After that, the MS signals were recorded as a function of temperature from 100 C to 450 C with a heating rate of 10 C/min under 40 mL/min of 2.5% (v/v) H2 diluted in inert gases [2.5:82.5:15% (v/v) H2/He/Ar]. In CO2-TPD measurement, about 50 mg of catalyst was in-situ reduced at 200 C under 20 mL/min of 5%H2/Ar for 1 h, followed by purging under 20 mL/min of Ar for 1 h and then cooling down to 50 C. At this temperature, CO2 adsorption (15% CO2/Ar) was done for 1 h. Physically adsorbed CO2 was subsequently removed under 20 mL/min of Ar for 1 h. Finally, the MS signals were recorded as a function of temperature from 50 C to 800 C (10 C/min) under 20 mL/min of Ar. H2 pulse chemisorption measurement was carried out on a BELCAT II analyzer (Microtrac).