Electronic interactions between a stable electride and a nano-alloy control the chemoselective reduction reaction

The electronic effects induced by the synergy of stable C12A7:e– electride and bimetallic Ru–Fe nanoparticles efficiently control the chemoselective reduction reaction.

H 2 -temperature-programmed reduction (H 2 -TPR) profiles were measured in a BELCAT-A instrument (MiccrotracBEL, Japan). A 500 mg samples were pretreated in O 2 (30 mL/min) at 623 K for 30 min to remove CO adsorbed on the surface and then cooled to room temperature.
Subsequently, reducing gas composed of 5% H 2 /95% Ar was employed at a flow rate of 30 mL/min and a heating rate of 10 K/min from ambient to 1173 K. The consumption of H 2 was monitored by a thermal conductivity detector (TCD) and mass spectrometer (Bell Mass, MiccrotracBEL, Japan). To investigate the oxidation and reduction of the bimetallic system during the H 2 -TPR characterization, we investigated the structure of 5wt%Ru-5wt%Fe/SiO 2 by XRD analysis after the pretreatment the same as Ru-Fe/C12A7:e− and re-reduction in 5% H 2 /95% Ar, respectively (Fig. S12).
FT-IR spectra of adsorbed CO were measured using a spectrometer (FT/IR-6100, Jasco) equipped with a mercury-cadmium-tellurium detector at a resolution of 4 cm −1 . Samples were pressed into self-supported disks. A disk was placed in a silica-glass cell equipped with KBr windows and connected to a closed gas-circulation system to allow thermal adsorption-desorption experiments. The disk was pretreated with circulated H 2 at 350 °C for 2 hours and then cooled to room temperature. After the pretreatment, the disk was cooled to −170°C under vacuum to obtain a background spectrum. Pure CO (99.99999%) were supplied to the system through a liquidnitrogen trap. The infrared spectrum of the sample at −170°C prior to CO adsorption was used as the background for difference spectra obtained by subtracting the backgrounds from the spectra of CO-adsorbed samples.   We loaded 5wt%Ru-5wt%Fe onto the surface of amorphous SiO 2 under the same preparation condition as Ru-Fe/C12A7:e − . As we expected, the RuFe alloy with a hexagonal close-packed phase (space group: P63/mmc, JCPDS No. 65-6545) is formed on the support.   Conv. [%] Sel. [%] Ref.  Temp.
We appropriately tune of Ru-Fe loading amount from 2 wt% to 10 wt%, the mean size of the metal nanoparticles was increased from 15 to 20 nm with metal nanoparticles aggregated gradually. Accordingly, the selectivity to cinnamyl alcohol decreased a lot although the conversion slightly elevated (Table 1, entry 4; Table S2, entries 7−8). The larger nanoparticles aggregation would decrease the fraction of metal-support interface, reducing the selectivity to cinnamyl alcohol.     We measured the XRD pattern of 5wt%Ru-5wt%Fe/SiO 2 with oxidation treatment, which is the same as the pretreatment of H 2 -TPR (O 2 , 623 K, 30 mins). Part of the hexagonal RuFe alloy phase remained and RuO 2 and Fe 2 O 3 phases were also observed in the XRD pattern (Fig. R1a).
Although phase separation between Ru oxide and Fe oxide occurred during the oxidation pretreatment, the re-reduction process brought about the RuFe alloy formation again (Fig. R1b).
Therefore, we think that RuO 2 and Fe 2 O 3 are present in close proximity to each other on the surface of the RuFe alloy after the oxidation treatment. As a result, H 2 -TPR peaks for Ru-Fe catalysts are observed in the intermediate temperature region between that of Ru and Fe catalysts ( Fig. 3a).