Ultrasound-assisted preparation of a highly active and selective Co-B amorphous alloy catalyst in uniform spherical nanoparticles

Uniform spherical Co-B amorphous alloy nanoparticles were prepared by ultrasound-assisted reduction of Co(NH3)2+6 with BH−4 in aqueous solution, and the particle size was adjusted by changing either the ultrasound power or the ultrasonication time. During liquid-phase cinnamaldehyde (CMA) hydrogenation, the as-prepared Co-B catalyst exhibited much higher activity and better selectivity to cinnamyl alcohol (CMO) than the regular Co-B obtained by direct reduction of Co2+ with BH−4. The higher activity can be attributed to both the higher dispersion of Co active sites (SCoSCo) and the higher intrinsic activity (RSRS). The higher selectivity can be attributed to both the uniform Co-B amorphous alloy particles and the strong electronic interaction between Co and B, which enhances the competitive adsorption of CO group against CC group in the CMA molecule. Meanwhile, the stronger adsorption for hydrogen on Co active sites was more favorable for CO hydrogenation in comparison with the CC hydrogenation.