Synthesis and catalysis of chemically reduced metal–metalloid amorphous alloys

Abstract

Amorphous alloys structurally deviate from crystalline materials in that they possess unique short-range ordered and long-range disordered atomic arrangement. They are important catalytic materials due to their unique chemical and structural properties including broadly adjustable composition, structural homogeneity, and high concentration of coordinatively unsaturated sites. As chemically reduced metal-metalloid amorphous alloys exhibit excellent catalytic performance in applications such as efficient chemical production, energy conversion, and environmental remediation, there is an intense surge in interest in using them as catalytic materials. This critical review summarizes the progress in the study of the metal-metalloid amorphous alloy catalysts, mainly in recent decades, with special focus on their synthetic strategies and catalytic applications in petrochemical, fine chemical, energy, and environmental relevant reactions. The review is intended to be a valuable resource to researchers interested in these exciting catalytic materials. We concluded the review with some perspectives on the challenges and opportunities about the future developments of metal-metalloid amorphous alloy catalysts.

Effects of Ultrasound and Microwaves on Selective Reduction: Catalyst Preparation and Reactions

“…[65,66] The Ni-Mo-B prepared by ultrasonic reduction exhibited higher activity than the conventional amorphous alloy catalyst. [25] Moreover, the catalyst prepared by sonication exhibited excellent robustness. Co/SiO2 prepared under US was deactivated by less than 10% in 4 days.…”

“…[59,60] Particle size can generally be controlled by adjusting the sonication power or time. [61,62] Pei et al [25] reported the US-assisted synthesis of metal-metalloid amorphous alloys in which the US-assisted reduction gave rise to mono-dispersed and spherical Ru-B nanoparticles with a much smaller size of 2.4-4.9 nm than the broadly distributed particles of 15-50 nm prepared conventionally. In addition, the US-assisted method can induce a higher surface elemental B/M ratio.…”

“…[21][22][23][24] The US-assisted chemical reduction method has been successfully applied in the preparation of amorphous alloys with homogeneous particle size. [25] When a cavitation bubble violently collapses near a solid surface, the high-speed jets of liquid are driven into the surface of a particle. [17] These jets and shock waves can cause surface coating removal as well as producing localized high temperatures and pressures.…”

Chemistry, nanostructure and magnetic properties of Co–Ru–B–O nanoalloys

“…[1] In this context, H 2 appears as a clean energy carrier with a high energy density (142MJ.kg precursor with sodium borohydride in aqueous medium leads to the formation of ultrafine and usually amorphous powders (Co-B materials) with enhanced activity not only for reaction (1) but also for many organic reactions [9][10][11][18][19]. Despite being prepared and used in a good number of papers, the exact nature of these nanoalloys is still under intense discussion [9][10][11]18].…”

“…Co-B based nanoalloys are the most employed in literature [9][10][11]. Reaction of a cobalt precursor with sodium borohydride in aqueous medium leads to the formation of ultrafine and usually amorphous powders (Co-B materials) with enhanced activity not only for reaction (1) but also for many organic reactions [9][10][11][18][19]. Despite being prepared and used in a good number of papers, the exact nature of these nanoalloys is still under intense discussion [9-11, characterized by the formation of very small metallic nanoparticles embedded in an amorphous matrix.…”