Strategy to Design-Synthesize Bimetallic Nanostructures Using the Alcohol Reduction Method

Abstract

Bimetallic nanomaterials have attracted much attention from various fields such as catalysis, optics, magnetism, and so forth. The functionality of such particles is influenced very much by the intermetallic interactions than their individual contribution. However, compared with the synthesis of monometallic nanoparticles, the reaction parameters that need to be controlled for tuning the size, shape, composition, and crystal structure of bimetallic nanoparticles becomes challenging. This study focuses on synthesizing of bimetallic nanostructures using the alcohol reduction method, where the control over the reducing power is conceivable by varying the combination of the alcohol type, complexing agent, and metal salts. Consequently, various Cu−Co nanostructures such as Cu−Co core−shell (size ranged between 40 and 15 nm) and hollow alloy nanoparticles and nanotubes were successfully synthesized by incorporating diffusion and etching phenomena during the reduction reaction. Moreover, time-resolved sampling revealed that the formation of a Cu−Co alloy hollow nanostructure has been realized by the diffusion of the Cu core into the Co shell by controlling the reduction time gap between Cu and Co and the crystal structure besides the reduction sequences. It should be noted that the synthesis of a high-temperature (∼1300 °C) Cu−Co alloy phase was carried out at 170 °C. Among the Cu−Co alloy nanostructures, Cu−Co hollow alloy nanoparticles exhibited enhanced catalytic activity compared to metallic Cu and other Cu−Co nanostructures from the degradation reaction of methylene blue. The enhanced catalytic performance was considered to be mainly due to the alloy structure.

Co–Ru Nanoalloy Catalysts for the Acceptorless Dehydrogenation of Alcohols

“…Although the potential value corresponding to the onset of solvent oxidation does not necessarily correspond to the thermodynamic value (overpotential may contribute), it is possible to conclude that BD is a stronger reducing agent than octan-1-ol, particularly at high temperature. This is in line with previous results: mono-alcohols are milder reducing agents than polyols . Since an increase in the reduction rate leads to an increase in supersaturation because of a higher number of metal atoms generated, it is expected that the highest supersaturation values will be obtained with BD rather than with octan-1-ol.…”

“…This is in line with previous results: mono-alcohols are milder reducing agents than polyols. 43 Since an increase in the reduction rate leads to an increase in supersaturation because of a higher number of metal atoms generated, 44 it is expected that the highest supersaturation values will be obtained with BD rather than with octan-1-ol. Our results can thus tentatively be explained considering that the high supersaturation obtained with BD is detrimental for the formation of an alloy, the use of octan-1-ol is a way to obtain a better control of the nucleation step and may explain why this solvent is more suitable for the formation of the desired alloy.…”

Synthesis of Electromagnetic Wave-Absorbing Co–Ni Alloys and Co–Ni Core–Shell Structured Nanoparticles

“…In the case of Co and Ni, conditions to form Co–Ni alloys become favorable if they crystallize in the same structure. However, since Co could precipitate either in the hcp or fcc phase in the nanometer range, this facilitates the formation of either core–shell or alloy structures, respectively, as observed in the synthesis of Cu–Co nanostructures. ,, Here, the crystal size has been found to affect the hcp or fcc phase formation substantially. Thus, the metals should crystallize under a similar crystal structure besides co-reduction to form alloy nanoparticles.…”

“…These results suggest that adding oleylamine influences the particle size, which reduces with the increase in the oleylamine concentration. Additionally, the particle size is believed to have strongly influenced the Co crystal phase. , However, to examine the effect of oleylamine on the formation of Co–Ni particles in detail, time-resolved sampling and in situ UV–vis and XAS measurements were carried out in the next section.…”

“…Thus, a suitable reducing agent with milder reducing power that allows the control over reduction rate should be considered. The authors have observed that straight-chain alcohols can be a potential candidate as a reductant for controlled synthesis of bimetallic nanostructures. , Further, recently, the synthesis of Cu–Co core–shell and alloy nanoparticles has been successfully demonstrated by controlling the reduction reaction rate via an appropriate combination of alcohols, complexing agents, and metal salts . Thus, in this paper, we attempted the synthesis of Co–Ni alloy nanoparticles with different compositions by controlling the reduction kinetics of metal ions using the alcohol reduction method, focusing on the reducing solvent and surfactant.…”