Continuous Flow-Electrochemical Coupling Technology for Metal Nanoparticle Synthesis: Applications for Catalysis

Nanometallic materials (nano-Ms) have garnered considerable attention owing to their unique size-dependent properties. However, the complexity and limitations of the techniques used to prepare nano-Ms have hindered their further development. Here, a simple and scalable technological strategy is proposed for the synthesis of ultrafine nanometals. The metal oxides (Co 3 O 4, NiO, and CuO) with sizes ranging from approximately 100 to 300 nm were converted into ultrafine nanometals (Co, Ni, and Cu) of around 5 nm through a continuous flow-electrochemical coupling reactor. This transformation occurred via a conversion reaction during limited galvanostatic discharge/charge cycles. The ultrafine nanometals produced through the continuous flow-electrochemical coupling reaction technology in a continuous flow-electrochemical reactor exhibited a substantial increase in the surface area and grain boundaries due to the reduction in particle size. The increased electrocatalytic active sites allow the prepared ultrafine nanometals to possess excellent electrochemical oxygen evolution reaction activities. This strategy based on the continuous flow-electrochemical coupling reaction is not limited to the synthesis of Co, Ni, and Cu; it can be extended to other nanotransition metals as well. The outcome of this study provides a general strategy for the efficient synthesis of ultrafine nanometals with uniform ultrasmall particle sizes on a large scale, specifically tailored for electrocatalysis applications.