High-throughput synthesis of multi-element alloy nanoparticles using solvothermal continuous-flow reactor

High-throughput synthesis of multi-element alloy nanoparticles (MEA NPs) is essential for accelerating the discovery of advanced materials with complex compositions. Herein, we developed an automated continuous-flow reactor system capable of synthesising a wide variety of MEA NPs under controlled solvothermal conditions (up to 400 °C and 35 MPa). The system demonstrates a high screening throughput, capable of preparing up to 20 distinct samples in a single, automated run, with each synthesis requiring only 30 minutes. A key throughput optimising feature is the parallel process execution, whereby precursor preparation and system cleaning are performed concurrently via the reactor heating, synthesis, and cooling cycles. All washing procedures, for both the precursor preparation module and reactor unit, are fully automated, further minimising downtime. We demonstrated its versatility by successfully synthesising a wide range of MEA NPs, including high-entropy alloys, composed of various combinations of d- and p-block metals. The synthesized materials, ranging from bimetallic RuPd to ten-element CoNiCuRuRhPdInSnIrPt alloys, were all crystalline, single-phase face-centred cubic solid solutions. Furthermore, the platform enables the direct one-step synthesis of supported MEA catalysts, such as RuRhPdIrPt/CeO₂. For this supported catalyst, we achieved a practical mass throughput with a theoretical production rate of 0.5 g h^-1 for the MEA NPs (corresponding to 27 g h^-1 for the total catalyst including the support). The final product yield was approximately 56% under the current protocol, which is designed to prevent cross-contamination by automatically discarding the initial and final portions of the product slurry. We anticipate this yield can be readily improved in a system configuration optimized for mass throughput rather than for high-throughput screening. This study presents a scalable and versatile system for high-throughput MEA NPs synthesis and offers a practical solution for bridging the gap between computational predictions and experimental materials development.