Bimetallic (NiFe) and Trimetallic (NiFeCr) Nanoalloys from Metal Oxides Using a Microwave Hydrogen Plasma

Metallic nanoalloys (NAs) have garnered significant interest due to their superior properties compared to monometallic nanoparticles (NPs), resulting from their tunable composition, synergistic effects between constituent metals, and multifunctional behavior. Conventional synthesis techniques often require expensive precursors, hazardous solvents, and a multistep process. Therefore, the direct conversion of inexpensive, naturally occurring metal oxides into high‐value NAs using a green, gas‐based reducing agent such as hydrogen holds significant potential. In this work, the use of an atmospheric‐pressure hydrogen plasma powered by microwave energy is demonstrated to produce bimetallic and trimetallic NPs from their corresponding oxides within residence times of tens of milliseconds. FeNi NPs are produced from a mixture of Fe ₃ O ₄ and NiO particles having a size of around ≈30 μm. The composition of these particles is shown to be tunable by varying the composition of the feed material. Furthermore, trimetallic FeNiCr NPs are synthesized using Cr ₂ O ₃ as the third precursor, demonstrating the process's flexibility in incorporating different metal oxides.