Synthesis of Vertically-Aligned Fractal Mo₂C Nanorods via CVD

Transition metal carbides (TMCs) are known for their superior properties, including catalytic behavior, electrical conductivity, and mechanical strength making them highly appealing for advanced applications. Among TMCs, Mo₂C is a promising candidate for advanced applications such as HER, Field Emission, sensors, and optoelectronic applications with properties such as Pt-like electronic structure, and thermal and chemical stability. Particularly for catalytic applications, nanostructures with high surface area are crucial, hence one-dimensional (1D) nanostructures like nanorods and nanowires are essential components for these systems. Therefore, the controlled synthesis of 1D nanomaterials is vital for improving the performance of these systems.<br/>Existing methods for synthesizing 1D Mo₂C nanostructures by chemical vapor deposition (CVD) are mostly based on the carburization of 1D molybdenum oxide templates. This approach involves complex and lengthy processes with limited control. To address these challenges we present a novel CVD approach. By heating the gallium-molybdenum stack at 1000°C under an inert atmosphere and introducing a hydrocarbon precursor (CH₄), we promote the synthesis of vertically aligned fractal molybdenum carbide nanorods. In this process, gallium is an effective catalyst facilitating the solubility of carbon and molybdenum in gallium which is crucial for the formation of molybdenum carbide nanostructures. After removing gallium by hydrofluoric acid etching vertically aligned molybdenum carbide nanorods with high surface area are successfully produced. Characterization of resulting 1D molybdenum carbide structures was achieved through scanning electron microscope and Raman Spectroscopy providing insights into their morphology. This innovative synthesis method not only eliminates the reliance on the template materials but also offers a pathway for the scalable production of self-aligned 1D molybdenum carbide nanostructures for various applications including hydrogen evolution reaction, field emission, and sensors. (This study is supported by the Air Force Office of Scientific Research, grant number FA9550-18-1-7048.)