Metal sulfide filled carbon nanotubes and synthesis methods thereof

A method of synthesizing filled carbon nanotubes (CNTs), the method comprising:

• providing a substrate in a reaction chamber;
• disposing a catalyst comprising a metal on the substrate;
• providing a sulfur-containing organic compound to the reaction chamber;
• performing a chemical vapor deposition technique to simultaneously grow multi-walled CNTs and fill the multi-walled CNTs with a metal sulfide comprising the metal, thereby synthesizing the filled CNTs filled with the metal sulfide;
• collecting the filled CNTs via ultrasonication;
• and
• using a magnet to purify the filled CNTs during the collecting, after the collecting, or both,
• the multi-walled CNTs having an average filling ratio of the metal sulfide of at least 0.99,
• the multi-walled CNTs having an average length of at least 10 μm,
• the metal being nickel and the metal sulfide being Ni3S2,
• the providing of the sulfur-containing organic compound to the reaction chamber comprising:
• providing a supply of the sulfur-containing organic compound outside the reaction chamber;
• and
• sending a gas through the supply of the sulfur-containing organic compound and into the reaction chamber such that the sulfur-containing organic compound is bubbled into the reaction chamber with the gas,
• the sulfur-containing organic compound being thiophene,
• the method further comprising, before disposing the catalyst on the substrate, cleaning the substrate via ultrasonication using at least one solvent, and
• the reaction chamber comprising a tube of a first material with a boat of the first material disposed therein, the boat comprising a surface to which the substrate is provided.