Electrochemical Properties for Hydrogen Production of Nitrogen‐Doped Sponge‐Like Carbon Nanotubes as High‐Surface Area Catalyst

Nitrogen‐doped sponge carbon nanotubes (SCNTs) are synthesized using catalytic chemical vapor deposition (CCVD). In the CCVD experiment, a catalyst precursor composed of hematite, silicon oxide, and copper is exposed to the pyrolysis of toluene and N, N‐dimethylformamide solution for one hour at a growth temperature of 950 °C. The effect of Cu concentration in the catalyst on the yield and morphology of the SCNTs is investigated. The SCNTs are characterized using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The synthesized SCNTs exhibit tangled carbon nanotubes (CNTs) with rough surfaces. The incorporation of Cu induces notable morphological changes in the SCNTs, increasing their surface roughness and diameter, reaching a maximum of 102 nm. Cyclic voltammetry measurements demonstrate that the electrochemical surface area for acid‐treated SCNTs is 731.85 cm 2 cm −2 geo , whereas pristine SCNTs exhibit 23.34 cm 2 cm −2 geo . The catalytic performance of the SCNTs in the hydrogen evolution reaction (HER) is evaluated. Although the initial presence of Cu negatively affects the HER activity, acid treatment mitigates this drawback. The optimized sample reaches an overpotential of 368 mV at −10 mA cm −2 .