Homologous metal-free electrocatalysts grown on three-dimensional carbon networks for overall water splitting in acidic and alkaline media

A homologous, metal-free electrolyzer in both acidic and alkaline media was developed, consisting of self-supported carbon nitride/carbon nanotube/carbon fiber (C3N4-CNT-CF) and sulfur-doped carbon nitride/carbon nanotube/carbon fiber (S-C3N4-CNT-CF) as oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts, respectively. The self-supported C3N4-CNT-CF electrode was proven to be an effective catalyst for the OER, due to the high N content of carbon nitride sheets and enhanced charge transport ability by the synergistic effect between the well-designed three-dimensional hierarchical carbon network and layered carbon nitride. In the meantime, the S-C3N4-CNT-CF was also proven to be an efficient, stable metal-free electrode for the HER. The homologous C-3-N-4-CNT-CF parallel to S-C3N4-CNT-CF water splitting system presents low onset potential and good stability in both acidic and alkaline media, indicating a potential carbon-based, metal-free full water splitting electrolyzer with low cost.