Fuel cells coupled with water electrolysis to generate electricity have potential to solve current sustainable energy challenges. Metal-free heteroatom-based carbon nanotube electrocatalysts have shown promising activity for water electrolysis.

Qiang Wu, Zheng Hu, and colleagues, Nanjing University, China, have developed sulfur and nitrogen co-doped carbon tubes (SNCT) as electrocatalysts for the oxygen reduction (ORR) and hydrogen evolution reactions (HER) in acidic media. They annealed carbonaceous tubes with cysteine at high temperatures (700–1000 °C), and obtained SNCT samples. They evaluated the material’s properties using transmission electron microscopy (TEM, pictured) and X-ray photoelectron spectroscopy (XPS).

The catalyst exhibited a record high onset potential of 851 mV (vs. reversible hydrogen electrode) for ORR. High HER activity was also observed with a low overpotential of 76 mV and good stability. According to the team, these results demonstrate the potential of carbon-based metal-free electrocatalysts for the production of clean energy.

• Sulfur and Nitrogen Codoped Carbon Tubes as Bifunctional Metal-Free Electrocatalysts for Oxygen Reduction and Hydrogen Evolution in Acidic Medium,
  Tao Sun, Qiang Wu, Yufei Jiang, Zhiqi Zhang, Lingyu Du, Lijun Yang, Xizhang Wang, Zheng Hu,
  Chem. Eur. J. 2016.
  DOI: 10.1002/chem.201601535