Zhenhui Kang, Shuit-Tong Lee, Soochow University, China, and colleagues have developed a highly efficient way to use sunlight to split water into hydrogen and oxygen. They use a metal-free carbon nanodot–carbon nitride (C₃N₄) nanocomposite as photocatalyst. C₃N₄ catalyzes the oxidation of water to hydrogen peroxide. Normally, hydrogen peroxide poisons the catalyst. However, the nanodots of this catalyst break the hydrogen peroxide into water and oxygen. They also allow the catalyst to absorb more light.

The catalyst consists of low-cost, Earth-abundant, environmentally friendly materials and has an excellent overall solar-to-hydrogen conversion efficiency of 2 %. According to the researchers after optimization it has great potential to significantly lower the cost of hydrogen production.

• Metal-free efficient photocatalyst for stable visible water splitting via a two-electron pathway,
  J. Liu, Y. Liu, N. Liu, Y. Han, X. Zhang, H. Huang, Y. Lifshitz, S.-T. Lee, J. Zhong, Z. Kang,
  Science 2015, 347, 970–974.
  DOI: 10.1126/science.aaa3145