Water Splitting for Hydrogen

Green, cheap, efficient photocatalyst for stable visible water splitting: a revolution in hydrogen production for fuel applications?

Prof. Yeshayahu (Shay) Lifshitz

A novel photocatalyst made of carbon and nitrogen proves to be highly efficient in solar water splitting enabling cheap and stable generation of hydrogen.

Production of H2 and O2 from overall water splitting using solar energy is a promising means of renewable energy storage. In the past 40 years, a host of inorganic and organic systems have been developed as photocatalysts for water splitting driven by visible light. These photocatalysts however still suffer from very low solar to hydrogen energy conversion efficiency and/or poor stability (their performance deteriorates within a few hours). The poor performance of these catalysts hindered the utilization of the simple process of photocatalysis for practical hydrogen production.

Lee, Lifshitz, Kang and co-workers (from Soochow University in Jiangsu, China and Technion, Haifa, Israel) have now developed a new photocatalyst: a carbon nanodot-carbon nitride nanocomposite. This new catalyst has long-term stability (its catalytic activity remains the same within more than 200 days) and is made of C and N – cheap, earth-abundant and non-polluting elements. The photocatalyst’s impressive performance for solar water splitting is realized through two stages as schematically described in the attached figure: (1) Carbon nitride is splitting water to peroxide and hydrogen, (2) Carbon nanodots are decomposing peroxide to water and oxygen. The carbon nanodots also increase the light absorbance of the solar spectrum in its most intense wavelength (orange light). The solar to hydrogen energy conversion efficiency of the new catalyst is 2%, more than ten times larger than previously reported values. Following the techno-economical analysis of the US department of energy (DOE) a catalyst with a 2% efficiency facilitates hydrogen production cost of about 6$/Kg, not much larger than the maximum target cost of DOE (4$/Kg).

Prof. Lifshitz holds 3 academic degrees in Physics: B.Sc. (Hebrew Univ.), M.Sc. (Tel-Aviv Univ.), Ph.D. (Weizmann Inst.). He was a senior researcher at the Soreq Nuclear Research Center where he was the founding head of the Space Qualification Section, responsible for qualification tests of materials and electronic devices used in Israeli satellites. He is internationally known as the originator of the “subplantation model” which is the basis of modern deposition technology and was the first to explain the nucleation of diamond in sub-atmospheric laboratory processes. Currently he is the Alfred and Marion Bar chair professor at the department of Materials Science and Engineering at Technion. Since 2014 he is also a Chair professor at Soochow University, China, where the present research was performed. Prof. Lifshitz was listed as one of the world’s top 100 materials scientists of the 2000-2010 decade by “Thomson Reuters” and the education appendix of Times Magazine. The current Science paper of Prof. Lifshitz adds up to several other Science and Nature papers he co-authored.

The research is being carried out in collaboration with the Russell Berrie Nanotechnology Institute.

Source:
Liu et al, “Metal-free efficient photocatalyst for stable visible water splitting via a two-electron pathway”, Science, 347(6225), 970, 27 September 2015.