Electrolyte-assisted polarization leading to enhanced charge separation and solar-to-hydrogen conversion efficiency of seawater splitting
Yiyang Li, Hui Zhou, Songhua Cai, D. Prabhakaran, Wentian Niu, Alexander I. Large, Georg Held, Robert A. Taylor, Xin‐Ping Wu, Shik Chi Edman Tsang
Abstract
Abstract Photocatalytic splitting of seawater for hydrogen evolution has attracted a great deal of attention in recent years. However, the poor energy conversion efficiency and stability of photocatalysts in a salty environment have greatly hindered further applications of this technology. Moreover, the effects of electrolytes in seawater remain controversial. Here we present electrolyte-assisted charge polarization over an N-doped TiO 2 photocatalyst, which demonstrates the stoichiometric evolution of H 2 and O 2 from the thermo-assisted photocatalytic splitting of seawater. Our extensive characterizations and computational studies show that ionic species in seawater can selectively adsorb on photo-polarized facets of the opposite charge, which can prolong the charge-carrier lifetime by a factor of five, leading to an overall energy conversion efficiency of 15.9 ± 0.4% at 270 °C. Using a light-concentrated furnace, a steady hydrogen evolution rate of 40 mmol g −1 h −1 is demonstrated, which is of the same order of magnitude as laboratory-scale electrolysers.