Carbon Nitride Makes Hydrogen Cheaply

Carbon nitride is an inexpensive, stable, and metal-free photocatalyst for producing hydrogen from water, reports a group led by Xinchen Wang of the International Joint Laboratory, a joint venture between the Max Planck Institute of Colloids & Interfaces, in Potsdam, Germany, and Fuzhou University, in China, and Kazunari Domen of the University of Tokyo (Nat. Mater., DOI: 10.1038/nmat2317). Typical H₂-producing catalysts either require precious metals such as platinum or ruthenium or, in the case of synthetic polymer semiconductors, ultraviolet light. Wang, Domen, and colleagues found that "graphitic" carbon nitride—layers of C₃N₄ sheets—can produce H₂ in visible light without metal additives when triethanolamine is present as a sacrificial electron donor. Density functional computations indicate that the material likely oxidizes H₂O to O₂ at the nitrogen atoms and reduces H⁺ to H₂ at the carbon atoms. The unoptimized carbon nitride system produced up to 4µmol of H₂ per hour, roughly an order of magnitude less than photocatalysts that use precious metals. The result "opens new vistas for the search of energy production schemes" using commonly available materials, the authors write.