Spent Tea Leaf Templating of Cobalt-Based Mixed Oxide Nanocrystals for Water Oxidation

The facile synthesis of nanostructured cobalt oxides using spent tea leaves as a hard template is reported. Following an impregnation-calcination and template removal pathway, sheetlike structures containing nanosized crystallites of Co3O4 are obtained. Co3O4 incorporated with Cu, Ni, Fe, and Mn (M/Co = 1/8 atomic ratio) are also prepared, and the materials are thoroughly characterized using X-ray diffraction, electron microscopy, and N-2 sorption. The method is applicable to several commercial tea leaves and is successfully scaled up to prepare over 7 g of Co3O4 with the same nanostructure. The oxides are then tested for electrochemical water oxidation, and Cu, Ni, and Fe incorporations show beneficial effect on the catalytic activity of Co3O4, achieving performance comparable to levels from benchmark electrocatalysts. These data suggest that tea leaf templating can be utilized as a facile and promising approach to prepare nanostructured functional catalyst.