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 N₂ 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.