Microalgae-derived Co 3 O 4 nanomaterials for catalytic CO oxidation.

Efficient carbon monoxide oxidation is important to reduce its impacts on both human health and the environment. Following a sustainable synthesis route toward new catalysts, nanosized Co 3 O 4 was synthesized based on extracts of microalgae: Spirulina platensis , Chlorella vulgaris , and Haematococcus pluvialis . Using the metabolites in the extract and applying different calcination temperatures (450, 650, 800 °C) led to Co 3 O 4 catalysts with distinctly different properties. The obtained Co 3 O 4 nanomaterials exhibited octahedral, nanosheet, and spherical morphologies with structural defects and surface segregation of phosphorous and potassium, originating from the extracts. The presence of P and K in the oxide nanostructures significantly improved their catalytic CO oxidation activity. When normalized by the specific surface area, the microalgae-derived catalysts exceeded a commercial benchmark catalyst. In situ studies revealed differences in oxygen mobility and carbonate formation during the reaction. The obtained insights may facilitate the development of new synthesis strategies for manufacturing highly active Co 3 O 4 nanocatalysts.