This study explores the synthesis of Co₃O₄ nanomaterials using extracts from three microalgae species—Spirulina platensis, Chlorella vulgaris, and Haematococcus pluvialis—as a sustainable alternative to traditional chemical or physical methods. The extracts, rich in metabolites such as proteins, carbohydrates, and carotenoids, were used to synthesize Co₃O₄ nanomaterials through a biological approach. The nanomaterials were then calcined at different temperatures (450, 650, and 800°C) to obtain catalysts with varying properties. The resulting Co₃O₄ nanomaterials exhibited distinct morphologies, including octahedral, nanosheet, and spherical structures, with surface segregation of phosphorus and potassium from the extracts. These elements significantly enhanced the catalytic activity of the nanomaterials in CO oxidation. When normalized by specific surface area, the microalgae-derived catalysts outperformed a commercial benchmark catalyst. In situ studies revealed differences in oxygen mobility and carbonate formation during the reaction, indicating the potential of these nanomaterials for CO oxidation. The study also highlights the role of phosphorus and potassium in enhancing catalytic activity, despite the presence of sodium and chlorine, which were reported to reduce oxygen mobility. The results suggest that the use of microalgae-derived Co₃O₄ nanomaterials could provide an environmentally friendly and efficient solution for CO oxidation, with potential applications in automotive catalytic converters, petrochemical refineries, and fuel cells. The findings emphasize the importance of exploring sustainable synthesis methods for highly active Co₃O₄ nanocatalysts.This study explores the synthesis of Co₃O₄ nanomaterials using extracts from three microalgae species—Spirulina platensis, Chlorella vulgaris, and Haematococcus pluvialis—as a sustainable alternative to traditional chemical or physical methods. The extracts, rich in metabolites such as proteins, carbohydrates, and carotenoids, were used to synthesize Co₃O₄ nanomaterials through a biological approach. The nanomaterials were then calcined at different temperatures (450, 650, and 800°C) to obtain catalysts with varying properties. The resulting Co₃O₄ nanomaterials exhibited distinct morphologies, including octahedral, nanosheet, and spherical structures, with surface segregation of phosphorus and potassium from the extracts. These elements significantly enhanced the catalytic activity of the nanomaterials in CO oxidation. When normalized by specific surface area, the microalgae-derived catalysts outperformed a commercial benchmark catalyst. In situ studies revealed differences in oxygen mobility and carbonate formation during the reaction, indicating the potential of these nanomaterials for CO oxidation. The study also highlights the role of phosphorus and potassium in enhancing catalytic activity, despite the presence of sodium and chlorine, which were reported to reduce oxygen mobility. The results suggest that the use of microalgae-derived Co₃O₄ nanomaterials could provide an environmentally friendly and efficient solution for CO oxidation, with potential applications in automotive catalytic converters, petrochemical refineries, and fuel cells. The findings emphasize the importance of exploring sustainable synthesis methods for highly active Co₃O₄ nanocatalysts.