Pada penelitian ini, nanopartikel NiCo₂O₄ telah berhasil dipreparasi menggunakan metode green synthesis dengan memanfaatkan metabolit sekunder dalam ekstrak daun cocor bebek (Bryophyllum pinnatum) sebagai sumber basa lemah dan capping agent dalam pembentukan nanopartikel. Ekstrak daun cocor bebek (Bryophyllum pinnatum) dari hasil uji fitokimia diketahui mengandung metabolit sekunder antara lain alkaloid, flavonoid, saponin, dan terpenoid. Dengan %rendemen dan %konsentrasi ekstrak masing-masing sebesar 1,71% dan 0,55%.  Karakterisasi FTIR, XRD, SEM dan TEM digunakan untuk mengkarakterisasi nanopartikel hasil sintesis. Karakterisasi FTIR menunjukkan bahwa nanopartikel NiCo₂O₄ menghasilkan puncak serapan pada bilangan gelombang 569 cm^-1 dan 655 cm^-1 yang disebabkan vibrasi stretching Ni-O dan vibrasi stretching Co-O. Karakterisasi XRD menunjukkan bahwa nanopartikel NiCo₂O₄ hasil sintesis memiliki struktur spinel kubik. Hasil karakterisasi SEM dan TEM diketahui nanopartikel NiCo₂O₄ memiliki morfologi spherical dengan ukuran rata-rata sebesar 25,84 nm. Aktivitas katalitis nanopartikel NiCo₂O₄ terhadap reduksi 2,4,6-trinitrofenol menghasilkan persentase reduksi sebesar 80,46% dengan mengikuti kinetika hukum laju reaksi pseudo orde satu.

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In this study, NiCo₂O₄ nanoparticle were succesfully preparated with green synthesis method using Bryophyllum pinnatum leaf extract as weak base source and capping agent for the growth nanoparticle. Bryophyllum pinnatum leaf extract from phytochemicals test are known to contain alkaloids, flavonoids, saponins, and terpenoids. With %yield and %concentration extract is 1,71% and 0,55% respectively. FTIR, XRD, SEM and TEM were used to characterize the synthesized nanoparticle. The characterization of FTIR showed that NiCo₂O₄ nanoparticles showed peaks at wave numbers 569 cm^-1 and 655 cm^-1 caused by stretching of Ni-O and stretching of Co-O respectively. The characterization of XRD showed that the synthesized NiCo₂O₄ nanoparticles has a cubic spinel structure. The SEM and TEM characterization revealed that NiCo₂O₄ nanoparticles has spherical morphology with an average size of 25.84 nm. The catalytic activity of NiCo₂O₄ nanoparticles for reduction of 2,4,6-trinitrophenols with a persentage reduction of 80.46% in 50 minutes and the reaction follows pseudo first order kinetics.