Preparation of Co_3−xCa_xO₄ nanostructure catalyst for improved hydrogen production from sodium borohydride

Hydrogen energy is becoming increasingly important because it is a clean and renewable source of energy. The present work reports the preparation of calcium doped Co₃O₄ as a catalyst for hydrogen production from sodium borohydride. Techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and FTIR spectroscopy were used to characterize Co_3−xCa_xO₄ nanostructures. XRD peaks have been indexed to the standard cubic structure of Co₃O₄. The estimated average crystal size ranged from 14 to 16 nm. The vibrational modes of calcium doped Co₃O₄ were detected in the FTIR spectra. The data analysis of XPS spectroscopy is used to explore the chemical composition of the Co_3-xCa_xO₄ surface. SEM micrographs showed mesoporous Co₃O₄ with a porous structure that is made up of cobalt oxide nanoparticles. The specific surface areas of Co₃O₄, Co_2.9Ca_0.1O₄, Co_2.8Ca_0.2O₄, and Co_2.7Ca_0.3O₄ are 192, 57, 63, and 70 m²/g, respectively. The addition of calcium reduced the optical energy gap of Co₃O₄ from 1.95 to 1.85 eV. All the prepared catalysts showed a photoluminescence (PL) emission peak around 427 nm. The Co₃O₄, Co_2.9Ca_0.1O₄, Co_2.8Ca_0.2O₄, and Co_2.7Ca_0.3O₄ catalysts showed high catalytic activity, with Co_2.8Ca_0.2O₄ showing the highest rate of hydrogen production (3025 mL/g.min).