Porous NiCo2O4 nanorods as efficient catalysts for UV-assisted reduction of p-nitrophenol

Abstract

The catalytic reduction of nitroaromatic pollutants using transition metal oxides has attracted increasing attention as an alternative to noble-metal-based catalysts. Among these materials, spinel NiCo₂O₄ has emerged as a promising catalyst owing to its mixed-valence redox chemistry, good electrical conductivity, and low cost. However, the relationship between its morphological characteristics and catalytic performance remains insufficiently understood. In this work, NiCo₂O₄ nanostructures were synthesized through a polyvinylpyrrolidone (PVP)-assisted hydrothermal method followed by thermal annealing at different temperatures to investigate the influence of morphology on p-nitrophenol (PNP) reduction. The optimised sample exhibited an optical bandgap of approximately 2.9 eV and achieved 99.5% conversion of PNP under UV irradiation. The enhanced catalytic performance is attributed to the nanorod morphology, improved active surface area, and efficient interfacial electron transfer. The catalyst retained more than 97% of its activity after five catalytic cycles, demonstrating good stability. These results demonstrate the potential of morphology-engineered NiCo₂O₄ nanorods for catalytic reduction of nitroaromatic pollutants.