Gallic acid assisted synthesis of novel CuO/Ni/Fe3O4 nanocomposite for catalytic CO2 methanation and photocatalytic hydrogen generation

Abstract

This study investigates the synthesis of CuO/Ni/Fe₃O₄ nanocomposite (NC) using gallic acid, as well as its catalytic performance in CO₂ methanation and photocatalytic hydrogen generation. UV-visible spectroscopy analysis revealed a prominent absorption peak at 370 nm and a band gap energy of 1.26 eV, indicating favorable optical properties for photocatalysis. FTIR analysis identified key functional groups, including a significant O-H peak at 3366 cm⁻¹, C-H stretching at 2926 cm⁻¹, and metal-oxygen bonding vibrations at 580 and 461 cm⁻¹, confirming the presence of Cu-O, Fe-O, and Ni-O bonds, indicative of successful nanoparticle formation. XRD analysis showed distinct peaks at 2θ values corresponding to cubic and monoclinic crystal structures, with calculated crystallite sizes of approximately 30 nm and a surface area of 29 m²/g. The nanocomposite exhibited 37% crystallinity and a density of 6.88 g/cm³. Thermal stability tests revealed only a 5.7% weight loss between 589 and 785 °C. Catalytic tests showed a maximum CO₂ conversion rate of 94.8% at 420 °C, with CH₄ selectivity exceeding 90% across all temperatures. In photocatalytic hydrogen production, the NC achieved an initial rate of 165 µmol/g.h, reaching a total yield of 741 µmol/g after 5 h. The catalyst maintained efficiency over four cycles, highlighting its stability and reusability. These findings emphasize the potential of CuO/Ni/Fe₃O₄ NC as a promising catalyst for sustainable energy production and carbon utilization, combining a green synthesis method with high catalytic efficiency.

Graphical Abstract