Green synthesis of nickel-integrated chitosan-modified CeO₂ nanocatalyst for the efficient hydrogenation of 4-NP and azo dyes

This paper reports the green synthesis and characterization of nickel-integrated chitosan-modified cerium oxide (CHS-CeO₂@Ni) nanocatalyst aimed at the efficient hydrogenation of 4-nitrophenol (4-NP) and the reduction of azo dyes such as methyl orange (MO) and Congo red (CR). The CHS-CeO₂@Ni nanocatalyst was synthesized via a green method, where Arnebia benthamii plant extract was used as a reducing agent to deposit nickel nanoparticles onto the CHS-CeO₂ nanocomposite. Results confirmed the successful integration of Ni into the CHS-CeO₂ matrix, resulting in a highly crystalline, mesoporous structure with a substantial surface area of 78.447 m²/g. The catalytic activity was evaluated in reducing MO, CR, and 4-NP in the presence of NaBH₄. The nanocatalyst exhibited remarkable efficiency, reducing MO and CR in 16 and 14 min, respectively, with pseudo-first-order rate constants of 0.173 min^-1 and 0.179 min^-1. For 4-NP, complete reduction to 4-aminophenol was achieved within 19 min, with a rate constant of 0.112 min^-1. The enhanced catalytic performance is attributed to the synergistic interaction between cerium oxide and nickel nanoparticles, highlighting the potential of CHS-CeO₂@Ni as a sustainable solution for environmental remediation.