Hydrochar Produced from Orange Peel Essential Oil Extraction Residues as a Support for Nanoparticles in Hydrogen...

This work explores the valorization of orange peel residues from essential oil extraction as support for Co/Pt nanoparticles in the catalytic hydrolysis of sodium borohydride (NaBH₄) for hydrogen production. Hydrochar was produced via hydrothermal carbonization at 130 °C for 6 h, preserving surface functional groups that facilitate metal nanoparticle dispersion. Co/Pt nanoparticles were successfully deposited on the hydrochar, as confirmed by TEM, SEM, EDS, and XRD analyses, revealing homogeneous distribution and nanoscale size. FTIR, TGA and BET characterization demonstrated a chemically rich, mesoporous structure, conducive to high catalytic performance. The catalytic activity was evaluated through NaBH₄ hydrolysis under varying metal loadings, NaOH concentrations, NaBH₄ concentrations, and temperatures. Monometallic Pt and Co achieved hydrogen generation rates (HGR) of 2573 and 4074 mL·min^-1·g^-1, respectively, while a 50:50 Co/Pt bimetallic composition showed a synergistic effect, reaching 3359 mL·min^-1·g^-1. Durability assays indicated that the catalyst retained approximately 95% of its initial activity over ten consecutive cycles. Kinetic isotope effect (KIE) experiments using H₂O and D₂O revealed a high KIE value of 4.97, indicating that water activation is the rate-determining step. This work demonstrates that orange peel residues can be efficiently repurposed as a sustainable catalyst support, combining waste valorization with environmentally friendly hydrogen production. The approach offers a cost-effective and green strategy for generating hydrogen while contributing to circular economy initiatives.