Non-noble metal catalysis for environmental benign energy: Ni-Co nanoferrites for high-rate hydrogen generation

Abstract

Sustainable and cost-effective catalytic systems are essential for the environmental viability of hydrogen energy technologies. This study addresses this challenge by designing a series of non-noble Ni1-xCoxFe2O4 (x = 0-1) spinel nano catalysts via an energy-efficient sol-gel route for hydrogen production through sodium borohydride (NaBH4) methanolysis. Structural and spectroscopic characterization by XRD, SEM/EDS, FTIR, and Raman confirmed the formation of phase-pure cubic spinels across the entire composition range. Rietveld refinement revealed a systematic lattice contraction with increasing Ni2+ content, consistent with Vegard's law, while vibrational analyses evidenced cation redistribution within the Fd-3 m spinel framework. Catalytic screening identified Ni0.75Co0.25Fe2O4 as the optimal composition, delivering a high hydrogen generation rate of 31 699 mL & centerdot;min- 1 & centerdot;gcat-1 under mild conditions. This superior activity is attributed to a strong Ni/Co synergistic effect, reflected in a low apparent activation energy of 14.49 kJ & centerdot;mol- 1. Kinetic evaluation using the Eyring approach yielded activation parameters (Delta H = 11.85 kJ & centerdot;mol- 1, Delta S = -199.81 J & centerdot;mol- 1 & centerdot;K- 1), indicating an associative surface reaction mechanism. Temperature-programmed analyses (H2-TPR, O2-TPO, NH3-TPD) further showed that the optimal catalyst possesses accessible redox couples and a favourable distribution of acid sites, lowering energetic barriers for BH4- activation. The catalyst demonstrated excellent durability, retaining 96% of its initial activity over five consecutive cycles. This work establishes Ni0.75Co0.25Fe2O4 as a high-performance, sustainable, and reusable catalyst for chemical hydrogen storage, aligning with green chemistry principles and contributing to environmentally benign energy solutions.