Design of a High-Efficiency Magnetically Separable Fe3O4@Al2O3/Co-Cs Catalyst for Sustainable Hydrogen Generation via NaBH4 Hydrolysis: Experimental and DFT Insights

Abstract

We report the first successful synthesis of a novel magnetically recoverable nanocatalyst, Fe3O4@Al2O3/Co-Cs, incorporating cesium (Cs) as a co-catalytic promoter for efficient and sustainable hydrogen generation via NaBH4 hydrolysis. In this system, magnetite (Fe3O4) serves as a magnetic core, enabling facile separation and recyclability, whereas the Al2O3 shell enhances thermal stability, structural integrity, and active-site dispersion. Cobalt (Co) acts as the primary active metal, whereas Cs is introduced here for the first time in NaBH4 hydrolysis as an electronic promoter, significantly enhancing electron transfer and accelerating the hydrogen generation rate (HGR). Comprehensive characterization using FTIR, XRD, FE-SEM/EDX, and BET analyses confirmed the successful formation of a hierarchical core-shell structure. FE-SEM images revealed a flower-like morphology composed of aggregated nanosheets and nanoparticles that promoted efficient mass transfer and gas diffusion. Catalytic performance tests conducted at 30 degrees C demonstrated a high hydrogen generation rate of 17.24 L g- 1 min- 1. The apparent activation energy was determined to be 27.18 kJ mol-1, indicating favorable reaction kinetics under mild conditions. Thermodynamic analysis revealed a low enthalpy of adsorption (Delta Hads = 35.66 +/- 0.01 kJ mol-1) and a small entropy change (Delta S degrees = 0.09022 +/- 0.01 kJ mol- 1 K-1), suggesting favorable interactions between the reactants and catalyst surface. Density functional theory (DFT) calculations further confirmed that the Fe3O4@Al2O3/Co-Cs system exhibited enhanced adsorption strength and reduced activation barriers, facilitating NaBH4 hydrolysis through efficient charge transfer, intermediate stabilization, and synergistic catalytic effects. Overall, this study highlights the novel role of cesium as an alkali metal promoter in NaBH4 hydrolysis, opening new opportunities for the design of advanced non-noble metal catalysts for hydrogen generation.