Hydrogen generation from sodium borohydride using a lanthanum/ nitrogen Co-doped chitosan catalyst in alcohol-based media

Abstract

A lanthanum and nitrogen co-doped chitosan (La and N doped-CS) hybrid catalyst was strategically designed for high-efficiency hydrogen production through sodium borohydride (SB) solvolysis in alcohol-based media. The material was prepared via a simple one-pot synthesis that combined nitric acid-assisted nitrogen doping with thermal treatment at 300 degrees C, with the optimal formulation obtained at a chitosan-to-La2O3 mass ratio of 1:0.5. Structural and surface characterization (XPS, TEM, EDS, FTIR) confirmed a nitrogen content of 8.3 at% and a uniform distribution of La2O3 nanoparticles (average size: 20.56 nm). Catalytic evaluations demonstrated hydrogen generation rates (HGR) of 7274 mLmin-1gcat-1 in methanol and a substantially higher value of 20264 mLmin-1gcat-1 in a binary methanol/ethylene glycol (EG) (8:2 v/v) system. The superior performance in the mixed solvent was attributed to synergistic effects arising from reduced viscosity, enhanced proton availability, and favorable catalyst-solvent interfacial interactions. Under optimized conditions, complete SB conversion occurred within 2 min-significantly faster than in single-solvent systems (8-17 min). Mechanistic analysis indicates that the remarkable activity results from: (i) nitrogen-induced electronic modulation promoting BH4-adsorption, (ii) La-mediated alcohol activation via Lewis basic sites, and (iii) improved mass transport due to nanoscale particle dispersion. These results establish La and N doped-CS as a robust and scalable catalyst platform for on-demand hydrogen generation, with strong potential for both portable and stationary energy applications.