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Abstract: Co-B nanoparticles supported over carbon films were synthesized by using pulsed laser deposition (PLD) and used as catalysts in the hydrolysis of sodium borohydride (NaBH4) to produce molecular hydrogen. Amorphous Co-B-based catalyst powders, produced by chemical reduction of cobalt salts, were used as target material for nanoparticles-assembled Co-B film catalysts preparation through PLD. Various Ar pressures (10–50Pa) were used during deposition of carbon films to obtain extremely irregular and porous-carbon support with high surface area prior to Co-B film deposition. Surface morphology of the catalyst films was studied using scanning and transmission electron microscopy, while structural characterizations were carried out using X-ray diffraction. The hydrogen generation rate attained by carbon-supported Co-B catalyst film is significantly higher as compared to unsupported Co-B film and to conventional Co-B powder. Morphological analysis along with NaBH4 hydrolysis tests showed that the Co-B nanoparticles produced with PLD act as active catalytic centers for hydrolysis while the carbon support provides high initial surface area for the Co-B nanoparticles with better dispersion and tolerance against aggregation. The hydrogen generation rate obtained by the present catalyst film was also investigated as a function of Co-B loading, carbon morphology, and solution temperature. The high performance of our carbon-supported Co-B film is well supported by the obtained very low activation energy (∼31kJ (mol)−1) and exceptionally high H2 generation rate (8.1LH2 min−1 (gofcatalyst)−1) in the hydrolysis of NaBH4. [Copyright &y& Elsevier]

Abstract: Nanoparticle-assembled Co-B thin films were synthesized by Pulsed Laser Deposition (PLD) and used as catalysts for the hydrolysis of NH3BH3 (ammonia borane, AB) to produce molecular hydrogen. Amorphous Co-B-based catalyst powders, produced by chemical reduction of cobalt salts, were used as target material for Co-B thin film catalysts preparation through PLD. Surface morphology of Co-B powder and film catalyst was studied using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Compositional and structural characterizations were carried out using X-photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques, respectively. The efficiency of both powder and film catalysts was tested by comparative kinetic analysis of the AB hydrolysis for hydrogen production. It was observed that nanoparticles produced during the laser ablation process act as active catalytic centers to produce significantly higher rate (about 6 times) of H2 than the same amount of the corresponding Co-B powders. Almost complete conversion (95%) of AB was obtained, as confirmed by 11B NMR, by using Co-B films at room temperature. Active Co-B nanoparticles on the surface of the PLD-deposited films is able to decrease the activation energy, for hydrolysis of AB, to the very low value of 34kJmol−1. We also found that by adding small amount of NaBH4 to the NH3BH3 solution increases the efficiency of the Co-B catalyst films, thus generating H2 with higher rate. Maximum H2 generation rate of about ∼8.2LH2 min−1 (g of Co)−1 and ∼13LH2 min−1 (g of Co)−1 was measured by hydrolysis of AB and mixture of (AB+NaBH4) solutions, respectively. [Copyright &y& Elsevier]