Co-B nanoparticles supported on carbon film synthesized by pulsed laser deposition for hydrolysis of ammonia borane

摘要

Thin films of Carbon-supported Co-B nanoparticles were synthesized by using Pulsed Laser Deposition (PLD) and used as catalysts in the hydrolysis of 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 nanoparticles-assembled Co-B film catalysts preparation through PLD. Various Ar pressures (10-50 Pa) 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 Electron Microscopy, while structural characterization was 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 conventional Co-B powder. Almost complete conversion (95%) of AB was obtained at room temperature by using present film catalyst. Morphological analysis showed that the Co-B nanoparticles produced after the laser ablation process 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 efficient nature of our carbon-supported Co-B film is well supported by the obtained very low activation energy (~29 kJ (mol) ~(-1)) and exceptionally high H_2 generation rate (13.5 L H_2 min~(-1) (g of Co)~(-1)) by the hydrolysis of AB.