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Abstract: Hydrogen generation by catalytic hydrolysis of sodium borohydride (NaBH4) is studied by using Co–B-based thin film catalyst synthesized by pulsed laser deposition (PLD) technique. Co–B nanoparticles, produced in the catalyst film after the laser ablation process, act as active centers producing significantly higher H2 generation rate than Co–B bulk powder. Surface morphology was studied by using scanning electron microscopy and compositional analysis was established by using X-photoelectron and infrared spectroscopies. Films were deposited at different PLD set-up parameters in order to understand the possible role of size and density of the nanoparticles in the catalytic process. Cobalt has been found here to act as an efficient catalyst only when alloyed with boron which partially prevents cobalt oxidation. In particular we report that when used as suitable thin films, Co–B produces H2 with a maximum generation rate of about 3300ml/min per gram of catalyst. [Copyright &y& Elsevier]

Nanocatalysts, in the form of nanoparticles assembled coatings (NPACs) of Co 3 O 4 , were synthesized by pulsed laser deposition (PLD) with optimized parameters. Phase explosion phenomena occurring at high laser fluences produce nanoparticles (NPs) with an average size of ∼5 nm having narrow size distribution (3–10 nm) and low degree of agglomeration, which are randomly arranged in the form of coating on the substrate surface. In comparison with chemically synthesized Co 3 O 4 crystalline powder, the NPACs deposited by PLD showed significantly higher catalytic activity for H 2 generation by hydrolysis of NaBH 4 . Maximum H 2 generation rate obtained by NPACs (5010 ml min −1 g cat −1 ) is about 5 times higher than that produced by Co 3 O 4 powder (1000 ml min −1 g cat −1 ), which is mainly attributed to high surface area and large number of active sites provided by the Co 3 O 4 NPs in the coating owing to their size and shape. By varying the O 2 pressure during PLD, two different cobalt oxide phases, namely Co 3 O 4 and CoO, were formed in NPACs and found that Co 3 O 4 phase is more active for hydrolysis than CoO phase with lower oxidation number. The morphology and crystallinity of Co 3 O 4 NPACs were tuned by varying the laser fluence and substrate temperature respectively, and their effect on H 2 generation rate was studied. The results showed that the NPs with mixed amorphous-nanocrystalline phase on the surface act as active sites for favorable interaction and NaBH 4 conversion. [ABSTRACT FROM AUTHOR]