Abstract:

Fe,Co,Ni,Cu and Zn catalysts were synthesized with impregnation-reduction method,which were evaluated for the hydrogen generation via catalytic hydrolysis of BH₃NH₃.It was found that,Fe existed as Fe₂B in Fe catalysts;Co existed as metallic Co;Ni existed metallic Ni and Ni（OH）₂·2H₂O;Cu existed as metallic Cu and Cu₂O;Zn existed as Zn₄SO₄（OH）₆·4H₂O in their corresponding catalysts.In addition,the highest catalytic activity was obtained over Co catalyst,while the lowest cat-alytic activity was observed over Zn catalyst.The catalytic activity over Fe catalysts,Co catalysts,Ni catalysts,Cu catalysts and Zn catalysts was ranked in the order from big to small as Co catalysts,Ni catalysts,Cu catalysts,Fe catalysts and Zn cata-lysts.It was obvious that the catalytic activity over Co,Ni and Cu catalysts with their corresponding metallic state was superior to that obtained over Fe catalyst containing Fe₂B alloy phase.Furthermore,nearly no catalytic activity can be observed over Zn catalyst,since it cannot be reduced to metallic state under the preparation condition in this work.When CoCl₂ was reduced at 303 K using NaBH₄,the reducing agent with molar ratio as 1∶1.3,the highest catalytic activity towards hydrogen production can be achieved.According to the kinetic calculation,it was suggested that the hydrolysis of BH₃NH₃ towards hydrogen gener-ation over Co catalyst was a zero order and the first order reaction in corresponding to the concentration of BH₃NH₃ and amount of used Co catalyst,respectively.The activation energy was 58 kJ/mol.

Key words: Co, transition metal, ammonia borane, hydrogen generation