Effects of carbon-supported nickel catalysts on MgH2 decomposition

This paper analyzes the improvement of MgH2 decomposition by the addition of nickel-based catalysts, mostly carbon-supported nickel catalysts. Our study shows that some experimental parameters such as the catalyst content, its composition, the method of preparation, and milling time strongly affect its activity toward MgH2 decomposition. We observe that carbon- supported nickel catalysts have superior performance than those just containing carbon and nickel physically mixed and, especially, than those containing only nickel. This emphasizes the role played by carbon and by the nickel-carbon interaction on the activity of such MgH2-based materials. A decrease, followed by differential scanning calorimetry (DSC), in the decomposition temperature of MgH2 Of 150 degrees C can be achieved with some selected supported catalysts. Suitable selection of the catalyst preparation conditions leads to materials for which decomposition of 6.6 wt % hydrogen occurs in just 9 min at 300 degrees C, in comparison to 240 min required for undoped MgH2, and is stable after five cycles. Comparison between catalysts supported on different carbon materials having similar compositions but different nickel particle size shows no relevant differences in their isothermal decomposition kinetics.