Electroless-deposited Co-based Catalysts For Hydrogen Generation From Alkaline NaBH₄ Solution

To overcome the problems of energy shortage and environmental pollution, it is important to develop the hydrogen-energy technology. As an efficient way of hydrogen utilization, proton exchange membrane fuel cells (PEMFCs) can generate energy through the reaction of hydrogen and oxygen in the atmosphere. However, one of the major problems facing the practical application of PEMFCs is the lack of safe and efficient hydrogen supply technique. Recently, NaBH4 has been widely studied due to its high hydrogen content (10.6 wt%) and favorable properties including high stability of its alkaline solution, environmentally benign character, recyclable product, and relatively low cost. From the hydrolysis process, high-purity hydrogen gas can be controllably released from the alkaline NaBH4 solution in the presence of selected catalysts. Up to now, noble metals such as Pt and Ru have been reported to exhibit high catalytic activity for the hydrolysis of NaBH4. However, the high price and limited abundance of noble metal-based catalysts restricts their wide application. Thus, it is essential to develop catalysts with low cost and high catalytic efficiency. In this dissertation, we have studied the preparation, characterization and catalytic tests of Co-based low-cost catalysts for hydrogen generation from NaBH4 hydrolysis. The main results are summarized as follows.(1) With Cu sheet as a substrate, we have synthesized Co-P and Co-B catalysts through electroless deposition method. The effects of morphologies, compositions, and structures of the catalysts are investigated in detail by adjusting preparation parameters such as pH value, reactant concentration, and deposition time and deposition temperature. We also studied the deposition rate of Co-P catalyst as a function of preparation parameters.(2) The as-prepared Co-P and Co-B have been used as the catalysts for hydrogenation from alkaline NaBH4 solution. The results show that the Co-P catalyst formed in the bath solution with pH value of 12.5, NaH2PO2 concentration of 0.8 M, and the deposition time no more than 6 min presents the highest hydrogen generation rate of 1846 mL min-1 g-1. For Co-B catalysts, the sample prepared from the solution with pH value of 12.5, NaBH4 concentration of 0.8 g L-1, depositing temperature of 40℃, an optimal hydrogen generation rate of 4218 mL min-1 g-1 was attained.. Furthermore, the prepared Cu-supported alloys could be used repeatedly for several cycles.The present results should help to promote the further practical application of Co-based alloys as low-cost catalysts for hydrogen generation from hydrolysis of NaBH4 solution.