Ruthenium supported on nitrogen-doped porous carbon for catalytic hydrogen generation from NH3BH3 hydrolysis

Global climatic changes and extreme weather variations attributed to high carbon emissions have motivated inquests into alternative energy sources. Hydrogen is one of the most promising energy carriers and viable candidate for replacing fossil fuels. Hydrogen has a high calorific value upon combustion and can be obtained from various sources hence it has attracted much attention. On the other side of the coin, hydrogen is flammable, explosive, easy to diffuse and has a low bulk density at room temperature.

The key to promote the implementation of hydrogen energy economy in the future is by providing efficient and safe hydrogen storage technology. Recently, ammonia borane has been reported to show good chemical hydrogen storage, credit to its high hydrogen content, but at the same time has generate serious drawbacks in terms of thermolysis and hydrolysis. Fortunately, economical and efficient regeneration technologies have been reported. These techniques have reported the use of noble earth elements, such as platinum, as catalysts during hydrogen pyrolysis. This takes the entire process somewhere north of ‘expensive’. Therefore, a more economical and yet efficient metal catalyst is highly desirable.

In a recent publication in International Journal of Hydrogen Energy, Guilin University of Electronic Technology scientists: Professor Hailiang Chu, Mr. Nianpu Li, Professor Shujun Qiu, Professor Yongjin Zou, Professor Cuili Xiang, Professor Fen Xu, Professor Lixian Sun all from the Guangxi Key Laboratory of Information Materials successfully synthesized ruthenium supported on nitrogen-doped porous carbon catalyst by in situ reduction. Ruthenium is less expensive in comparison with platinum hence their report takes the entire human race a step closer to the cleanest and most renewable energy source.

Following successful synthesis of ruthenium supported on nitrogen-doped porous carbon catalysts, its structure and composition were systematically characterized. The team also investigated the efficiency to which the catalyst hydrolyzed the ammonia borane. Materials used for the research included: hydrochloride semicarbazide, glucose, hydrochloric, potassium hydroxide, ethanol, ammonia borane and ultra-pure water.

The research team observed that the hydrogen production reaction only took 90 seconds at a temperature of 298 K, to achieve maximum rate of hydrogen production with a reduced activation energy of 24.95 kJ mol^-1. In particular, they reported the turnover frequency for hydrogen production to be about 813 mol_H2·mol_Ru^-1·min^-1. Furthermore, they showed that even after 5 recycles of the ruthenium catalyst, its performance maintained at 67% of the initial maximum hydrogen generation value recorded.

In summary, the study by Guilin University of Electronic Technology researchers presented the preparation of nitrogen-doped porous carbon (Ru/NPC) materials by a simple hydrothermal method followed by its utilization as a carrier to support ruthenium metal catalyst for hydrogen generation from hydrolysis of ammonia borane. Excellent catalytic activity was reported. Altogether, the results suggest that Ru/NPC prepared by in situ reduction has a future as it is highly efficient for catalyzing the hydrolytic dehydrogenation of ammonia borane.