| The efficient production and storage of hydrogen is a major problem faced by the development of hydrogen energy.Hydrogenation by hydrolysis has received great attention due to its mild reaction conditions,high hydrogen purity,and no harm to the environment.Metal borohydride has attracted much attention from scholars because of its high hydrogen capacity.It is of great research value and practical significance to explore borohydride as hydrogen production materials with high hydrogen yield and excellent hydrolysis performance.In this paper,NaBH4-ZnCl2 composites,NaZn（BH4）3,Mg（BH4）2 and their ammoniates were prepared by ball milling and their hydrolysis properties were optimized.The regulation of hydrolysis properties was achieved and the hydrolysis mechanism was elucidated.Hydrogen production material stable to air,with high hydrogen production and adjustable hydrolysis properties have been created,possessing potential application value in a mobile hydrogen source system.Firstly,NaBH4-ZnCl2 composites were prepared by ball milling with Na BH4 and ZnCl2.The hydrolysis properties of NaBH4-ZnCl2 composites were tested.The ZnCl2 content,ball milling time and temperature were optimized for the hydrolysis properties of the composites.With the increase of ZnCl2 mass fraction,the hydrogen production rate of NaBH4-ZnCl2composites gradually increased.When the mass fraction of ZnCl2 was 35 wt%,hydrogen yield reached 1964 mL/g.At the same time,the influence of ball milling time and temperature on the hydrolysis performance of NaBH4-Zn Cl2 composites was also discussed.The hydrolysis activation energy of composites was calculated by Arrhenius equation.The hydrolysis mechanism was elucidated by the analysis of hydrolysis by-product.Based on the formation of bimetallic borohydride Na Zn（BH4）3 in NaBH4-ZnCl2composites and the amphoteric metal property of Zn may improve the pH required for the hydrolysis of sodium borohydride and then regulate its hydrolysis performance,this article further tried to synthesize bimetallic borohydride Na Zn（BH4）3 and its hydrogen production by hydrolysis and alcoholysis.Hydrolysis reaction of NaZn（BH4）3 produced 1740 m L/g H2 in 5min,and only high-purity hydrogen was released during the hydrolysis process,showing excellent hydrolysis performance and hydrogen production performance even at low temperature.At the same time,NaZn（BH4）3 still reacted with methanol even at-18°C,showing good alcoholysis performance.Based on the rapid rate of hydrogen production from NaZn（BH4）3 and instability to air,ammonization was used to prepare ammoniates.The ammoniates were stable to air and adjustable rate was obtained.In view of the adoption of ammonization for stable hydrolysis materials,this article further explored the preparation of Mg（BH4）2 based on Na BH4 with higher hydrogen yield.The introduction of ammonia controls the air stability of Mg（BH4）2 and its hydrogen production properties.The air stability and the hydrolysis performance were regulated.The hydrolysis reaction of Mg（BH4）2 can produce 1700 mL/g H2 within 1 min,and the hydrogen yield can reach 3004 m L/g H2.It is currently reported as the hydrogen production material with largest hydrogen yield.The borohydride ammoniates were also obtained by introducing ammonia,which effectively controlled the hydrogen production rate and hydrogen yield of Mg（BH4）2 and improved the air stability of Mg（BH4）2. |
