Study On Hydrogen Production By Hydrolysis Of Sodium Borohydride Catalyzed By Multi-component Alloy FeCoNiCrMn_x

With the depletion of fossil energy,research on new renewable energy sources is imminent.Hydrogen is recognized as the most attractive clean renewable energy source.Hydrogen production by sodium borohydride is widely concerned by researchers because of its high storage capacity,high purity of hydrogen production,simple and easy to control reaction conditions,safety and pollution-free.The key to hydrogen production by sodium borohydride hydrolysis is the development and research of catalysts.In this paper,a multi-component alloy FeCoNiCrMnx was used as a catalyst for the hydrogen production of sodium borohydride.The selective corrosion of the alloy was carried out by controlling the corrosion process,so that the catalytic active sites were exposed on the surface of the alloy.Through the adjustment of corrosion process,element addition and annealing process,the performance of multi-component alloy FeCoNiCrMnx catalyzed by hydrogen hydrolysis of sodium borohydride was studied systematically.The effect of Mn on the structure and catalytic properties of multi-component FeCoNiCrMnx was studied by adjusting the content of Mn in the alloy.As the content of Mn increases from x=1 to x=6,the microstructure of the alloy exhibits a uniform f.c.c.single phase,but the corrosion resistance of the alloy is significantly reduced.After etching with a 1 mol/l hydrochloric acid solution,the alloy undergoes significant elemental selective corrosion,and a large amount of Mn element is etched away while exposing a large amount of active sites Ni and Co to promote catalytic hydrogen production.With the addition of the Mn element content,the hydrogen production rate was increased from 0.30 ml/(min·g)to 16.56 ml(min·g)at 30?,0.1 wt.%NaOH,0.1 wt.%NaBH4.The multi-component alloy with the best catalytic performance was selected as FeCoNiCrMn6.The effect of annealing process on the catalytic performance of multi-component alloy FeCoNiCrMn6 was further studied.The results show that the phase rich in Mn and Cr precipitates on the grain boundary under the condition of annealing at 600? for 12 h.The precipitation phase hinders the progress of the intergranular corrosion form,resulting in a decrease in the selective corrosion resistance of the alloy.During the etching process,less active particles are exposed than the original sample,so that the alloy strips catalyze the hydrolysis of sodium borohydride to reduce the hydrogen production performance.Based on the above studies,the kinetic factors affecting the catalytic rate of multi-component alloy FeCoNiCrMn6 were further studied.Studies have shown that the concentration of NaOH and NaBH4 promoted and then inhibited the hydrogen production rate of the catalyst.The NaBH4 and NaOH concentrations of the catalyst at the optimum catalytic hydrogen production rate were both 2%.The rate of hydrogen production by sodium borohydride hydrolysis is in a first-order reaction relationship with the amount of catalyst.According to the hydrolysis kinetic data of sodium borohydride,the activation energy of the catalyst was calculated to be Ea=55.75 kJ·mol-1.The hydrogen generation rate was 129.20 ml/(g·min)in a solution of NaOH and NaBH4 having a mass fraction of 2%at 30?.The unit surface area is used instead of the unit mass,and the hydrogen production rate is converted to 18.46 L/(m2·min).Catalyst cycle experiments show that the catalyst has a certain cycle stability performance during use.