Study On Hydrogen Production From Sodium Borohydride Catalyzed By Corrosion Strips Of FeCoNiCrMn₅ Alloy

Hydrogen is recognized as the most ideal green energy in the 21st century.NaBH4 hydrolysis hydrogen production technology has the advantages of high hydrogen storage density,high purity,environmental friendliness and controllable reaction,which has become one of the research hotspots in the current new energy industry.Among them,the development and research of efficient and inexpensive catalysts is the key.In this paper,the preparation,structure and performance characterization of FeCoNiCrMn5(abbreviated as Mns)alloy strip catalyst and the influence of process parameters on hydrogen production by NaBH4 are studied,which provides a new and efficient catalyst for the research of non-precious metal catalyzed hydrogen production by NaBH4.The crystal structure of the Mn5 alloy strip prepared by cold rolling and rapid solidification is a single phase of FCC The alloy strip shows obvious element selective corrosion in the corrosion process,of which hydrochloric acid has the strongest selective corrosion ability and can obtain larger surface area and more active sites compared with other corrosion solutions.The hydrogen production rates of cold rolling and rapid solidification are 4.93 L-min-1·m-2 and 3.87 L·min-1·m-2 respectively under the solution conditions of 30℃,0.1 wt.%NaOH and 0.1 wt.%NaBH4 after 90 s corrosion with 3 mol·L-1 hydrochloric acid solution,indicating that the cold rolled strip has more excellent catalytic performance.The microstructure of Mn5 rolled strip and its effect on catalytic performance were studied by adjusting corrosion time.The results show that the catalytic activity increases first and then stabilizes.In the first 30 s,the active sites Ni and Co were exposed mainly through selective corrosion of Mn element,making the strip have catalytic activity.From 30 to 90 s,the surface crack of the strip gradually extends to the depth direction,and the thickness of the corrosion layer increases continuously,which provides a larger surface area for the catalyst and also exposes more active sites.The catalytic activity is optimized at 90 s.After 90 s,the corrosion layer falls tends to be stable and the hydrogen production rate also tends to be stable due to excessive corrosion.The effects of low temperature and high temperature annealing processes on the structure and performance of catalysts were systematically studied.The results show that after low temperature annealing,the cold rolled strip still maintains FCC single phase,but the hydrogen production rate decreases from the original state of 4.93 L-min-1·m-2 to 2.67 L-min-1·m-2.This is because the low temperature annealing releases the residual stress during cold rolling,which increases the corrosion resistance of the alloy.After high temperature annealing,the microstructure is a coarse FCC phase and elemental Mn and Cr-rich σ phase distributed on the phase boundary.During corrosion,preferential corrosion of Mn and σ phase causes enrichment of Co and Ni sites on the catalyst surface,and hydrogen production per unit time increases from 6.41 mL·min-1 to 8.12 mL·min-1.However,the larger size and easy corrosion of precipitated phase also greatly increase the surface area of the catalyst and generally reduce the activity of the sites.The effects of kinetic and thermodynamic parameters on the hydrogen production performance of NaBH4 were studied.The results show that the hydrogen production rate increases first and then decreases with the increase of NaBH4 and NaOH concentration.The amount of catalyst and the temperature of the reaction system have a positive correlation with the hydrogen production rate.The activation energy Ea of NaBH4 hydrolysis reaction is 35.98 kJ·mol-1.The expression of the hydrogen production rate catalyzed by Mn5 rolled strip is established according to the reaction order.Under the optimal parameters(2 wt.%NaBH4,3 wt.%NaOH)and the system temperature of 30℃,the hydrogen production rate of Mn5 cold rolled strip catalyst is 27.05 L·min-1·m-2.Ten consecutive cycles of catalyst experiment show that the catalyst has certain firmness and cycle stability during use.