Hydrogen Production Optimization And Mechanism Analysis Of Active Aluminum Alloy Hydrolysis

Active aluminum alloy bulk materials can produce high purity hydrogen as energy carriers under hydrolysis conditions.The preparation method,storage,and transport of alloys is relatively simple,so it is regarded as a kind of hydrogen production materials with great application potential.However,due to the demand of a stable hydrogen supply rate and high hydrogen production ratio for on-demand hydrogen supply system,obtaining high energy density aluminum alloy bulk materials with high energy conversion efficiency and stable hydrogen release rate characteristics have become a current research hotspot.According to the typical hydrogen release characteristics of Al-Ga-In₃Sn and Al-Ga-In Sn₄ alloys,the phase composition,microstructure,component distribution and thermal effect temperature of the GB phase particles are analyzed and adjusted through the composition design.The Al-rich alloys with high energy conversion efficiency and a stable output of hydrogen are expected,which benefit to significantly improve the application potential of alloys in on-demand hydrogen supply systems.In this study,the basic experiments and theoretical analysis are combined to determine the corresponding activation mechanism of Al atoms and the law of its action on hydrogen production performance via Al-H₂O reaction,which have guiding significance for promoting the application of active Al-rich alloys in the field of hydrogen production.The main contents and conclusions of this thesis are summarized as following:1.Because In₃Sn has an important contribution to the high hydrogen production yield of alloys,combined with the low melting point of In and its high hydrogen evolution potential,the In dosage will continue to increase in 90Al-Ga-In₃Sn alloy in order to achieve a reduction of hydrogen release rate.With the increase of indium in the alloys,the In phase appears in the as-cast alloys together with the In₃Sn phase.The presence of In phase has a certain inducing effect on the morphology transformation of GB phase particles from granular to linear morphology.The changed morphologies change the connection between GB phase particles and Al grain,thereby reducing the actual interface contact area between the two.Cooperating with the high hydrogen evolution potential characteristics of In,the reduction of the hydrogen release rate of 90Al-Ga-In₃Sn alloy is realized.Unfortunately,the regulation of the hydrogen release rate is accompanied by a certain energy loss.This work provides a new phase and morphology reference of GB phase particle for the realization of the stable hydrogen release rate of alloys,and also provides a new idea for the influence mechanism of the particle morphology transformation.2.Through the introduction of Mg in 90Al-Ga-In₃Sn,the effects of non-extra-doped In and Mg₂Sn on the hydrogen production performance are explored.Via analyzing the influence of Mg doping on the phase compositions,GB phase particles morphologies and the related elements distribution,as well as the electrochemical properties of the alloys,it is found that the change in hydrogen release performance of the alloys is mainly due to the appearance of Mg₂Sn and a small amount of In single substance in the alloys caused by the introduction of Mg element.On the one hand,the existence of Mg₂Sn phase in the alloys further verifies and clarifies the dominant effect of In phase on the of linear morphology GB phase particles.On the other hand,its existence can maintain the stable and slow hydrogen release of the alloys,at the same time,improving the reduction of the energy conversion efficiency of alloys caused by the existence of In phase.This work focuses on the in-depth study of the mechanism of Mg on the Al-Ga-In₃Sn alloy,which is of great significance for obtaining the preferred Al-Ga-In₃Sn-based alloy that can release hydrogen efficiently and smoothly.3.The 90Al-Ga-In Sn₄ alloy with hydrolysis reaction barrier is activated by the introduction of low melting point metal Bi to develop an active Al-Ga-In Sn₄-based alloys that can release hydrogen efficiently and smoothly.On the one hand,the introduction of Bi in the alloys leads to the formation of In Bi intermetallic compounds in the alloys which further promotes the equiaxed growth of GB phase particles,meanwhile,Al grains get refined.On the other hand,it effectively reduces the thermal effect temperature of GB phase particles during Al-H₂O reaction process,thereby promoting the formation of liquid phase reaction sites in the alloys.In summary,the introduction of Bi realizes the effective activation to 90Al-Ga-In Sn₄ alloy and improves the hydrogen production yield of the alloy.This work not only provides a method to optimize Al-Ga-In Sn₄ alloy,but also explains the essential reason for the excellent hydrogen release performance of Al-Ga-In Sn₄-Bi alloy.4.Al-Ga-In-Sn quaternary alloys with high energy density（95 wt%）are prepared by conventional high-temperature melting method.In combination with the minimum initiating reaction temperature of the alloys and the Ga-In-Sn ternary diagram,the content of Ga and In₃Sn due to the change of In/Sn ratio are calculated.The inverse proportion distribution between In₃Sn content and Ga in grain boundary is found.In addition,the typical morphology changes of GB phase particles are observed due to In/Sn ratio change.By virtue of the high fluidity and surface tension of liquid metals,the mechanism of GB phase particles with different morphologies on the activation mechanism of aluminum during the Al-H₂O reaction and the corresponding Al-H₂O hydrogen production performance are deeply explored.This work not only explains the reasons for the difference in hydrogen production performance among alloys with different GB phase particles’morphological characteristics,but also clarifies the liquid-drived activation mechanism of high aluminum alloys,which is providing more theoretical supports for the promotion and application of high energy density Al-Ga-In-Sn alloys.