Hydrolysis hydrogen production mechanism of Mg10Ni10Ce alloy surface modified by SnO_(2) nanotubes in different aqueous systems

(Mg-10wt%Ni)-10wt%Ce(Mg10Ni10Ce)was ball-milled with SnO_(2)nanotubes and Mg10Ni10Ce-xSnO_(2)(x¼0,5,10 and 15 wt%)composites have been prepared.The phase compositions,microstructures,morphologies and hydrolysis H2 generation performance in different aqueous systems(distilled water,tap water and simulated seawater)have been investigated and the corresponding hydrolysis mechanism of Mg10Ni10Ce and Mg10Ni10CeeSnO_(2)has been proposed.Adding a small amount of SnO_(2)nanotubes can significantly enhance the hydrolysis reaction of Mg10Ni10Ce,especially the initial hydrolysis kinetics and the final H_(2) generation yield.Unfortunately,the Mg10Ni10Ce-xSnO_(2)hardly reacts with distilled water at room temperature.The hydrolysis reaction rate of Mg10Ni10Cee5SnO_(2)composite in tap water is still very slow with only 17.3%generation yield after 1 h at 303 K.Fortunately,in simulated seawater(3.5 wt%NaCl solution),the hydrolytic H2 generation behavior of the Mg10Ni10Cee5SnO_(2)composite has been greatly improved,which can release as high as 468.6 mL g^(-1 )H_(2) with about 60.9%generation yield within 30 s at 303 K.The Cl destroys the passivation layer on MgeNieCe alloy surface and the added SnO_(2)nanotubes accelerate the hydrolysis reaction rate and enhance the H2 generation yield.The Mg10Ni10Cee5SnO_(2)composite can rapidly generate a large amount of H2 in simulated seawater in a short time,which is expected to be applied on portable H2 generators in the future.

H_2 generation kinetics/thermodynamics and hydrolysis mechanism of high-performance La-doped Mg-Ni alloys in Na Cl solution——A large-scale and quick strategy to get hydrogen

In this work,La-doped Mg-Ni multiphase alloys were prepared by resistance melting furnace(RMF)and then modified by high-energy ball milling(HEBM).The hydrolysis H_(2) generation kinetics/thermodynamics of prepared alloys in Na Cl solutions have been investigated with the help of nonlinear and linear fitting by Avrami-Erofeev and Arrhenius equations.Combining the microstructure information before and after hydrolysis and thermodynamics fitting results,the hydrolysis H_(2) generation mechanism based on nucleation&growth has been elaborated.The final H_(2) generation capacities of 0La,5La,10La and 15 La alloys are 677,653,641 and 770 m L·g^(-1)H_(2) in 240 min at291 K,respectively.While,the final H_(2) generation capacities of HEBM 0La,5La,10La and 15 La alloys are 632,824,611 and 653 m L·g^(-1)H_(2) in 20 min at 291 K,respectively.The as-cast 15La alloy and HEMB 5La alloy present the best H_(2) production rates and final H_(2) production capacities,especially the HEBM 5La can rapidly achieve high H_(2) generation capacity(670 and 824 m L·g^(-1)H_(2) )at low temperature(291 K)within short time(5 and 20 min).The difference between the H_(2) generation capacities is mainly originated from the initial nucleation rate of Mg(OH)_(2) and the subsequent processes affected by the microstructures and phase compositions of the hydrolysis alloys.Relative low initial nucleation rate and fully growth of Mg(OH)_(2) nucleus are the premise of high H_(2) generation capacity due to the hydrolysis H_(2) generation process consisted by the nucleation,growth and contacting of Mg(OH)_(2) nucleus.To utilization H_(2) by designing solid state H_(2) generators using optimized Mg-based alloys is expected to be a feasible H_(2) generation strategy at the moment.