H2 generation kinetics/thermodynamics and hydrolysis mechanism of high-performance La-doped Mg-Ni alloys in NaCl solution—A large-scale and quick strategy to get hydrogen

Abstract

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 H2 generation kinetics/thermodynamics of prepared alloys in NaCl 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 H2 generation mechanism based on nucleation & growth has been elaborated. The final H2 generation capacities of 0La, 5La, 10La and 15 La alloys are 677, 653, 641 and 770 mL·g − 1 H2 in 240 min at 291 K, respectively. While, the final H2 generation capacities of HEBM 0La, 5La, 10La and 15 La alloys are 632, 824, 611 and 653 mL·g − 1 H2 in 20 min at 291 K, respectively. The as-cast 15La alloy and HEMB 5La alloy present the best H2 production rates and final H2 production capacities, especially the HEBM 5La can rapidly achieve high H2 generation capacity (670 and 824 mL·g − 1 H2) at low temperature (291 K) within short time (5 and 20 min). The difference between the H2 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 H2 generation capacity due to the hydrolysis H2 generation process consisted by the nucleation, growth and contacting of Mg(OH)2 nucleus. To utilization H2 by designing solid state H2 generators using optimized Mg-based alloys is expected to be a feasible H2 generation strategy at the moment.

Keywords

• H2 generation
• La-doped Mg-Ni alloys
• Kinetics
• Thermodynamics
• Hydrolysis mechanism