Local High Concentration Alkali Field Accelerated Silicon Hydrolysis for Hydrogen Production

Abstract

Silicon is considered as a promising portable hydrolytic hydrogen production material due to its abundant raw materials, high theoretical capacity (1600 mL/g) and facile storage. However, the low hydrolysis activity and slow hydrolysis rate of silicon hinder its practical application. To address this issue, we introduced CaH2, another relatively cheap and safe material for hydrolyzing, to form Si-based composites via a flexible ball milling method. The above composites showed ideal yield (1213 mL/g in 3 min), reaction conversion (95.5%) and fast hydrolysis kinetics (225 mL/(s·g)) in deionized water, which is one of the best hydrolysis performances of Si-based composites so far. The hydrolytic process can be divided into two steps: the splitting hydrolysis of CaH2 and the continuous hydrolysis of Si. Combine the dynamic in-situ structural analysis with the analogue simulation, it can be confirmed that the formation of local high concentration alkali field is the key to promote the complete hydrolysis and achieve high yield and fast kinetics of the composites. Our work provided a novel idea for the theoretical design of hydrolytic hydrogen production compounds and promoted the practical application of low cost and portable hydrolytic hydrogen production materials.

Keywords: Hydrogen storage and production, Hydrolysis, Highly-active silicon, Hydrides, Local high concentration