On-site hydrolytic H2 production by CaH2/(Al/Si) composites via Na+ bridging effect for fuel cell

Abstract

Inorganic materials can solve transportable and on-site hydrolytic hydrogen generation issues. CaH₂/(Al/Si) composites are preferable due to their notable chemical properties. However, these composites require pretreatments, an inert environment, and long hours of physical ball milling for high homogeneity and synergistic effects. CaH₂ also inhibits the hydrolysis reaction by forming its products on the Al/Si surface, which hinders the direct utilization of composites. This work represents the first investigation of NaH-CaH₂(Al/Si) fuel composites, which greatly overcome these limitations and can be directly used for on-site hydrogen generation and proton exchange membrane (PEM) fuel cells. The NaH-CaH₂(Al/Si) fuel composites were prepared by using a straightforward mixing method with variable composition ratios, showing high H₂ yield and fuel cell (FC) performance. NaH addition provides the bridge effect, which opens up a new way to enable efficient hydrolysis and greatly enhances the hydrolysis activity of CaH₂/(Al/Si) composites. The novel fuel composites (NaH-CaH₂/Al) have extraordinary FC performance and a 0.42 W/cm² peak power density greater than commercial hydrogen generators. It provides high H₂ yield 84.4 % for NaH-CaH₂/Al and 82  % for NaH-CaH₂/Si compared to NaOH-CaH₂(Al/Si), NaCl-CaH₂(Al/Si), and KCl-CaH₂(Al/Si) composites. The NaH bridge effect hinders the direct water contact and stops the formation of Ca(OH)₂ around Al/Si, which provides adequate pathways for the CaH₂(Al/Si) hydrolysis. The impressive capabilities of novel fuel composites are anticipated to offer practical uses in fuel cells, automobile applications, and portable/on-board H₂ generation.