Synthesis of high-specific-surface-area analcime from coal fly ash for hydrogen storage without external silica-alumina sources.

To address the valorization of coal fly ash and the limited hydrogen storage performance of zeolitic materials, a modified hydrothermal synthesis process is presented for producing analcime (ANA) with greatly-reduced crystalline impurities using pretreated coal fly ash without the addition of external silica-alumina sources. The ANA sample crystallized for 24 h at 375 K delivers a remarkably high specific surface area of 197.8 m2 g-1 together with a hydrogen-storage capacity of 0.57 mmol g-1. A positive correlation between specific surface area and hydrogen-adsorption capacity is demonstrated. This work provides a low-cost and efficient approach to the valorization of coal fly ash and further explores the hydrogen-storage potential of waste-derived analcime zeolite.