Fly-Ash-Based Zeolite Beta: A Low-Cost Material for High- Sensitivity Gas Sensors

Abstract

Zeolite Beta was successfully synthesized from coal fly ash using an alkali fusion–
hydrothermal method assisted by tetraethylammonium hydroxide (TEAOH) as a structure-
directing agent and evaluated as a gas-sensing material. The crystalline BEA framework was
confirmed by X-ray diffraction, while thin films deposited on interdigitated electrode substrates
enabled electrical measurements. The fabricated sensor exhibited distinct responses to NH₃,
CO₂, H₂, ethanol, and acetone vapors, with ethanol (74% ΔR/R) and ammonia (68% ΔR/R)
showing the highest sensitivities. Response and recovery times ranged between 30–55 s and
55–70 s, respectively, indicating fast and reversible adsorption–desorption dynamics. The
selectivity towards polar gases and VOCs highlights the role of the BEA framework’s large
pore system and surface activity in gas–solid interactions. Compared with other zeolite-based
sensors, the fly-ash-derived Zeolite Beta demonstrated superior performance, establishing it as
a cost-effective and environmentally sustainable material for gas detection and monitoring
applications.