Zeolite applications in fuel cells: Water management and proton conductivity

Zeolites are increasingly used in fuel cell, from fuel conversion and conditioning to membrane additives as well as support for electrocatalysts. Zeolites’ ionic conductivity and capacity for water adsorption and retention were exploited to create zeolite and zeolite-PFSA proton conducting membranes for PEMFC. HZSM-5 micromembranes of different Si/Al ratios (from ∞ for Sil-1 to 30) were fabricated in a regular array on silicon followed by assembly and test for fuel cell performance. HZSM-5 with high aluminum content exhibits good proton conductivity and better PEMFC performance that approaches that of Nafion MEA. A rational approach in the design of structured HZSM-5-PFSA composite membrane was demonstrated. The PFSA was confined in subnanoliter volumes within zeolite sleeves to obtain self-humidifying membrane and enhanced PEMFC performance (i.e., up to nine-fold in MPD) at elevated temperatures (i.e., up to 100 °C) and dry conditions. Higher water retention and improved membrane thermomechanical properties are believed to be responsible.

► A rational approach in the design of PEMFC proton-exchange membranes.
► PFSA-zeolite membrane that harmonizes the material's form.
► Structured composite membrane through subnanoliter confinement of PFSA in HZSM-5 sleeves.
► Miniaturization of zeolite proton-conducting membrane good performance.