15% TiO2 Boosts Fluorine-Free Fuel Cell Membrane Performance Under Humidity

A new study in the journal Ionics reports a phosphonated poly(vinyl alcohol)–boric acid composite membrane reinforced with titanium dioxide, evaluated across water uptake, dimensional stability, ion exchange capacity, mechanical strength, proton conductivity, oxidative stability, and single-cell fuel cell performance.

The addition of TiO2 raised water uptake from 36–37% in the base membrane to 40–45%, while thickness and surface area changes remained limited. The optimal formulation, PPVA-B-15T, containing 15 wt% TiO2, achieved a maximum water uptake of 45%, an ion exchange capacity of 1.04 meq g−1, a tensile strength of 64 MPa, and a proton conductivity of 0.030 S cm−1 at 80 °C and 100% relative humidity. That conductivity fell to roughly 0.0044 S cm−1 when humidity dropped to 40% RH, underscoring how strongly water availability governs proton transport in this membrane family.

FTIR and SEM analyses supported the dispersion of TiO2 within the phosphonated PVA–boric acid matrix and pointed to interfacial Ti–O–P interactions. Under these conditions, the PPVA-B-15T membrane delivered a current density of 710 mA cm−2 at 0.60 V in a single cell, with a maximum power density of 0.48 W cm−2. Notably, under dry feed conditions the same composition still maintained a power density of 0.46 W cm−2 at 60 °C, suggesting the composite retains much of its output even without humidified gases.

Durability results were also reported. Membranes containing TiO2 retained 84–87% of their initial mass after 96 hours of Fenton exposure, a standard oxidative-stability test, and PPVA-B-15T showed the lowest 24-hour open-circuit voltage loss among the composites at 18.6%. During 100 hours of potentiostatic operation at 0.60 V, 80 °C, and 100% RH, the membrane retained 83.1% of its initial current density. The authors conclude that electrochemical response is governed by transport continuity rather than by total water uptake or ion exchange capacity, and that higher TiO2 loadings beyond 15 wt% reduced proton conductivity, mechanical properties, and cell performance. The findings position phosphonated PVA–boric acid/TiO2 composites as candidates for fluorine-free proton exchange membranes, though the results come from laboratory single-cell testing and longer-term operational data remain limited.

Subject of Research: Humidity-dependent proton transport and fuel cell performance of fluorine-free phosphonated PVA–boric acid/TiO2 composite membranes

Article Title: Relative humidity dependent proton transport and PEM fuel cell performance of phosphonated PVA-boric acid/TiO2 composite membranes

Article References: Yagizatli, Y., Cali, A., Sahin, A., & Balbasi, M. (2026). Relative humidity dependent proton transport and PEM fuel cell performance of phosphonated PVA-boric acid/TiO2 composite membranes. Ionics. https://doi.org/10.1007/s11581-026-07618-5

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07618-5

Keywords: proton exchange membrane, fuel cells, TiO2 composite, fluorine-free membrane, proton conductivity, relative humidity, polyvinyl alcohol, boric acid, water uptake, oxidative stability, power density, Relative