Titanium Oxide Tungstate Nanotubes Improve Fuel Cell Performance

Titanium oxide tungstate nanotubes could improve fuel cell performance. The chemical oxidative stability of the tungstate-functionalized sulfonated poly ether ether ketone (SPEEK) membranes is one of the key requirements for the durability and performance of the fuel cells, which was estimated using Fenton's reagent method.

Membranes of pure SPEEK and all fabricated composites showed less than 4% weight loss after immersion in Fenton's reagent for 144 hours, which indicates good chemical stability. The decreased stability of the membranes may be due to the breakage of the ether bonds of the SPEEK polymer chains.

The polarization curves of SPEEK and SPEEK 6% W-TNT in a homemade fuel cell with Pt electrodes that was operated at 80 °C. The performance study showed that SPEEK 6% W-TNT showed a higher OCV (0.945 V) than the SPEEK membrane (0.845 V), due to the fact that the composite membrane is denser than pure SPEEK, which may reduce the fuel crossover behavior.

The power density and current density of SPEEK 6% W-TNT were 352 mW cm^-2 and 690 mA cm^-2, respectively, while the SPEEK membrane showed a power density of 245 mW cm^-2 and a current density of 540 mA cm^-2. The higher hydroxide conductivity of the SPEEK 6% W-TNT membrane may be due to the presence of additional ion exchange sites and increased water uptake level, which leads to higher fuel cell performance.

When testing in a fuel cell setup, the composite film SPEEK 6% W-TNT exhibited a maximum power density of 352 mW cm^-2. Above 6 wt% W-TNT filler, the aggregation and blocking effects of nanotubes reduced the proton conductivity. The results indicate that the incorporation of W-TNT filler in the SPEEK matrix improves the fuel cell performance due to the improved surface area (protonation), water absorption, ion exchange capacity, and proton conductivity of the active sites.

Therefore, it was shown that the use of titanium oxide tungstate nanotubes of hollow nature as well as bonded ion exchange groups (tungstic acid) as fillers in composite membranes assisted in ion conduction by Grotthuss and jumping mechanisms, forming an excellent electrolyte for PEMFCs.

Cited paper: Elumalai V, Deenadhayalan T, Kathleen Asitha A, et al. Preparation of tungstic acid functionalized titanium oxide nanotubes and its effect on proton exchange membrane fuel cell[J]. SN Applied Sciences, 2019, 1(4): 1-12.

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