Dopant-Driven Nanostructured Loose-Tube SnO₂ Architectures: Alternative Electrocatalyst Supports for Proton Exchange Membrane Fuel Cells

Abstract

A novel complex loose-tube (fiber-in-tube) morphology (Nb)−SnO 2 has been prepared by conventional, single-needle electrospinning, and a mechanism for the formation of fiber-in-tube structures is proposed. The presence of niobium drives the morphology of electrospun tin oxide from dense fibers to loose tubes by enhancing the Kirkendall effect where precursor salts diffuse to the fiber surface during calcination. The highest electronic conductivity (0.02 S cm −1 ) of the cassiterite structured niobiumdoped tin oxides is observed with 5 wt % Nb doping. The loose-tube morphology materials have been further functionalized by depositing Pt nanoparticles prepared by a microwave assisted polyol method, and the samples examined by electron microscopy and studied for their electrochemical properties. The electrochemically active surface area of 13 wt % Pt on Nb−SnO 2 is >50 m 2 g −1 , and is more stable to voltage cycling than Pt/C.

Negligible degradation upon in situ voltage cycling of a PEMFC using an electrospun niobium-doped tin oxide supported Pt cathode

“…22 While several studies have described the preparation of electrospun TiO 2 fibres for application in PEMFC cathodes, 2,23-27 investigation of Pt loaded SnO 2 fibres prepared by electrospinning revealed unique electrocatalytic activity for the hydrogen oxidation reaction while inhibiting the ORR, and are potentially used in the anode side. 30 The doping drove the morphology to hollow fibres and also increased the electrical conductivity to 2 Â 10 À2 S cm À1 at RT, a value that is in the range of other recently reported doped SnO 2 nanomaterials. 30 The doping drove the morphology to hollow fibres and also increased the electrical conductivity to 2 Â 10 À2 S cm À1 at RT, a value that is in the range of other recently reported doped SnO 2 nanomaterials.…”

“…30 For the preparation of Nb-SnO 2 , 0.78 g of tin(II) chloride (98%, Sigma-Aldrich) and 0.06 g of niobium(V) chloride (98% min, Merck) were dissolved in 5.7 mL of absolute ethanol (puriss., Sigma-Aldrich) and added to a solution of 0.8 g of polyvinylpyrrolidone (average M w B 1 300 000, Aldrich) in 3.1 mL of N,N-dimethylformamide (98% min, Fluka). 30 For the preparation of Nb-SnO 2 , 0.78 g of tin(II) chloride (98%, Sigma-Aldrich) and 0.06 g of niobium(V) chloride (98% min, Merck) were dissolved in 5.7 mL of absolute ethanol (puriss., Sigma-Aldrich) and added to a solution of 0.8 g of polyvinylpyrrolidone (average M w B 1 300 000, Aldrich) in 3.1 mL of N,N-dimethylformamide (98% min, Fluka).…”

Sb-Doped SnO2Aerogels Based Catalysts for Proton Exchange Membrane Fuel Cells: Pt Deposition Routes, Electrocatalytic Activity and Durability

“…[21][22][23] Most of the dopant elements added to the SnO 2 matrix are known to inhibit particle growth and modify the material morphology. 21,24 Nb- [25][26][27][28] or Sb- 25,26,[29][30][31][32][33][34][35][36][37] doped SnO 2 materials have already been tested as catalyst support. Pt/SnO 2 -based electrocatalysts have demonstrated high mass activity for the ORR, sometimes surpassing that of Pt/C electrocatalysts.…”

Electrospinning of Nanofibers for Energy Applications

“…Electrospun Pt/SnO 2 NFs were used as the anode electrocatalyst material for PEMFCs [164], which exhibited a high electrochemically-active surface area (81.17 m 2 /g-Pt). A diffusion-limited current was achieved at 0.07 V. Cavaliere et al [165] prepared the Pt supported on the electrospun Nb-SnO 2 with a loose-tube (fiber-in-tube) morphology (Figure 6), which exhibited a higher electrochemical stability than conventional Pt/C electrodes. Cavaliere et al [166] also synthesized Pt supported on electrospun Nb-SnO 2 with a loose-tube structure as the cathode material for fuel cells, who studied in situ fuel cell operation under accelerated stress tests and confirmed that the voltage loss was negligible degradation.…”

“…% Nb) prepared using heating rates of 1, 5 and 10 °C/min during calcination. Reproduced with permission from [165]. Copyright American Chemical Society, 2013.…”