Carbon-Supported Pt–TiO[sub 2] as a Methanol-Tolerant Oxygen-Reduction Catalyst for DMFCs

Abstract

Carbon-supported Pt-TiO 2 ͑Pt-TiO 2 /C͒ catalysts with varying at. wt ratios of Pt to Ti, namely, 1:1, 2:1, and 3:1, are prepared by the sol-gel method. The electrocatalytic activity of the catalysts toward oxygen reduction reaction ͑ORR͒, both in the presence and absence of methanol, is evaluated for application in direct methanol fuel cells ͑DMFCs͒. The optimum at. wt ratio of Pt to Ti in Pt-TiO 2 /C is established by fuel cell polarization, linear sweep voltammetry, and cyclic voltammetry studies. Pt-TiO 2 /C heattreated at 750°C with Pt and Ti in an at. wt ratio of 2:1 shows enhanced methanol tolerance, while maintaining high catalytic activity toward ORR. The DMFC with a Pt-TiO 2 /C cathode catalyst exhibits an enhanced peak power density of 180 mW/cm 2 in contrast to the 80 mW/cm 2 achieved from the DMFC with carbon-supported Pt catalyst while operating under identical conditions. Complementary data on the influence of TiO 2 on the crystallinity of Pt, surface morphology, and particle size, surface oxidation states of individual constituents, and bulk and surface compositions are also obtained by powder X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive analysis by X-ray, and inductively coupled plasma optical emission spectrometry.Direct methanol fuel cells ͑DMFCs͒ have reached a high level of development and are now almost universally referred to as the sixth fuel cell type. In applications, they are set to function as power sources for a range of mobile applications, a situation brought about by the convenience of the storage of liquid fuels. For the expansion of the applications of DMFCs, efforts are being expended to develop improved electrocatalysts for the anode and for the cathode where methanol tolerance is preferred. 1 In the literature, 2 four classes of oxygen-reduction catalysts have been employed with the DMFCs, namely, ͑i͒ noble metal catalysts, such as platinum, which when dispersed in particulate form on carbon exhibit high activity for oxygen reduction ͑however, these catalysts show little methanol tolerance͒; ͑ii͒ macrocyclic derivatives of transition-metal compounds, such as Co and Fe porphyrins, phthalocyanines, and tetraazaannulenes, which yield low current densities because of their relatively poor activity toward oxygen reduction reaction ͑ORR͒ ͑furthermore, their dispersion on high surface area substrates needs to be ameliorated͒; ͑iii͒ metallic oxides, particularly of the second and third row transition metals, which are not acid stable; and ͑iv͒ transition-metal compounds with other nonmetallic counterions derived from the chalcogenides, such as RuSe, which are active toward ORR but not with methanol oxidation, allowing them to be used in DMFCs even when methanol permeation takes place from the anode to the cathode. However, oxygen reduction activities of chalcogenide-based catalysts are much lower than that of Pt. Because of the above reasons, methanol-tolerant Pt-based catalysts are preferred in DMFCs for prolong...

Excellent Durability of Substoichiometric Titanium Oxide As a Catalyst Support for Pd in Alkaline Direct Ethanol Fuel Cells

“…TiO 2 was combined with carbon black as catalyst supports for oxygen reduction reaction (ORR) in acidic media. 12,13 It was found that the addition of TiO 2 helped to enhance the ORR activity of the catalysts. TiO 2 was also found to improve the stability of cathodic catalysts in PEMFCs.…”

Oxygen reduction reaction increased tolerance and fuel cell performance of Pt and RuxSey onto oxide–carbon composites

“…Pt deposited on such substrates shows an increase of the activity for the oxygen reduction reaction (ORR) as compared to Pt/C. These substrates also exhibit an enhancement of stability [22,24], and an improvement of tolerance towards carbon monoxide [17,18,29,30] and methanol [20,28,29,[31][32][33]. Recently, it has been reported that Pd nanoparticles supported on carbon-modified TiO 2 (rutile) showed a higher activity for formic acid electrooxidation than Pd/C [34].…”

A solid-polymer-electrolyte direct methanol fuel cell (DMFC) with Pt-Ru nanoparticles supported onto poly(3,4-ethylenedioxythiophene) and polystyrene sulphonic acid polymer composite as anode

“…One of the main drawbacks of the solidpolymer-electrolyte direct methanol fuel cells (SPEDMFCs) is the sluggish anode reaction, which, coupled with the inefficient cathode reaction gives rise to low overall cell performance. [4][5][6][7][8][9][10] As revealed in the literature, several efforts have been made to enhance the electro-oxidation of methanol by tailoring the carbon-supported Pt-Ru catalyst. 11,12 But the choice of a suitable carbon support still remains a factor as it affects the performance of supported catalyst through interactions between the catalyst and the support that modify the catalyst activity.…”