Photocatalytically Generated Pt∕C–TiO[sub 2] Electrocatalysts with Enhanced Catalyst Dispersion for Improved Membrane Durability in Polymer Electrolyte Fuel Cells

Abstract

Platinum/carbon/titanium oxide ͑Pt/C-TiO 2 ͒ electrocatalysts were prepared by a heterogeneous photocatalysis method wherein the semiconductor optoelectronic properties of TiO 2 were exploited to facilitate photoreduction of a platinum precursor on the surface of the composite whole yielding excellent platinum dispersion. The TiO 2 loading in the electrocatalyst was varied in the ranges: 5-10 wt % and the Pt content was varied from 5 to 50 wt %. The physical and electrochemical characteristics of these new-generation electrocatalysts were benchmarked against commercial Pt/C samples. Membrane electrode assemblies were prepared using these composite electrocatalysts and tested with hydrogen as fuel and oxygen/air as oxidants. The fluoride emission rate ͑in units of mol/h cm 2 ͒ was estimated by condensate water analyses and found to be reduced by approximately an order of magnitude upon addition of TiO 2 . Implicatiońs of these data for optimization of polymer electrolyte fuel cells in terms of durability and performance are presented.

Platinum-carbon black-titanium dioxide nanocomposite electrocatalysts for fuel cell applications

“…2 Briefly, commercially available carbon blacks and TiO 2 (Degussa P-25) were mixed in a pre-selected wt% ratio and dispersed in 50 mL of deionized water (Corning Megapure) with the aid of an ultrasonic bath. The dispersion was then transferred to a 500 mL volumetric flask where 13⋅5 mL HCOOH (96%) and the required amount of platinum salt precursor (K 2 PtCl 6 , Pt 40⋅11%, Alfa Aesar) to generate different Pt wt%, ranging from 5 to 50, were added and then the total volume was adjusted to 500 mL.…”

“…In all the cases, further analyses of these RDE data revealed electron stoichiometry values close to 4 signalling that the ORR on the Pt/C-TiO 2 surface was by-passing the free radical generating 2e -intermediate step. 2 This finding has positive implications for the PEM stability in the MEA as electrochemically generated hydrogen peroxide is one of the sources of free radical species responsible for PEM degradation in an operating fuel cell (see above). carbon first undergoes corrosion as signalled by the rapid positive excursion of the electrode potential.…”

“…The presence of small amounts of an oxide semiconductor such as titanium dioxide (TiO 2 ) results in the quenching of reactive oxygen species resulting from the electroreduction of dioxygen (O 2 ); this then translates to enhanced membrane stability as probed by fluoride emission tests. 2 In this paper, we build on these initial data with more extensive characterization of our nanocomposite electrocatalysts. Aside from the usual suite of electrochemistry tools, electrochemical impedance spectroscopy (EIS) was also used in this study.…”

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

“…Chemical modification of carbon nanotubes [1][2][3] or nanostructured carbon [4][5][6][7][8][9][10][11][12] has been undertaken. Another strategy to stabilize the support is to develop metal-oxide substrates as reported for SiO 2 [13], NbO 2 [14], MnO x [15], WO x [16,17], SnO 2 [18] and TiO x [15,[19][20][21][22][23][24][25][26][27][28]. Pt deposited on such substrates shows an increase of the activity for the oxygen reduction reaction (ORR) as compared to Pt/C.…”

Preparation and Characterization of Nano Structured Pt−MOx/C for Oxygen Reduction Reaction in Acidic Medium

“…Pt-TiO 2 /C shows improved stability in polymer electrolyte membrane fuel cells (PEMFCs) compared with Pt/C [22].In spite of the amount of titanium dioxide and the crystalline phase (TiO 2 anatase/rutile phase) it was found that, it modifies the strength of the interaction between the substrate and the metal nanoparticles [23,24]. The good effect of addition TiO 2 may be attributed to two factors which are: the changes in the Pt-d electronic properties and the geometric effect that leads to the Pt-Pt bonding distance contraction and hence results in a sensible improvement of the electrochemical reactions [25,26].Titanium oxidebased cathode, synthesized from oxy-titanium tetra-pyrazinoporphyrazine by the oxidation under a low partial pressure of oxygen using carbon nanotubes as a support, showed high reactivity in the four-electron reduction of oxygen [27].…”