Understanding the Oxygen Reduction Reaction Activity and Oxidative Stability of Pt Supported on Nb‐Doped TiO₂

Abstract

Commercial fuel cell electrocatalyst degradation results from carbon electrocatalyst support oxidation at high operating potential transients. Guided by density functional theory (DFT) calculations, Nb‐doped TiO2 (NTO) was synthesized, which exhibits a unique combination of high surface area, high electrical conductivity, and high porosity. This catalyst retained 78 % of its initial electrochemically active surface area compared with 57.6 % retained by Pt/C following the DOE/FCCJ protocol for accelerated stability test. Strong metal–support interactions, which were predicted by DFT calculations and confirmed experimentally by X‐ray photoelectron spectroscopy and kinetics measurements, resulted in 21 % higher oxygen reduction reaction mass activity (at 0.9 V vs. reversible hydrogen electrode) on Pt/NTO compared with commercial Pt/C. The ex situ activity and durability of Pt/NTO translated to a fuel cell. The rise in electrode ohmic resistance and non‐electrode concentration overpotential indicate that improving the conductivity of NTO and optimizing the catalyst ink formulation are critical next steps in the development of Pt/NTO‐catalyzed proton exchange membrane fuel cells.

Rutile Ti0.9Ir0.1O2‐Supported Low Pt Loading: An Efficient Electrocatalyst for Ethanol Electrochemical Oxidation in Acidic Media

“…The Pt binding energies of the metallic Pt(0) state of the as‐obtained rutile Ti 0.9 Ir 0.1 O 2 ‐supported Pt electrocatalyst was observed at ≈70.85 eV for Pt 4f 7/2 and ≈74.09 eV for Pt 4f 5/2 that was negatively shifted in comparison with the Pt binding energies (Pt 4f 7/2 of ≈71.15 eV and the Pt 4f 5/2 of ≈74.39 eV) of the carbon‐supported Pt catalyst (Figure 7c). The negative shift of the Pt binding energy of the as‐obtained rutile Ti 0.9 Ir 0.1 O 2 ‐supported Pt electrocatalyst indicated the electron transfer from the noncarbon Ti 0.9 Ir 0.1 O 2 nanosupport to Pt nanocatalyst, which has also been reported for Pt anchored on other doped metal oxides, [ 4,5,13,14,17–19,35 ] resulting in the modification of the electronic structure and the downshift of the d‐band center of the Pt. [ 6,7,36,37 ] According to the previous studies, [ 6,13,36,38–43 ] the downshift of the d‐band center of the Pt could reduce the binding strength of the adsorbed CO‐like species that produced on the surface of the as‐prepared 15.5 wt% Pt/rutile Ti 0.9 Ir 0.1 O 2 electrocatalyst in acidic and facilitate to react with the adsorbed OH which is the active oxygen species for ethanol electrochemical oxidation and thus the electrochemical performance of the as‐obtained rutile Ti 0.9 Ir 0.1 O 2 ‐supported low Pt‐loading electrocatalyst toward ethanol electro‐oxidation could be significantly enhanced.…”

“…Titanium dioxide (TiO 2 ), including three main crystalline phases such as anatase, rutile, and brookite, has been sparked significant interest as potential promising support for Pt‐based electrocatalysts because of its superior durability under electrochemical media as well as the strong metal–support interaction, leading to improving the fuel cell performance. [ 11–14 ] Wu et al [ 15 ] explored the effect of rutile TiO 2 and anatase TiO 2 nanostructures on the methanol electrochemical oxidation of the TiO 2 ‐supported PtAg catalyst, indicating that the rutile TiO 2 structure is superior to anatase TiO 2 as nanosupport for the bimetallic PtAg nanoparticle toward methanol oxidation both in acidic and alkaline environments. However, the reported procedures with the further calcination at high temperature have been normally utilized to prepare the rutile TiO 2 nanostructures, resulting in the large particle size and thus the significantly decreased surface area, limiting the distribution of the catalytic Pt nanoparticles.…”

Enhancement of Activity and Development of Low Pt Content Electrocatalysts for Oxygen Reduction Reaction in Acid Media

“…An interesting case involves the combination of the catalytic metal (Pt) and the functionalized oxide (Nb-TiO 2 ) support [ 48 ]. The analysis, based on density functional theory (DFT) calculations, implies that, following the introduction of platinum onto Nb-doped TiO 2 , the d-band center of Pt has been decreased, and its electronic structure has been altered.…”

“…It has been postulated that Ti III defects or oxygen-vacancies in titanium sub-stoichiometric oxides can act as charge electron recombination sites facilitating stable performance of the Pt-containing catalytic system during ORR [ 12 , 51 , 52 ]. Doping with transition metals is another promising approach to obtain a defective non-stoichiometric titanium oxide support components [ 48 , 53 , 54 , 55 , 56 ] but further research is needed along this line.…”

Metal/semiconductor interfaces in nanoscale objects: synthesis, emerging properties and applications of hybrid nanostructures

“…but not directly from BH 4 À ). 281 The oxygen reduction reaction (ORR) is a reaction in the eld of batteries (Li-O 2 batteries, for example) 282 and fuel cells, 283 where an electrocatalyst (most commonly a precious metal) is responsible for the transformation of O 2 into H 2 O (in the case of Pt(100) the ORR is performed via the oxygen dissociation mechanism). 284 Using the interaction between the metal-oxide support and the metal, [285][286][287][288] the energetics of the catalyst can be improved.…”