TiO2–RuO2 electrocatalyst supports exhibit exceptional electrochemical stability

Lo, Chih‐Ping; Wang, Guanxiong; Kumar, Arun; Ramani, Vijay

doi:10.1016/j.apcatb.2013.03.039

Cited by 46 publications

(54 citation statements)

References 58 publications

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“…Mixed-metal oxides such as TiO 2 -RuO 2 and SiO 2 -RuO 2 have been shown to be an excellent alternative to carbon-based electrocatalyst supports due to their high electrochemical stability across a wide potential window (34). Ex situ stability tests (in an RDE) performed on these materials indicated no changes in the double-layer pseudocapacitance for 10,000 cycles (under an aggressive start/stop stability protocol).…”

Section: Significancementioning

confidence: 99%

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Platinum supported on titanium–ruthenium oxide is a remarkably stable electrocatayst for hydrogen fuel cell vehicles

Parrondo

Han

Niangar

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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131

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We report a unique and highly stable electrocatalyst-platinum (Pt) supported on titanium-ruthenium oxide (TRO)-for hydrogen fuel cell vehicles. The Pt/TRO electrocatalyst was exposed to stringent accelerated test protocols designed to induce degradation and failure mechanisms identical to those seen during extended normal operation of a fuel cell automobile-namely, support corrosion during vehicle startup and shutdown, and platinum dissolution during vehicle acceleration and deceleration. These experiments were performed both ex situ (on supports and catalysts deposited onto a glassy carbon rotating disk electrode) and in situ (in a membrane electrode assembly). The Pt/TRO was compared against a state-of-the-art benchmark catalyst-Pt supported on high surfacearea carbon (Pt/HSAC). In ex situ tests, Pt/TRO lost only 18% of its initial oxygen reduction reaction mass activity and 3% of its oxygen reduction reaction-specific activity, whereas the corresponding losses for Pt/HSAC were 52% and 22%. In in situ-accelerated degradation tests performed on membrane electrode assemblies, the loss in cell voltage at 1 A · cm −2 at 100% RH was a negligible 15 mV for Pt/TRO, whereas the loss was too high to permit operation at 1 A · cm −2 for Pt/HSAC. We clearly show that electrocatalyst support corrosion induced during fuel cell startup and shutdown is a far more potent failure mode than platinum dissolution during fuel cell operation. Hence, we posit that the need for a highly stable support (such as TRO) is paramount. Finally, we demonstrate that the corrosion of carbon present in the gas diffusion layer of the fuel cell is only of minor concern.noncarbon catalyst supports | PEFC | start-stop protocol | TiO 2 -RuO 2 | carbon corrosion C arbon has traditionally been the most common material of choice for polymer electrolyte fuel cell (PEFC) electrocatalyst supports (1) due to its low cost, high abundance, high electronic conductivity (30 S · cm −1 ), and high Brunauer, Emmett, and Teller (BET) surface area (200-300 m 2 · g −1 ), which permits good dispersion of the platinum (Pt) catalyst (2-4). The (in) stability of the carbon-supported platinum electrocatalyst is a key issue that currently precludes widespread commercialization of PEFCs for automotive applications. Carbon is known to undergo electrochemical oxidation to carbon dioxide, as shown in Eq. 1. The standard electrode potential for this reaction is 0.207 V vs. standard hydrogen potential (SHE; all potentials henceforth reported vs. SHE, unless otherwise stated). Under normal PEFC operating conditions, the electrode potential is <0.1 V at the anode and between 0.6 V and 0.8 V at the cathode. Despite the fact that the cathode potential is usually significantly higher than the standard potential for carbon oxidation (with an effective overpotential of 0.4-0.6 V), the actual rate of carbon oxidation is very slow due to intrinsic kinetic limitations; in other words, a very low standard heterogeneous rate constant (5).During operation of automotive PEFC stacks, fuel/air ...

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Section: Significancementioning

confidence: 99%

“…The relatively high particle size resulted in lower values for the electrochemically active surface area (ECA). Detailed characterization of the support and catalyst are provided in our previous work (34).…”

Section: Significancementioning

confidence: 99%

Platinum supported on titanium–ruthenium oxide is a remarkably stable electrocatayst for hydrogen fuel cell vehicles

Parrondo

Han

Niangar

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

131

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“…32,[38][39][40][41][42][43][44][45] However, these oxides and carbide-based supports do not usually have the necessary electron conductivities to obtain electrodes with acceptable performance. Our group has synthesized high-surface-area mixed-metal oxide and doped metal oxide supports that are highly corrosion resistant and possess more than adequate electron conductivity (> ∼5 Scm -1 ) 32,36 and BET surface area (30-300 m 2 g -1 ) to be used in PEFC electrodes. When catalyzed with Pt, these materials show ORR activity approaching that of Pt/C and demonstrated electrochemical stability in a PEFC even upon rigorous potential cycling.…”

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confidence: 99%

“…17,29 To avoid this issue, several researchers have investigated noncarbon, corrosion-resistant materials as alternate catalyst supports for fuel cell electrodes. 28,[30][31][32][33][34][35][36][37] In addition to being resistant to corrosion under a wide potential window, any viable alternate catalyst supports should possess adequate electron conductivity and surface area. A wide range of non-carbon supports based on metal oxides and metal carbides have been explored with several of them exhibiting good electrochemical stability.…”

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confidence: 99%

“…When catalyzed with Pt, these materials show ORR activity approaching that of Pt/C and demonstrated electrochemical stability in a PEFC even upon rigorous potential cycling. 32,36,37,[46][47][48] The generation of H 2 O 2 during PEFC operation is known to be catalyzed by the carbon present in the electrodes. 49 This is a concern in terms of PEM oxidative degradation, since H 2 O 2 can further react in the presence of transition metal ions present as impurities in the membrane electrode assembly (MEA) via the Fenton reaction to form ROS such as the hydroxyl and/or the hydroperoxyl free radicals.…”

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Contribution of Electrocatalyst Support to PEM Oxidative Degradation in an Operating PEFC

Prabhakaran

Wang

Parrondo

et al. 2016

J. Electrochem. Soc.

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The contribution of the electrocatalyst support to polymer electrolyte membrane (PEM) oxidative degradation in an operating polymer electrolyte fuel cell was investigated. A corrosion-resistant non-carbon catalyst support based on mixed ruthenium and silicon oxides (RuO 2 -SiO 2 ; RSO) was compared against a benchmark carbon-based support (Vulcan XC 72; C). The rates of in-situ reactive oxygen species (ROS) generation (Pt/C: 9.0 ± 0.20 × 10 −5 s −1 ; Pt/RSO: 5.9 ± 0.19 × 10 −5 s −1 ) and macroscopic PEM degradation measured ex-situ as the fluoride emission rate (FER; Pt/C: 2.7 ± 0.32 × 10 −5 ppm cm -2 s -1 ; Pt/RSO: 2.5 ± 0.31 × 10 −5 ppm cm -2 s -1 ) were significantly lower for platinum supported on RSO than for platinum supported on carbon. There was an excellent correlation between the in-situ ROS generation rate and the FER, thereby confirming the causal relationship between ROS generation and PEM degradation. The lower rate of ROS generation over RSO and Pt/RSO was attributed to a lower net rate of electrochemical H 2 O 2 generation during the oxygen reduction reaction (ORR). Rotating ring-disk electrode experiments confirmed that the net electrochemical H 2 O 2 generation rate on Pt/RSO was about twice lower than that on Pt/C. Kinetic parameters estimated for the ORR supported a direct 4e -pathway on both Pt/RSO (with i k of 4.5 mAcm -2 , n = 3.97 and a Tafel slope of 64 mVdec -1 ) and Pt/ C (with i k of 4.1 mAcm -2 , n = 3.93 and a Tafel slope of 68 mVdec -1 ). In conjunction with its high corrosion-resistance, this finding further illustrates the viability of RSO (and analogs such as ruthenium-titanium oxide) as outstanding PEFC electrocatalyst supports. Polymer electrolyte fuel cells (PEFCs) have attracted a lot of interest as electrochemical energy conversion sources for multiple applications in the automotive, stationary power, portable power, and military sectors due to their high efficiency, modularity and environmental benefits.1-3 The commercialization of PEFCs, particularly for the automobile sector, has been hindered by high cost and insufficient component durability. 2,4 The high cost of component materials, such as platinum (Pt) electrocatalyst 5,6 and Nafion electrolyte membranes are among the main factors influencing the cost of PEFCs.4,7-9 Recent advances in the design of PEFCs enable high performance with very low total Pt loadings (ca. 0.15 mg Pt cm -2 ) and using very thin polymer electrolyte membranes (PEMs; e.g. Nafion 211, ca. 25 μm, or even lower thickness variants). 4,10,11 However, the long-term durability of PEFC components still remains a major concern. The key issues affecting PEFC durability include electrode degradation via carbon corrosion, 1,12-15 Pt dissolution, 5,16-19 catalyst sintering 20,21 and electrolyte degradation via PEM oxidative degradation.2,3,22 Carbon corrosion and PEM degradation are key degradation modes that need to be mitigated. Carbon corrosion is primarily caused by oxidation of carbon at higher electrode potentials that are encountered during transient...

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Hierarchically StructuredPtand Non‐Pt‐Based Electrocatalysts forPEMFuel Cells

Trogadas

Coppens

2019

Handbook of Green Chemistry

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Hierarchical Pt/non‐Pt alloy electrocatalysts demonstrate high activity, surface area, and stability, transforming them into attractive candidates for electrocatalysis in fuel cells. Oxygen reduction reaction ( ORR ) and methanol oxidation reaction ( MOR ) activity, as well as other electrochemical properties of these hierarchical electrocatalysts supported on metal oxides or carbonaceous materials are presented, along with a short review of their synthesis methods.

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TiO2–RuO2 electrocatalyst supports exhibit exceptional electrochemical stability

Cited by 46 publications

References 58 publications

Platinum supported on titanium–ruthenium oxide is a remarkably stable electrocatayst for hydrogen fuel cell vehicles

Platinum supported on titanium–ruthenium oxide is a remarkably stable electrocatayst for hydrogen fuel cell vehicles

Contribution of Electrocatalyst Support to PEM Oxidative Degradation in an Operating PEFC

Hierarchically StructuredPtand Non‐Pt‐Based Electrocatalysts forPEMFuel Cells

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