Pt In Catalysts Research Articles

Low Temperature PEFC Performance of Unsupported Pt-Ni Aerogel Cathode Catalyst Layers

The commercialization of polymer electrolyte fuel cells (PEFCs) requires Pt-based, O2-reduction reaction (ORR) catalysts with improved stability and activity, in order to be able to reach cathode Pt-loadings << 0.4 mgPt·cm-2. This can be done by alloying platinum with other metals such as Ni (as to increase its ORR-activity), while complementary developing novel catalysts that can endure the oxidizing conditions concomitant to PEFC startup/shutdown, which cause the corrosion (and progressive failure) of the carbon-supported Pt-catalysts (Pt/C) used in state-of-the-art PEFCs. Aiming to tackle both requirements, in our previous work we showed that an optimized cathode catalyst layer (CL) based on an unsupported, bimetallic Pt-Ni nanochain network (aerogel) displayed a PEFC ORR-activity ≈2.5-fold larger than a commercial Pt/C at 80 °C and 100 % relative humidity (RH), while preserving 90 % of this initial performance after an accelerated stress test that mimicked PEFC startup/shutdown (vs. only 40 % for Pt/C) [1]. However, those studies did not include PEFC measurements at lower temperatures and relative humidity (RH) conditions which are relevant for PEFC powered vehicles, and that have been shown to be problematic for other unsupported Pt-based catalysts [2].To tackle this needs, we first had to re-assess the procedures used for the preparation of aerogel CLs. More precisely, in our previous work [1] aerogel-based catalyst-coated membranes (CCMs) were prepared by hand spraying, which is highly dependent on the handler and can therefore lead to irreproducibility. To overcome this issue, we have used an automated spray-coating machine that on the other hand requires a larger amount of material for operation, thus implying the need for an up-scale of the aerogel synthesis up to 125 mg batches (≈ 5-fold larger than those prepared for our previous work). Following a careful optimization of this spraying procedure, we managed to prepare an up-scaled, automatically sprayed aerogel CCM that displayed a PEFC performance similar to our previous best results in Ref. 1. This Pt3Ni CL was subsequently submitted to additional PEFC tests at temperatures ≤ 60 °C and under RH conditions between 100 and 20 %, whereby the latter can imply issues in the evacuation of product liquid water caused by the limited water storage capacity (i.e., void volume) of the pores in such ultra-thin CLs (≈ 1.5 μm). Specifically, our PEFC tests included electrochemical impedance spectroscopy (EIS) measurements from which we estimated the effect of temperature and RH on the proton transport resistance through the catalyst layer, thus allowing us to quantify the mass transport losses along this broad range of temperature and RH [3]. Based on these results, specific temperature and RH conditions were selected to conduct additional current up-transient failure tests [2, 4].

A Hydrothermally Stable Single-Atom Catalyst of Pt Supported on High-Entropy Oxide/Al2O3: Structural Optimization and Enhanced Catalytic Activity.

A catalyst with high-entropy oxide (HEO)-stabilized single-atom Pt can afford low-temperature activity for catalytic oxidation and remarkable durability even under harsh conditions. However, HEO is easy to harden during sintering, which results in a few defective sites for anchoring single-atom metals. Herein, we present a sol-gel-assisted mechanical milling strategy to achieve a single-atom catalyst of Pt-HEO/Al2O3. The strong interaction between HEO and Al2O3 effectively inhibits the growth of HEO microparticles, which leads to generation of more surface defects because of the nanoscale effect. Meanwhile, another strong interaction between Pt and HEO stabilizes single-atom Pt on HEO. Temperature-programmed techniques further verify that the reactivity of surface lattice oxygen species is enhanced because of the Pt-O-M bonds on the surface of HEO. Unlike conventional single-atom Pt catalysts, Pt-HEO/Al2O3 as a heterogeneous catalyst not only exhibits superior stability against hydrothermal aging but also presents long-term reaction stability for CO catalytic oxidation, which exceeds 540 h. The present work opens a new door for rational design of hydrothermally stable single-atom Pt catalysts, which are highly promising in practical applications.

Enhanced catalytic performance of isobutane direct dehydrogenation over Pt-In catalysts: Effect of different fluorides modified hydrotalcite-like derivatives

A series of MgF2-modified hydrotalcite-like (HT) derivatives supported Pt-In catalysts PtInHTR-X (X = NH4F, NaF and KF, R = reduced catalyst) were prepared by combination of hydrothermal method, alkali-etching and impregnation strategy and applied to direct dehydrogenation of isobutane to isobutene. The catalysts and precursors were characterized by XRD, SEM, TEM, XPS, TG, O2-TPO and low temperature N2 adsorption-desorption isotherms. The formation of MgF2 phase as dopant to modify the catalyst can influence the pore structure and even the surface acid properties of catalysts. Especially, compared with the three catalysts, PtInHTR-KF catalyst had better stability of isobutene selectivity of over 95% after 9 h reaction, and PtInHTR-NH4F and PtInHTR-NaF catalysts exhibited more stable isobutane activity of 60%. One of the reasons for this catalytic performance is that small particles of MgF2 and unsaturated MgF2 can provide weak acidic sites which can inhibit coke deposition. And it was found the improved catalytic performance was also related to the appropriate In3+/In0 ratio, well-dispersed Pt species and the excellent anti-sintering ability of catalysts modified MgF2.

Highly N2-Selective Activated Carbon-Supported Pt-In Catalysts for the Reduction of Nitrites in Water

The catalytic reduction of nitrites over Pt-In catalysts supported on activated carbon has been studied in a semi-batch reactor, at room temperature and atmospheric pressure, and using hydrogen as the reducing agent. The influence of the indium content on the activity and selectivity was evaluated. Monometallic Pt catalysts are very active for nitrite reduction, but the addition of up to 1 wt% of indium significantly increases the nitrogen selectivity from 0 to 96%. The decrease in the accessible noble metal surface area reduces the amount of hydrogen available at the catalyst surface, this favoring the combination of nitrogen-containing intermediate molecules to promote the formation of N2 instead of being deeply hydrogenated into NH4+. Several activated carbon-supported Pt-In catalysts, activated under different calcination and reduction temperatures, have been also evaluated in nitrite reduction. The catalyst calcined and reduced at 400°C showed the best performance considering both the activity and the selectivity to nitrogen. This enhanced selectivity is ascribed to the formation of Pt-In alloy. The electronic properties of Pt change upon alloy formation, as it is demonstrated by XPS.

Numerical Analysis of Silica Coating Effect on Pt Cathode Catalyst in Polymer Electrolyte Fuel Cells

In order to accelerate the development of polymer electrolyte fuel cells (PEFCs), it is important to optimize the structure of catalyst layers (CLs) including Pt particles, ionomer loading, and porosity, resulting in the improvement of performance. Numerical analysis can assist in designing the optimized CLs without trial and error. In this study, the effects of silica-coated Pt catalysts (SiO2/Pt/C) were investigated by experimental measurements and numerical analysis in order to obtain manufacturing guidelines by designing optimized CLs for PEFCs. In the experimental results, the SiO2/Pt/C showed lower performance than non-coated Pt catalysts (Pt/C) under relative humidity (RH) of 80% at 80°C. In the case of the SiO2/Pt/C, the addition of two parameters including the enhancement of proton conductivity and an increase in the oxygen diffusion resistance in the CLs, attributed to silica layers, were considered. The distribution of current density at 0.8 A cm−2 of the SiO2/Pt/C at each humidity condition (100%RH, 80%RH, 60%RH, 40%RH) is more homogeneous and reached closer to the gas diffusion layer compared to those of the Pt/C. The result indicates that it is possible to improve durability by increasing the reaction located near the polymer electrolyte membrane. For both catalysts, the overvoltages at 0.8 A cm−2 were similar to each other, except for that of proton resistance in ionomer and oxygen diffusion in the ionomer.

MgF2-Modified Hydrotalcite-Derived Composites Supported Pt-In Catalysts for Isobutane Direct Dehydrogenation

Here, a simple method was developed to prepare an MgF2-modified hydrotalcite-derived composite, which was used as support for the Pt-In catalyst for isobutane direct dehydrogenation. The catalysts, composites, and their precursors were characterized by numerous characterization techniques. The results provided evidence for the MgF2 promoter effect on the physical–chemical properties and dehydrogenation performance of the supported Pt-In catalysts. The catalyst with MgF2 shows exceptional isobutene selectivity that can be stabilized at 95%, and the conversion increases from 50% to 58% during the reaction process. Moreover, the existence of MgF2 plays an important role in the resistance to coke formation and Pt sintering by improving the Pt dispersion, inhibiting the reduction of the In3+ species, and adjusting the acidity of the catalyst.

Elucidating the Influence of the d-Band Center on the Synthesis of Isobutanol

As the search for carbon-efficient synthesis pathways for green alternatives to fossil fuels continues, an expanding class of catalysts have been developed for the upgrading of lower alcohols. Understanding of the acid base functionalities has greatly influenced the search for new materials, but the influence of the metal used in catalysts cannot be explained in a broader sense. We address this herein and correlate our findings with the most fundamental understanding of chemistry to date by applying it to d-band theory as part of an experimental investigation. The commercial catalysts of Pt, Rh, Ru, Cu, Pd, and Ir on carbon as a support have been characterized by means of SEM, EDX-mapping, STEM, XRD, N2-physisorption, and H2-chemisorption. Their catalytic activity has been established by means of c-methylation of ethanol with methanol. For all catalysts, the TOF with respect to i-butanol was examined. The Pt/C reached the highest TOF with a selectivity towards i-butanol of 89%. The trend for the TOFs could be well correlated with the d-band centers of the metal, which formed a volcano curve. Therefore, this study is another step towards the rationalization of catalyst design for the upgrading of alcohols into carbon-neutral fuels or chemical feedstock.

Boosting the Microbial Electrosynthesis of Acetate from CO2 by Hydrogen Evolution Catalysts of Pt Nanoparticles/rGO

Microbial electrosynthesis (MES) is an effective approach to driving the CO2 reduction to multi-carbon organic products using renewable energy. In this work, the MES of acetate from CO2 was realized by mixed bacterial consortia, in which Acetobacterium sp. acted as the dominant acetate synthesis microbial flora. To improve synthesis efficiency of MES process, hydrogen evolution reaction (HER) electrocatalyst of Pt nanoparticles on reduced graphene oxide (PtNPs/rGO) was embedded on the biocathode of carbon felt. Results showed that loading the HER catalyst of PtNPs/rGO can significantly improve the MES performance. When 0.04 mg/cm2 Pt nanoparticles was loaded on the cathode, the highest acetate synthesis rate can reach 26.2 g/m2/day, which was twofold higher than that of bare carbon felt. Moreover, PtNPs/rGO incorporated carbon felt cathode showed much lower overpotential than bare carbon felt for hydrogen evolution reaction. Hence, the increased local H2 concentration around cathode enhanced the MES performance. These findings suggested that the artificial composite system composed by HER electrocatalysts will be a promising approach to enhance the electron utilization and CO2 reduction reaction, which acted as a prospective move to meet the needs of carbon cycling and sustainable energy in the future. The microbial electrosynthesis efficiency of acetate from CO2 can be enhanced by hydrogen evolution catalysts using Pt Nanoparticles/rGO .

A Remarkably Efficient Phase-Transfer Catalyzed Amination of α-Bromo-α, β-Unsaturated Ketones in Water

Tandem conjugate addition–alkylation reaction of various amines with α-bromo-α, β-unsaturated ketones resulted in near-quantitative conversions into the corresponding aziridines when the reaction was carried out in the presence of 10 mol% of phase-transfer, PT catalysts in water. Some chiral quaternary ammonium salts derived from Cinchona alkaloids were investigated as water-stable PT catalysts. The scope and limitations of the reaction have also been investigated. The catalytic performances were significantly improved in comparison with the corresponding ordinary quaternary ammonium salt catalysts, and excellent yields (81%–96%) were obtained. Although an increase in the rate of aziridination has been accomplished, no stereoselectivity was observed. The positive values of the protocol have been confirmed.

(Invited) Designing Electrocatalysts for Controlling Selectivity of Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is arguably one of the most important electrochemical reactions affecting the efficiency of energy conversion devices such as fuel cells [1] and metal-air batteries [2]. Oxygen (O2) can be reduced in two ORR pathways are possible: the four-electron (4 e–) pathway to generate water (H2O) by complete reduction and the two-electron (2 e–) pathway to hydrogen peroxide (H2O2) involving partial O2 reduction [3,4]. Although the 2 e– pathway ORR has been regarded as an adverse side reaction that impedes the efficient 4 e– pathway, it has recently garnered a surge of interest as a means of the electrochemical production of H2O2.In this presentation, we present a catalyst design strategy for controlling catalytic selectivity of ORR. We have developed a general synthetic strategy that can produce atomically dispersed precious metal catalysts of Os, Ru, Rh, Ir, and Pt, which served as model catalysts for unravelling catalytic activity and selectivity trends for the ORR [5]. The atomically dispersed precious metal catalysts generally showed higher selectivity for H2O2 production, due to their isolated geometry, than their nanoparticle counterparts for the ORR. Among the atomically dispersed catalysts, the H2O2 selectivity was changed by the types of metals, with atomically dispersed Pt catalyst showing the highest selectivity. A combination of experimental results and density functional theory calculations revealed that the selectivity trend of atomically dispersed catalysts could be correlated to the binding energy difference between *OOH and *O species. In terms of 2 e− ORR activity, the atomically dispersed Rh catalyst showed the best activity. We also present our recent results on the design of carbon-based and non-precious metal catalysts for the selective 2 e– ORR for H2O2 production [6,7].

Performance Parameters of Inductively Coupled Plasma Optical Emission Spectrometry and Graphite Furnace Atomic Absorption Spectrometry Techniques for Pd and Pt Determination in Automotive Catalysts.

Palladium (Pd) and platinum (Pt) are extensively used as catalysts in the petrochemical and automotive industries, and due to high demand for them on the market, their recycling from spent supported catalysts is clearly needed. To assess the content of Pd and Pt in catalysts in order to establish their commercial value or to evaluate the recovery efficiency of technologies used for recycling, reliable analytical methods for determination of these elements are required. Spectrometric methods, such as inductively coupled plasma optical emission spectrometry (ICP-OES) and graphite furnace atomic absorption spectrometry (GFAAS) are powerful tools that can be employed for the determination of Pd and Pt in various sample matrices. However, these methods allow only the injection of liquid samples. In this regard, the digestion of solid sample by microwave-assisted acid extraction procedures at high pressures and temperatures is often used. In this study, a microwave acid digestion method was optimized for the extraction of Pd and Pt from spent catalysts, using a four-step program, at a maximum 200 °C. The resulting solutions were analyzed using ICP-OES, at two different wavelengths for each metal (Pd at 340.458 and 363.470 nm, and Pt at 265.945 and 214.423 nm, respectively) and using GFAAS (Pd at 247.64 nm, Pt at 265.94 nm). Five types of spent catalyst were analyzed and the standard deviations of repeatability for five parallel samples were less than predicted relative standard deviations (PRSD%) calculated using Horvitz’s equation for all the analyzed samples.

Selective hydrogenation of α‐pinene on a nickel supported aluminophosphate catalyst: Process optimization and reaction kinetics

Abstractcis‐Pinane, the hydrogenation product of pinene, is a key chemical intermediate and its production is an important forest chemical process. In this study, α‐pinene was hydrogenated using a nickel‐supported aluminophosphate catalyst (Ni/APO‐PT) in the batch mode of operation. The pore structure of the catalyst was characterized, the process parameters were studied, the hydrogenation process was optimized, and the kinetic study was conducted. The results showed that the conversion of pinene was positively correlated with temperature, duration, and catalyst dosage. In contrast, the selectivity of cis‐pinane was negatively correlated with temperature and catalyst dosage. An optimization was performed using the response surface methodology (RSM). A selectivity of 96.2% was obtained with α‐pinene conversion of 98.5% under optimal conditions, that is, a temperature of 405 K, reaction time of 60 min, hydrogen pressure of 3 MPa, and catalyst loading of 3.32 wt%. The reusability of the catalyst was studied, and the catalyst was found to maintain efficient activity for seven cycles. The kinetics of hydrogenation were investigated using both linear and nonlinear methods in the absence of diffusional limitation. In the temperature range from 403 to 433 K, the hydrogenation of α‐pinene to pinane was compatible with the pseudo‐first‐order process, and the activation energies for the formation of cis‐pinane and trans‐pinane were 41.8 and 56.1 kJ/mol, respectively. This study shows that the performance of the Ni/APO‐PT catalyst is similar to that of noble metals and the catalyst has the potential for industrial applications.

Improved Electrocatalytic Activity and Durability of Pt Nanoparticles Supported on Boron-Doped Carbon Black

A facile strategy is proposed to synthesize boron-doped ECP600 carbon black (B-ECP600), and the catalyst of Pt supported on boron-doped ECP600 (Pt/B-ECP600) shows smaller particle sizes and a higher electrochemical surface area (95.62 m2·gPt−1) and oxygen reduction reaction activity (0.286 A·mgPt−1 for mass activity; 0.299 mA·cm−2 for area specific activity) compared to the catalyst of Pt supported on ECP600 (Pt/ECP600). The results show that the boron doping of the carbon supports plays an important role in controlling the size and dispersion of Pt nanoparticles and the O2 adsorption/dissociation of the oxygen reduction reaction. A further accelerated durability test proves that boron doping can greatly enhance the stability of carbon support and thus improves the electrochemical performance of the catalyst during the long-time running. All these results suggest boron-doped carbon has great potential for application in fuel cells.

An approach to avoid the mix potential for Pt-based cathode catalysts in the direct ethanol fuel cell

It is well known that Pt nanoparticles could simultaneously catalyze the oxygen reduction and ethanol oxidation reactions when oxygen and ethanol molecules coexist in the same electrolyte, greatly limiting the practical application of the best cathode catalyst of Pt in the new energy battery of direct ethanol fuel cell (DEFC) due to the issue of ethanol crossover. However, in our recent experiments, it is interesting to find that on the surface of few Pt nanoparticles, only the oxygen reduction reaction is improved and the ethanol oxidization almost does not occur, meaning that the mix potential caused by the ethanol crossover in the DEFC could be avoided through controlling the Pt loading. Simulations indicate that the binding energy of oxygen molecule on a typical stable Pt atom cluster with only six Pt atoms was about 3.79 times that of ethanol molecule, revealing that small-size oxygen molecules would more preferentially occupy the active sites on the surface of few Pt nanoparticles catalysts than large-size ethanol molecules, showing a promising potential for resolving the issue of mix potential and promoting the application of robust Pt cathode catalyst in the DEFC.

An Efficient Acetalization Method for Biomass‐Derived Furfural with Ethanol Using γ‐Al2O3‐Supported Catalysts

AbstractIn this paper, the mono and bimetallic catalysts of Rh, Pt and Ni supported on γ‐Al2O3 were tested for the selective acetalization of furfural to produce furfural diethyl acetal in a mixture containing furfural diluted in ethanol. Ni1.5Rh1.5/γ‐Al2O3 exhibited the highest catalytic activity among all the tested catalysts, with an 85% furfural conversion and 100% furfural diethyl acetal selectivity at 100 °C and 30 min of reaction. Catalyst characterization showed that Ni1.5Rh1.5/γ‐Al2O3 presented particle sizes smaller than 1.2 nm, and the active metals were partially oxidized (RhIII and NiII). A direct correlation between conversion and weak acidity of mono and bimetallic catalysts was obtained. Interestingly, despite exhibiting strong acidity, γ‐Al2O3 alone was little active in the process, which evidenced the role of the metal in acetalization of furfural into ethanol. In‐situ DRIFTS experiments indicated that furfural is easily adsorbed onto these small particles as Niδ+‐(η1‐O,C‐FFR) and Rhδ+‐ethoxide species and rapidly transforms into furfural diethyl acetal and water. The catalyst was recycled four times, with a loss in catalytic activity of approximately 19%. The Ni1.5Rh1.5/γ‐Al2O3 catalyst was also successfully applied in the condensation of a variety of biomass derivatives.

Producción de bio-hidrógeno con catalizadores metálicos

Many applications, including energy applications, require handling pressurized hydrogen gas. However, an alternative option allows the use of a donor that generates hydrogen in situ (either by transfer and / or catalytic reforming), instead of using molecular hydrogen. Ethanol and formic acid, which are biorefinery streams, were used as donors. The effect of metallic catalysts of Pd and Pt, supported on C, g-Al2O3 and zeolite USY, on the generation of hydrogen was evaluated using different ratios between the active phase and the donor, and different times and temperatures of reaction in a high pressure reactor (up to 1000 psi). The catalysts were characterized by DRX, SEM, FTIR and FRX. At the same time, High-Pressure Differential Scanning Calorimetry (HP DSC) was performed for the most promising systems with a ramp of 10 °C/min. Gas chromatography was used to analyze the production of hydrogen. Findings show that the system that generates more hydrogen, with 88%, is 5% Pd/C over 30% formic acid at 300 °C, 500 rpm and a ratio catalyst mass to donor from 1 to 10 (0.028 m).

Highly Efficient Catalysts of Bimetallic Pt-Ru Nanocrystals Supported on Ordered ZrO2 Nanotube for Toluene Oxidation.

ZrO2 nanotube arrays and their supported bimetallic platinum and ruthenium (PtxRuy/ZrO2; x + y = 1 mmol %, x/y = 1:0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.5:0.5, 0:1) nanocomposites were fabricated by employing SBA-15-OH as a hard template and an impregnation method, respectively. A controlled ordered nanotube array structure formed from the fabricated catalysts, and it showed a good performance for toluene oxidation. The specific physicochemical properties of the catalysts were examined through various analytical means. The PtxRuy/ZrO2 possessed a high surface area, and the Pt-Ru nanoparticles were dispersed uniformly on the ZrO2 nanotube surface. The Pt0.7Ru0.3/ZrO2 catalyst performed best among all of the samples, with T90% and T100% (temperatures for 90 and 100% conversion of toluene) of 140 and 160 °C, respectively, at a weight hourly space velocity of 36 000 mL/(h·g). These bimetallic catalysts exhibit excellent characteristics for toluene oxidation, such as higher turnover frequencies and lower apparent activation energy (Ea) values, which probably result from the synergistic effect of the Pt-Ru noble metals that leads to a high reducibility and oxygen adsorption capacity. The excellent activity, stability, and economics of the Pt0.7Ru0.3/ZrO2 catalyst allow for its application in toluene removal.

Rational Design of Single Atomic Co in CoNx Moieties on Graphene Matrix as an Ultra‐Highly Efficient Active Site for Oxygen Reduction Reaction

AbstractThe sharp increase in current energy consumption needs the development of fuel cells (FCs) as one of sustainable, renewable, efficient and eco‐friendly electrochemical conversion systems of energy. The performance of electrocatalysts is crucially important for commercialization of FCs. Commercial Pt based catalysts are used due to their high catalytic activity. However, widespread commercialization is impossible because of the scarcity and poor durability of Pt based catalysts. We are on our quest to find a more stable and affordable alternative catalyst of Pt based catalysts. In particular, single‐atom catalysts supported on graphene are greatly attractive because of their unique characteristic and high catalytic activity. In this work, graphene is hydrothermally treated by sulfuric acid to introduce the ion‐exchanging sites. Then, Co2+ ion‐exchanging, 2‐methylimidazole coordination and pyrolysis process are subsequently conducted to prepare highly‐dispersed single‐atom Co species catalyst with outstanding ORR activity and durability. This work presents a new direction for a rational design of single‐atom catalyst on carbon matrix.

Improved photocatalytic HER activity of α-Sb monolayer with doping and strain engineering

A potential alternative catalyst of Pt for hydrogen evolution reaction is a great research interest in the area of renewable energy. Here, the hydrogen evolution reaction activity of α-Sb monolayer with transition-metal doping and uniaxial strain was investigated with density functional theory. The binding strength between H and TM atom could be increased by introducing optimal dopants which reduces hydrogen adsorption free energy. The change of hydrogen adsorption free energy is linear dependent on the bond order. Especially, hydrogen adsorption free energy of Cr@Sb was adjusted to almost 0 eV. In addition, tunable hydrogen adsorption free energy with uniaxial strain also observed in doped Sb monolayer. Our study provides more possibilities for new materials design of hydrogen evolution reaction.

Impact of Nonadsorbed Ionomer on Viscosity of Catalyst Inks for Polymer Electrolyte Fuel Cells

Abstract In a catalyst ink for polymer electrolyte fuel cells (PEFCs), some of the ionomer is adsorbed on the carbon-supported Pt catalyst (Pt/C), which enhances the ink stability, while the rest is dispersed in the solvent as a nonadsorbed ionomer. To clarify the effect of nonadsorbed ionomer on the ink viscosity, the amount of nonadsorbed ionomer in the catalyst ink was evaluated by small-angle neutron scattering (CV-SANS). At high-shear viscosity, the nonadsorbed ionomer was found to act as ionomer solution described by the Huggins equation. Moreover, comparison with the CV-SANS results revealed that the conventional filtration method overestimates the amount of nonadsorbed ionomer in a catalyst ink.