Understanding the role of K on PtCo/Al2O3 for preferential oxidation of CO in H2

CO preferential oxidation reaction (CO-PROX) can effectively eliminate CO in H₂ rich atmosphere to avoid CO poison the Pt anode of Proton Exchange Membrane Fuel Cell (PEMFC). To match the operation temperature window for PEMFC, PtCo nanoparticles supported on K modified Al₂O₃ (PtCo/K–Al₂O₃) were prepared to promote CO-PROX activity. The addition of K species weakened the interaction between PtCo nanoparticle and support, which improved the dispersion of Pt particles and redox property of PtCo/Al₂O₃. It also facilitated the formation of Pt₃Co species and active surface ?OH groups, which were involved in CO-PROX reaction. According to in situ DRIFTS spectra, HCO₃^? and HCOO^? were intermediates of PtCo/K–Al₂O₃ catalyzed CO-PROX at low temperature and high temperature, respectively. Thus, the addition of 1 wt% K to PtCo/Al₂O₃ (PtCo/1K–Al₂O₃) could completely oxidize CO in the temperature range of 127–230 °C with O₂ selectivity at 50%. The 100% CO conversion temperature window of PtCo/1K–Al₂O₃ is expanded by 100 °C in comparison of PtCo/Al₂O₃.     

Electrochemically synthesized polypyrrole/MWCNTs-Al2O3 ternary nanocomposites supported Pt nanoparticles toward methanol oxidation

As known, a good support enhances the activity and durability of any catalyst. In the current study, polypyrrole (PPY)/nanocomposite (MWCNTs and Al₂O₃) films were fabricated by electrochemical polymerization of pyrrole solution with a certain amount of nanoparticles on titanium substrates and were used as new support materials for Pt catalyst. The modified electrodes were characterized by Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) techniques. High catalytic activity and long-time stability toward methanol oxidation of Pt/PPY–MWNTs-αAl₂O₃ catalyst have also been verified by cyclic voltammetry results and chronoamperometric response measurements. This catalyst exhibits a vehemently high current density (345.03 mA cm^?2) and low peak potential (0.74 v) for methanol oxidation. Other electrochemical measurements (electrochemical impedance spectroscopy (EIS), CO stripping voltammetry and Tafel test) clearly confirmed that Pt/PPY–MWNTs-αAl₂O₃/Ti electrode has a better performance toward methanol oxidation compared to the other electrodes and that can be used as a promising electrode material for application in direct methanol fuel cells (DMFCs).     

Platinum supported catalysts for carbon monoxide preferential oxidation: Study of support influence

The aim of this work is to study the influence of the addition of different oxides to an alumina support, on surface acidity and platinum reducibility in platinum-based catalysts, as well as their effect on the activity and selectivity in CO preferential oxidation, in presence of hydrogen. A correlation between surface acidity and acid strength of surface sites and metal reducibility was obtained, being Pt-support interaction a function of the acid sites concentration under a particular temperature range. In platinum supported on alumina catalysts, CO oxidation follows a Langmuir-Hinshelwood mechanism, where O₂ and CO compete in the adsorption on the same type of active sites. It is noteworthy that the addition of La₂O₃ modifies the reaction mechanism. In this case, CO is not only adsorbed on the Pt active sites but also on La₂O₃, forming bridge bonded carbonates which leads to high reactivity at low temperatures. An increase on temperature produces CO desorption from Pt surface sites and favours oxygen adsorption producing CO₂. CO oxidation with surface hydroxyl groups was activated producing simultaneously CO₂ and H₂.     

Development and performance of a K–Pt/γ-Al2O3 catalyst for the preferential oxidation of CO in hydrogen-rich synthesis gas

Proton exchange membrane fuel cells are widely employed in micro combined heat and power cogeneration (micro-CHP) systems, and the feed to them should be essentially free of CO. CO preferential oxidation is an effective method for the thorough removal of CO from synthesis gas. A series of K–Pt/γ-Al₂O₃ catalysts are prepared and tested for their CO cleaning capabilities. The catalyst is prepared from potassium nitrate acid, chloroplatinic acid and γ-Al₂O₃ powder by normal or ultrasonic impregnation. The catalyst performance is investigated in a micro-reactor system. The effects of K loading, Pt loading, ultrasonic processing, space velocity, O₂-to-CO ratio and operation temperature on catalyst performance are studied. A CO concentration of less than 10 ppm is achieved when the CO concentration in the feed gas is 0.45%. It was found that both ultrasonic processing and the addition of K promote the catalyst performance. The 15K1.0Pt/Al–U catalyst exhibits the best performance.     

Superhydrophobic Pt–Pd/Al2O3 catalyst coating for hydrogen mitigation system of nuclear power plant

Passive auto-catalytic recombiner (PAR) system is an important hydrogen mitigation method which has been applied in most modern light water nuclear reactors. The two challenges for the highly efficient PAR are the detrimental effect of water and poisoning by fission products. In this study, to address the two challenges, superhydrophobic Pt–Pd/Al₂O₃ catalyst coatings were prepared by wet impregnation method and the grafting of 1H,1H,2H,2H-perfluorooctyltriethoxysilane.The formation of a Pt–Pd intermetallic compound was confirmed by in situ diffuse reflectance infrared Fourier transform infrared spectroscopy for the Pt–Pd/Al₂O₃ catalyst. The Pt–Pd/Al₂O₃ catalyst exhibited a superior resistance of water poisoning to the monometallic catalysts. In addition, compared with the monometallic catalysts, the least influence by the iodine poisoning was observed for the Pt–Pd/Al₂O₃ catalyst, which is attributed to the smallest influence on the bindings of H₂ and O₂ on the Pt–Pd intermetallic compound by the iodine addition. For the reactor with the superhydrophobic Pt–Pd/Al₂O₃ catalyst coating, under the conditions simulating the nuclear accident, the reaction was ignited immediately as soon as the hydrogen was introduced at 298 K and the hydrogen conversion kept 100% when the reaction temperature exceeded 398 K. The superhydrophobic Pt–Pd/Al₂O₃ catalyst coating showed great potential for the mitigation of hydrogen containing various poisons during the nuclear accident.     

The cleanup of CO in hydrogen for PEMFC applications using Pt,Ru, Co,and Fe in PROX reaction

An experimental investigation is performed into the cleanup of CO in hydrogen for proton exchange membrane fuel cell (PEMFC) using Pt/Al₂O₃ and Ru/Al₂O₃ catalysts. Additionally, the effects of adding the transition metals Co and Fe to a Ru/Al₂O₃ catalyst are examined. The results show that as the level of Pt addition is increased, the maximum CO conversion rate is achieved at a lower temperature. With Ru/Al₂O₃ catalysts, the CO conversion rate increases significantly with increasing Ru addition at temperatures lower than 80 °C For both catalysts, the methane yield increases with increasing temperature and increasing noble metal addition. At temperatures in the range of 100–140 °C, the CO conversion rate and methane yield of the Pt- and Ru-based preferential oxidation (PROX) reactions are both insensitive to the density of the honeycomb carrier. The CO conversion rate is significantly improved by the addition of Fe at temperatures lower than 160 °C and by the addition of Co at temperatures higher than 200 °C. Of the two metals, Fe results in a greater reduction of the methane yield at high temperatures. Finally, both catalysts achieve a stable cleanup performance over the course of a 12-h stability test and suppress the CO concentration to an acceptable level for PEMFC applications.     

Experimental optimization analysis on operating conditions of CO removal process from hydrogen-rich reformate

The catalytic effects of CO preferential oxidation and methanation catalysts for deep CO removal under different operating conditions (temperature, space velocity, water content, etc.) are systematically studied from the aspects of CO content, CO selectivity, and hydrogen loss index. Results indicate that the 3 wt% Ru/Al₂O₃ preferential oxidation catalysts reduce CO content to below 10 ppm with a high hydrogen consumption of 11.6–15.7%. And methanation catalysts with 0.7 wt% Ru/Al₂O₃ also exhibit excellent CO removal performance at 220–240 °C without hydrogen loss. Besides, NiCl_x/CeO₂ methanation catalysts possess the characteristics of high space velocity, high activity, and high water-gas resistance, and can maintain the CO content at close to 20 ppm. Based on these experimental results, the coupling scheme of combining NiCl_x/CeO₂ methanation catalysts (low cost and high reaction space velocity) with 0.7 wt% Ru/Al₂O₃ methanation catalysts (high activity) to reduce CO content to below10 ppm is proposed.     

Study on water–gas shift reaction performance using Pt-based catalysts at high temperatures

The water–gas shift reaction (WGSR) performance was experimentally studied using Pt-based catalysts for temperature, time factor and steam to carbon (S/C) molar ratio at ranges of 750–850 °C, 10–20 g_cat h/mol_CO, and 1–5, respectively. Al₂O₃ spheres were used as the catalyst support. For the high S/C cases, it was found that CO conversion can be enhanced when Pt/CeO₂/Al₂O₃ catalyst was used as compared with Pt/Al₂O₃. For the low S/C ratio cases, CO conversion enhancement was not significant with the addition of CeO₂. It was also found that CO conversion was not influenced by the CeO₂ amount to a large extent. Using bimetallic Pt–Ni/CeO₂/Al₂O₃ catalyst, it was found that higher CO conversion can be obtained as compared with CO conversions obtained from monometallic catalysts (Pt/Al₂O₃ or Pt/CeO₂/Al₂O₃). The experimental data also indicated that good thermal stability can be obtained for the Pt-based catalysts studied.     

Three-dimensional porous Mn–Ni/Al2O3 microspheres for enhanced low temperature CO hydrogenation to produce methane

CO methanation has attracted much attention because it transforms CO in syngas and coke oven gas into CH₄. Here, porous Al₂O₃ microspheres were successfully used as catalyst supports meanwhile the Mn was used as a promoter of Ni/Al₂O₃ catalysts. The as-obtained Ni/Al₂O₃ and Mn–Ni/Al₂O₃ samples display a micro-spherical morphology with a center diameter near 10 μm. Versus the Ni/Al₂O₃ catalyst, the 10Mn–Ni/Al₂O₃ catalyst exhibits a high specific surface area of 92.5 m²/g with an average pore size of 7.0 nm. The 10Mn–Ni/Al₂O₃ catalyst has the best performance along with can achieve a CO conversion of 100% and a CH₄ selectivity of 90.7% at 300 °C. Even at 130 °C, the 10Mn–Ni/Al₂O₃ catalyst shows a CO conversion of 44.0% and a CH₄ selectivity of 84.1%. The higher low-temperature catalytic activity may be since the catalyst surface contains more CO adsorption sites and thus has a stronger adsorption performance for CO. Density functional theory (DFT) calculations confirm that the Mn additive enhances the adsorption of CO, especially for the 10Mn–Ni/Al₂O₃ catalyst with the strongest adsorption energy.     

Two-dimensional Mo2C: An efficient promoter for hydrogen storage and release from a liquid organic hydrogen carrier

Two-dimensional Mo₂C (2D-Mo₂C) is reported for the first time as an effective promoter of a Pt/Al₂O₃ catalyst for both the hydrogenation and dehydrogenation of the liquid organic hydrogen carrier (LOHC) pair, dibenzyltoluene (DBT) and perhydro-dibenzyltoluene (H18-DBT), respectively. Addition of 6.2 wt% 2D-Mo₂C to a Pt/Al₂O₃ catalyst resulted in a significant increase in both the degree of hydrogenation and dehydrogenation compared to the unpromoted catalyst. An analysis of the initial (120 min) perhydro-DBT dehydrogenation kinetics in the temperature range of 270–330 °C, resulted in a reduction in apparent activation energy from 119.5 ± 3.8 kJ/mol for the Pt/Al₂O₃ catalyst to 110.4 ± 5.6 kJ/mol for the 6.2 wt% 2D-Mo₂C/Pt/Al₂O₃ catalyst. The 6.2 wt% 2D-Mo₂C/Pt/Al₂O₃ catalyst was also more stable than the unpromoted catalyst over several consecutive cycles of hydrogenation and dehydrogenation. Catalyst characterization showed that addition of 2D-Mo₂C resulted in an increase in particle size and electron density of the Pt, which enhanced both the hydrogenation and dehydrogenation reactions, despite the fact that the 2D-Mo₂C alone was inactive for both reactions.     

On the role of size controlled Pt particles in nanostructured Pt-containing Al2O3 catalysts for partial oxidation of methane

The effect of the Pt loadings and particles sizes on the stability of Pt(x wt%)/Al₂O₃ catalysts were investigated in the partial oxidation of methane (POM) reaction. The Al₂O₃ support was prepared by sol-gel method and different Pt loadings, varying from 0.5 to 2.0 wt% were incorporated to alumina through the incipient wetness impregnation method. The physicochemical features of the catalysts were determined by XRD, ICP-OES, Nitrogen-sorption, UV–Visible, H₂-TPR, CO-DRIFTS, SEM-EDS, XPS and HRTEM techniques. The metal dispersion was evaluated in the cyclohexane dehydrogenation reaction. Lower Pt loadings resulted in well dispersed Pt^o nanoparticles with an enhanced activity in cyclohexane dehydrogenation and POM reactions. With increasing Pt loading to 2.0 wt%, the Pt nanoparticles of the Pt(2.0 wt%)/Al₂O₃ showed a methane conversion of 63% in 24 h of time on stream, and the catalyst was very selective to H₂ and CO. Based on the HRTEM, XPS and Raman spectroscopy techniques, an increment in the Pt loadings evidenced an enrichment of Pt^o clusters on the surface, however, no heavy carbon deposits formation was observed.     

Selective CO oxidation with real methanol reformate over monolithic Pt group catalysts: PEMFC applications

Alumina supported Pt group metal monolithic catalysts were investigated for selective oxidation of CO in hydrogen-rich methanol reforming gas for proton exchange membrane fuel cell (PEMFC) applications. The results are described and discussed in the present paper and show that Pt/γ_Al2O3$\mathrm{Pt}/\gamma {\mathrm{Al}}_2{\mathrm{O}}_3$ was the most promising candidate to selectively oxidize CO from an amount of about 1 vol% to less than 100 ppm. We have investigated the effect of the O₂ to CO feed ratio, the feed concentration of CO, the presence of H₂O and/or CO₂, and the space velocity on the activity, selectivity and stability of Pt/Al₂O₃ monolithic catalysts. Afterwards, the Pt/Al₂O₃ catalyst was scaled up and applied in 5 kW hydrogen producing systems based on methanol steam reforming and autothermal reforming. The hydrogen produced was then used as fuel for an integrated PEMFC.     

Partial oxidation of ethanol on supported Pt catalysts

This work studied the effect of the nature of the support on the performance of Pt/Al₂O₃, Pt/ZrO₂, Pt/CeO₂ and Pt/Ce_0.50Zr_0.50O₂ catalysts on partial oxidation of ethanol. The reducibility and oxygen transfer capacity were evaluated by temperature-programmed reduction (TPR) and oxygen storage capacity (OSC) experiments. The results showed that the support plays an important role on the products distribution of the partial oxidation of ethanol. Acetic acid was the main product on Pt/Al₂O₃ catalyst whereas methane and acetaldehyde were the only products detected on Pt/ZrO₂, Pt/CeO₂ and Pt/Ce_0.50Zr_0.50O₂ catalysts.The products distribution obtained on Pt/ZrO₂, Pt/CeO₂ and Pt/Ce_0.50Zr_0.50O₂ catalysts was related to their redox properties. The OSC experiments showed that the oxygen exchange capacity was higher on Pt/CeO₂ and Pt/Ce_0.50Zr_0.50O₂ catalysts. A high oxygen storage capacity favored the formation of acetate species, which could be decomposed to CH₄ and/or oxidized to CO₂ via carbonate species. On the other hand, the lower oxygen exchange capacity of Pt/ZrO₂ catalyst led to a higher ethoxy species formation. These species can be dehydrogenated and desorb as acetaldehyde. Then, the higher selectivity to acetaldehyde observed on Pt/ZrO₂ catalyst could be assigned to its low oxygen storage/release capacity.In the case of Pt/Al₂O₃ catalyst, the production of acetic acid could be related to its acidic properties, since this material did not show redox properties, as revealed by OSC analysis.     

Defect engineering by steam treatment over Pt/CeO2 catalyst promoting C–H activation in partial oxidation of methane

Reducible oxides such as ceria have been certified to significantly enhance the catalytic activity of redox reactions. In this study, Pt/CeO₂ catalyst was treated with steam, a good deal of hydroxyl groups came into being on surface to form Pt–OH species, thus achieving a high degree of Pt dispersion. The results of O₂-TPD, XPS, Raman and EPR indicated that the dissociation of steam at surface vacancy was in favor of activation and removal of lattice oxygen and generation of oxygen vacancies. DFT calculation and in situ DRIFTS results showed that the oxygen vacancy was favorable for activating C–H bond in methane. The Pt/CeO₂–H₂O catalyst with abundant oxygen vacancies presented outstanding catalytic activity than that of Pt/CeO₂, the CH₄ conversion rate, CO and H₂ selectivity was 62%, 60% and 58%, respectively. What's more, defective engineering promoting methane partial oxidation can be extended to all kinds of redox reactions.     

Experimental studies on syngas catalytic combustion on Pt/Al2O3 in a microreactor

Synthesis gas (a mixture of CO and H₂) oxidation is studied over a supported Pt/Al₂O₃ catalyst in a novel microreactor fabricated for studying the intrinsic chemical kinetics of highly exothermic reactions. CO was found to significantly inhibit H₂ oxidation. In contrast, H₂ addition promotes CO oxidation at low mole fractions but has a small promoting effect at high hydrogen mole fractions. As a result, the apparent reaction order of H₂ changes from positive to zero. The change in hydrogen reaction order is associated with hysteresis. Possible mechanisms for the observed behavior are discussed.     

Promotional effect of Mg in trimetallic nickel-manganese-magnesium nanocrystalline catalysts in CO2 reforming of methane

In the present paper, the dry reforming reaction was studied over the 10 wt%Ni-3wt.%Mn-x wt.% Mg (x = 2, 4 and 6 wt%) catalysts supported on γ-Al₂O₃ with mesoporous structure. The physicochemical characteristics of the samples were determined by XRD, BET, TPO, and SEM techniques. Mesoporous γ-Al₂O₃ carrier with the high BET area (186 m²/g) was synthesized by a simple sol–gel method and the Ni, NiMn and Mg promoted catalysts possessed nanocrystalline mesoporous structure with the BET area in the range of 127–176 m²/g. The average pore radius of the prepared catalysts were smaller than 11 nm. All the synthesized samples exhibited a CH₄ conversion in the range of 60–65% at 700 °C. The small differences in methane conversion in all catalysts could be related to the same nickel loading. According to the TPR results, the Mg addition caused an increase in the reducibility of the nickel catalyst and the Mg-promoted sample exhibited a higher conversion compared to the monometallic catalyst, due to its higher reducibility. The results showed that the textural characteristics of the catalysts were affected by the content of Mg. The results indicated that the NiMn/Al₂O₃ catalyst promoted by 4 wt% Mg showed the highest CH₄ conversion in all studied reaction temperatures (550–700 °C). Furthermore, only one oxidation peak was detected for all catalysts in TPO analysis, which was related to the filamentous form carbon. The 10Ni/Al₂O₃ and 10Ni3Mn4Mg/Al₂O₃ catalysts exhibited the highest and the lowest amount of deposited filamentous carbon, respectively. The 10Ni3Mn4Mg/Al₂O₃ catalyst was stable during the 20 h time on stream without any decline in CH₄ conversion.     

Preparation of mesoporous nanocrystalline CuO–ZnO–Al2O3 catalysts for the H2 purification using catalytic preferential oxidation of CO (CO-PROX)

In this article, CuO–ZnO–Al₂O₃ catalysts with various copper contents were synthesized by a co-precipitation method and employed for the elimination of carbon monoxide from a mixture of 97% H₂, 1% CO and 2% O₂ at atmospheric pressure via carbon monoxide preferential oxidation (CO-PROX). The influence of the copper and zinc contents on the physicochemical characteristics and catalytic performance was investigated. The prepared samples were characterized using the N₂ adsorption-desorption (BET), X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM) and temperature programmed reduction (TPR) techniques. The increment in CuO loading improved the activity of CuO–ZnO–Al₂O₃ catalysts for CO oxidation reaction. Among the prepared catalysts, the 50%CuO-3% ZnO-47% Al₂O₃ catalyst calcined at 400 °C with a BET area of 82.3 m²/g exhibited the best activity with a CO conversion of 88.9% at 125 °C. The effects of the presence of CO₂ and H₂O in the reaction feed stream and gas hourly space velocity (GHSV) were also studied.     

Evaluation of catalyst activity for release of hydrogen from liquid organic hydrogen carriers

This contribution investigate the effect of parameters for production of hydrogen by catalytic dehydrogenation of perhydrodibenzyltoluene (H18-DBT). The sensitivity of the dehydrogenation reaction to temperature (290–320 °C) is justified by an increase in degree of dehydrogenation (DoD) from 40 to 90% when using 1 wt % Pt/Al₂O₃ catalyst. However, the increase in temperature increases the hydrogen production rate and decreases the hydrogen purity by increasing the formation of by-products. In addition, the DoD of 96% is obtained when 2 wt % Pt/Al₂O₃ is used at 320 °C. The DoD obtained for Pd, Pt, and Pt–Pd catalysts is 11, 82 and 6%, respectively. Therefore, Pd is not a metal of choice for dehydrogenation of H18-DBT, in both monometallic and bimetallic system. The ab-initio density functional theory (DFT) calculations are consistent with this observation. Furthermore, dehydrogenation of H18-DBT followed 1st order reaction kinetics and the activation energies for 1 wt % Pt/Al₂O₃, 1 wt % Pd/Al₂O₃ and 1:1 wt % Pt–Pd/Al₂O₃ catalysts are: 205, 84 and 66 kJ/mol, respectively.     

Methanation of CO2 over alumina supported nickel or cobalt catalysts: Effects of the coordination between metal and support on formation of the reaction intermediates

This study focused on the potential coordination between nickel or cobalt and alumina in Ni/Al₂O₃ and Co/Al₂O₃ catalysts and the impacts on their catalytic performances in methanation of CO₂. The results exhibited that Co/Al₂O₃ catalyst was far more active than Ni/Al₂O₃ catalyst, due to the varied reaction intermediates formed in methanation. The DRIFTS results of methanation of CO₂ exhibited that, over bare alumina, bicarbonate, formate and carbonate were the main intermediate species, which could be formed at even 80 °C. Over unsupported Ni catalyst, the formaldehyde species (H₂CO*) and CO* species were dominated. Over the Ni/Al₂O₃ catalyst, however, the reaction intermediates formed were determined by alumina and accumulated on surface of the catalysts. The coordination effects between nickel and alumina in Ni/Al₂O₃ were thus not remarkable in terms of enhancing catalytic activity when compared to that in Co/Al₂O₃ catalyst. Over unsupported Co catalyst and the bare alumina, the reaction intermediates formed were roughly similar. Nevertheless, the combination of Co and alumina in Co/Al₂O₃ catalyst could effectively facilitate the conversion of bicarbonate, formate and carbonate species. CO₂ could be activated over metallic cobalt sites, which could migrate and integrate with the hydroxyl group in alumina to form bicarbonate and further to formate and CO* species, and be further hydrogenated over cobalt sites to CH₄. Such a coordination between alumina and cobalt species promoted the catalytic performances.     

Preferential CO oxidation on Ru/Al2O3 catalyst: An investigation by considering the simultaneously involved methanation

The CO removal with preferential CO oxidation (PROX) over an industrial 0.5% Ru/Al₂O₃ catalyst from simulated reformates was examined and evaluated through considering its simultaneously involved oxidation and methanation reactions. It was found that the CO removal was fully due to the preferential oxidation of CO until 383 K. Over this temperature, the simultaneous CO methanation was started to make a contribution, which compensated for the decrease in the removal due to the decreased selectivity of PROX at higher temperatures. This consequently kept the effluent CO content as well as the overall selectivity estimated as the ratio of the removed CO amount over the sum of the consumed O₂ and formed CH₄ amounts from apparently increasing with raising reaction temperature from 383 to 443 K when the CO₂ methanation was yet not fully started. At these temperatures the tested catalyst enabled the initial CO content of up to 1.0 vol.% to be removed to several tens of ppm at an overall selectivity of about 0.4 from simulated reformates containing 70 vol.% H₂, 30 vol.% CO₂ and with steam of up to 0.45 (volume) of dry gas. Varying space velocity in less than 9000 h⁻¹ did not much change the stated overall selectivity. From the viewpoint of CO removal the article thus concluded that the methanation activity of the tested Ru/Al₂O₃ greatly extended its working temperatures for PROX, demonstrating actually a feasible way to formulate PROX catalysts that enable broad windows of suitable working temperatures.