During the last two decades, PT‐based relaxor ferroelectric crystals such as (1−x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 (PZN–PT), (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT), and ...(1−x−y)Pb(In1/2Nb1/2)O3–yPb(Mg1/3Nb2/3)O3–xPbTiO3 (PIN–PMN–PT or PIMNT) crystals, are widely studied due to their huge piezoelectric properties and super‐high electro‐mechanical coupling factors. They have excellent properties with compositions around the morphotropic phase boundary (MPB). It is gratifying that the PT‐based relaxor crystals are replacing traditional PZT piezo‐ceramics in many application fields. Most ferroelectrics with oxygen‐octahedral structure, which show outstanding electro‐mechanical properties, also have excellent optical performances. Ferroelectric single crystals with large electro‐optic (EO) modulation are widely applied in laser communication devices. For the practical applications, the knowledge of detailed optical parameters is desirable. This paper tries to show a global review on the optical properties of PT‐based relaxor ferroelectric crystals. In the present review, optical properties of the crystals are systematically summarized, including refractive index dispersion, transmittance, band gap, EO, acousto‐optic, and photorefractive properties. These properties change with the crystal composition, orientation, and poling condition. The purpose of the review is to provide a resource for the researchers who are concerned with basic physical investigation or optical device applications of the PT‐based relaxor ferroelectric crystals.
Optical properties of PZN‐PT, PMN‐PT, and PIN‐PMN‐PT (PIMNT) crystals are systematically summarized, including refractive index dispersion, transmittance, band gap, electro‐optic, acousto‐optic, and photorefractive properties. These properties change with the crystal composition, orientation, and poling condition. This review provides a resource for the researchers who are concerned with basic physical investigation or optical device applications of PT‐based relaxor ferroelectric crystals.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Proton exchange membrane fuel cells (PEMFCs) with high efficiency and nonpollution characteristics have attracted massive attention from both academic and industrial communities due to their ...irreplaceable roles in building the future sustainable energy system. However, the stability issue of Pt‐based catalysts for oxygen reduction reaction (ORR) has become a central constraint to the widespread deployment of the devices relative to the catalytic activity. This review aims to provide comprehensive insights into how to improve the stability of Pt‐based catalysts for ORR. First, the basic physical chemistry behind the catalyst degradation, including the fundamental understandings of carbon corrosion, catalyst dissolution, and particle sintering, is highlighted. After a discussion of advanced characterization techniques for the catalyst degradation, the design strategies for improving the stability of Pt‐based catalysts are summarized. Finally, further insights into the remaining challenges and future research directions are also provided.
Strategies to improve the stability of Pt‐based catalysts for the oxygen reduction reaction are comprehensively reviewed. The basic physical chemistry behind the catalyst degradation is highlighted. After a discussion of advanced characterization techniques for the catalyst degradation, design strategies for improving the stability of Pt‐based catalysts are proposed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In the present work, combination of bi-metallic and tri-metallic Pt, Ir, Sn electro-catalysts was prepared by impregnation reduction method on carbon Vulcan XC-72 to improve upon electro-oxidation of ...ethanol in direct ethanol fuel cell. The prepared electro-catalysts were characterized by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analyses. XRD and TEM analyses reveal that the prepared catalysts are of nano size (6–10nm) range. It is shown that Pt lattice parameter decreases with the addition of Ir, and increases with the addition of Sn in Pt–Ir–Sn/C catalyst. The electro-catalytic activities characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) techniques reveal that the addition of small amount of Ir in Pt–Sn/C electro-catalyst exhibits higher activity towards ethanol oxidation than the Pt–Sn/C (20% Pt and 20% Sn by wt) electro-catalyst. The single direct ethanol fuel cell (DEFC) test at 90°C, 1bar with catalyst loading of 1mg/cm2 and 2M ethanol as anode feed showed an enhancement of catalytic activity in following order: Pt–Ir–Sn/C (20% Pt, 5% Ir and 15% Sn by wt)>Pt–Ir–Sn/C (20% Pt, 10% Ir and 10% Sn by wt)>Pt–Sn/C (20% Pt and 20% Sn by wt)>Pt–Ir–Sn/C (10% Pt, 15% Ir and 15% Sn by wt)>Pt–Ir/C (20% Pt and 20% Ir by wt)> Pt/C (40% Pt by wt). Pt–Ir–Sn/C (20% Pt, 5% Ir and 15% Sn by wt) exhibited highest performance among all the catalysts prepared with power density of 29mW/cm2 in DEFC operating at 90°C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The influence of applied current density and chloride ion concentration on the ability of Ti/Pt/PbO2 and Ti/Pt/SnO2–Sb2O4 anodes for the electrochemical oxidation of humic acid and sanitary landfill ...leachate samples was assessed and compared with that of BDD anode. For the experimental conditions used, results show that both organic load and nitrogen removal rates increase with the applied current density and chloride ion concentration, although there is an optimum COD/Cl−0 ratio below which there is no further increase in COD removal. Metal oxide anodes present a similar performance to that of BDD, being the results obtained for Ti/Pt/PbO2 slightly better than for Ti/Pt/SnO2–Sb2O4. Contrary to BDD, Ti/Pt/PbO2 promotes lower nitrate formation and is the most suitable material for total nitrogen elimination. The importance of the optimum ratio of Cl−/COD/NH4+ initial concentrations is discussed.
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•Ti/Pt/PbO2 and Ti/Pt/SnO2–Sb2O4 anodes have similar performance to that of BDD.•Ti/Pt/PbO2 presents better performance than Ti/Pt/SnO2–Sb2O4 for pollutants removal.•Ti/Pt/PbO2 promotes the lowest nitrate formation and the highest TN elimination rate.•Optimum COD/Cl− for maximum chloride indirect oxidation performance•COD and TN removals increase with current density and in the presence of Cl−.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Bimetallic Pt–Co nanoparticles (NPs) were prepared and characterized by scanning transmission electron microscopy, in situ X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction, and ...catalytic conversion for propane dehydrogenation with and without added H2. In addition, the surface extended X-ray absorption fine structure (EXAFS) obtained by fitting the difference spectrum between the fully reduced and room-temperature-oxidized catalysts suggest that the surface structure remains Pt3Co, although the core changes from Pt to Pt3Co and to PtCo. At low Co loading, the bimetallic nanoparticles form a Pt3Co intermetallic surface alloy with Pt-rich core. With increasing Co loading, a full alloy forms where both the surface and NP compositions are Pt3Co. A further increase in Co loading leads to a Co-rich NP core, likely PtCo, with a surface of Pt3Co. Although Pt–Co intermetallic alloys form two different phases and several morphologies, the surface structures are similar in all catalysts. Although both monometallic Pt and Co are active for alkane dehydrogenation, all bimetallic Pt–Co catalysts are significantly more olefin selective than either single metal. The turnover rates of the bimetallic catalysts indicate that Pt is the active atom with little contribution from Co atoms. The high olefin selectivity is suggested to be due to Co acting as a less active structural promoter to break up large Pt ensembles in bimetallic NPs.
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IJS, KILJ, NUK, PNG, UL, UM
In our research, we present the controlled synthesis of poly(vinylpyrrolidone) (PVP) protected Pt–Pd nanoparticles of various alloy and core-shell morphologies by modified polyol method with the ...assistance of AgNO
3. The Pt–Pd alloy and core-shell nanoparticles were characterized by transmission electron microscopy (TEM), high-resolution TEM, and electrochemical measurements. The comparison of electrocatalytic properties of Pd–Pt bimetallic nanoparticles was described to confirm their highest catalytic performance. Importantly, the catalytic activity of Pt–Pd alloy and core-shell nanoparticles was investigated to develop novel electrocatalysts in direct methanol fuel cells (DMFCs). The results showed that the core-shell nanoparticles with the thin nanoshells as monolayers exhibit as great nanocatalysts. The correlation among structure, size and morphology was presented in their catalytic characterization.
► The Pt-Pd alloy and core-shell bimetallic nanoparticles are synthesized. ► The epitaxial growth mode of the Pd-monolayers shells on the Pt nanocores is observed. ► The Pt-Pd or Pd-Pd core-shell nanoparticles with the thin Pt or Pd nanoshells in the forms of the monolayers exhibit their great electrocatalysis for direct methanol fuel cells (DMFCs). ► Interestingly, the size issues in the catalytic activity are really not as important as morphology and nanostructure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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•Computational screening confirmed the high reactivity of Pt-substituted TiO2.•Pt substituted TiO2 was prepared by the modified sol–gel method.•Pt substituted TiO2 exhibited improved ...activity for MEK combustion.•The computational screening result had been confirmed experimentally.
This study developed a VOC (methyl ethyl ketone (MEK)) removal catalyst and examined it computationally and experimentally. Computational screening, focusing on CH4 adsorption, showed that Pt-substituted TiO2(110) surface strongly attracts CH4 (Eads = 51.1 kJ/mol), facilitating initial CH bond cleavage on the surface. The predicted screening results suggested that Pt-substituted TiO2(110) would also be highly active toward MEK combustion because the catalysts activating the highly stable molecule of methane would have a high potential to activate MEK with weaker CH bonds compared to methane. The further in-depth computational analysis exploring the adsorption energies (Eads = 63.9 kJ/mol (0Pt) → 122.8 kJ/mol (1Pt) → 152.9 kJ/mol (2Pt)), the dissociation kinetics of adsorbed MEK and O2 confirmed the high reactivity toward MEK combustions on Pt-substituted TiO2; CH bond cleavage of MEK occurs with low energy barriers of <∼55 kJ/mol. Finally, the computational results were verified experimentally. The experimental results showed that sol–gel prepared Pt/TiO2 catalyst provides an enhanced reactivity than the widely used impregnated catalyst for VOCs removal, and its high reactivity stems from the Pt-substituted site in TiO2. The proposed high reactivity of Pt-substituted TiO2 would provide fundamental and applicative insights to improve the reactivity by reducing the cost of developing VOCs removal catalysts using noble metal elements. Beyond the development of VOCs removal catalysts, we believed that the proposed approach combined with computational screening, in-depth computational analysis, and experimental verifications would be a promising and practical strategy for developing other catalysts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, a series of x wt% Pt@TiO2 (x = 0.18, 0.42, and 0.84) catalysts with highly dispersed Pt nanoparticles (NPs) are synthesized via pyrolysis method using Ti-based metal-organic frameworks ...(MOFs) as precursors. Physicochemical properties of the catalysts are characterized by a number of analytical techniques. It is shown that all samples possess mesoporous structure with surface area of 59–75.6 m2/g, thus can suppress the aggregation of Pt NPs, and enhance toluene adsorption and diffusion. The 0.84 wt% Pt@TiO2 catalyst exhibits the best catalytic performance for toluene oxidation (T90% =150 °C at space velocity = 20,000 mL/ (g h)), which is attributed to the higher surface area, abundant adsorbed oxygen and Pt0 species, and strong interaction between Pt NPs and TiO2. In addition, the possible reaction mechanism of toluene oxidation is proposed based on in situ DRIFTS technique.
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•Mesoporous Pt@TiO2 is synthesized via pyrolysis of Ti-MOF.•0.84 wt% Pt@TiO2 exhibits excellent catalytic performance for toluene oxidation.•Mesoporous Pt@TiO2 suppresses the aggregation of Pt NPs.•Excellent performance is due to high surface area, abundant adsorbed oxygen and Pt0 species.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Pt-ZnO-In2O3 nanofibers (NFs) are designed by dispersing Pt loaded ZIF-8 nanoparticles in PVP/In(NO3)3 precursors.•The average sizes of Pt nanoparticles obtained in this work are only ∼3 nm.•Gas ...sensing investigations indicate that the sensor based on Pt-ZnO-In2O3 NFs exhibit the superior acetone response•The sensor based on the Pt-ZnO-In2O3 NFs exhibits fast response and recovery times to 100 ppm acetone at 300 °C.
Ultra-small Pt nanoparticles functionalized In2O3 nanofibers have been designed by using a new catalyst loading platform (Pt@ZIF-8), which involves three steps including the synthesis of ZIF-8 nanoparticles, the preparation of Pt@ZIF-8 and the subsequent transformation to Pt-ZnO-In2O3 composite nanofibers by electrospinning. The experimental results demonstrate that the average sizes of Pt nanoparticles obtained in this way are only ∼3 nm, which is helpful to obtain highly sensitive gas sensors due to the ultra-small Pt nanoparticles. Gas sensing investigations indicate that the sensor based on Pt-ZnO-In2O3 nanofibers exhibit the superior acetone response (Ra/Rg = 57.1 to 100 ppm at 300 °C), ultra-fast response and recovery time (1/44s) and low detection limit (0.5 ppm). In this study, the excellent acetone gas sensing property of Pt-ZnO-In2O3 nanofibers attributes to the chemical sensitization and electrical sensitization of the ultra-small Pt nanoparticles, the n-n heterojunctions between ZnO and In2O3, and the p-n heterojunction produced between p-type PtO2 and n-type In2O3 (ZnO).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The metal‐supported CeO2 catalysts (such as Pt/CeO2) have been considered as the most promising exhaust‐treatment catalyst to meet the future emission standard. However, the Pt‐O‐Ce interface on ...Pt/CeO2 system seems to over‐stabilize the Pt sites to cause low activity for CO oxidation. In this work, by adding Fe oxides, the enhanced Pt‐FeOx interaction was formed with the disappearance of the Pt‐O‐Ce interface, facilitating the electron transfer from the support to the atomically dispersed Pt on the Pt‐FeOx interface for the dramatically CO (preferential) oxidation performance. The single‐atom Pt/1.5FeOx/CeO2 performed the best catalytic activity with a reaction rate of 0.58 s−1 at 144 °C (T100). Such strategy in resorting the special metal‐support interaction to tune the active sites can be extended to other metal‐oxide systems for further optimized catalysis.
Metal‐supported CeO2 catalysts (e.g. Pt/CeO2) are considered most promising for exhaust treatment to meet the future emission standards. Here, by adding Fe oxides, enhanced Pt‐FeOx interaction was formed with the disappearance of the Pt‐O‐Ce interface over Pt/1.5FeOx/CeO2, contributing to a dramatically improved CO oxidation performance.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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