A synthesis strategy for the preparation of ultrathin free‐standing ternary‐alloy nanosheets is reported. Ultrathin Pd‐Pt‐Ag nanosheets with a thickness of approximately 3 nm were successfully ...prepared by co‐reduction of the metal precursors in an appropriate molar ratio in the presence of CO. Both the presence of CO and the interplay between the constituent metals provide fine control over the anisotropic two‐dimensional growth of the ternary‐alloy nanostructure. The prepared Pd‐Pt‐Ag nanosheets were superior catalysts of ethanol electrooxidation owing to their specific structural and compositional characteristics. This approach will pave the way for the design of multicomponent 2D nanomaterials with unprecedented functions.
Ultrathin Pd‐Pt‐Ag nanosheets with a thickness of approximately 3 nm were successfully prepared by the co‐reduction of suitable metal precursors in an appropriate molar ratio in the presence of CO. These nanosheets are superior catalysts of ethanol electrooxidation owing to their specific structural and compositional characteristics.
Precise control over the topology of plasmonic metal–semiconductor heteronanostructures is essential for fully harnessing their plasmonic function and hence for designing innovative solar energy ...conversion platforms. Here, we present a rational synthesis strategy for the realization of plasmonic metal–semiconductor heteronanocrystals with intended configurations through the site-selective overgrowth of semiconductor Cu2O on desired sites of anisotropic Au nanocrystals. Both the exploitation of structural characteristics of Au nanocrystals and the selective stabilization of their surfaces are keys to the construction of heteronanocrystals with a specific configuration. Our approach can provide an opportunity to precisely explore the link between the solar energy conversion efficiency and the structure of heteronanocrystals as well as to obtain important insights into the underpinning mechanism. Heteronanocrystals produced by Cu2O overgrowth preferentially on the multiple high-curvature sites of Au nanocrystals exhibited prominent photocatalytic hydrogen production activity due to efficient charge separation by strong plasmon excitation at the Au–Cu2O interface and subsequent sustainable hot electron transfer from Au to Cu2O.
Au nanocrystals (NCs) with an unprecedented hexoctahedral structure enclosed exclusively by high-index {321} facets have been prepared for the first time. Manipulating the NC growth kinetics by ...controlling the amount of reductant and the reaction temperature in the presence of a suitable surfactant was the key synthetic lever for controlling the morphology of the Au NCs. The hexoctahedral Au NCs exhibited efficient optical and surface-enhanced Raman scattering activities due to their unique morphological characteristics.
Highly monodisperse 5 nm Pd–Ni alloy nanoparticles (NPs) were prepared by the reduction of Pd(acac)2/Ni(acac)2 mixtures with tert-butylamine-borane complex (TBAB) in the presence of oleic acid (OA) ...and oleylamine (OAm). Employing TBAB as an effective reductant and OA/OAm combination as an effective stabilizing agent is crucial to the formation of monodisperse Pd–Ni NPs. Experimental results collectively verify that the Pd–Ni alloy NPs form through the sequential nucleation-interdiffusion process and the simultaneous reduction of both metal precursors by the one-pot protocol is the key to the formation of homogeneous NPs. The Pd–Ni NPs were well-dispersed on carbon supports and chemically dealloyed after acetic acid washing through the selective dissolution of the less noble Ni component. The Pd–Ni NP catalysts exhibited much higher electrocatalytic activity and stability for ethanol oxidation than those of a commercial Pd/C catalyst.
For producing a drop-in bio jet fuel, one-step hydrotreatment, which includes deoxygenation, isomerization and cracking in one step, is essential to overcome the typical biofuel drawbacks due to high ...oxygen content, out of jet fuel range hydrocarbons, and low isomerization degree. Herein, Co- or/and Mo-supported Beta(25) zeolites with various Co/Mo ratios were prepared as transition metal-supported zeolite catalysts without the need for sulfidation of conventional transition metal catalysts. Based on the catalyst characterization, the Co/Mo ratio alters the metal phase with the appearance of CoMoO
4
and the altered Co metal phase strongly influences the acidic properties of Beta(25) by the formation of Lewis (L) acid sites with different strengths as Co
3
O
4
and CoMoO
4
for strong and weak L acid sites, respectively. The catalytic activities were investigated for hydrotreatment of methyl palmitate as a biofuel model compound of fatty acid methyl esters. Primarily, Co is required for deoxygenation and Mo suppresses overcracking to enhance the yield of jet fuel range hydrocarbons. The Co/Mo ratio plays an important role to improve the C
8
-C
16
selectivity by modifying the acidic properties to inhibit excessive cracking. Co
5
Mo
10
/Beta(25) achieved the best catalytic performance with the conversion of 94.2%, C
8
-C
16
selectivity of 89.7 wt%, and high isomer ratio of 83.8% in organic liquid product. This unique modification of acidic properties will find use in the design of optimal transition metal-supported zeolite catalysts for selective one-step hydrotreatment to produce bio jet fuel range hydrocarbons.
For selective one-step hydrotreatment to produce bio jet fuel range hydrocarbons, Co- or/and Mo-supported Beta(25) zeolites with various Co/Mo ratios were investigated in terms of changes in the metal phase and acidic properties.
The synthesis of shape-, facet-, and composition-controlled Pd-based nanocrystals and the study of their catalytic reaction mechanisms are significant to and challenging for the development of ...advanced catalysts applicable to direct liquid-fuel cells (DLFCs). In the present study, we prepared (100)-faceted β-PdH cubes and (111)-faceted β-PdH octahedra, which offered the opportunity to investigate the link between catalytic performance and the shape/facet/composition of nanocrystals. The β-PdH cubes and octahedra remarkably boosted catalytic activity and stability to the formic acid/methanol oxidation reaction (FAOR/MOR), due to the ligand effect originating from the interstitial alloying of β-PdH. Notably in this regard, β-PdH cubes exhibited the highest FAOR/MOR activity among Pd-based catalysts, owing to the relatively high CO tolerance on the Pd(100) facets. Our results confirm that simultaneous control of ligand and facet effects is an effective approach to the design of catalysts suitable for liquid fuel oxidation electrocatalysis.
We report a universal sulfide-assisted synthesis strategy to prepare dumbbell-like M–Ag heterodimers (M = Pd, Au, Pt). Sulfide ions can give fine control over the reaction kinetics of Ag precursors, ...resulting in the anisotropic overgrowth of Ag to realize the dumbbell-like heterodimers irrespective of the surface facets or components of the M domain. The M–Ag heterodimers were facilely transformed to M–Ag2S heterodimers via a simple sulfidation reaction. This study provides a versatile approach to realizing not only metal–metal heterodimers but also semiconductor–metal heterodimers and will pave the way for designing heteronanostructures with unprecedented morphologies and functions.
Display omitted
•High propylene selectivity and yield in the ETP reaction were obtained on P-SSZ-13.•ETP activity was enhanced by changes in acidity and reaction intermediates diffusion.•The optimum ...phosphorus content for the SSZ-13 in the ETP reaction was studied.•Alkyl naphthalene-based hydrocarbon pool mechanism of the ETP reaction was confirmed.
A highly selective means of producing propylene via the ethylene-to-propylene (ETP) reaction is required to manage the supply-demand balance of light olefins. To improve the catalytic activity of the ETP reaction, a phosphorus-modified SSZ-13 zeolite (P-SSZ-13) was prepared by introducing phosphorus to the SSZ-13 zeolite via a simple impregnation method. The P-SSZ-13 catalyst exhibited increased propylene selectivity and yield compared to the pristine catalyst. According to solid-state NMR spectroscopy and STEM-EDS observation, the phosphorus species were mainly located on the outer part of the crystal as a form of polyphosphate. To reveal the effect of the phosphorus loading on the enhancement of ETP reactivity, a series of surface-modified SSZ-13 catalysts were prepared and investigated. It was found that the polyphosphate species in the P-SSZ-13 catalyst not only weakened the acidity of the zeolite by bonding with the framework aluminum species but also reduced the diffusion out of the relatively large-sized hydrocarbon species by partially blocking the pore mouths. The change in the diffusivity of the hydrocarbons over the SSZ-13 catalysts also affected the ETP reactivity. The relationship between the amount of phosphorus and the ETP reactivity of the P-SSZ-13 catalysts could also be clearly demonstrated in terms of the change in both acidity and intracrystalline diffusivity. Moreover, 13C MAS NMR measurement with isotopic switch experiment confirmed the alkyl naphthalene-based hydrocarbon pool mechanism over the P-SSZ-13 for the ETP reaction.
Display omitted
•Effect of silica in silica-supported Ni/Al catalysts on deoxygenation was investigated for biojet fuel production.•Physicochemical properties of silica-supported Ni/Al were altered ...by pore structure, size, and acidity of silica support.•Deoxygenation of methyl palmitate was evaluated in correlation with controlled physicochemical properties of catalysts.•Ni/Al-SBA-15(40)at 60°C showed the best biojet fuel range hydrocarbon yield of 82.7% on deoxygenation of methyl palmitate.
To develop an efficient catalyst for deoxygenation (DO) as the first step in biojet fuel production with silica-supported Ni/Al catalysts, the effects of silica supports were investigated in terms of pore structure, acidity, and pore size. The pore structures of silica were covered from microporous SiO2 to mesoporous SBA-15, SBA-16, and KIT-6. Then, taking a simple tubular structure of Ni/Al-SBA-15 with the best biojet fuel yield, samples with various acidity and pore sizes were further prepared through manipulation of the amount of aluminum (Al)-incorporation and the temperature of hydrothermal synthesis, respectively. The DO reactivity of the prepared silica-supported Ni/Al catalysts was assessed with methyl palmitate as a model compound of biomass feedstock. Based on the altered physicochemical properties of not only the silica support but also the supported Ni, the relationship between the variation of silica supports and their DO catalytic properties was investigated. This work provides a better understanding of silica-supported Ni/Al catalysts and how to design selective catalysts for DO reaction to maximize the biojet fuel hydrocarbon yield.
