PtZn Alloy Research Articles

Sustainable catalytic pathways for biofuel precursors: quantitative conversion of glucose to gluconic acid using Pt-Zn biochar catalyst

Achieving quantitative conversion of biomass-derived feedstocks under ambient environmental conditions (20°C, atmospheric air, 0.1 MPa) is a critical milestone for sustainability in chemical processes. Herein, the quantitative conversion of glucose to gluconic acid was accomplished under ambient environmental conditions without any additives using a Pt-Zn intermetallic nanoparticle-supported biochar catalyst prepared from raw rice straw (Pt-Zn/strawC) via a straightforward one-pot solvothermal reaction with ethylene glycol solvent. Spectroscopic analyses verified the formation of the Pt-Zn intermetallic alloy and confirmed strong electronic metal-support interactions. The Pt-Zn/strawC catalyst (Pt:Zn molar ratio of 1:6) was highly selective for the conversion of glucose to gluconic acid, whereas yields as high as 99.9% (98.9% gluconic acid, 1.0% glucaric acid) were reached at 20 oC under base-free and additive-free conditions. Isotope measurements and density functional theory revealed synergistic interactions in the Pt-Zn alloy, wherein the alloy tended to absorb glucose and active O2 into superoxide radical (O2·). This work demonstrates a chemocatalytic method that is practical for environmental conditions and provides a new avenue for sustainable conversion of lignocellulosic biomass to chemical products.

Complex-assisted PtZn alloy formation for propane dehydrogenation

Complex-assisted PtZn alloy formation for propane dehydrogenation

Interface Engineering of PtZn Alloy and Nb2O5 for Promoting Ammonia Oxidation Reaction and Hydrogen Evolution Reaction.

Ammonia electrolysis is a promising technology to obtain green hydrogen with zero-carbon emission, in which ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) occur at the anode and cathode, respectively. However, the lack of efficient catalysts hinders its practical application. Herein, PtZn alloy is combined with Nb2O5 to construct a bifunctional heterostructure catalyst (PtZn-Nb2O5/C). The optimal sample with Nb2O5 content of 7.05 wt % demonstrates the best performance with a peak current density of 304.1 mA mg-1Pt for AOR, and it is only reduced by 17.0% after 4000 cycles of durability tests. For HER, it has a low overpotential of 34 mV at -10 mA cm-2 under the alkaline condition. This can be ascribed to the interfacial interaction between the PtZn alloy and Nb2O5, which adjusts the adsorption behavior of OHad to concurrently promote AOR and HER activity. This work thus proposes a viable strategy to design an efficient bifunctional catalyst for hydrogen generation from ammonia electrolysis.

Demetallation and reduction induced ultra-dispersed PtZn alloy confined in zeolite for propane dehydrogenation

Developing efficient bimetallic Pt-based catalyst is highly desired for propane dehydrogenation (PDH) process. Typical co-impregnation method often results in inhomogeneous distributions of metal species on supports. Herein, we reported a facile method to support PtZn bimetal alloy nanoparticles onto Beta zeolite, mainly existing as highly dispersed Pt1Zn1 alloy species. Zn@Beta was first synthesized by hydrothermal method with the aid of ethylenediamine (EDA), leading to the introduction of Zn atoms into zeolite lattice. An impregnation process was subsequently employed to support Pt species. During this process, skeleton Zn atoms migrated out of the framework and were then reduced together with Pt in flowing H2, leading to the formation of PtZn alloy with mainly Pt1Zn1 structures. Cs-corrected high-angle annular dark-field scanning transmission election microscope and X-ray absorption fine structure analyses revealed that this method was more conducive to the formation of PtZn alloy compared with the co-impregnation method. The obtained catalyst of 0.3Pt1Zn@Beta exhibited initial propane conversion of 36.8% and propylene selectivity of 99.3% combined with low deactivation rate (0.004 h–1) over 24 h with propane WHSV of 4.7 h–1 at 550 °C. The catalyst also exhibited good PDH performance in a long-term reaction (180 h) and robustness during regeneration reactions by simply flushing hydrogen.

PtZn alloy nanoparticles with enhanced activity and stability synthesized by a simplified polyol process for electro-oxidation of ammonia

This work reports the synthesis of bimetallic alloy PtZn nanoparticles (NPs) using one-pot glycerol-assisted polyol technique in the presence of Pt(acac)2 and Zn(acac)2 for the electrocatalysis of ammonia fuels. Three different compositions of PtnZn/C (n = 1, 2, 3) electrocatalysts are synthesized in which Pt-content is varied with a fixed Zn-content. PtZn NPs are characterized by X-ray diffractometry (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM) for their crystal structures, elemental compositions, and morphological studies. The high-angle annular dark field-scanning TEM-EDS elemental mapping has confirmed that NPs are alloyed with Pt and Zn elements. The electronic structures of alloy NPs are further analyzed by X-ray photoelectron spectroscopy and found a ligand effect resulting in the downshift of d-band center. The incorporation of Zn in NPs decreases the oxygenated species on Pt surface proven by cyclic voltammetry. PtZn NPs are employed for the electrocatalysis of ammonia fuels, namely NH4OH, NH4Cl, NH4NO3, and (NH4)2SO4, where PtZn/C system has shown better electrocatalytic activity than Pt/C. Stability tests are conducted using chronoamperometry for all electrocatalysts of which PtZn/C electrocatalysts have been observed to have good sustainability in the electrochemical environment compared to Pt/C.

PtZn nanoparticles supported on porous nitrogen-doped carbon nanofibers as highly stable electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction (ORR) electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles (NPs) on a porous carbon support with large surface area. However, such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores, in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support. Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers. Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential (E1/2) of 0.911 ​V versus reversible hydrogen electrode (vs. RHE) and enhanced durability with only decreasing 11 ​mV after 30,000 potential cycles, compared to a more significant drop of 24 ​mV in E1/2 of Pt/C catalysts (after 10,000 potential cycling). Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support, inhibiting the migration and aggregation of NPs during the ORR.

Selectively oxygen reduction reaction and strongly suppressed CO poisoning on PtZn nanoalloys decorated on N-doped carbon sphere

The development of a high-performance oxygen reduction reaction (ORR) catalyst with a low Pt content, high activity, and long-term durability is crucial as it can become a core item in the fuel cell market. In this study, the amount of Pt used in the catalyst is reduced by more than three-fold compared with commercial catalysts. Concurrently, a PtZn alloy, which does not use expensive transition metals, is introduced as an active species. Nitrogen-doped carbon sphere (CS), which serves as an electron sink, is used as a support; it acts as a Lewis base site and facilitates H+ adsorption during the ORR. The analytical results reveal that the introduction of Zn is significantly more favorable for the ORR compared with N-doping. O2-pulse temperature-programmed desorption (TPD) reveals that most of the O2 molecules are adsorbed on Zn, and CO-pulse TPD demonstrates that Zn suppresses CO poisoning in the PtZn alloys. The mass and specific activities of the Pt1Zn1/N-CS electrode at 0.9 V are 5.94 A mg–1 and 0.79 mA cm–2, respectively, and a rotational frequency of 2.5 e-site–1 s–1 is achieved. The electrochemical performance remains unchanged even after 5000 cycles. The ORR on the Pt1Zn1/N-CS electrode does not occur randomly on Pt and Zn; Pt and Zn selectively attract and reduce *O, *OH, or *OOH which generated as intermediates.

Highly efficient propane dehydrogenation promoted by reverse water–gas shift reaction on Pt-Zn alloy surfaces

CO2-assisted propane dehydrogenation has been developed in propylene production technology to deal with thermodynamic equilibrium limitations. However, the rational design of catalysts is a crucial challenge in achieving high catalytic performances. Herein, we report the successful fabrication of highly dispersed PtZn alloy on hierarchical zeolites for CO2-assisted propane dehydrogenation through the reverse water–gas shift reaction (RWGS). Compared with monometallic Pt, the synergistic effect of PtZn plays a crucial role in both direct propane dehydrogenation and RWGS, resulting in an outstanding catalytic performance with a high turnover frequency (TOF) of 1.82 × 104h−1. From the catalytic point of view, Pt-Zn alloy surfaces facilitate the equilibrium shift in propane conversion by consuming produced H2 through RWGS with weakening CO-metal surface interaction revealed by operando studies and DFT calculations. These findings illustrate the conceptual design of alloy catalysts and allow insights into the mechanistic details of CO2-assisted alkane dehydrogenation.

Exceptional Selectivity to Olefins in the Deoxygenation of Fatty Acids over an Intermetallic Platinum–Zinc Alloy

AbstractDirect deoxygenation of long‐chain fatty acids can produce both saturated alkanes (CnH2n+2) and unsaturated olefins (CnH2n). However, the selectivity for the production of olefins via the decarbonylation route is relatively low because of the more favorable decarboxylation pathway. We present an atomically ordered intermetallic PtZn alloy on carbon catalyst (PtZn/C) with a record‐high total selectivity (97 %) for undecane (C11H24) and undecene (C11H22) in the deoxygenation of lauric acid (C12H24O2). Interestingly, the selectivity for C11H22 is as high as 67.0 % on PtZn/C, which is significantly higher than that of 27.5 % obtained on the Pt/C counterpart under the same reaction conditions. Characterization and theoretical calculation results reveal that the intermetallic PtZn alloy not only inhibits the decarboxylation route by increasing the energy barrier of −COO* cleavage, but also facilitates the decarbonylation route by decreasing CO desorption energy, and therefore the major product is switched from alkanes to olefins.

Exceptional Selectivity to Olefins in the Deoxygenation of Fatty Acids over an Intermetallic Platinum-Zinc Alloy.

Direct deoxygenation of long-chain fatty acids can produce both saturated alkanes (Cn H2n+2 ) and unsaturated olefins (Cn H2n ). However, the selectivity for the production of olefins via the decarbonylation route is relatively low because of the more favorable decarboxylation pathway. We present an atomically ordered intermetallic PtZn alloy on carbon catalyst (PtZn/C) with a record-high total selectivity (97 %) for undecane (C11 H24 ) and undecene (C11 H22 ) in the deoxygenation of lauric acid (C12 H24 O2 ). Interestingly, the selectivity for C11 H22 is as high as 67.0 % on PtZn/C, which is significantly higher than that of 27.5 % obtained on the Pt/C counterpart under the same reaction conditions. Characterization and theoretical calculation results reveal that the intermetallic PtZn alloy not only inhibits the decarboxylation route by increasing the energy barrier of -COO* cleavage, but also facilitates the decarbonylation route by decreasing CO desorption energy, and therefore the major product is switched from alkanes to olefins.

Boosting propane dehydroaromatization by confining PtZn alloy nanoparticles within H-ZSM-5 crystals

A Pt–Zn@H-ZSM-5 catalyst with Pt–Zn alloy nanoparticles confined in H-ZSM-5 crystals exhibits a significantly improved performance in the propane dehydroaromatization reaction.

In situ topologically induced PtZn alloy @ ZnTiOx and the synergistic effect on glycerol oxidation

In this work, we prepared a PtZn@ZnTiOx/ZnTiO3 catalyst by using PtCl62−/ZnTi layered-double-hydroxide (LDH) as precursor and revealed the in-situ topological process through modulating the reduction conditions. The Cs-corrected HAADF-STEM and XAFS verified the formation of PtZn alloy structure and also indicated the generated ZnTiOx coating layer exhibited the feature of low-coordination. In glycerol oxidation, the obtained catalyst possessed obvious advantages in intrinsic activity and glyceric acid selectivity compared with bare PtZn alloy and Pt catalysts. Confirmed by O2-TPD and XPS analysis, the alloy effect with Zn and abundant oxygen vacancies in ZnTiOx layer could enhance the glycerol oxidation activity by promoting the oxygen activation. A series of FTIR analysis revealed that the enhanced selectivity was assigned to the low-coordination ZnTiOx at the interface, optimizing the intermediate glyceraldehyde adsorption form. Additionally, an excellent reusability with 76.2 % glycerol conversion and 61.3 % glyceric acid selectivity after 5 cycles was exhibited over PtZn@ZnTiOx/ZnTiO3 catalyst.

PtZn Intermetallic Compound Nanoparticles in Mesoporous Zeolite Exhibiting High Catalyst Durability for Propane Dehydrogenation

A PtZn alloy nanoparticle catalyst for propane dehydrogenation was synthesized by simple coimpregnation of Pt(NH3)4(NO3)2 with Zn(NO3)2 onto a mesoporous material, which was built with siliceous MF...

Hierarchical confinement of PtZn alloy nanoparticles and single-dispersed Zn atoms on COF@MOF-derived carbon towards efficient oxygen reduction reaction

A COF@MOF-derived catalyst has been synthesized for the first time. Pt–Zn intermetallic nanoparticles and atomic Zn distributions were supported on hollow carbons. The catalyst displayed high activity towards the oxygen reduction reaction.

A mass-producible integrative structure Pt alloy oxygen reduction catalyst synthesized with atomically dispersive metal-organic framework precursors

Oxygen reduction reaction (ORR) catalyst is one of the most significant influential factors for the application of proton exchange membrane fuel cells. This work introduces a mass-producible high-performance PtZn alloy integrative structure ORR catalyst, synthesized with the atomically dispersive metal-organic framework precursors. This PtZn catalyst displays excellent catalytic activity with the onset reduction potential of 1.0 VRHE@ 0.16 mA cm−2 (Reversible hydrogen electrode; RHE) and the half-wave potential of 0.934 VRHE for the ORR catalysis. The calculated specific activity and mass activity at 0.9 V are 9.44 A m−2 and 544 A gPt−1, respectively, which are 5.62 times and 5.77 times as high as the commercial Pt/C. The mass activity is remarkably higher than the target put forward by the Department of Energy (DOE; 440 A gPt−1). Furthermore, this PtZn catalyst also exhibits outstanding stability after the 10,000 potential cyclic degeneration test. The ORR current is much higher than Pt/C in the whole potential range not only before but also after the 10,000 potential cycles with identical Pt loading. This catalyst has a multifarious active-site catalytic structure with PtZn alloyed particles and atomically dispersive metal-N active sites on the N-doped graphited carbon matrix, exhibiting appealing ORR catalytic activity and sound stability for the application and scalable production of fuel cell catalysts.

Erratum to: Highly active zigzag-like Pt-Zn alloy nanowires with high-index facets for alcohol electrooxidation

Erratum to: Highly active zigzag-like Pt-Zn alloy nanowires with high-index facets for alcohol electrooxidation

Hydrogen Diffusion Guided Design of Pt‐Based Alloys for Inhibition of Butadiene Over‐Hydrogenation

Alloying Pt with other metals is an effective strategy to tune its performance towards selective hydrogenation reactions. Herein, we have demonstrated a process to screen Pt-based alloys for inhibition of butadiene over-hydrogenation with a model comprising isolated single atoms (ISA) embedded into Pt(111). DFT calculations reveal that the diffusion energy barrier of H co-adsorbed with 1-butene is a key parameter for the screening. The output from the ISA model was validated by testing several typical Pt-based alloys towards butadiene hydrogenation. Furthermore, an unexpected higher selectivity to cis-2-butene compared to the trans isomer and 1-butene over the PtZn alloy was explored employing the ISA model.

Role of Ultrathin Carbon Shell in Enhancing the Performance of PtZn Intermetallic Nanoparticles as an Anode Electrocatalyst for Direct Formic Acid Fuel Cells

AbstractIntroducing a carbon shell to Pt‐based intermetallic nanoparticles (iNPs) is an effective approach to prepare structurally ordered electrocatalysts for fuel cell applications. However, it remains a huge challenge to synthesize small‐sized Pt‐based iNPs with a concisely controlled carbon shell based on fully understanding the role of the carbon shell in the electrocatalytic performance. Herein, we report the preparation of ultrathin carbon shell (UCS)‐coated, small‐sized PtZn iNPs, which are obtained by using the simple heat treatment of polypyrrole‐coated PtZn/C (PPy−PtZn/C), which can produce a carbon shell in situ and simultaneously transfer a disordered PtZn alloy into ordered intermetallic PtZn. Interestingly, the thickness of the carbon shell can be well‐controlled by tuning the polymerization time of pyrrole (Py). The obtained PtZn iNPs (an average diameter of ca. 4 nm) coated with UCS (ca. 0.5 nm thickness) shows the best electrocatalytic performance toward the formic acid oxidation reaction. Moreover, the UCS−PtZn iNPs offers remarkable long‐term stability as an anode electrocatalyst in a constructed direct formic acid fuel cell. The results demonstrate that the UCS formed in situ only acts as a physicochemical protecting shell with high permeability for the reactants, but it does not block the catalytic reaction sites of iNPs.

Highly active zigzag-like Pt-Zn alloy nanowires with high-index facets for alcohol electrooxidation

The development of highly efficient Pt-based alloy nanocatalysts is important but remains challenging for fuel cells commercialization. Here, a new class of zigzag-like platinum-zinc (Pt-Zn) alloy nanowires (NWs) with rough surface and controllable composition is reported. The merits of anisotropic one-dimensional nanostructure, stable high-index facets and coordinatively unsaturated Pt sites endow the composition-optimal Pt94Zn6 NWs with a mass activity of 7.2 and 6.2 times higher than that of commercial Pt black catalysts toward methanol/ethanol oxidation, respectively. Alloying-induced d-band electron modulation and lattice strain effects weaken the adsorption strength of poisoning species, which originally enhances the catalytic activity of Pt-Zn NWs. This study provides a new perspective of Pt-Zn electrocatalysts with intrinsic mechanism for enhanced catalytic performance.

Atomically Precise Strategy to a PtZn Alloy Nanocluster Catalyst for the Deep Dehydrogenation of n-Butane to 1,3-Butadiene

The development of on-purpose 1,3-butadiene (BDE) technologies remains an active area in catalysis research due to the importance of BDE in industrial polymer production. Here, we report on a non-oxidative dehydrogenation catalyst for the production of BDE prepared by atomically precise installation of platinum sites on a Zn-modified SiO2 sup-port via Atomic Layer Deposition (ALD). In situ reduction x-ray adsorption spectroscopy (XAS) experiments, X-ray photoelectron spectroscopy (XPS), CO chemisorption, and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging of activated PtZn/SiO2 material, revealed the formation of a uniform, well-distributed sub-nano to nanometer PtZn (1.2 ± 0.3 nm) alloy as the active catalytic species.