Pd Dimer Research Articles

Dilute Pd−Ni Alloy through Low‐temperature Pyrolysis for Enhanced Electrocatalytic Hydrogen Oxidation

AbstractDesigning highly active and cost‐effective electrocatalysts for the alkaline hydrogen oxidation reaction (HOR) is critical for advancing anion‐exchange membrane fuel cells (AEMFCs). While dilute metal alloys have demonstrated substantial potential in enhancing alkaline HOR performance, there has been limited exploration in terms of rational design, controllable synthesis, and mechanism study. Herein, we developed a series of dilute Pd−Ni alloys, denoted as x% Pd−Ni, based on a trace‐Pd decorated Ni‐based coordination polymer through a facile low‐temperature pyrolysis approach. The x% Pd−Ni alloys exhibit efficient electrocatalytic activity for HOR in alkaline media. Notably, the optimal 0.5 % Pd−Ni catalyst demonstrates high intrinsic activity with an exchange current density of 0.055 mA cm−2, surpassing that of many other alkaline HOR catalysts. The mechanism study reveals that the strong synergy between Pd single atoms (SAs)/Pd dimer and Ni substrate can modulate the binding strength of proton (H)/hydroxyl (OH), thereby significantly reducing the activation energy barrier of a decisive reaction step. This work offers new insights into designing advanced dilute metal or single‐atom‐alloys (SAAs) for alkaline HOR and potentially other energy conversion processes.

Dilute Pd-Ni Alloy through Low-temperature Pyrolysis for Enhanced Electrocatalytic Hydrogen Oxidation.

Designing highly active and cost-effective electrocatalysts for the alkaline hydrogen oxidation reaction (HOR) is critical for advancing anion-exchange membrane fuel cells (AEMFCs). While dilute metal alloys have demonstrated substantial potential in enhancing alkaline HOR performance, there has been limited exploration in terms of rational design, controllable synthesis, and mechanism study. Herein, we developed a series of dilute Pd-Ni alloys, denoted as x% Pd-Ni, based on a trace-Pd decorated Ni-based coordination polymer through a facile low-temperature pyrolysis approach. The x% Pd-Ni alloys exhibit efficient electrocatalytic activity for HOR in alkaline media. Notably, the optimal 0.5 % Pd-Ni catalyst demonstrates high intrinsic activity with an exchange current density of 0.055 mA cm-2, surpassing that of many other alkaline HOR catalysts. The mechanism study reveals that the strong synergy between Pd single atoms (SAs)/Pd dimer and Ni substrate can modulate the binding strength of proton (H)/hydroxyl (OH), thereby significantly reducing the activation energy barrier of a decisive reaction step. This work offers new insights into designing advanced dilute metal or single-atom-alloys (SAAs) for alkaline HOR and potentially other energy conversion processes.

Deconvoluting the Individual Effects of Nanoparticle Proximity and Size in Thermocatalysis.

Nanoparticle (NP) size and proximity are two physical descriptors applicable to practically all NP-supported catalysts. However, with conventional catalyst design, independent variation of these descriptors to investigate their individual effects on thermocatalysis remains challenging. Using a raspberry-colloid-templating approach, we synthesized a well-defined catalyst series comprising Pd12Au88 alloy NPs of three distinct sizes and at two different interparticle distances. We show that NP size and interparticle distance independently control activity and selectivity, respectively, in the hydrogenation of benzaldehyde to benzyl alcohol and toluene. Surface-sensitive spectroscopic analysis indicates that the surfaces of smaller NPs expose a greater fraction of reactive Pd dimers, compared to inactive Pd single atoms, thereby increasing intrinsic catalytic activity. Computational simulations reveal how a larger interparticle distance improves catalytic selectivity by diminishing the local benzyl alcohol concentration profile between NPs, thus suppressing its readsorption and consequently, undesired formation of toluene. Accordingly, benzyl alcohol yield is maximized using catalysts with smaller NPs separated by larger interparticle distances, overcoming activity-selectivity trade-offs. This work exemplifies the high suitability of the modular raspberry-colloid-templating method as a model catalyst platform to isolate individual descriptors and establish clear structure-property relationships, thereby bridging the materials gap between surface science and technical catalysts.

Understanding selective hydrogenation of phenylacetylene on PdAg single atom alloy: DFT insights on molecule size and surface ensemble effects

Single atom alloys (SAAs) have proven to be effective catalysts, offering customizable properties for diverse chemical processes. Various metal combinations are used in SAAs and Pd dispersed materials are frequently employed in catalyzing hydrogenation reactions. Herein, we explore the hydrogenation of phenylacetylene to styrene and ethylbenzene on PdAg SAA using density functional theory calculations. Our results show that while PdAg SAA does improve the activity of the host Ag towards hydrogenation, a dilute PdAg SAA surface with isolated Pd-atoms is not selective towards partial hydrogenation of phenylacetylene. Additionally, we investigate how the size of the reactant molecule, the size of the metal alloy ensemble, and the ligand effect impact the hydrogenation process. The SAA enhances the binding strengths of various organic adsorbates, although this effect diminishes as the adsorbate size increases. Our findings indicate the dilute PdAg exhibits selectivity towards hydrogenation of smaller molecules such acetylene due to its distinct adsorption geometry. The selective hydrogenation of phenylacetylene necessitates a surface Pd dimer ensemble. Our research highlights the importance of both reactant molecule size and surface configurations in SAA catalysts. This is particularly crucial when dealing with the adsorption of sizable organic molecules where the functional group can adopt different adsorption modes.

Synthesis and Crystal Structures of Rhomb-Shaped Dimeric Pd(II) Complexes with Arylethynyl-Substituted 2,2′-Bipyridine through CH⋯π Interactions in the Crystalline States

Two molecular structures of a complex C26H16Cl2N2Pd (1) with a benzene hemisolvate (1•0.5C6H6) and a complex C34H20Cl2N2Pd (2) revealed similar conformations: one side of the arylethynyl group is flat to the bipyridine plane while the other side of the arylethynyl group is highly twisted to the plane because rhomb-like dimer fragments are formed between respective two complexes through CH⋯π interactions. The Hirshfeld surface analysis indicates that the most important contributions for the crystal packing of 1 are from H⋯H (33.6%), C⋯H/H⋯C (28.3%), Cl⋯H/H⋯Cl (17.8%), and C⋯C (10.6%) interactions and those of 2 are from H⋯H (36.5%), C⋯H/H⋯C (26.0%), Cl⋯H/H⋯Cl (15.7%), and C⋯C (12.3%) interactions, indicating the remarkable CH⋯π and electron distribution of molecules by Cl ions. The benzene solvate molecule of 1•0.5C6H6 performs to fill the internal space instead of the naphthyl group. Detailed crystallographic and DFT studies were performed to understand the molecular structures and the corresponding supramolecular associations.

Reaction mechanism of decomposition of phosphine-bridged Pd(I)-Pd(I) dimers into Pd(II) monomers by molecular iodine

Mechanistic studies on decomposition of Pd(I)-Pd(I) dimers via Pd(II)-Pd(II) intermediates into Pd(II) monomers were performed by the reaction of [Pd2I2(dppm)2] (1) (dppm = bis(diphenylphosphino)methane) and [Pd2(p3)2](BF4)2 (2) (p3 = bis(diphenylphosphinoethyl)phenylphosphine) with molecular iodine, where dppm and p3 are bridging “short-bite” bidentate and “regular-bite” tridentate phosphine ligands, respectively. It was previously reported that the decomposition rate constant for the Pd(II)-Pd(II) intermediate of 1, [Pd2I4(dppm)2], to give the monomeric [PdI2(dppm)] was independent of the I2 concentration under the pseudo-first-order conditions with excess I2. On the other hand, we have found that the decomposition was retarded by an addition of I2, which reduces the nucleophilicity and donating ability of the iodido ligand by association of I2 to give the I-–I2 interaction. The activation parameters of the decomposition with a large negative ΔS‡ value similar to substitution reactions of usual four-coordinate squarer-planar palladium(II) complexes suggested the associative intramolecular substitution mechanism. The oxidation of 2 to the Pd(II)-Pd(II) intermediate, [Pd2I2(p3)2]2+, and its decomposition into the monomeric [PdI(p3)]+ by I2 were also investigated kinetically and both reactions were also retarded with an increase in the I2 concentration. From the activation parameters of the intramolecular decomposition, it was indicated that the associative character was reduced because of breakdown of the sterically restricted framework. Such different properties in solution of 1 and 2 were applied complementarily to Heck-type C–C coupling reaction and dehalogenation reaction of aryl halide, respectively.

Pd/Co3O4(111) Interface Formation

The formation of the metal–oxide interface in the Pd/Co3O4(111) model catalyst was investigated by means of density functional theory (DFT), synchrotron radiation photoelectron spectroscopy (SRPES), and scanning tunneling microscopy (STM). The electronic metal–support interaction results in a substantial charge transfer at the interface yielding atomically dispersed Pd2+ species and partially oxidized Pdδ+ aggregates coupled with a partial reduction of Co3O4(111). Atomically dispersed Pd2+ species at the fcc site on the Co3O4(111) surface were found to be the most energetically favorable configuration. In comparison to the dispersed Pd2+ species, the formation of Pd dimers, trimers, and tetramers was found to be less favorable. The analysis of the Bader charges revealed a substantial net positive charge on Pd atoms in dimers, trimers, and tetramers which is consistent with the formation of partially oxidized Pdδ+ aggregates detected by SRPES. The analysis of the charge distribution in Co3O4(111) revealed a partial reduction of Co3+ to Co2+ cations in the first and second Co layers. According to DFT, Pdδ+ aggregates are prone to oxidation to PdO in the presence of O2 and H2O. The partially oxidized Pdδ+ and Pd4Ox aggregates form 1 to 2 monolayer thick clusters which serve as nuclei for the growth of metallic Pd0 nanoparticles. At high Pd coverage, Pd nanoparticles coalesce resulting in the growth of two-dimensional islands that densely cover the Co3O4(111) substrate.

A density functional theory study of adsorption and dissociation of H2 molecule on small PdnAgm (n + m ≤ 4) metal clusters

The adsorption and dissociation of hydrogen molecule on small PdnAgm (n + m ≤ 4) clusters is studied employing density functional theory (DFT) calculations. The lowest energy structures of the PdnAgm clusters are initially presented. Based on the obtained structures, various geometries of H2 adsorption and dissociation with these clusters are examined. The cluster size and composition of the PdnAgm clusters are found to control the nature of the adsorption process. The results suggest that molecular adsorption is more favorable on the Pd atom and mixed clusters, while hydrogen dissociation is more favorable on the Pdn (n = 2–4) clusters. The Pd dimer and trimer are found to be the most reactive clusters for hydrogen adsorption, while single Ag atom is the least reactive one. The natural bond orbital (NBO) population analysis indicates that hydrogen atoms tend to draw electrons from the metal clusters in the dissociative form and donate electrons to the metal clusters in the molecular adsorption form. The density of states (DOS) of the PdnAgm trimers are also presented and discussed. The interaction and stabilities of cluster on the graphene support has also been performed.

Atom level revelation of the synergistic effect between Pd and Au atoms in PdAu nanoalloy catalyst for aerobic oxidation of 5-hydroxymethylfurfural

PdAu nanoalloy catalyst is widely used in liquid phase aerobic oxidation reactions. However, how Pd and Au atoms in PdAu nanoalloy catalyst worked synergistically and whether single atom isolated Pd or Au atoms are superior than their nanoparticle or nanoalloy counterparts in liquid phase are less investigated. Here, with nitrogen doped carbon as supporting material, Pd, Au dual single-atom-catalysts (SACs) and PdAu nanoalloy catalyst are prepared and compared in catalyzed aerobic oxidation of 5-hydroxymethylfurfural (HMF). The results show that Pd, Au dual SACs had much worse catalytic activity for the transformation of HMF into 2,5-furandicarboxylic acid (FDCA). Remarkably, PdAu nanoalloy catalyst gives excellent catalytic activity. DFT calculations demonstrate that the charge state of Pd sites can be varied obviously with the changing of surrounding coordination atoms. Pd dimer in Au (111) was shown to be the most favorable active sites. This work emphasizes the importance of coordination atoms type, number in catalyst synthesis on their catalytic activity and opens an avenue in future rational design of Pd and Au based SAC.

Mechanistic Studies for Pd(II)(O2) Reduction Generating Pd(0) and H2O: Formation of Pd(OH)2 as a Key Intermediate.

Molecular oxygen (O2) remains to be an ideal yet underutilized feedstock for the oxidative transformation of organic substrates and renewable energy systems such as fuel cells. Palladium (Pd) has shown particular promise in enabling these applications. The present study describes a Pd-mediated O2 reduction to water via C-H activation of 9,10-dihydroanthracene (DHA) by a Pd(II) η2-peroxo complex 1O2. The reaction yields stoichiometric anthracene and Pd(0) product 1 and is notable in two respects. First, plots of concentrations of the reaction participants over time have distinctly sigmoidal shapes, indicating that conversion accelerates over time and implying autocatalysis. Second, the reaction proceeds via a genuine monometallic Pd(II) dihydroxide 1(OH)2 directly observed to grow and decay as an intermediate. Confirming its role as an intermediate, the dihydroxide 1(OH)2 was found to mediate C-H oxidation of DHA on par in activity with the peroxo compound 1O2. Mechanistic studies with density functional theory (DFT) calculations suggested that both 1O2 and 1(OH)2 react with DHA by hydrogen atom transfer (HAT) and that autocatalysis in the 1O2 reaction results from oxidative addition of the initial Pd(II) complex 1O2 to the Pd(0) product 1. This reaction forms a transient bis(μ-oxo) Pd(II) dimer 1O21 that is more active in the HAT oxidation of DHA than the initial 1O2.

Salt-Enhanced Oxidative Addition of Iodobenzene to Pd: An Interplay Between Cation, Anion, and Pd–Pd Cooperative Effects

Halide salts facilitate the oxidative addition of organic halides to Pd(0). This phenomenon originates from a combination of anionic, cationic, and Pd-Pd cooperative effects. Exhaustive computational exploration at the density functional theory level of the complexes obtained from [Pd0(PPh3)2] and a salt (NMe4Cl or LiCl) showed that chlorides promote phosphine release, leading to a mixture of mononuclear and dinuclear Pd(0) complexes. Anionic Pd(0) dinuclear complexes exhibit a cooperativity between Pd(0) centers, which favors the oxidative addition of iodobenzene. The higher activity of Pd(0) dimers toward oxidative addition rationalizes the previously reported kinetic laws. In the presence of Li+, the oxidative addition to mononuclear [Pd0L(Li2Cl2)] is estimated barrierless. LiCl coordination polarizes Pd(0), enlarging both the electrophilicity and the nucleophilicity of the complex, which promotes both coordination of the substrate and the subsequent insertion into the C-I bond. These conclusions are paving the way to the rational use of the salt effects in catalysis for the activation of more challenging bonds.

Crystal Facet Structure Dependence and Promising Pd-Based Catalytic Materials for Resistance toward Deactivation and Catalytic Performance in Direct Oxidative Esterification.

Designing an effective Pd-based catalytic material with higher stability and catalytic performance for direct oxidative esterification is a great challenge. In this work, a systematic study on the activation mechanism of H2O on the different crystal facets of monometallic Pd, bimetallic Pd-Pb(Bi), and trimetallic Pd-Pb-Bi catalysts was first performed, which showed that the (111) crystal facet of Pd-Pb-Bi had stronger stability of resistance toward deactivation induced by H2O. Further, a detailed direct oxidative esterification mechanism on the screened crystal facet was investigated, where Pd-Pb-Bi catalytic materials showed higher stability and intrinsic catalytic performance for direct oxidation esterification, which was attributed to a dimer Pd-active unit and the synergistic effect of Pb and Bi compared to that of Pd-Pb(Bi) and Pd and also applied to other aldehydes with electron-donating groups producing corresponding esters. Meanwhile, the essential relationship between structures of Pd-based catalytic materials and catalytic performance for direct oxidation esterification was obtained. This work opens up a new simultaneous path for improving the stability of resistance toward deactivation and catalytic performance for direct oxidative esterification of Pd-based catalytic materials, which can be realized by regulating the surface-active unit with dimer Pd adsorbed more O-preadsorbed using Pb and Bi promoters.

A density functional theory study on the catalytic performance of metal (Ni, Pd) single atom, dimer and trimer for H2 dissociation

• H 2 dissociation on transition metal (TM = Ni, Pd) single atom, dimer and trimer doped on Au substrate have been studied. • The H 2 dissociation in the form of Ni, Pd trimer exhibited the best catalytic performance. • The H 2 dissociation process follow the BEP relation on different structural units. Elucidating the effect of different structural units in the catalyst on catalytic performance was very important for the development of the excellent heterogeneous catalyst. This work used density functional theory (DFT) approach to investigate H 2 dissociation over transition metal (TM = Ni, Pd) single atom, dimer and trimer doped on Au substrate. The influence of different structural units toward the catalytic performance was elucidated. The results showed that the catalytic performance of Ni, Pd trimer was stronger than those of Ni, Pd single atom and dimer. Therefore, it was proposed that for the H 2 dissociation, the structural units in the form of Ni, Pd trimer exhibited the best catalytic performance. It was also obtained that the H 2 dissociation process followed the BEP relation on different structural units. This work provides insights about structural units for the reasonable design of the excellent heterogeneous catalysts toward dissociation reactions.

Enhanced methane-sensing performances of Pd (monomer or dimer) decorated or doped γ-Graphyne: A DFT insight

In the present article, the interaction of CH4 with Pd(monomer)-, Pd(dimer)-decorated or Pd-doped γ-Graphyne (γ-GYN), are explored by the dispersion-corrected form of density functional theory (DFT-D2). The most stable geometry, adsorption energy, and electronic properties including energy band structure, the density of electronic states, and negative charge transfer are presented. The obtained results present the adsorption or absorption process in Pd(monomer)-, Pd(dimer)-decorated or Pd-doped γ-GYN is a chemical type and exothermic. Because of Pd adsorption/absorption on γ‒GYN, the out-of-plane wrinkle formed on the γ-GYN plane that leads to structural asymmetry. Due to the charge transfer from Palladium atom(s) to γ‒GYN, all three compounds have become n-type semiconductor with smaller bandgaps. The CH4 adsorption onto Pd(dimer)-decorated γ-GYN, in comparison to the other two compounds, provides a greater amount of energy (about -0.554 eV), Pd(dimer)-decorated γ-GYN more efficient for a thermo-based CH4 sensor. Also, the out-of-plane wrinkles of the Pd(dimer)-decorated γ‒GYN is increased due to methane adsorption and the total negative charge transferred from methane to Pd(dimer)- decorated γ‒GYN. Owing to the significant change in the bandgap of Pd(dimer)-decorated γ‒GYN due to the adsorption of CH4, the Pd(dimer)-decorated γ‒GYN can be used in resistivity-based CH4 sensors as well.

A Supported Pd2Dual‐Atom Site Catalyst for Efficient Electrochemical CO2Reduction

AbstractDual‐atom site catalysts (DACs) have emerged as a new frontier in heterogeneous catalysis because the synergistic effect between adjacent metal atoms can promote their catalytic activity while maintaining the advantages of single‐atom site catalysts (SACs), like 100 % atomic utilization efficiency and excellent selectivity. Herein, a supported Pd2DAC was synthesized and used for electrochemical CO2reduction reaction (CO2RR) for the first time. The as‐obtained Pd2DAC exhibited superior CO2RR catalytic performance with 98.2 % CO faradic efficiency at −0.85 V vs. RHE, far exceeding that of Pd1SAC, and coupled with long‐term stability. The density functional theory (DFT) calculations revealed that the intrinsic reason for the superior activity of Pd2DAC toward CO2RR was the electron transfer between Pd atoms at the dimeric Pd sites. Thus, Pd2DAC possessed moderate adsorption strength of CO*, which was beneficial for CO production in CO2RR.

A Supported Pd2Dual‐Atom Site Catalyst for Efficient Electrochemical CO2Reduction

AbstractDual‐atom site catalysts (DACs) have emerged as a new frontier in heterogeneous catalysis because the synergistic effect between adjacent metal atoms can promote their catalytic activity while maintaining the advantages of single‐atom site catalysts (SACs), like 100 % atomic utilization efficiency and excellent selectivity. Herein, a supported Pd2DAC was synthesized and used for electrochemical CO2reduction reaction (CO2RR) for the first time. The as‐obtained Pd2DAC exhibited superior CO2RR catalytic performance with 98.2 % CO faradic efficiency at −0.85 V vs. RHE, far exceeding that of Pd1SAC, and coupled with long‐term stability. The density functional theory (DFT) calculations revealed that the intrinsic reason for the superior activity of Pd2DAC toward CO2RR was the electron transfer between Pd atoms at the dimeric Pd sites. Thus, Pd2DAC possessed moderate adsorption strength of CO*, which was beneficial for CO production in CO2RR.

CeO2 supported Pd dimers boosting CO2 hydrogenation to ethanol

Hydrogenation of CO2 into valuable chemicals is of great significance but very challenging due to its chemical inertness and selectivity controlling. Here, we report that CeO2 supported Pd dimers can efficiently convert CO2 to ethanol with significantly higher activity and selectivity compared to those in literatures, which gives a selectivity of 99.2 % to ethanol with a space-time yield of 45.6 gethanol gPd−1 h−1. The Pd dimers possessing unique Pd2O4 configuration and high homogeneity enables to directly dissociate CO2 to CO, trigger CC coupling but appropriately inhibit further C2+ coupling, which benefits to selectively form ethanol. The Pd2O4 configuration can strongly bind CO on Pd2/CeO2, which prevents CO desorption and promotes the coupling between CO and CH3 intermediates to form the precursor of ethanol. The strategy of constructing atom-precision active sites reported in this work opens new avenues to develop highly selective catalysts for CO2/CO hydrogenation reactions.

Selective hydrogenation of acetylene on Cu-Pd intermetallic compounds and Pd atoms substituted Cu(111) surfaces.

The selective hydrogenation of acetylene was studied on the ordered Cu-Pd intermetallic compounds (L10-type CuPd, L12-type Cu3Pd, and L12-type CuPd3) and Pd-modified Cu(111) surfaces through first-principles calculations. The catalytic selectivity and activity of Cu-Pd alloy catalysts are closely related to the crystal structure and composition of Cu-Pd intermetallic compounds and the size of Pd ensembles of Cu-based dilute alloy surface for the selective hydrogenation of acetylene to ethylene. Significantly, we found that the ordered Cu-Pd alloy surface containing isolated Pd atoms (i.e., L12-type Cu3Pd(111) surface) is highly efficient for the selective hydrogenation reaction of C2H2 + H2→ C2H4. The contiguous Pd atom ensembles (Pd dimer and trimer) are catalytically active towards C2H2 + H → C2H3 and C2H3 + H → C2H4 reactions than the single Pd atom on a Pd-decorated Cu(111) surface. However, the small Pd ensembles on Cu(111) present a low chemical activity for H2 dissociation compared with the ordered Cu-Pd intermetallic compounds. Our theoretical results provide a strategy of crystal phase and composition control for enhancing the selectivity and activity of Cu-Pd catalysts towards acetylene selective hydrogenation.

Germylation of Arenes via Pd(I) Dimer Enabled Sulfonium Salt Functionalization.

While aryl germanes have recently found usage as coupling partners in powerful catalytic applications, the synthetic access to this promising functionality is currently limited. This report details the straightforward synthesis of functionalized aryl triethylgermanes via formal C-H functionalization. Building on the concept of directing-group-free and site-selective C-H functionalization of arenes to thianthrenium salt intermediates, we showcase their efficient couplings with triethylgermane (Et3Ge-H) at room temperature, which was enabled by the air- and moisture-stable Pd(I) dimer, [Pd(μ-I)(PtBu3)]2. The method tolerates numerous functional groups, including valuable (pseudo)halides.

Probe into the effects of surface composition and ensemble effect of active sites on the catalytic performance of C2H2 semi-hydrogenation over the Pd-Ag bimetallic catalysts

Aiming at identifying the effects of surface composition and ensemble effect for the Pd-Ag bimetallic catalysts on the catalytic performance of C2H2 semi-hydrogenation, the selectivity and activity of C2H4 formation over the Ag-doped Pd, Pd-doped Ag catalysts and PdAg intermetallic compounds with different surface composition and ensemble effect are examined utilizing density functional theory calculations. The results indicated that the Pd-Ag bimetallic catalysts without Pd atoms, with isolated Pd atom or Pd dimer on the surface show poor C2H4 selectivity; while those with surface Pd trimer exhibit better C2H4 selectivity, especially, the Pd-doped Ag catalysts present better catalytic performance and low cost. This study not only helps scientists understand reaction theories associated with the experiment of C2H2 semi-hydrogenation over the Pd-Ag bimetallic catalysts, but also helps them advance the design of high-performance, cost-effective and structure-tunable Pd-Ag bimetallic catalysts for C2H2 removal from C2H4, which has broad impact on catalyst development.