Weak Acetylene Adsorption Terminated Carbon–Carbon Coupling Kinetics on Silver Electrocatalysts

Abstract

Open AccessCCS ChemistryRESEARCH ARTICLES11 Mar 2022Weak Acetylene Adsorption Terminated Carbon–Carbon Coupling Kinetics on Silver Electrocatalysts Rui Bai†, Jinjin Li†, Jin Lin, Zhenpeng Liu, Chen Yan, Lei Zhang and Jian Zhang Rui Bai† Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710129 , Jinjin Li† Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710129 , Jin Lin Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710129 , Zhenpeng Liu Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710129 , Chen Yan Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710129 , Lei Zhang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710129 and Jian Zhang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] Key Laboratory of Special Functional and Smart Polymer Materials of Ministry of Industry and Information Technology, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710129 State Key Laboratory of Solidification Processing and School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072 https://doi.org/10.31635/ccschem.022.202101750 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Owing to serious poison of downstream olefin polymerization catalysts from acetylene impurities, selective reduction of acetylene to ethylene is a pivotal process in petrochemical industry. However, during thermocatalytic and electrocatalytic acetylene semihydrogenation, acetylene C–C coupling inevitably occurs on current catalysts. The resultant oligomeric species (particularly long-chain hydrocarbons) block active sites and mass transportation, and eventually decrease catalytic activity and stability. In this work, we report Ag nanowires (NWs) as high-performance electrocatalysts for acetylene semihydrogenation, where the C–C coupling is unprecedentedly suppressed by weakening acetylene adsorption. In pure acetylene, 1,3-butadiene Faradaic efficiency (FE) of Ag NWs is only 2.1%, which is far lower than 41.2% for Cu nanoparticles at −0.2 V versus reversible hydrsogen electrode. Ethylene partial current density of Ag NWs reaches 217 mA/cm2 at 0.85 V, which is considerably higher than those for state-of-the-art Cu-based electrocatalysts. Markedly, no 1,3-butadiene is produced on Ag NWs in a large two-electrode flow cell fed with crude ethylene containing 1 vol % acetylene, presenting thorough termination of acetylene C–C coupling. In situ electrochemical Raman spectroscopy and theoretical investigations reveal that weak acetylene adsorption on Ag surfaces is intrinsically responsible for prohibiting their oligomerization. This work will spark the rapid development of high-performance and stable electrocatalysts for reducing alkynes to olefins. Download figure Download PowerPoint Introduction As a significant chemical feedstock, ethylene is widely employed for the manufacture of polyethylene, ethylene propylene rubber, polyvinyl chloride, and so on.1,2 However, the ethylene stream produced through steam cracking or thermal pyrolysis of hydrocarbons unavoidably contains small amounts of acetylene impurities (∼0.5–3 vol %), which will poison the downstream olefin polymerization Ziegler–Natta catalysts, eventually resulting in inferior polymer products.3–5 Therefore, for industrial applications, it is principally required that acetylene content must be <5 ppm in polymer-grade ethylene feedstock. To remove acetylene impurities from crude ethylene streams, thermocatalytic hydrogenation of acetylene using Pd-based catalysts is currently utilized in industry. Nonetheless, there are still several major long-term challenges for thermocatalytic acetylene hydrogenation6–9: (1) relatively high hydrogenation temperature (100–250 °C); (2) utilization of excessive hydrogen gas; (3) competitive over hydrogenation toward ethane; and (4) serious oligomerization that forms coke. Therefore, our and Zhang's groups simultaneously developed an electrocatalytic acetylene semihydrogenation approach for selectively reducing acetylene impurities to ethylene in an ethylene-rich stream under ambient conditions.10–12 Nevertheless, during this electrochemical process (particularly at low current densities), the C–C coupling between reaction intermediates of acetylene unavoidably proceeds on Cu-based electrocatalysts, generating oligomeric compounds including 1,3-butadiene and long-chain hydrocarbons generally called "green oil."13–15 These accumulated long-chain oligomeric species irreversibly block surface active sites and mass transfer, thus seriously deactivating the Cu-based electrocatalysts.16–18 In principal, 1,3-butadiene is commonly regarded as the precursor of long-chain hydrocarbons.19,20 Therefore, the exploration of novel electrocatalysts for effectively suppressing C–C coupling kinetics is urgently desirable for reliably achieving high acetylene conversion and ethylene selectivity over a long-term operation. In this work, we fabricate Ag nanowires (Ag NWs) as electrocatalysts for catalytic acetylene semihydrogenation, where the C–C coupling kinetics of acetylene is thoroughly suppressed. In comparison with 41.2% for Cu nanoparticles (Cu NPs), the Faradaic efficiency of 1,3-butadiene on Ag NWs dramatically decreases to 2.1% at −0.2 V versus the reversible hydrogen electrode (RHE) under pure acetylene stream. Moreover, Ag NWs deliver an ethylene partial current density of up to 217 mA/cm2 at −0.85 V. Such electrocatalytic activity and selectivity of Ag NWs are remarkably superior to previously reported Cu-based electrocatalysts. As a result, Ag NWs in a large two-electrode flow cell (25 cm2) fed with crude ethylene stream present an acetylene conversion of 99.8% and an ethylene specific selectivity of ∼99% at 2.2 mA/cm2. Importantly, no 1,3-butadiene is concomitantly formed on Ag NWs, suggesting that the C–C coupling pathway of acetylene is terminated on Ag surfaces. Combining in situ electrochemical Raman spectroscopy and theoretical investigations, weak acetylene adsorption on Ag surfaces is revealed to be intrinsically responsible for obstructing the acetylene oligomerization pathway. Experimental Methods Preparation of the Ag NWs and Ag NPs Typically, 3.5 g FeCl3·6H2O was mixed sufficiently with 25 mL ethylene glycol solution containing 200 mg polyvinylpyrrolidone (PVP) (Mw = 4400–5400) and 250 mg AgNO3. After heating at 130 °C for 5 h, the resulting Ag NWs were achieved through water washing and centrifugation. Finally, Ag NWs aqueous solution was collected as a stock solution (15 mg/mL determined by inductively coupled plasma mass spectrometry). The Ag NPs were synthesized by a Au seed growth method. 5 mL PVP aqueous solution (5 wt %, Mw = 4400–5400) and 0.25 mL HAuCl4 (10 mM) were added into 5 mL H2O. Then, 1.2 mL NaBH4 (0.1 M) aqueous solution was quickly injected into the above solution under vigorous stirring. Then, a Au seed solution was obtained after 6 h aging. Subsequently, 25 μL Au seed solution was mixed with 50 mL H2O, 15 mL PVP aqueous solution (5 wt %, Mw = 4400–5400), 15 mL acetonitrile, and 1.5 mL ascorbic acid (0.1 M). Eventually, 1 mL AgNO3 (0.1 M) was added into the above solution under vigorous stirring for 30 min. The Ag NPs were achieved after water washing and centrifugation. Electrocatalytic measurements A CH Instrument 760E Potentiostat was employed to perform all electrochemical measurements at room temperature. Three-electrode flow-cells, saturated Hg/HgO, Ni foam, and gas diffusion electrode (GDE) loaded with electrocatalysts were performed as the reference electrode, counter electrode, and working electrode, respectively. All potentials were referred to the RHE using the following equation: ERHE = EHg/HgO + 0.098 V + 0.059 V × pH. Two-electrode flow-cells used Ni foam as the anode and GDE coated with catalysts as the cathode. Electrocatalytic acetylene semihydrogenation was typically carried out at an acetylene flow rate of 20 sccm unless specified. Cyclic voltammetry curves were executed in 1 M KOH aqueous solution at a scan rate of 100 mV/s. Linear sweep voltammetry (LSV) scans were performed in 1 M KOH aqueous solution at a scan rate of 5 mV/s. The amperometric curves (i-t) were recorded at different potentials for analyzing the reaction products. The chronopotentiometry was conducted for evaluating the catalyst stability. The electrochemical impedance spectroscopy (EIS) was tested in 1 M KOH aqueous solution under pure acetylene at −0.2 V versus RHE with a frequency range of 10 kHz to 0.01 Hz. Characterizations Transmission electron microscopy (TEM) was carried out on a FEI Talos F200X (FEI Company, USA) at an acceleration voltage of 200 KV. Scanning electron microscopy (SEM), elemental mapping, and energy dispersive spectra were performed on a field-emission FEI-Verios G4 (FEI Company, USA) microscope operating at 15 kV. X-ray diffraction (XRD) patterns were recorded on a MAXima X XRD-7000 (Shimadzu Corporation, Japan) with Cu Kα X-ray source. X-ray photoelectron spectroscopy (XPS) was measured using Kratos AXIS Supra (Shimadzu Corporation, Japan) equipped with Al Kα radiation. The binding energy of the C 1s peak (284.8 eV) was employed as a standard to calibrate the binding energies of other elements. In situ Raman spectroscopy investigations were collected on a Horiba LabRAM HR Evolution spectrometer (Horiba Scientific, France) using the excitation wavelength of 532 nm. Theoretical calculation details All the density functional theory (DFT) calculations were carried out by using the Vienna Ab Initio Simulation Package.21,22 The electron ion interaction was described with the projector augmented wave method,23,24 whereas the electron exchange and correlation energy were solved under the generalized gradient approximation utilizing the revised Perdew–Burke–Ernzerhof exchange-correlation functional.25 An energy cut-off of 450 eV and a second-order Methfessel–Paxton electron smearing with σ = 0.2 eV were applied. The convergences criteria of optimizations for energy and force were set to be 10−5 eV and 0.02 eV/Å, respectively. A vacuum layer of 15 Å was set between the periodically repeating slabs to avoid obvious interactions, and dipole corrections were applied. The Ag (111), Cu (111), and Pd (111) surfaces were simulated with p(4 × 4)-4L supercells. (3 × 3 × 1) grid K-points were used to sample the Brillouin zone. The computed energies were corrected into free energies with the following equation: ΔG = ΔE + ΔZPE + ΔH −TΔS, where the zero-point energies (ZPE) of adsorbates were from the calculated vibrational frequencies within the harmonic approximation. The enthalpy and entropic contributions were calculated within the harmonic approximation for surface species and the ideal gas approximation for a gas phase species. The free energy change of each step that involved a proton-electron transfer was simulated with computational hydrogen electrode model as developed by Nørskov group,26,27 which provided an elegant approach of avoiding the explicit treatment of solvated protons. Results and Discussion To probe the kinetics of acetylene coupling to 1,3-butadiene, we initially carried out theoretical investigations on three typical metal catalysts (Ag, Cu, and Pd) for thermocatalytic or electrocatalytic acetylene hydrogenation. Accordingly, the adsorption energies of the reactants and intermediates during the formation of 1,3-butadiene were obtained using DFT calculations.28,29 Figure 1a and Supporting Information Figures S1–S2 show the free energy diagrams of acetylene coupling to 1,3-butadiene on the (111) surfaces of Ag, Cu, and Pd catalysts. Clearly, all hydrogenation processes on the three catalyst surfaces were exothermic. The adsorption of the first (C2H2*) and second (C2H2* + C2H3*) acetylene on Cu and Pd surfaces were all energetically downhill. Thus, acetylene molecules could densely cover Cu and Pd surfaces so that the C–C coupling of adjacent intermediates unavoidably occurred, particularly at low reduction potentials. However, for Ag surfaces, the adsorption energies of C2H2* and C2H2* + C2H3* were 0.36 and 0.26 eV, respectively. Such endothermic acetylene adsorption could lead to their low density on Ag catalysts and thus reduce their coupling probability. Figure 1 | (a) Free energy diagrams of acetylene coupling to 1,3-butadiene on the (111) facets of three different transition metals (Ag, Cu, and Pd). (b) Polarization curves and (c) related 1,3-butadiene Faradaic efficiencies of electrocatalysts in 1 M KOH aqueous solution under pure acetylene flow. Download figure Download PowerPoint Afterward, the electrocatalytic acetylene coupling performances of Ag, Cu, and Pd NPs were experimentally evaluated in 1 M KOH aqueous solution via a three-electrode flow cell (1 cm2) fed with a pure acetylene stream ( Supporting Information Figures S3–S4). The chemical and structural information of Ag, Cu, and Pd NPs were confirmed using the SEM, TEM, XRD, and XPS characterizations ( Supporting Information Figures S5–S7). Here, all potentials were referenced to the RHE. Figure 1b and Supporting Information Figure S4 depict the current densities and FE distributions of 1,3-butadiene, ethylene, and hydrogen at different applied potentials. The FEs of 1,3-butadiene for Cu NPs at −0.2 V and Pd NPs at −0.4 V were 41.2% and 3.7%, respectively. In contrast, over all applied potentials from −0.4 to −0.9 V, no 1,3-butadiene was detected for Ag NPs (Figure 1c and Supporting Information Figure S4c), unambiguously demonstrating that the C–C coupling of acetylene was thoroughly prohibited. Unfortunately, ethylene FE and partial current density of Ag NPs at −0.85 V were only 51% and 54 mA/cm2, respectively, which were much lower than 89% and 96 mA/cm2 for Pd NPs as well as 87% and 106 mA/cm2 for Cu NPs. The poor electrocatalytic activity of Ag NPs for acetylene semihydrogenation was attributed to the strong competition of the hydrogen evolution reaction (HER). To enhance the electrocatalytic activity of acetylene semihydrogenation and simultaneously suppress the formation of 1,3-butadiene, Ag NWs were synthesized by heating 25 mL ethylene glycol aqueous solution containing 3.5 g FeCl3·6H2O, 200 mg PVP, and 250 mg AgNO3. The TEM and SEM images of Ag NWs in Figures 2a and 2b reveal that the average diameter and length of Ag NWs are about 60–120 nm and 6–15 μm, respectively. The related elemental mapping image shows the uniform distribution of Ag over the NWs (Figure 2c). As further indicated in the high-resolution TEM (HRTEM) image and corresponding electron diffraction pattern, the lattice distances of 0.204 and 0.235 nm were assigned to the (200) and (111) facets of Ag, respectively (Figure 2d). Figure 2e depicts the XRD pattern of the Ag NWs. The observed diffraction peaks at 38.1°, 44.7°, 64.1°, 78.2°, and 81.5° were indexed to the (111), (200), (220), (311), and (222) planes of the face-centered-cubic silver crystal (JCPDS Card No. 04-0783). The XPS analysis was further employed for understanding surface chemical states of the Ag NWs (Figure 2f). Characteristic Ag 3d5/2 and 3d3/2 peaks were observed at 368.4 and 374.4 eV, respectively. Figure 2 | The characterizations of Ag NWs. Low-magnification (a) TEM and (b) SEM images of Ag NWs. (c) The corresponding elemental Ag mapping image of Ag NWs. (d) HRTEM image and related electron diffraction pattern of Ag NWs. (e) XRD pattern and (f) XPS spectrum of Ag NWs. Download figure Download PowerPoint Next, the electrocatalytic performance of the Ag NWs was first measured in 1 M KOH aqueous solution using a flow cell (1 cm2) under pure acetylene flow ( Supporting Information Figures S8–S10). Notably, similar to the Ag NPs, no ethane was detected for the Ag NWs from −0.2 to −0.9 V (Figure 3a). 1,3-Butadiene FE of Ag NWs was about 2.1% at −0.2 V, which was much lower than 41.2% for Cu NPs and those values for previously reported Cu-based electrocatalysts (47% for Cu microparticles [MPs] at −0.3 V, 12% for layered double hydroxide-derived copper [LD-Cu] at −0.28 V, and 3% for Cu dendrites at −0.5 V) (Figure 3c). Meanwhile, the hydrogen FE of Ag NWs remarkably decreased to <1% in comparison with 48% for Ag NPs at −0.85 V versus RHE. These results powerfully evidence that the side reactions of acetylene C–C coupling and HER are simultaneously suppressed on the Ag NWs ( Supporting Information Figure S12). As a result, the ethylene FE of Ag NWs reached ∼99% at −0.85 V, which was substantially higher than 51% for Ag NPs and 87% for Cu NPs. The Ag NWs thus acquired an ethylene partial current density of 217 mA/cm2 at −0.85 V (Figure 3b), which was extremely higher than 54 mA/cm2 for Ag NPs and the state-of-the-art electrocatalysts (150 mA/cm2 for Cu dendrites at −0.8 V, 62 mA/cm2 for LD-Cu at −0.6 V, and 24 mA/cm2 for Cu MPs at −0.6 V). In addition, the EIS was recorded at −0.2 V in a frequency range of 10 kHz to 0.01 Hz ( Supporting Information Figure S12). In contrast to >334 Ω for Ag NPs and ∼30 Ω for Cu NPs, the charge transfer resistance of Ag NWs was as low as ∼10 Ω, suggesting rapid semihydrogenation kinetics of acetylene. Figure 3 | (a) Faradaic efficiencies of Ag NWs in 1 M KOH aqueous solution under pure acetylene flow. (b) Ethylene partial current densities of electrocatalysts in 1 M KOH aqueous solution under pure acetylene flow. (c) Comparison of acetylene semihydrogenation performance between Ag NWs and the reported Cu-based electrocatalysts including Cu dendrites10, LD-Cu,12 and Cu MPs.34 Download figure Download PowerPoint To gain profound insights into the outstanding electrocatalytic performance of Ag NWs, in situ electrochemical Raman spectroscopy was performed to unveil the underlying acetylene hydrogenation mechanism ( Supporting Information Figure S13). The Raman peaks at 1600 cm−1 for Pd NPs and 1687 cm−1 for Cu NPs were attributed to C≡C stretching vibration (Figures 4a and 4b). In contrast, the characteristic acetylene peaks on Ag NPs and Ag NWs positively shifted to 2070 and 2085 cm−1 (Figures 4c and 4d).30–32 These results indicate that acetylene adsorption on Ag surfaces was much weaker than those on Cu and Pd catalysts, which accorded well with the theoretical results. As the potential of Ag NWs reached −0.2 V, two new peaks were recorded at 1118 and 1521 cm−1, which were assigned to symmetric CH2 scissors and C=C stretch modes of adsorbed ethylene, respectively.33 The distinctive peaks of adsorbed ethylene on Ag NPs were observed at 1123 and 1507 cm−1 at −0.8 V, whereas the adsorbed ethylene peaks on Pd NPs (1123 and 1507 cm−1) and Cu NPs (1118 and 1501 cm−1) appeared at −0.6 V. Evidently, the C=C stretch peak of Ag NWs showed a positive shift versus those for Ag NPs, Pd NPs, and Cu NPs. These results unambiguously expose the weak ethylene absorption on Ag NWs, which facilitates the fast desorption of ethylene from Ag surfaces. Notably, characteristic Raman signals of long-chain hydrocarbons were recognized on Pd NPs (1123 cm−1 for C–C bonds with overlap of C–H vibration, 1507 cm−1 for trans-C=C vibration, 2235 cm−1 for first overtone of 1123 and 2610 cm−1 for mixing 1123 and 1507 cm−1) and Cu NPs (1118 cm−1 for C–C bonds with overlap of C–H vibration, 1501 cm−1 for trans-C=C vibration, 2233 cm−1 for first overtone of 1118 and 2608 cm−1 for mixing 1118 and 1501 cm−1).31 In comparison, Ag NPs and Ag NWs showed no distinctive peaks of oligomerization products, verifying that the C–C coupling process of acetylene was effectively terminated. Figure 4 | In situ electrochemical Raman spectra of (a) Pd NPs, (b) Cu NPs, (c) Ag NPs, and (d) Ag NWs in 1 M KOH aqueous solution in pure acetylene stream. Download figure Download PowerPoint For assessing the practical implementation of Ag NWs, electrocatalytic acetylene semihydrogenation performance was subsequently examined in a two-electrode flow cell (1 cm2) coupling cathodic acetylene semihydrogenation with anodic oxygen evolution reaction. As displayed in Figure 5a, the current density of Ag NWs is 91 mA/cm2 at a cell voltage (Ecell) of 3 V. Meanwhile, Ag NWs manifested an ethylene FE (FEethylene) of 98% at 30 mA/cm2 (Figure 5b). Remarkably, no 1,3-butadiene was formed on Ag NWs. Over a 120 h durability test at 10 mA/cm2, Ag NWs retained ethylene FEs of >93% (Figure 5c). The structural and chemical information of Ag NWs after the long-term stability measurement were characterized using the SEM and related elemental mapping ( Supporting Information Figure S14). No obvious variations of Ag NWs were observed, indicating the structural robustness of Ag NWs during the electrocatalytic acetylene semihydrogenation process. Figure 5 | Electrocatalytic acetylene semihydrogenation performance of Ag NWs in a two-electrode flow cell (1 cm2). (a) LSV curve of Ag NWs in 1 M KOH aqueous solution under pure acetylene flow. (b) Ethylene FE and corresponding applied voltage (Ecell) at different current densities. (c) Long-term electrocatalytic stability test at 10 mA/cm2 in pure acetylene stream. Download figure Download PowerPoint To the industrial for acetylene impurities from ethylene-rich electrocatalytic acetylene semihydrogenation of Ag NWs was performed in a two-electrode flow cell (25 cm2) fed with crude ethylene containing 1 vol % acetylene at a flow rate of 10 Figure shows acetylene conversion and ethylene specific selectivity of Ag NWs at different current densities. Notably, no 1,3-butadiene ethane were the termination of C–C coupling and over hydrogenation reactions on Ag NWs. The acetylene conversion of Ag NWs reached 99.8% at 2.2 mA/cm2, and the specific selectivity of ethylene was as high as ( Supporting Information Figure Meanwhile, electrocatalytic acetylene semihydrogenation of Ag NWs was evaluated at different flow of crude As in Figure and Supporting Information Figure Ag NWs acetylene of and at flow of and respectively. However, the specific selectivity of ethylene Afterward, the long-term stability of Ag NWs for acetylene semihydrogenation in crude ethylene flow was measured at 2.2 mA/cm2 using a large two-electrode flow cell (25 cm2). Remarkably, Ag NWs achieved acetylene conversion of and ethylene specific selectivity of over h (Figure Figure 6 | Electrocatalytic acetylene semihydrogenation performance of Ag NWs in crude ethylene using a large two-electrode flow cell (25 cm2). (a) selectivity of ethylene and acetylene conversion versus current densities at a flow rate of 10 sccm in crude (b) The acetylene conversion and corresponding specific selectivity of ethylene at different flow of crude (c) The long-term stability test at 2.2 mA/cm2. Download figure Download PowerPoint that the acetylene adsorption on surfaces a for coupling Accordingly, Ag NWs weak acetylene adsorption are as novel electrocatalysts for reducing acetylene to ethylene, where the coupling of acetylene is unprecedentedly terminated. As a result, the Ag NWs acetylene ethylene and which are superior to state-of-the-art electrocatalysts, for electrocatalytic acetylene Therefore, the of active sites for weak acetylene adsorption and the profound understanding on coupling kinetics of acetylene only a for selective acetylene a new for high-performance electrocatalysts to suppress or coupling reactions and so Supporting Information Supporting Information is and and of is no of to Information This work was by the for the Science of Shaanxi and the Science of and the Key and of and the of Northwestern Polytechnical The to the of Northwestern Polytechnical for the XRD, SEM, and TEM Lin Chen in a with In of Chen of for of Chen with for of Acetylene from Chen Chen Chemistry and in Materials for Acetylene from Liu Chen Zhang Chen of to of Acetylene to Ethylene in the of a on a (111) in Acetylene Zhang Zhang over to Liu Zhang Zhang Zhang Zhang Electrocatalytic of Acetylene for the of Zhang Chen Liu Yan Lin Zhang Liu Zhang Electrocatalytic Acetylene by in Zhang Zhang Acetylene to Ethylene with and Zhang Chen of the in of Acetylene over a of a Acetylene of Acetylene at and for Evolution for of Acetylene in of and Al the of of Acetylene on of in the of a during the of of for and a for Ab Initio a Nørskov Adsorption within to the Nørskov of the for at a Nørskov the of into of and for Acetylene on A Functional of 1,3-Butadiene in Acetylene over the Functional and of Acetylene on A Raman Liu Lin of Acetylene on by Raman Raman of and in Ethylene on and as by Raman Chen Zhang Ethylene via Electrocatalytic of Acetylene Information Chemical to the of Northwestern Polytechnical for the XRD, SEM, and TEM

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