Polyvalent MnOx/C Electrocatalyst for HighlyEfficient Nitrogen Reduction Reaction

Yipiao BI Xue GONG Fa YANG Mingbo RUAN Ping SONG Weilin XU

Citation:  BI Yipiao, GONG Xue, YANG Fa, RUAN Mingbo, SONG Ping, XU Weilin. Polyvalent MnOx/C Electrocatalyst for HighlyEfficient Nitrogen Reduction Reaction[J]. Chinese Journal of Applied Chemistry, 2020, 37(9): 1048-1055. doi: 10.11944/j.issn.1000-0518.2020.09.200085 shu

多价MnOx/C电催化剂用于高效氮还原反应

    通讯作者: 徐维林, weilinxu@ciac.ac.cn
  • 基金项目:

    广东联合基金 U1601211

    国家自然科学基金 21433003

    国家自然科学基金 2017YF9127900

    国家自然科学基金 21721003

    国家自然科学基金 2018YFB1502302

    国家杰出青年科学基金(21925205)、广东联合基金(U1601211)和国家自然科学基金(21733004,21633008,2017YF9127900,21721003,2018YFB1502302,21433003)项目资助

    国家自然科学基金 21633008

    国家杰出青年科学基金 21925205

    国家自然科学基金 21733004

摘要: 氨在人类的生产生活中起着重要的作用,但目前工业上合成氨广泛采用的Haber-Bosch法耗能大,且污染严重。而N2电还原反应(ENRR)被认为是一种有效的替代方法,由于N2的键能较高,目前仍然缺乏高活性的催化剂。在这里,通过简单的浸渍法和氧化还原法制备了多价态的MnOx/C催化剂,该催化剂具有较高的氮还原反应活性(氨产率达到7.8 μgNH3/(h·mgcat),法拉第效率高达9.2%)。进一步研究表明,多价态MnOx/C催化剂具有高氮还原反应活性的主要原因是不同价态的Mn离子(Mn2+、Mn3+、Mn4+)之间存在协同效应。

English

  • NH3 is one of the most important chemicals in industry and the earth's ecological cycle[1]. So far, the majority of NH3 on earth has been manufactured by the Haber-Bosch process invented in the last century. This method not only needs harsh reaction conditions (high temperature and high pressure), but also consumes a large amount fossil energy and produces a lot of greenhouse gases[2-3]. Due to the crisis of both energy and environment, it is very desirable to develop an alternative ammonia synthesis process that can be carried out gently, efficiently, environmentally friendly and low-energy.

    Up to now, there are three main ways to fix nitrogen under mild conditions, including biological nitrogen fixation[4-6], photocatalytic nitrogen fixation[7-9]and electrochemical nitrogen fixation[10-11]. Among them, the production of biological nitrogen fixation is insufficient to meet the needs of human beings and limits its large-scale industrial development. Photocatalytic nitrogen fixation has a problem of low utilization rate of renewable energy. Therefore, electrocatalytic nitrogen reduction reaction (ENRR) has been paid more and more attention from researchers in recent decade[12-14]. Nitrogen nitrogen triple bond (N≡N) in N2 has a strong dipole moment and a high bond energy (940.9 kJ/mol), making it difficult to break, which is one of the biggest challenges for nitrogen fixation under mild conditions[15-16]. Therefore, ENRR under ambient conditions requires a highly efficient electrocatalyst to reduce the activation energy, thereby increasing the reaction rate. In recent years, many ENRR catalysts have been developed, including noble metal catalysts, such as Au[17], Pd[18], Ru[19-21], and Rh[22], and non-precious metal catalysts such as Fe[23-25], Mo[26-28], Cr[29], etc., in addition to some hetero-atom doped non-metallic catalysts[30-32]. However, the application of noble metal catalysts is severely restricted due to their limited resources and high costs. And currently non-precious mental catalysts suffer from low production rate and Faradic efficiency (FE). So alternative non-precious metal electrocatalysts with high ammonia production rate and FE are particularly desirable. Transition metals are abundant on earth and their oxides can be prepared easily in a large scale[33]. In the present, only few of transition metal oxides (such as NbO2[34], Fe3O4[35], and MoO3[36]) have been studied as ENRR catalysts. Therefore, the study of more transition metal oxide nanocatalysts is of great significance for the developing of highly efficient and low cost electrocatalysts for NRR.

    Among them, Mn is an element that can promote nitrogenase activity of NRR, and its oxide may have excellent ENRR activity. Sun et al first reported Mn3O4 nanotubes as ENRR catalysts in 2018, with 3% FE in neutral electrolyte (-0.8 V vs RHE)[37]. After that, the same team proved that the Mn (200) surface has excellent ENRR activity with FE up to 8% in the neutral solution[38]. Recently, they further reported that the MnO2 with O vacancies supported on a titanium mesh are also active for NRR but with limited activity[39].

    Here, we report a highly efficient NRR electrocatalyst based on manganese oxide supported on activated carbon (MnOx/C), prepared by a method of impregnation redox reaction and subsequent high-temperature calcination. Such catalyst shows high NRR activity (with FE up to 9.2% and ammonia production rate up to 7.8 μgNH3/(h·mgcat)) and remarkable durability/selectivity for ammonia production in acidic aqueous solution. Such work deeps our understanding to the Mn-based NRR process.

    Salicylic acid, NaOH, N2H4·H2O, NH4OH, sodium citrate, sodium hypochlorite (NaClO), p-dimethylaminobenzaldehyde (p-C9H11NO), sodium citrate dehydrate (C6H5Na3O7·2H2O), sodium nitroferricyanide dihydrate (Na2[Fe(CN)5NO]·2H2O), MnSO4, MnO, Mn2O3, MnO2 and KMnO4 were purchased from Sigma-Aldrich Chemical Reagent Co., Ltd. Carbon black is BP2000. Ultrapure water, which was purified with a Millipore system.

    Element mapping analysis test instrument is Philips TECNAI G2 analytical high resolution transmission electron microscope (TEM), with operating voltage of 200 kV; scanning electron microscope (SEM) test instrument is XL 30 ESEM FEG field emission SEM; Using Mg as the radiation source, the X-ray photoelectric spectrum (XPS) was measured on Kratos XSAM-800 spectrometer; Absorbance is measured by UV-visible (UV-Vis) absorbance photometry in Agilent Cary 60.

    We have made improvements on the preparation of carbon-supported manganese oxides (MnOx/C) as described in literature[40]. Quickly, 50 mg of carbon black was mixed with an aqueous solution of MnSO4, then the KMnO4 was added after stirring for 4 hours, the suspension was maintained at a controlled temperature (95 ℃) for 20 min. The obtained product was centrifuged with deionized water for several times and then dried at 110 ℃. Finally, the powder was placed into a quartz boat and then heat-treated under Ar/H2 (5%H2) gas atmosphere in a tube furnace. The pyrolysis products were washed with plenty of deionized water and dried at 60 ℃ under vacuum overnight.

    Mix 30 mg of MnO, Mn2O3 and MnO2 with 70 mg of activated carbon BP-2000, respectively, then add an appropriate amount of deionized water, stir for several hours, centrifuge and dry the product overnight.

    Before the NRR test, Nafion membrane was pretreated with deionized water, H2SO4 and H2O2 to protonate it. The steps are as follows: First, it was boiled in ultrapure water for 1 hour, and then treated in an aqueous solution of H2O2 (5%) at 80 ℃ for 1 hour. Then, it was treated in 0.05 mol/L H2SO4 at 80 ℃ for 3 hours, and finally washed in water. Electrochemical measurements were performed using a standard three-electrode system using a CHI 750E electrochemical analyzer(CH Instruments, Inc) with MnOx/C as the working electrode, graphite rod as the counter electrode and saturated Ag/AgCl (saturated KCl electrolyte) as the reference electrode. All potentials were corrected using the automatic IR compensation function on the potentiostat. All experiments were performed at room temperature. For the N2 reduction experiment, 0.05 mol/L H2SO4 electrolyte was purged with N2 for 30 minutes before each measurement. A chronoamperometry test was then performed in a N2 saturated 0.05 mol/L H2SO4 solution in H-type cell, which was separated by a Nafion membrane.

    In this case, based on the reaction between KMnO4 and MnSO4:KMnO4+MnSO4 → MnOx, different amount of MnOx was deposited on carbon support at room temperature. To study the ENRR activity of these catalysts, the linear sweep voltammetry (LSV) curves of these catalysts were obtained in Ar- or N2-saturated 0.05 mol/L sulfuric acid. Fig.S1(in Supporting Information) and Fig. 1A show that the one with Mn of 30% (named as MnOx-30/C) presents the largest response current to NRR, indicating the highest NRR activity.

    Figure 1

    Figure 1.  (A) LSV curves of MnOx/C catalysts with different metal (Mn) loadings in N2 saturated 0.05 mol/L H2SO4 electrolyte; (B) LSV curves of MnOx-30/C after heat-treatment at different temperatures in N2 saturated 0.05 mol/L H2SO4 electrolyte; (C) LSV curves of MnOx-30/C-350 catalyst in N2 and Ar saturated 0.05 mol/L H2SO4 electrolyte; (D) Chronoamperometry curve of MnOx-30/C-350 in N2 saturated 0.05 mol/L H2SO4 electrolyte at different potentials

    To further optimize the performance of the catalyst MnOx-30/C, the sample was further heat-treated at different temperatures under Ar-H2 (5%) atmosphere. As shown in Fig.S2 (in Supporting Information) and Fig. 1B-1C, the catalyst obtained at 350 ℃ (named as MnOx-30/C-350) shows the best NRR activity as indicated by the largest response current to NRR.

    To quantify the amounts of possible products (NH3 or N2H4) of NRR on these catalysts, indophenol blue method and Watt and Chrisp method[41]were adopted to obtain the standard curves for these two possible NRR product (NH3 and N2H4) as shown in Fig.S3 and Fig.S4 (in Supporting Information), respectively. Based on such standard curves, the liquid NRR products on these catalysts could be quantified by fixing the electrode potential at different values for 2 hours (the working electrode was prepared based on carbon paper with catalyst loading of 0.5 mg/cm2). For the optimal catalyst MnOx-30/C-350, to quantify the possible NRR products formed on it, as shown in Fig. 1D, the NRR products were accumulated for 2 hours at different potentials. Fig. 2A-2B show the absorption spectra of the solution obtained at different potentials. Based on the standard absorption spectra of NH3 and N2H4 shown in Fig.S3A-S4A (in Supporting Information), Fig. 2A shows clearly that NH3 is indeed produced potential-dependently as indicated by the absorption peak at 655 nm, while no N2H4 formation in the whole potential range as indicated by the no absorption at 460 nm shown in Fig. 2B, indicating a 100% selectivity of NRR for ammonia production. Based on the standard curves of NH3 shown in Fig.S3B, we further calculated the yield and FE of ammonia from NRR at different potentials as shown in Fig. 2C. It shows that the maximum NH3 yield of 7.8 μgNH3/(h·mgcat) was achieved at -0.66 V(vs.RHE), while the maximum FE of 9.2% was achieved at -0.56 V, higher than most of the recently reported NRR catalysts (see Support Information Table S1).

    Figure 2

    Figure 2.  ENRR product analysis on optimal catalyst MnOx-30/C-350 in N2-saturated 0.05 mol/L H2SO4 solution. (A) UV-Vis absorption spectra of NH4+ ions solution at different potentials; (B) UV-Vis absorption spectra of N2H4·H2O solution at different potentials; (C) NH3 yield and FE at different potentials; (D) NH3 yield and FE of MnOx-30/C-350 in 8 cycles of test at potential of -0.56 V

    In order to exclude the possible influence of external pollution sources, we conducted product analysis of Ar-saturated solution at optimal potential of -0.56 V and nitrogen saturated solution at open circuit voltage. As shown in Fig.S5 (in Supporting Information), no NH3 could be detected in the above two electrolytes. Similarly, we also observed no NH3 formation on either carbon paper (see Supporting Information Fig.S6) or pure carbon black supported by carbon paper (see Supporting Information Fig.S7). All these results confirm that the formation of NH3 can only be attributed to the active components of MnOx for NRR.

    We further evaluated the NRR durability of the optimal catalyst MnOx-30/C-350 at -0.56 V. Fig. 2D shows that after 8 cycles of repeated testing (2 hours at -0.56 V in each cycle), the values of both FE and yield of NH3 on MnOx-30/C-350 catalyst keep almost constant, consistent with the observed stable current density at fixed potential as show in Fig.S8 (in Supporting Information). All these results indicate the remarkable durability of MnOx-30/C-350 for long-term NRR process.

    To deeply understand such durability, SEM analysis was conducted. As the SEM images shown in Fig. 3A-3B, no obvious morphology variation could be observed after long-term (16 hours at -0.56 V) NRR process, indicating an excellent structure stability of the catalyst. The distribution of MnOx on MnOx-30/C-350 was also evaluated via high-angle annular dark-field scanning TEM (HAADF-STEM) and element mapping analysis. As shown in Fig. 3C-3F, MnOx was dispersed uniformly on carbon support. Such homogeneous distribution could explain in part the observed remarkable durability.

    Figure 3

    Figure 3.  (A) SEM images of MnOx-30/C-350 before testing; (B) SEM images of MnOx-30/C-350 after long-term testing (16 hours at -0.56 V); (C-F) HAADF-STEM and element mapping images of MnOx-30/C-350

    To deeply understand the origin of the observed ENRR performance on catalyst MnOx-30/C-350, NRR catalytic activities of univalent MnO/C, Mn2O3/C and MnO2/C were also prepared with Mn content of 30% and studied at fixed potentials of -0.56 V and -0.66 V to obtain the FE and yield information, respectively (see Support Information Fig.S9).

    Fig. 4A shows clearly that polyvalent MnOx presents better ENRR performance than other univalent manganese oxide. Based on such result, chemical composition of MnOx/C treated at different calcination temperatures were investigated by XPS. As shown in Fig. 4B and 4C, three different oxidative states (Mn2+, Mn3+ and Mn4+) of Mn coexist in MnOx-30/C, while after calcination at 350 ℃, the content of Mn4+ decreased and the contents of both Mn2+ and Mn3+ increased probably due to the reduction of Mn4+ by H2 at high temperature. Such results along with observed higher NRR performance of MnOx-30/C-350 than that of MnOx-30/C (Fig. 1B) indicate that the Mn2+ and Mn3+ are the apparent main active components for the observed high NRR performance via a synergistic effect between them. To further confirm such point, the chemical compositions of MnOx-30/C after heat-treated at different temperatures were further revealed via high resolution XPS. As shown in Table S2 (in Supporting Information) and Fig. 4D, with the temperature increase, the content of Mn4+ decreased step-by-step slowly, while the contents of both Mn2+ and Mn3+ increased gradually. Fig. 4D also shows clearly that the optimal NRR performance achieves only at an optimal composition (Mn2+:31.2%, Mn3+:29.5%, Mn4+:39.3%) obtained at 350 ℃, after the heat-treatment at higher temperature, the further content decrease of Mn4+ or the further content increase of Mn2+ and Mn3+ leads to the performance decrease inversely. Such fact indicates that the Mn4+ is also an important component for the observed high NRR performance. It means, the synergist effect for ENRR on such MnOx/C occurs among the sites of Mn2+, Mn3+, and Mn4+ simultaneously rather than only between Mn2+ and Mn3+.

    Figure 4

    Figure 4.  (A) Performance test results of univalent MnO/C, Mn2O3/C, MnO2/C and polyvalent MnOx-30/C-350 (FE and yield were test at -0.56 V and -0.66 V, respectively); (B) XPS pattern of MnOx-30/C; (C) XPS pattern of MnOx-30/C-350. (D) Contents of Mn in different valence in MnOx-30/C after calcinated at different temperatures and corresponding FE of NH3

    In summary, a series of MnOx/C catalysts with multiple valence states of Mn was synthesized for highly efficient NRR process. In acidic solution, the optimal MnOx-30/C-350 presents high FE (up to 9.2%) at -0.56 V with NH3 yield up to 7.8 μg NH3/(h·mgcat) at -0.66 V and remarkable stability. It was further revealed that the high NRR performance could be due to the synergistic effect among different valence Mn ions of Mn2+, Mn3+, and Mn4+. This work presents a new catalytic system for the development of cost-effective highly efficient NRR catalysts.

    Supporing information [LSV curves, UV-Vis and XPS spectra of diferent Mn0x, catalysts] is arailable free of charge ria the Internet at htp://yzhx.ciac.jl.cn.


    1. [1]

      Mukherjee S, Cullen D A, Karakalos S. Metal-Organic Framework-Derived Nitrogen-Doped Highly Disordered Carbon for Electrochemical Ammonia Synthesis Using N2 and H2O in Alkaline Electrolytes[J]. Nano Energy, 2018, 48:  217-226. doi: 10.1016/j.nanoen.2018.03.059 doi: 10.1016/j.nanoen.2018.03.059

    2. [2]

      Lv C, Yan C, Chen G. An Amorphous Noble-Metal-Free Electrocatalyst that Enables Nitrogen Fixation under Ambient Conditions[J]. Angew Chem Int Ed, 2018, 57:  6073-6076. doi: 10.1002/anie.201801538 doi: 10.1002/anie.201801538

    3. [3]

      Shipman M A, Symes M D. Recent Progress Towards the Electrosynthesis of Ammonia from Sustainable Resources[J]. Catal Today, 2017, 286:  57-68. doi: 10.1016/j.cattod.2016.05.008 doi: 10.1016/j.cattod.2016.05.008

    4. [4]

      Li S J, Bao D, Shi M M. Amorphizing of Au Nanoparticles by CeOx-RGO Hybrid Support Towards Highly Efficient Electrocatalyst for N2 Reduction under Ambient Conditions[J]. Adv Mater, 2017, 29:  1700001. doi: 10.1002/adma.201700001 doi: 10.1002/adma.201700001

    5. [5]

      Hao Y, Dong X, Zhai S. Hydrogenated Bismuth Molybdate Nanoframe for Efficient Sunlight-Driven Nitrogen Fixation from Air[J]. Chem-Eur J, 2016, 22:  18722-18728. doi: 10.1002/chem.201604510 doi: 10.1002/chem.201604510

    6. [6]

      Burgess B K, Wherland S, Newton W E. Nitrogenase Reactivity:Insight into the Nitrogen-Fixing Process Through Hydrogen-Inhibition and HD-Forming Reactions[J]. Biochemistry, 1981, 20:  5140-5146. doi: 10.1021/bi00521a007 doi: 10.1021/bi00521a007

    7. [7]

      Wang L, Xia M, Wang H. Greening Ammonia toward the Solar Ammonia Refinery[J]. Joule, 2018, 2:  1055-1074. doi: 10.1016/j.joule.2018.04.017 doi: 10.1016/j.joule.2018.04.017

    8. [8]

      Zhu D, Zhang L, Ruther R E. Photo-illuminated Diamond as a Solid-state Source of Solvated Electrons in Water for Nitrogen Reduction[J]. Nat Mater, 2013, 12:  836-841. doi: 10.1038/nmat3696 doi: 10.1038/nmat3696

    9. [9]

      Li X, Wang W, Jiang D. Efficient Solar-Driven Nitrogen Fixation over Carbon-Tungstic-Acid Hybrids[J]. Chem-Eur J, 2016, 22:  13819-13822. doi: 10.1002/chem.201603277 doi: 10.1002/chem.201603277

    10. [10]

      Guo C, Ran J, Vasileff A. Rational Design of Electrocatalysts and Photo(electro)catalysts for Nitrogen Reduction to Ammonia (NH3) under Ambient Conditions[J]. Energy Environ Sci, 2018, 11:  45-56. doi: 10.1039/C7EE02220D doi: 10.1039/C7EE02220D

    11. [11]

      Yandulov D V, Schrock R R. Catalytic Reduction of Dinitrogen to Ammonia at a Single Molybdenum Center[J]. Science, 2003, 301:  76-78. doi: 10.1126/science.1085326 doi: 10.1126/science.1085326

    12. [12]

      Murakami T, Nishikiori T, Nohira T. Electrolytic Synthesis of Ammonia in Molten Salts under Atmospheric Pressure[J]. J Am Chem Soc, 2003, 125:  334-335. doi: 10.1021/ja028891t doi: 10.1021/ja028891t

    13. [13]

      Zhang R, Ren X, Shi X. Enabling Effective Electrocatalytic N2 Conversion to NH3 by the TiO2 Nanosheets Array under Ambient Conditions[J]. ACS Appl Mater Interfaces, 2018, 10:  28251-28255. doi: 10.1021/acsami.8b06647 doi: 10.1021/acsami.8b06647

    14. [14]

      Kyriakou V, Garagounis I, Vasileiou E. Progress in the Electrochemical Synthesis of Ammonia[J]. Catal Today, 2017, 286:  2-13. doi: 10.1016/j.cattod.2016.06.014 doi: 10.1016/j.cattod.2016.06.014

    15. [15]

      Singh A R, Rohr B A, Schwalbe J A. Electrochemical Ammonia Synthesis-The Selectivity Challenge[J]. ACS Catal, 2017, 7:  706-709. doi: 10.1021/acscatal.6b03035 doi: 10.1021/acscatal.6b03035

    16. [16]

      Lu Y, Yang Y, Zhang T. Photoprompted Hot Electrons from Bulk Cross-Linked Graphene Materials and Their Efficient Catalysis for Atmospheric Ammonia Synthesis[J]. ACS Nano, 2016, 10:  10507-10515. doi: 10.1021/acsnano.6b06472 doi: 10.1021/acsnano.6b06472

    17. [17]

      Wang X, Wang W, Qiao M. Atomically Dispersed Au1 Catalyst towards Efficient Electrochemical Synthesis of Ammonia[J]. Sci Bull, 2018, 63:  1246-1253. doi: 10.1016/j.scib.2018.07.005 doi: 10.1016/j.scib.2018.07.005

    18. [18]

      Wang J, Yu L, Hu L. Ambient Ammonia Synthesis via Palladium-Catalyzed Electrohydrogenation of Dinitrogen at Low Overpotential[J]. Nat Commun, 2018, 9:  1-7. doi: 10.1038/s41467-017-02088-w doi: 10.1038/s41467-017-02088-w

    19. [19]

      Lin B, Liu Y, Heng L. Morphology Effect of Ceria on the Catalytic Performances of Ru/CeO2 Catalysts for Ammonia Synthesis[J]. Ind Eng Chem Res, 2018, 57:  9127-9135. doi: 10.1021/acs.iecr.8b02126 doi: 10.1021/acs.iecr.8b02126

    20. [20]

      Wang D, Azofra L M, Harb M. Energy-Efficient Nitrogen Reduction to Ammonia at Low Overpotential in Aqueous Electrolyte under Ambient Conditions[J]. ChemSusChem, 2018, 11:  3416-3422. doi: 10.1002/cssc.201801632 doi: 10.1002/cssc.201801632

    21. [21]

      Tao H, Choi C, Ding L. Nitrogen Fixation by Ru Single-Atom Electrocatalytic Reduction[J]. Chemistry, 2019, 5:  204-214. doi: 10.1016/j.chempr.2018.10.007 doi: 10.1016/j.chempr.2018.10.007

    22. [22]

      Liu H M, Han S H, Zhao Y. Surfactant-Free Atomically Ultrathin Rhodium Nanosheet Nanoassemblies for Efficient Nitrogen Electroreduction[J]. J Mater Chem A, 2018, 6:  3211-3217. doi: 10.1039/C7TA10866D doi: 10.1039/C7TA10866D

    23. [23]

      Wang Y, Jia K, Pan Q. Boron-Doped TiO2 for Efficient Electrocatalytic N2 Fixation to NH3 at Ambient Conditions[J]. ACS Sus Chem Eng, 2019, 7:  117-122. doi: 10.1021/acssuschemeng.8b05332 doi: 10.1021/acssuschemeng.8b05332

    24. [24]

      Chen S, Perathoner S, Ampelli C. Electrocatalytic Synthesis of Ammonia at Room Temperature and Atmospheric Pressure from Water and Nitrogen on a Carbon-Nanotube-Based Electrocatalyst[J]. Angew Chem, 2017, 56:  2699-2703. doi: 10.1002/anie.201609533 doi: 10.1002/anie.201609533

    25. [25]

      Wang M, Liu S, Qian T. Over 56.55% Faradaic Efficiency of Ambient Ammonia Synthesis Enabled by Positively Shifting the Reaction Potentia[J]. Nat Commun, 2019, 10:  1-8. doi: 10.1038/s41467-018-07882-8 doi: 10.1038/s41467-018-07882-8

    26. [26]

      Cheng H, Ding L X, Chen G F. Molybdenum Carbide Nanodots Enable Efficient Electrocatalytic Nitrogen Fixation under Ambient Conditions[J]. Adv Mater, 2018, 30:  1803694. doi: 10.1002/adma.201803694 doi: 10.1002/adma.201803694

    27. [27]

      Ren X, Cui G, Chen L. Electrochemical N2 Fixation to NH3 under Ambient Conditions:Mo2N Nanorod as a Highly Efficient and Selective Catalyst[J]. Chem Commun, 2018, 54:  8474-8477. doi: 10.1039/C8CC03627F doi: 10.1039/C8CC03627F

    28. [28]

      Zhang L, Ji X, Ren X. Electrochemical Ammonia Synthesis via Nitrogen Reduction Reaction on a MoS2 Catalyst:Theoretical and Experimental Studies[J]. Adv Mater, 2018, 30:  1800191. doi: 10.1002/adma.201800191 doi: 10.1002/adma.201800191

    29. [29]

      Yao Y, Yao Y, Feng Q. Chromium Oxynitride Electrocatalysts for Electrochemical Synthesis of Ammonia under Ambient Conditions[J]. Small Methods, 2019, 3:  1800324. doi: 10.1002/smtd.201800324 doi: 10.1002/smtd.201800324

    30. [30]

      Liu Y, Su Y, Quan X. Facile Ammonia Synthesis from Electrocatalytic N2 Reduction under Ambient Conditions on N-Doped Porous Carbon[J]. ACS Catal, 2018, 8:  1186-1191. doi: 10.1021/acscatal.7b02165 doi: 10.1021/acscatal.7b02165

    31. [31]

      Song P, Wang H, Kang L. Electrochemical Nitrogen Reduction to Ammonia at Ambient Conditions on Nitrogen and Phosphorus Co-Doped Porous Carbon[J]. Chem Commun, 2019, 55:  687-690. doi: 10.1039/C8CC09256G doi: 10.1039/C8CC09256G

    32. [32]

      Song Y, Johnson D, Peng R. A Physical Catalyst for the Electrolysis of Nitrogen to Ammonia[J]. Sci Adv, 2018, 4:  e1700336. doi: 10.1126/sciadv.1700336 doi: 10.1126/sciadv.1700336

    33. [33]

      Jin H, Guo C, Liu X. Emerging Two-Dimensional Nanomaterials for Electrocatalysis[J]. Chem Rev, 2018, 118:  6337-6408. doi: 10.1021/acs.chemrev.7b00689 doi: 10.1021/acs.chemrev.7b00689

    34. [34]

      Huang L, Wu J, Han P. NbO2 Electrocatalyst Toward 32% Faradaic Efficiency for N2 Fixation[J]. Small Methods, 2019, 3:  1800386. doi: 10.1002/smtd.201800386 doi: 10.1002/smtd.201800386

    35. [35]

      Liu Q, Zhang X, Zhang B. Ambient N2 Fixation to NH3 Electrocatalyzed by a Spinel Fe3O4 Nanorod[J]. Nanoscale, 2018, 10:  14386-14389. doi: 10.1039/C8NR04524K doi: 10.1039/C8NR04524K

    36. [36]

      Han J, Ji X, Ren X. MoO3 Nanosheets for Efficient Electrocatalytic N2 Fixation to NH3[J]. J Mater Chem A, 2018, 6:  12974-12977. doi: 10.1039/C8TA03974G doi: 10.1039/C8TA03974G

    37. [37]

      Wu X, Xia L, Wang Y. Mn3O4 Nanocube:An Efficient Electrocatalyst toward Artificial N2 Fixation to NH3[J]. Small, 2018, 14:  1803111. doi: 10.1002/smll.201803111 doi: 10.1002/smll.201803111

    38. [38]

      Wang Z, Gong F, Zhang L. Electrocatalytic Hydrogenation of N2 to NH3 by MnO:Experimental and Theoretical Investigations[J]. Adv Sci, 2019, 6:  1801182. doi: 10.1002/advs.201801182 doi: 10.1002/advs.201801182

    39. [39]

      Zhang L, Xie X Y, Wang H. Boosting Electrocatalytic N2 Reduction by MnO2 with Oxygen Vacancies[J]. Chem Commun, 2019, 55:  4627-4630. doi: 10.1039/C9CC00936A doi: 10.1039/C9CC00936A

    40. [40]

      Roche I, Chainet E, Chatenet M. Carbon-Supported Manganese Oxide Nanoparticles as Electrocatalysts for the Oxygen Reduction Reaction (ORR) in Alkaline Medium:Physical Characterizations and ORR Mechanism[J]. J Phys Chem C, 2007, 111:  1434-1443.

    41. [41]

      Watt G W, Chrisp J D. Spectrophotometric Method for Determination of Hydrazine[J]. Anal Chem, 1952, 24:  2006-2008. doi: 10.1021/ac60072a044 doi: 10.1021/ac60072a044

  • Figure 1  (A) LSV curves of MnOx/C catalysts with different metal (Mn) loadings in N2 saturated 0.05 mol/L H2SO4 electrolyte; (B) LSV curves of MnOx-30/C after heat-treatment at different temperatures in N2 saturated 0.05 mol/L H2SO4 electrolyte; (C) LSV curves of MnOx-30/C-350 catalyst in N2 and Ar saturated 0.05 mol/L H2SO4 electrolyte; (D) Chronoamperometry curve of MnOx-30/C-350 in N2 saturated 0.05 mol/L H2SO4 electrolyte at different potentials

    Figure 2  ENRR product analysis on optimal catalyst MnOx-30/C-350 in N2-saturated 0.05 mol/L H2SO4 solution. (A) UV-Vis absorption spectra of NH4+ ions solution at different potentials; (B) UV-Vis absorption spectra of N2H4·H2O solution at different potentials; (C) NH3 yield and FE at different potentials; (D) NH3 yield and FE of MnOx-30/C-350 in 8 cycles of test at potential of -0.56 V

    Figure 3  (A) SEM images of MnOx-30/C-350 before testing; (B) SEM images of MnOx-30/C-350 after long-term testing (16 hours at -0.56 V); (C-F) HAADF-STEM and element mapping images of MnOx-30/C-350

    Figure 4  (A) Performance test results of univalent MnO/C, Mn2O3/C, MnO2/C and polyvalent MnOx-30/C-350 (FE and yield were test at -0.56 V and -0.66 V, respectively); (B) XPS pattern of MnOx-30/C; (C) XPS pattern of MnOx-30/C-350. (D) Contents of Mn in different valence in MnOx-30/C after calcinated at different temperatures and corresponding FE of NH3

  • 加载中
计量
  • PDF下载量:  0
  • 文章访问数:  51
  • HTML全文浏览量:  5
文章相关
  • 发布日期:  2020-09-01
  • 收稿日期:  2020-03-22
  • 接受日期:  2020-05-07
  • 修回日期:  2020-04-15
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

/

返回文章