直接甲醇燃料電池(DMFCs)是透過將甲醇燃料以化學能形式直接轉換成電能的一種電池，其可攜帶性使之成為極具發展潛力的供電裝置。在此研究中分別藉由實驗與理論計算兩個面向來檢定DMFCs中的甲醇氧化反應(MOR)，並通過此研究揭示將Pt與具高度親氧性Sn進行氧化後，其對陽極觸媒PtSn所造成的重要影響。
關於實驗部分，原先的Pt3Sn nanorods(NRs)是透過甲酸還原法所合成，隨後透過改變不同溫度(150, 200, 250與300oC)與加溫時間(1, 1.5, 3與5 hr)的氧化後處理過程進行各式樣品的製備。其中經由不同的氧化條件所得到的PtSn NRs氧化程度皆不盡相同，所以藉HRTEM, XRD, EDX, XPS對觸媒的表徵進行鑑定，並由電化學測試瞭解其MOR的催化能力。透過實驗的結果可以發現，當Pt3Sn NRs在經過200oC加熱氧化三小時的條件下擁有約54 %的表面氧化度，也具備最為優異的MOR活性與觸媒穩定性。
計算的部分則分別探討甲醇在乾淨與經過氧化(表面具有氧原子吸附)的Pt表面、NR模型的脫氫反應及氧化反應。由結果顯示出，無論是乾淨的Pt表面亦或是NR，(100)面皆擁有較低的脫氫反應能與反應能障。之於經過氧化的表面，(100)面的氧化反應可以得到更進一步的提升。NR則因為同時具備(100)與(111)表面，且在side位點擁有最穩定的氧吸附。因此亦如實驗的結果，其將展現最優異的MOR催化活性與觸媒穩定性。

Direct methanol fuel cells (DMFCs), which directly convert the chemical energy of methanol fuel into electricity, are a promising candidate for portable electronic devices. In this study, we experimentally and computationally examined methanol oxidation reaction (MOR), the key anodic reaction in DMFCs, on PtSn materials to mechanistically reveal the important oxide effect from Pt and the high-oxophilic Sn.
Experimentally, Pt3Sn nanorods (NRs) was initially prepared by formic acid reduction method; post-oxidation processes with varied oxidation temperatures (150, 200, 250, and 300oC) and time (1, 1.5, 3 and 5 hours) have been further employed. Those PtSn NRs with different degrees of oxidations have been characterized by HRTEM, XRD, EDX and XPS and their MOR performance have been examined by electrochemical tests. The experimental results showed that Pt3Sn NRs oxidized at 200oC for 3 hours have a surface oxidation degree of 54 % and showed the best MOR activity and stability.
Computationally, we examined methanol decomposition and oxidation, key steps in MOR, on clean and oxidized (with surface oxygen) Pt surfaces and NR. Our results found that (100) facet on clean Pt surface and NR have lower reaction energies and activation barriers for decomposition reactions. On oxide surface, (100) facets can further assisted for the oxidation reactions. NR, which contains both (100) and (111) facets and has the most stable oxide on side sites, is expected to show the best MOR activity and stability, as observed from the experiment.

1. Lu, X., et al., Methanol Oxidation on Pt3Sn(111) for Direct Methanol Fuel Cells: Methanol Decomposition. ACS Applied Materials & Interfaces, 2016. 8(19): p. 12194-12204.
2. Zhao, L., et al., The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation. The Journal of Physical Chemistry C, 2015. 119(35): p. 20389-20400.
3. Stevanović, S., et al., Insight into the Effect of Sn on CO and Formic Acid Oxidation at PtSn Catalysts. The Journal of Physical Chemistry C, 2014. 118(1): p. 278-289.
4. Morrow, B.H., et al., CO Adsorption on Noble Metal Clusters: Local Environment Effects. The Journal of Physical Chemistry C, 2011. 115(13): p. 5637-5647.
5. Kolla, P. and A. Smirnova, Methanol Oxidation and Oxygen Reduction Activity of PtIrCo-Alloy Nanocatalysts Supercritically Deposited within 3D Carbon Aerogel Matrix. Electrochimica Acta, 2015. 182: p. 20-30.
6. Joghee, P., et al., High-Performance Alkaline Direct Methanol Fuel Cell using a Nitrogen-Postdoped Anode. ChemSusChem, 2014. 7(7): p. 1854-1857.
7. Lebedeva, N.P., et al., Role of Crystalline Defects in Electrocatalysis:  Mechanism and Kinetics of CO Adlayer Oxidation on Stepped Platinum Electrodes. The Journal of Physical Chemistry B, 2002. 106(50): p. 12938-12947.
8. Hassan, K.M., et al., Electrocatalytic oxidation of ethanol at Pd, Pt, Pd/Pt and Pt/Pd nano particles supported on poly 1,8-diaminonaphthalene film in alkaline medium. RSC Advances, 2018. 8(28): p. 15417-15426.
9. Xiao, Y.-X., et al., PtPd hollow nanocubes with enhanced alloy effect and active facets for efficient methanol oxidation reaction. Chemical Communications, 2021. 57(8): p. 986-989.
10. Dai, L.-X., et al., Self-supported composites of thin Pt–Sn crosslinked nanowires for the highly chemoselective hydrogenation of cinnamaldehyde under ambient conditions. Inorganic Chemistry Frontiers, 2015. 2(10): p. 949-956.
11. Yin, S., et al., Pt@Mesoporous PtRu Yolk–Shell Nanostructured Electrocatalyst for Methanol Oxidation Reaction. ACS Sustainable Chemistry & Engineering, 2019. 7(17): p. 14867-14873.
12. Bai, J., et al., Bimetallic Platinum–Rhodium Alloy Nanodendrites as Highly Active Electrocatalyst for the Ethanol Oxidation Reaction. ACS Applied Materials & Interfaces, 2018. 10(23): p. 19755-19763.
13. Xiang, H., et al., Bimetallic and postsynthetically alloyed PtCu nanostructures with tunable reactivity for the methanol oxidation reaction. Nanoscale Advances, 2020. 2(4): p. 1603-1612.
14. Zhong, W., Y. Liu, and D. Zhang, Theoretical Study of Methanol Oxidation on the PtAu(111) Bimetallic Surface: CO Pathway vs Non-CO Pathway. The Journal of Physical Chemistry C, 2012. 116(4): p. 2994-3000.
15. Zhang, Y., et al., Glycine-Assisted Fabrication of N-Doped Graphene-Supported Uniform Multipetal PtAg Nanoflowers for Enhanced Ethanol and Ethylene Glycol Oxidation. ACS Sustainable Chemistry & Engineering, 2019. 7(3): p. 3176-3184.
16. Shubina, T.E. and M.T.M. Koper, Quantum-chemical calculations of CO and OH interacting with bimetallic surfaces. Electrochimica Acta, 2002. 47(22): p. 3621-3628.
17. Herranz, T., et al., In Situ Study of Ethanol Electrooxidation on Monodispersed Pt3Sn Nanoparticles. ChemElectroChem, 2014. 1(5): p. 885-895.
18. Stevanovic, S., et al., Carbon Supported PtSn versus PtSnO2 Catalysts in Methanol Oxidation. International Journal of Electrochemical Science, 2020. 16: p. 210222.
19. Chen, H.-S., et al., Role of the Secondary Metal in Ordered and Disordered Pt–M Intermetallic Nanoparticles: An Example of Pt3Sn Nanocubes for the Electrocatalytic Methanol Oxidation. ACS Catalysis, 2021. 11(4): p. 2235-2243.
20. Axnanda, S., W.-P. Zhou, and M.G. White, CO oxidation on nanostructured SnOx/Pt(111) surfaces: unique properties of reduced SnOx. Physical Chemistry Chemical Physics, 2012. 14(29): p. 10207-10214.
21. Li, H.-H., et al., Scalable Bromide-Triggered Synthesis of Pd@Pt Core–Shell Ultrathin Nanowires with Enhanced Electrocatalytic Performance toward Oxygen Reduction Reaction. Journal of the American Chemical Society, 2015. 137(24): p. 7862-7868.
22. Fan, X., et al., One-nanometer-thick platinum-based nanowires with controllable surface structures. Nano Research, 2019. 12(7): p. 1721-1726.
23. He, Y.-B., et al., Pt Nanorods Aggregates with Enhanced Electrocatalytic Activity toward Methanol Oxidation. The Journal of Physical Chemistry C, 2010. 114(45): p. 19175-19181.
24. Krishnaswamy, R., et al., Synthesis of Single-Crystalline Platinum Nanorods within a Soft Crystalline Surfactant–PtII Complex. Chemphyschem : a European journal of chemical physics and physical chemistry, 2006. 7: p. 1510-3.
25. Chen, L., et al., Promoting electrocatalytic methanol oxidation of platinum nanoparticles by cerium modification. Nano Energy, 2020. 73: p. 104784.
26. Lee, W.-J., et al., Synthesis of highly dispersed Pt nanoparticles into carbon supports by fluidized bed reactor atomic layer deposition to boost PEMFC performance. NPG Asia Materials, 2020. 12(1): p. 40.
27. Bai, G., et al., Atomic Carbon Layers Supported Pt Nanoparticles for Minimized CO Poisoning and Maximized Methanol Oxidation. Small, 2019. 15(38): p. 1902951.
28. Liu, Z., et al., Pt3Sn Nanoparticles with Controlled Size:  High-Temperature Synthesis and Room-Temperature Catalytic Activation for Electrochemical Methanol Oxidation. The Journal of Physical Chemistry C, 2007. 111(38): p. 14223-14229.
29. Jiang, K., et al., Efficient Oxygen Reduction Catalysis by Subnanometer Pt Alloy Nanowires. Science Advances, 2017. 3: p. e1601705.
30. Xia, B.Y., et al., Ultrathin and Ultralong Single-Crystal Platinum Nanowire Assemblies with Highly Stable Electrocatalytic Activity. Journal of the American Chemical Society, 2013. 135(25): p. 9480-9485.
31. Lu, Y., S. Du, and R. Steinberger-Wilckens, Temperature-controlled growth of single-crystal Pt nanowire arrays for high performance catalyst electrodes in polymer electrolyte fuel cells. Applied Catalysis B: Environmental, 2015. 164: p. 389-395.
32. Li, L., et al., Ultrathin PtxSn1–x Nanowires for Methanol and Ethanol Oxidation Reactions: Tuning Performance by Varying Chemical Composition. ACS Applied Nano Materials, 2018. 1(3): p. 1104-1115.
33. Wang, Z., et al., Pt3Sn nanoparticles enriched with SnO2/Pt3Sn interfaces for highly efficient alcohol electrooxidation. Nanoscale Advances, 2021. 3(17): p. 5062-5067.
34. Shao, Y., G. Yin, and Y. Gao, Understanding and approaches for the durability issues of Pt-based catalysts for PEM fuel cell. Journal of Power Sources, 2007. 171(2): p. 558-566.
35. Nagao, H., M. Ichiji, and I. Hirasawa, Synthesis of Platinum Nanoparticles by Reductive Crystallization Using Polyethyleneimine. Chemical Engineering & Technology, 2017. 40(7): p. 1242-1246.
36. Meng, H., et al., Morphology controllable growth of Pt nanoparticles/nanowires on carbon powders and its application as novel electro-catalyst for methanol oxidation. Nanoscale, 2011. 3(12): p. 5041-5048.
37. Colmati, F., E. Antolini, and E.R. Gonzalez, Ethanol oxidation on a carbon-supported Pt75Sn25 electrocatalyst prepared by reduction with formic acid: Effect of thermal treatment. Applied Catalysis B: Environmental, 2007. 73(1): p. 106-115.
38. SILVA, D.F., OLIVEIRA NETO, A., SEGURA PINO, E., LINARDI, M., SPINACE, E. V., & INTERNATIONAL NUCLEAR ATLANTIC CONFERENCE, Effect of Pt: Sn Atomic Ratio On the Preparation of PtSn/C Electrocatalysts Using Electron Beam Irradiation. 2014. 2014.
39. Aramesh, N., et al., PtSn Nanoalloy Thin Films as Anode Catalysts in Methanol Fuel Cells. Inorganic Chemistry, 2020. 59(15): p. 10688-10698.
40. Chen, J.-Y., et al., Sub-1 nm PtSn ultrathin sheet as an extraordinary electrocatalyst for methanol and ethanol oxidation reactions. Journal of Colloid and Interface Science, 2019. 545: p. 54-62.
41. Huang, H., et al., Effects of heat treatment atmosphere on the structure and activity of Pt3Sn nanoparticle electrocatalysts: a characterisation case study. Faraday Discussions, 2018. 208(0): p. 555-573.
42. Devarajan, S.P., J.A. Hinojosa, and J.F. Weaver, STM study of high-coverage structures of atomic oxygen on Pt(111): p(2×1) and Pt oxide chain structures. Surface Science, 2008. 602(19): p. 3116-3124.
43. Michalak, W.D., et al., CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions. Journal of Catalysis, 2014. 312: p. 17-25.
44. van Spronsen, M.A., J.W.M. Frenken, and I.M.N. Groot, Observing the oxidation of platinum. Nature Communications, 2017. 8(1): p. 429.
45. Cho, S., et al., Oxidation study of pure tin and its alloys via electrochemical reduction analysis. Journal of Electronic Materials, 2005. 34(5): p. 635-642.
46. Zhou, W.-P., et al., Enhancement in Ethanol Electrooxidation by SnOx Nanoislands Grown on Pt(111): Effect of Metal Oxide–Metal Interface Sites. The Journal of Physical Chemistry C, 2011. 115(33): p. 16467-16473.
47. Limited, J.C.C.J.M.C., The Oxidation of the Platinum Metals. 1975: p. 19, (4)135-140.
48. Du, W., et al., Platinum-Tin Oxide Core–Shell Catalysts for Efficient Electro-Oxidation of Ethanol. Journal of the American Chemical Society, 2014. 136(31): p. 10862-10865.
49. https://www.imem.cnr.it/en/AdR/6/208/Structural-and-Surface-Characterization/Photoelectron-Spectroscopies.
50. Chung, D.Y., K.-J. Lee, and Y.-E. Sung, Methanol Electro-Oxidation on the Pt Surface: Revisiting the Cyclic Voltammetry Interpretation. The Journal of Physical Chemistry C, 2016. 120(17): p. 9028-9035.
51. Manoharan, R. and J. Prabhuram, Possibilities of prevention of formation of poisoning species on direct methanol fuel cell anodes. Journal of Power Sources, 2001. 96(1): p. 220-225.
52. Duan, Y., et al., Enhanced methanol oxidation and CO tolerance using oxygen-passivated molybdenum phosphide/carbon supported Pt catalysts. Journal of Materials Chemistry A, 2016. 4(20): p. 7674-7682.
53. Daubinger, P., et al., Electrochemical characteristics of nanostructured platinum electrodes – a cyclic voltammetry study. Physical Chemistry Chemical Physics, 2014. 16(18): p. 8392-8399.
54. Wakelin, T., et al., Catalysis of Methanol Oxidation on Bimetallic Ir/Pt(poly) Electrodes. Journal of nanoscience and nanotechnology, 2020. 20: p. 1148-1157.
55. Wang, K., et al., Palygorskite promoted PtSn/carbon catalysts and their intrinsic catalytic activity for ethanol oxidation. Electrochimica Acta, 2012. 70: p. 394–401.
56. Ramallo-López, J.M., et al., XPS and XAFS Pt L2,3-Edge Studies of Dispersed Metallic Pt and PtSn Clusters on SiO2 Obtained by Organometallic Synthesis:  Structural and Electronic Characteristics. The Journal of Physical Chemistry B, 2003. 107(41): p. 11441-11451.
57. Bharadwaj, N., A.S. Nair, and B. Pathak, Dimensional-Dependent Effects in Platinum Core–Shell-Based Catalysts for Fuel Cell Applications. ACS Applied Nano Materials, 2021. 4(9): p. 9697-9708.
58. Vandichel, M. and H. Grönbeck, CO Oxidation at SnO2/Pt3Sn(111) Interfaces. Topics in Catalysis, 2018. 61(14): p. 1458-1464.