在水分解電極催化方面，當今以氧化釕（RuO2）和氧化銥（IrO2）做為表現最佳之水分解反應催化劑。然而，這兩種催化劑的高成本始終是一個問題所在。鈣鈦礦氧化物作為潛在的替代物正受到越來越多的關注。鈣鈦礦通過成分控制和結構變化表現出非凡的物理和化學性能可調性。為了用作催化劑，可以透過改變成分組成進而提升產氧反應和氧還原反應效率、氧遷移率和離子電導率以增強催化性能。鈣鈦礦氧化物具有兩個晶格位，金屬可填充其中，以給出通式ABO3。通常，A位置可容納鑭系元素，鹼金屬或鹼土金屬陽離子，而B位置具有過渡金屬陽離子。不含貴金屬的鈣鈦礦氧化物對氧釋放反應和氧還原反應均顯示出雙功能活性。同時，鈣鈦礦可以承受陽離子和氧缺陷，而不會顯著改變晶格結構，並且它也是最便宜的材料，在將來是很有潛力的材料。
本研究使用化學合成法，合成了一類以A位置固定為鑭的LaMO3之單相高熵材料，其中M由5種不同的過渡金屬組成依照不同比例組成，這些金屬分別是鉻、猛、鐵、鈷和鎳。此外簡單的鈣鈦礦材料(M≤3的情況)和中熵鈣鈦礦材料(M=4)也同時以化學合成法合成以利於比較，與基於La的簡單鈣鈦礦相比，我們增強了電催化劑性能，並將根據材料特性討論催化劑的性能。

When it comes to electrode catalysis, Ruthenium oxide (RuO2) and Iridium oxide (IrO2) show apparent performance. However, the high cost of these two catalysts is always a concern. In this context, perovskite oxide is receiving increasing attention as a potential replacement. Perovskite exhibits extraordinary tunability of their physical and chemical properties through composition control and structural variation. For use as a catalyst, the redox behavior, oxygen mobility, and ionic conductivity can all be tailed to enhance the catalysis performance. In this study, we have synthesized a new class of high entropy LaMO3 where M consist of 4 to 5 different metals using a chemical route. We demonstrate enhanced electrocatalyst performance as compared to common perovskite based on La. The catalysts performance will be discussed in terms of the materials characteristics.

1. Jien-Wei Yeh, S.-K.C., Su-Jien Lin, Jon-Yiew Gan, Tsung-Shune Chin, Tao-Tsung Shun, Chun-Huei Tsau,and Shou-Yi Chang, Nanostructured High-Entropy Alloys with Multiple Principal Elements Novel Alloy Design Concepts and Outcomes. Adv. Eng. Mater., 2004.
2. Jien-Wei Yeh, S.-K.C., Jon-Yiew Gan, T.-S.C., SU-JIEN LIN, TAO-TSUNG, C.-H.T. SHUN, and SHOU-YI CHANG, Formation of Simple Crystal Structures in Cu-Co-Ni-Cr-Al-Fe-Ti-V Alloys with Multiprincipal Metallic Elements. Mater. Trans., 2004.
3. Huang, P.K. et al., Multi-Principal-Element Alloys with Improved Oxidation and Wear Resistance for Thermal Spray Coating. Adv. Eng. Mater., 2004. 6(12): p. 74-78.
4. Otto, F. et al., Relative effects of enthalpy and entropy on the phase stability of equiatomic high-entropy alloys. Acta Mater., 2013. 61(7): p. 2628-2638.
5. Zou, Y. et al., Size-dependent plasticity in an Nb25Mo25Ta25W25 refractory high-entropy alloy. Acta Mater., 2014. 65: p. 85-97.
6. Gali, A. and E.P. George, Tensile properties of high-entropy and medium-entropy alloys. Intermetallics, 2013. p. 74-78.
7. Gludovatz, B. et al., A fracture-resistant high-entropy alloy for cryogenic applications. Science, 2014. 345(6201): p. 1153
8. Kumar, N.A.P.K. et al., Microstructural stability and mechanical behavior of FeNiMnCr high entropy alloy under ion irradiation. Acta. Mater., 2016. 113: p. 230-244.
9. Bérardan, D. et al., Room temperature lithium superionic conductivity in high entropy oxides. J. Mater. Chemi. A, 2016. 4(24): p. 9536-9541.
10. Sarkar, A., et al., Multicomponent equiatomic rare earth oxides with a narrow band gap and associated praseodymium multivalency. Dalton Trans., 2017. 46(36): p. 12167-12176.
11. Sarkar, A. et al., Rare earth and transition metal based entropy stabilised perovskite type oxides. J. Eur. Ceram. Soc., 2018. 38(5): p. 2318-2327.
12. Dąbrowa, J. et al., Synthesis and microstructure of the (Co,Cr,Fe,Mn,Ni)3O4 high entropy oxide characterized by spinel structure. Mater. Letters, 2018. 216: p. 32-36.
13. Sarkar, A. et al., High entropy oxides for reversible energy storage. Nat. Commun., 2018. 9(1): p. 3400.
14. Wang, Q. et al., High entropy oxides as anode material for Li-ion battery applications: A practical approach. Electrochem. Commun., 2019. 100: p. 121-125.
15. Shafi, P.M. et al., Enhanced electrochemical performances of agglomeration-free LaMnO3 perovskite nanoparticles and achieving high energy and power densities with symmetric supercapacitor design. Chem. Eng. J., 2018. 338: p. 147-156.
16. Gray, H.B., Powering the planet with solar fuel. Nat. Chem., 2009.
17. Kanan, M.W. and D.G. Nocera, In situ formation of an oxygen-evolving catalyst in neutral water containing phosphate and Co2+. Science, 2008. 321(5892): p. 1072-5.
18. Yi-Chun Lu, Z.X., Hubert A. Gasteiger, Shuo Chen, Kimberly Hamad-Schifferli, and Yang Shao-Horn, Platinum−Gold Nanoparticles: A Highly Active Bifunctional Electrocatalyst for Rechargeable Lithium−Air Batteries. J. Am. Chem. Soc., 2010. 132, 35, 12170-12171.
19. Tarascon, M.A.J.-M., Building better batteries. Nature, 2008. p.451.
20. Suen, N.T., et al., Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives. Chem. Soc. Rev., 2017. 46(2): p. 337-365.
21. Wang, V.C., Exploring the kinetic and thermodynamic aspects of four-electron electrochemical reactions: electrocatalysis of oxygen evolution by metal oxides and biological systems. Phys. Chem. Chem. Phys., 2016. 18(32): p. 22364-72.
22. Zhong, H. et al., Recent Advances of Cobalt-Based Electrocatalysts for Oxygen Electrode Reactions and Hydrogen Evolution Reaction. Catal., 2018. 8(11).
23. AS Feiner, A.M., The Nernst Equation. J. Chem. Educ., 1994.
24. Fierro, M.A.P.a.a.J.L.G., Chemical Structures and Performance of Perovskite Oxides. Chem. Rev., 2001. 1981-2017.
25. Zhu, J. et al. Perovskite Oxides: Preparation, Characterizations, and Applications in Heterogeneous Catalysis. ACS Catal., 2014. 4(9): p. 2917-2940.
26. Perovskites by Design: A Toolbox of Solid-State Reactions. Chem. Mater., 2002. 1455-1471.
27. Ngamou, P.H.T. and N. Bahlawane, Influence of the Arrangement of the Octahedrally Coordinated Trivalent Cobalt Cations on the Electrical Charge Transport and Surface Reactivity. Chem. Mater., 2010. 22(14): p. 4158-4165.
28. Natile, M.M. et al., LaCoO3: Effect of synthesis conditions on properties and reactivity. Appl. Catal. B, 2007. 72(3-4): p. 351-362.
29. Mueller, D.N. et al., Redox activity of surface oxygen anions in oxygen-deficient perovskite oxides during electrochemical reactions. Nat. Commun., 2015. 6: p. 6097.
30. Zhu, H., P. Zhang, and S. Dai, Recent Advances of Lanthanum-Based Perovskite Oxides for Catalysis. ACS Catal., 2015. 5(11): p. 6370-6385.
31. Suntivich, J. et al., A perovskite oxide optimized for oxygen evolution catalysis from molecular orbital principles. Science, 2011. 334(6061): p. 1383-5.
32. Shao, Y. et al., Electrocatalysts for Nonaqueous Lithium–Air Batteries: Status, Challenges, and Perspective. ACS Catal., 2012. 2(5): p. 844-857.
33. Michael G. Walter, E.L.W., James R. McKone, Shannon W. Boettcher,† Qixi Mi, Elizabeth A. Santori, and a.N.S. Lewis, Solar Water Splitting Cells. Chem. Rev., 2010. 2010, 110, 6446–6473.
34. Bockris, J.O.M. and T. Otagawa, Mechanism of oxygen evolution on perovskites. J. Phys. Chem., 1983. 87(15): p. 2960-2971.
35. Lv, Y. et al., Copper/cobalt-doped LaMnO3 perovskite oxide as a bifunctional catalyst for rechargeable Li-O2 batteries. J. Alloys Compd., 2019. 801: p. 19-26.
36. Wang, Z. et al., Nickel-Doped La0.8Sr0.2Mn1–xNixO3 Nanoparticles Containing Abundant Oxygen Vacancies as an Optimized Bifunctional Catalyst for Oxygen Cathode in Rechargeable Lithium–Air Batteries. ACS Appl. Mate. Interfaces, 2016. 8(10): p. 6520-6528.
37. Cherevko, S. et al., Oxygen and hydrogen evolution reactions on Ru, RuO2 , Ir, and IrO2 thin film electrodes in acidic and alkaline electrolytes: A comparative study on activity and stability. Catal. Today, 2016. 262: p. 170-180.
38. Marshall, A.T. and R.G. Haverkamp, Electrocatalytic activity of IrO2–RuO2 supported on Sb-doped SnO2 nanoparticles. Electrochim. Acta, 2010. 55(6): p. 1978-1984.
39. Audichon, T. et al., IrO2 Coated on RuO2 as Efficient and Stable Electroactive Nanocatalysts for Electrochemical Water Splitting. J. Phys. Chem. C, 2016. 120(5): p. 2562-2573.
40. Li, M. et al., Facile synthesis of electrospun MFe2O4 (M = Co, Ni, Cu, Mn) spinel nanofibers with excellent electrocatalytic properties for oxygen evolution and hydrogen peroxide reduction. Nanoscale, 2015. 7(19): p. 8920-30.
41. Singh, N.K. and R.N. Singh, Electrocatalytic properties of spinel type NixFe3-xO4 synthesized at low temperature for oxygen evolution in KOH solutions. Indian J. Chem., 1999. 38A, 5.
42. Subbaraman, R., et al., Trends in activity for the water electrolyser reactions on 3d M(Ni,Co,Fe,Mn) hydr(oxy)oxide catalysts. Nat. Mater., 2012. 11(6): p. 550-557.
43. 林麗娟, X光繞射原理及其應用. X光材料分析技術與應用專題, 1994.
44. David B. and Williams, C.B.C., The Transmission Electron Microscope. 1996.
45. Département de Chimie, U.d.S., Sherbrooke, Québec, Canada J1K 2R1, electrochemical-impedance-spectroscopy-and-its-applications. 1999. MAOE, volume 32.
46. Connor, P. et al., The Determination of Electrochemical Active Surface Area and Specific Capacity Revisited for the System MnOx as an Oxygen Evolution Catalyst. Z. Phys. Chem., 2020. 234(5): p. 979-994.
47. McCrory, C.C., et al., Benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction. J. Am. Chem. Soc., 2013. 135(45): p. 16977-16987.
48. Han, H., et al., Electronically Double‐Layered Metal Boride Hollow Nanoprism as an Excellent and Robust Water Oxidation Electrocatalysts. Adv. Energy Mater., 2019. 9(13).
49. Macdonald, D.D., Chronopotentiometry. Transient Techniques in Electrochemistry. pp 119-184.
50. Ivanov, P.G., S.M. Watts, and D.M. Lind, Epitaxial growth of CrO2 thin films by chemical-vapor deposition from a Cr8O21 precursor. J. Appl. Phys., 2001. 89(2): p. 1035-1040.
51. Otagawa, J.O.M.B.a.T., Mechanism of Oxygen Evolution on Perovskites. J. Phys. Chem., 1983. 57, 2960-2971.
52. Cheng, F. et al., Rapid room-temperature synthesis of nanocrystalline spinels as oxygen reduction and evolution electrocatalysts. Nat. Chem., 2011. 3(1): p. 79-84.
53. Suntivich, J. et al., Design principles for oxygen-reduction activity on perovskite oxide catalysts for fuel cells and metal-air batteries. Nat. Chem., 2011. 3(7): p. 546