Structural Effect on the Oxygen Evolution Reaction in the Electrochemical Catalyst FePt

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1 New Physics: Sae Mulli, Vol. 65, No. 9, September 2015, pp DOI: /NPSM Structural Effect on the Oxygen Evolution Reaction in the Electrochemical Catalyst FePt Wonseok Jeong Gijae Kang Kyeyoup Kim Gabin Yoon Kisuk Kang Seungwu Han Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea (Received 9 June 2015 : revised 2 July 2015 : accepted 6 July 2015) We investigated the overpotential of the oxygen evolution reaction for the FePt catalyst by using a density functional theory calculation. We conducted the calculation for two types of FePt catalysts: FePt with an ordered L1 0 crystal structure and FePt with atoms randomly distributed at the face-centered-cubic (FCC) crystal sites. First, we investigated the surface energy of the L1 0 FePt surface and concluded that the reacting surface was a (111) surface because of its low surface energy. Next, we calculated the free energy of the oxygen evolution reaction (OER) steps and obtained the theoretical overpotentials for the two types of FePt catalysts. The overpotentials for the ordered L1 0 and the disordered FCC FePt catalysts were found to be 2.26 V and 2.17 V, respectively. The disordered FCC FePt is expected to have a higher catalyst activity than the ordered L1 0 FePt. PACS numbers: Jn, A-, E- Keywords: FePt, Water splitting, Catalyst, Oxygen evolution reaction (OER), ab initio FePt, ( , , ) L1 0 FePt FCC FePt., L1 0 FePt (111)., L1 0 FePt FCC FePt 2.26 V, 2.17 V FCC FePt 0.09 V. Pt 2.55 V כ. PACS numbers: Jn, A-, E- Keywords: FePt,,,, kensou3@snu.ac.kr This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 Structural Effect on the Oxygen Evolution Reaction in the Electrochemical Catalyst FePt Wonseok Jeong et al. 879 I... [1]. 2H 2 O O 2 + 4H + + 4e (1) (Oxygen Evolution Reaction, OER) (Hydrogen Evolution Reaction, HER),,. Cathode : 2H + + 2e H + H + + e H 2 (2) Anode : 2H 2 O OH + H 2 O + e + H + O + H 2 O + 2e + 2H + OOH + 3e + 3H + O 2 + 4e + 4H + (3) 1.23 V. (activation overpotential), (concentration overpotential), (resistance overpotential) (overpotential, η). (10 ma/cm 2 ) כ [2,3]. כ 1.23 V כ. Pt, TiO 2, Co, Bi, Pt. Pt (Oxygen Reduction Reaction, ORR) כ. Pt, Pt Fe, Co, Ni [4,5]. Pt, Fe Pt 1 1 FePt Pt (ORR activity) [6 8]. FePt (FCC) ( d-fept) Fe Pt. FePt 530 C, FCC Fe Pt (100) (200) (FCT) ( o-fept). L1 0 [9 11]. FePt,, FePt. Pt Fe 1 1 FePt. FePt FCC d-fept L1 0 o-fept [7]. o-fept d-fept (Density Functional Theory) FePt. II. EDISON Linear Combination of Atomic Orbitals Density Functional Theory SW [12] VASP (Vienna Ab initio Simulation Package) [13]. (Generalized Gradient Approximations, GGA) [16] PAW (Projector-augmented Wave Pseudopotential) [14,15]. 8 FePt, 15 Å (Periodic Boundary Condition). FePt 300 ev, 400 ev, k- point Γ. o-fept

880 New Physics: Sae Mulli, Vol. 65, No. 9, September 2015 Table 1. Surface energy and surface energy per fomular unit of d-fept with different surface coordinates.

1 1. 0.02 ev/å. W. H. Butler (Ferromagnetic Coupling) FePt כ [19]. (001). Fig. 1. (Color online) Lattice structure of o-fept with (a) (100), (b) (110), (c) (111) surface coordinates. III.

3 880 New Physics: Sae Mulli, Vol. 65, No. 9, September 2015 Table 1. Surface energy and surface energy per fomular unit of d-fept with different surface coordinates. Orientation Slab Energy Surface Energy [ev/fomular unit] [mev/å 2 ] (100) (110) (111) L1 0 FePt. a 3.91 Å c 3.74 Å c/a 0.95 [17]. d-fept 3.84 Å FCC Fe Pt [18] ev/å. W. H. Butler (Ferromagnetic Coupling) FePt כ [19]. (001). Fig. 1. (Color online) Lattice structure of o-fept with (a) (100), (b) (110), (c) (111) surface coordinates. III. o-fept o-fept. γ = E slab E bulk (4) 2A E slab E bulk A. Fig. 1, Table 1. (111), (111). o-fept d-fept Fig. 2. o-fept (111) (FCT)... 2H 2 O + OH + H 2 O + e + H + (5) OH + H 2 O O + H 2 O + e + H + (6) O + H 2 O OOH + e + H + (7) OOH O 2 + e + H + (8) Fig. 2. (Color online) Lattice structure of (a) o-fept and (b) d-fept. [20]. G1 = E(OH ) E( ) E(H 2 O) E(H 2) eu (9) G2 = E(O ) E(OH ) E(H 2) eu (10) G3 = E(OOH ) E(O ) E(H 2 O) E(H 2) eu (11) G4 = E(O 2 ) E(OOH ) + E( ) (H 2)] eu (12) U (Normal Hydrogen Electrode, NHE). (9)- (12) 4.92 ev כ. GGA-DFT

4 Structural Effect on the Oxygen Evolution Reaction in the Electrochemical Catalyst FePt Wonseok Jeong et al. 881 Table 2. Free energy of reactant and product with o-fept and d-fept catalyst. Free Energy [ev] O OH OOH H 2O H 2 o-fept d-fept Table 3. Free energy of reaction steps in 0 V and 1.23 V when o-fept catalyst is used [ev]. Voltage Step 1 Step 2 Step 3 Step 4 0 V V Table 4. Free energy of reaction steps in 0 V and 1.23 V when d-fept catalyst is used [ev]. Voltage Step 1 Step 2 Step 3 Step 4 0 V V Fig. 3. (Color online) OH molecule s position on the surface of (a) o-fept and (b) d-fept during OER.. ph 0 H + 0. (Table 2), OH Fig. 3. H 2 O, O 2, e כ, Table 3 Table 4. כ. η = max[ G1, G2, G3, G4]/e 1.23[V ] (13) Table 3 Table V 3, V. Fig. 4 כ. Fig. 4 o-fept d-fept 2.26 V, 2.17 V d-fept 0.09 V. Rossmeisl Pt 2.55 V כ, FePt [1]. (ORR) o-fept d-fept כ, d-fept. FePt כ. Fig. 4. (Color online) Free energy variation through OER with (a) o-fept and (b) d-fept catalyst. IV. (GGA) L1 0 o-fept FCC d-fept.

5 882 New Physics: Sae Mulli, Vol. 65, No. 9, September 2015 o-fept (111). o-fept d- FePt 2.26 V, 2.17 V. d-fept כ. Pt ( ) (No. NRF-2012-M3C1A ). REFERENCES [1] J. Rossmeisl, A. Logadottir and J. K. Nørskov, Chem. Phys. 319, 178 (2005). [2] M. G. Walter, E. L. Warren, J. R. McKone, S. W. Boettcher and Q. Mi et al., Chem. Rev. 110, 6446 (2010). [3] T. R. Cook, D. K. Dogutan, S. Y. Reece, Y. Surendranath and T. S. Teets et al., Chem. Rev. 110, 6474 (2010). [4] J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson and H. A. Hansen et al., Nat. Chem. 1, 552 (2009). [5] E. Antolini, J. R. C. Salgado and E. R. Gonzalez, Sci. Dir. 160, 957 (2006). [6] S. Guo and S. Sun, J. Am. Chem. Soc. 134, 2492 (2012). [7] J. Kim, Y. Lee and S. Sun, J. Am. Chem. Soc. 132, 4996 (2010). [8] V. Mazumder, M. Chi, K. L. More and S. Sun, J. Am. Chem. Soc. 132, 7848 (2010). [9] C. Rong, D. Li, V. Nandwana, N. Poudyal and Y. Ding et al., Adv. Mater. 18, 2984 (2006). [10] R. A. Ristau, K. Barmak, L. H. Lewis, K. R. Coffey and J. K. Howard, J. Appl. Phys. 86, 4527 (1997). [11] Z. R. Dai, S. Sun and Z. L. Wang, Nano Lett. 1, 443 (2001). [12] (accessed June 4, 2015). [13] G. Kresse and J. Furthmuller, Comput. Mater. Sci. 6, 15 (1996). [14] P. E. Blochl, Phys. Rev. B 50, (1994). [15] G. Kresse and D. Joubert, Phys. Rev. B 59, 1758 (1999). [16] J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996). [17] T. J. Klemmer, N. Shukla, C. Liu, X. W. Wu and E. B. Svedberg, Appl. Phys. Lett. 81, 2220 (2002). [18] M. S. Seehra, V. Singh, P. Dutta, S. Neeleshwar, Y. Y. Chen et al., Appl. Phys. 43, (2010). [19] Z. Lu, R. V. Chepulskii and W. H. Butler, Phys. Rev. B 81, (2010). [20] M. Bajdich, M. Garcia-Mota, A. Vojvodic, J. K. Nørskov and A. T. Bell, J. Am. Chem. Soc. 135, (2013).

Molybdenum compound MoP as an efficient. electrocatalyst for hydrogen evolution reaction

Electronic Supplementary Material (ESI) for Energy & Environmental Science. This journal is The Royal Society of Chemistry 2014 Molybdenum compound MoP as an efficient electrocatalyst for hydrogen evolution