NiFe Layered Double Hydroxide Electrocatalyst

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Single-Atom Au/NiFe Layered Double Hydroxide Electrocatalyst: Probing the Origin of Activity for Oxygen Evolution Reaction Jingfang Zhang, Jieyu Liu, Lifei Xi, Yifu Yu, Ning Chen, Shuhui Sun, Weichao Wang, Kathrin M. Lange, and Bin Zhang J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 08 Mar 2018 Downloaded from http://pubs.acs.org on March 8, 2018

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Single-Atom Au/NiFe Layered Double Hydroxide Electrocatalyst: Probing the Origin of Activity for Oxygen Evolution Reaction Jingfang Zhang,†,§ Jieyu Liu,‡,§ Lifei Xi,⊥,§ Yifu Yu,† Ning Chen,∥ Shuhui Sun,п Weichao Wang,‡,#,* Kathrin M. Lange,⊥,+ and Bin Zhang†,#,* †

Department of Chemistry, School of Science, and Tianjin Key Laboratory of Molecular Optoelectronic Science, Tianjin University, Tianjin 300072, China ‡ Department of Electronics, Nankai University, Tianjin 300071, China #

Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China Canadian Light Source, Saskatoon, S7N 2V3, Canada п Institut National de la Recherche Scientifique-Énergie Matériaux et Télécommunications, Varennes, Quebec J3X 1S2, Canada ∥

⊥

Young Investigator Group Operando Characterization of Solar Fuel Materials (EE-NOC), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin 12489, Germany + Universität Bielefeld, Physikalische Chemie, Universitätsstr. 25, D-33615 Bielefeld, Germany Supporting Information Placeholder ABSTRACT: A fundamental understanding of the origin of oxygen evolution reaction (OER) activity of transition-metalbased electrocatalysts, especially for single precious metal atoms supported on layered double hydroxides (LDHs), is highly required for the design of efficient electrocatalysts towards further energy conversion technologies. Here, we aim towards singleatom Au supported on NiFe LDH (sAu/NiFe LDH) to clarify the activity origin of LDHs system and a 6-fold OER activity enhancement by 0.4 wt% sAu decoration. Combining with theoretical calculations, the active behavior of NiFe LDH results from the in-situ generated NiFe oxyhydroxide from LDH during OER process. With the presence of sAu, sAu/NiFe LDH possesses an overpotential of 0.21 V in contrast to the calculated result (0.18 V). We ascribe the excellent OER activity of sAu/NiFe LDH to the charge redistribution of active Fe as well as its surrounding atoms causing by the neighboring sAu on NiFe oxyhydroxide stabilized by interfacial CO32- and H2O interfacing with LDH.

The oxygen evolution reaction (OER) has been extensively studied due to its critical role in the expansion of renewable energy technologies, including water splitting and rechargeable metalair batteries.1-3 Because of the intrinsically sluggish reaction kinetics of the OER, highly efficient electrocatalysts are desired to improve the energy conversion efficiency. Up to now, noble metal oxides (RuO2 and IrO2) are considered as active catalysts,4 but their high cost and scarcity severely impede their wide applications. Recently, much effort has focused on inexpensive and earth-abundant elements based materials as viable alternatives for OER, such as transition-metal sulfides/selenides,1,5-8 oxides,9-14 nitrides15 and (oxy)hydroxides.16-20 Surprisingly, NiFe layered double hydroxides (LDHs) stand out from these candidates because of their excellent OER performances,21-23 which stimulates the ongoing exploration and optimi-

zation of OER properties on these electrocatalysts.24-29 Though the pioneering reports on the oxyhydroxides as the real active species for LDHs during OER,30,31 the large activity gap between LDHs and oxyhydroxides still remains unexplainable. Therefore, it is highly desirable to obtain a fundamental understanding of the origin of outstanding OER activity on the surface of LDHs. Recent works have suggested that supported Au nanostructures can effectively enhance electrocatalytic activity by favorable local catalyst-gold interfacial interactions.32-35 In addition, an emerging class of single-atom metal modified catalysts exhibits higher catalytic activity than non-modified ones towards hydrogen evolution reaction.13,14 Considering the noble nature of Au, downsizing the nanometre-scale to single-atoms could effectively decrease Au usage and maximize atomic utilization efficiency.36-38 However, to date, there is no conclusion whether single-atom Au (sAu) is helpful to enhance OER activity of current electrocatalysts, especially for LDHs, or not. Herein, we employed sAu supported on NiFe LDH (sAu/NiFe LDH) catalyst as a model to evaluate the OER activity and understand the activity origin at the atomic level. Theoretical results demonstrate that active sites could be attributed to Fe atoms in NiFe oxyhydroxide supported by LDH and stabilized by CO32anions and H2O. sAu could transfer electrons to LDH, changing the charge distribution and thus further improving the catalytic performance. Subsequent experimental measurements exhibit an outstanding OER performance, validating our theoretical findings. Density functional theory calculations plus Hubbard-U approach that includes dispersion interactions (i.e., van der Waals effects) (DFT + U + vdW) were conducted on sAu/NiFe LDH to explore its OER activity. We defined the activity using the free energy difference (∆G) for each elementary step39,40 (see Supporting Information (SI) for details).

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Figure 1. (a) The two-layer slab model for sAu/NiFe LDH with interlayer CO32- anions and water molecules. (b) Proposed OER pathways with OH*, O* and OOH* intermediates for sAu/NiFe LDH. (c) Free energy diagram for the OER at different potentials on the surface of sAu/NiFe LDH model. It is known that OER activity is determined by the stabilities of the adsorbed intermediates (OH*, O*, OOH*) on the surface of catalysts and evaluated by the descriptor of free energy difference, i.e., ∆GO* - ∆GOH*.18,41,42 For the NiFe LDH, we find that the first step of the OER process involves the detachment of H from the topmost surface of the regular LDH, also certified by a previous study.29 Consequently, LDH could be covered with NiFeOOH during the OER.43 Even more complex local environments like Ni-O or Fe-O with structural defects can form during the OER process.31 Therefore, a two-layer periodic (1 × 2) slab composed of a LDH bottom layer and a NiFeOOH stepped surface with a single Au atom is constructed as simulation model for sAu/NiFe LDH, denoted as sAu/NiFeOOH-NiFe LDH (Figure 1a). With the absence of Au atom, the corresponding simulation model is denoted as NiFeOOH-NiFe LDH (Figure S1). Figure 1b shows the optimized pathways of OER on the sAu/NiFeOOH-NiFe LDH surface. Based on the free energy diagram of sAu/NiFeOOH-NiFe LDH for OER (Figure 1c), the rate-determining step is the formation of OOH* from O* with an overpotential of 0.18 V. The corresponding binding energies ∆EOH* and ∆EOOH* for s Au/NiFeOOH-NiFe LDH are 0.93 eV and 3.46 eV, resulting in a favorable Gibbs energy of the four elementary steps, i.e., ∆G01 = 1.33 eV, ∆G02 = 1.15 eV, ∆G03 = 1.41 eV and ∆G04 = 1.03 eV at standard conditions. Our calculated results are very close to the thermochemically ideal OER process (∆EOH* = 0.86 eV and 0

∆EOOH* = 3.3 eV, with ∆G01 = ∆G2 = ∆G03 = ∆G04 = 1.23 eV) predicted by Rossmeisl et al..44 In contrast, for the NiFeOOH-NiFe LDH without sAu, the overpotential increases up to 0.26 V for which the rate-determining step is the formation of O* from OH*. The decrease of overpotential after dispersing sAu on NiFe LDH catalyst implies that the Au-catalyst interface sites play a vital role in improving OER activity. To further examine the effect of a LDH bottom layer on the OER activity, we also construct a slab model of sAu/NiFeOOH to simulate the OER process (Figure S2). An onset overpotential of 0.23 V is obtained, which is larger than that of sAu/NiFeOOH-NiFe LDH (0.18 V). The theoretical results reveal that the LDH substrate along with interlayer CO32- anions in sAu/NiFeOOH-NiFe LDH maintains the charge balance of oxyhydroxide thus stabilizes the surface NiFeOOH layer and leads to optimal adsorption energies of OER intermediates on Fe active sites.

Figure 2. (a) TEM, (b) HAADF-STEM, (c) EDS mapping images of sAu/NiFe LDH. (d) The Au L3-edge XANES spectra of the experimental and simulated results for sAu/NiFe LDH as well as Au foil. Encouraged by these DFT results, we synthesized sAu/NiFe LDH on Ti mesh to further certify the results. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal that sAu/NiFe LDH still maintain nanosheet morphology of NiFe LDH (Figure S3) and no nanoparticles are observed (Figures S4a and 2a). Also, no peaks of Au appear in the XRD pattern (Figure S4b). Moreover, the high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) image clearly shows individual Au atoms uniformly dispersed on the surface of NiFe LDH (Figures 2b and S4c). Meanwhile, energy-dispersive X-ray spectroscopy (EDS) mapping images of s Au/NiFe LDH suggest that atomic Au is evenly distributed over the entire nanosheet (Figure 2c). According to the results of inductively coupled plasma mass spectrometry, the atomic ratio of Ni/Fe is 7.3 and the loading content of Au is 0.4 wt%. To confirm the local structure of Au speciation, X-ray absorption near-edge structure (XANES) measurements were performed (Figure 2d). The white line peak in the Au L3-edge XANES accords with an electronic transition from 2p3/2 to unoccupied 5d states. The XANES spectrum of Au foil exhibit almost no white line marked as A due to the almost completely filled 5d state of Au0. In contrast, feature A in the spectrum of sAu/NiFe LDH is sharp. The absence of feature B is also observed in the spectrum of Au foil. And the feature D for sAu/NiFe LDH locates at higher energy than that of Au foil. All these results suggest that sAu/NiFe LDH have a different gold atomic local structural environment compared to that of metallic Au. Moreover, the good accordance of experimental and simulated results of Au L3-edge XANES spectra indicate the presence of single-atom Au and an Au-O bond distance of 1.88 Å (Figure S5). All these results certify the successful formation of sAu/NiFe LDH. The OER activities of NiFe LDH and sAu/NiFe LDH were investigated (Figure 3a). When the current density of 10 mA cm-2 is required, sAu/NiFe LDH needs an overpotential of only 237 mV, while NiFe LDH needs a higher overpotential of 263 mV (Figure 3b). Consistently, galvanostatic measurements indicate sAu/NiFe LDH requires lower applied potential (Figure S6). Furthermore, the current density on sAu/NiFe LDH at an overpotential of 280 mV can reach 129.8 mA cm-2, which is about 6 times higher than that on NiFe LDH (21.5 mA cm-2) (Figure S7). The higher OER

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Journal of the American Chemical Society activity of sAu/NiFe LDH is also evidenced by specific (calculated by electrochemically active surface area) and mass activities (Figure S8 and Table S1). sAu/NiFe LDH show the advantages not only in improving OER activity but also lowering Au usage (Figures S9-10). The smaller Tafel slope and larger turnover frequency of sAu/NiFe LDH suggest its faster OER kinetic rate (Figures S7 and S11). Consistently, the Nyquist plots indicate a faster charge-transfer rate of sAu/NiFe LDH (Figure S12).45 In addition, s Au/NiFe LDH shows a nearly 100 % Faradaic efficiency toward OER (Figure S13). We further examine the stability of sAu/NiFe LDH (Figure 3c). After 2000 continuous cycles, no obvious activity decay is observed. Also, the current density can maintain around 100 mA cm-2 for 20 h. Moreover, the HAADF-STEM image and XANES spectra highlight that atomically dispersed Au preserve in sAu/NiFe LDH after OER test (Figures S14-15). As a result, sAu/NiFe LDH shows excellent OER activity and strong stability.

Figure 3. (a) Cyclic voltammetry (CV) curves of sAu/NiFe LDH, pure NiFe LDH and bare Ti mesh in 1 M KOH. (b) The overpotential (η) at 10 mA cm-2 (left) and Tafel slope (right) for s Au/NiFe LDH and pure NiFe LDH. (c) Polarization curves of s Au/NiFe LDH before and after 2000 cycles. Inset in (c) is timedependent current density curve. (d) Raman spectra of sAu/NiFe LDH at different potentials during anodic and cathodic sweep in a CV cycle. To reveal the electrocatalytic mechanism experimentally, an in situ Raman technology is employed. A series of Raman spectra for sAu/NiFe LDH are obtained as a function of the applied potential during a CV sweep (from 1.12 V to 1.44 V to 1.12 V), as shown in Figure 3d. During the anodic half sweep from 1.12 V to 1.32 V, the peaks observed at 462 and 535 cm-1 are attributed to Ni-O vibrations of defective or disordered NiFe LDH nanocrystals. As the potential is swept anodically to 1.44 V, at which OER occurs, the primary two peaks disappear and new peaks at 475 and 559 cm-1 appear. The pair of new peaks is assigned to characteristic bands in NiOOH, indicating the LDHs have been transformed into oxyhydroxides under the oxygen evolution potential. The result is consistent with our theory simulation for OER process of NiFe LDH. When the potential sweep is reversed to 1.12 V, the persistence of aforementioned peaks suggests that this transformation is not reversible, reinforced by ex situ XANES spectra of post-OER sAu/NiFe LDH (Figure S16). In other words, it is the in situ formed oxyhydroxide that acts as the catalytic species for OER.

Figure 4. Differential charge densities of NiFe LDH with and without Au atom when one O atom is adsorbed on the Fe site. Isosurface value is 0.004 eÅ−3. Yellow and blue contours represent electron accumulation and depletion, respectively. In order to address the reaction mechanism, we theoretically investigate the transformation of surface charge of s Au/NiFeOOH-NiFe LDH with O* (Figure 4). The Au atom locates upon one O atom. The orientation of Au-O bond is parallel to the c-axis. Each d orbital of Au is fully occupied by 2 electrons and each p orbital of O possesses 4/3 electrons averagely. After the adsorption of Au on O, the five degenerated d orbitals of Au are spatially redistributed. dz2 orbital of Au and pz orbital of O are hybridized and form energetically separated σ bonding state at 5.6 eV and σ* anti-bonding state at 0.2 eV (Figures S17-18). The spatially redistribution of d orbitals gives rise to the charge density around the ring region of Au parallel to the surface direction. The integrated charge density difference yields a net Au-to-LDH charge redistribution of 0.32 e, which transfers to surrounding O, Ni and Fe atoms, thus facilitating the adsorption of OH- and modify the adsorption energies of O* and OOH* intermediates, resulting in low overpotential in the rate-limiting step from O* to OOH*. In summary, DFT + U + vdW calculations on representative s Au/NiFe LDH catalyst are used to predict and investigate the origin of OER activity of LDH system and significant OER enhancement by sAu-decoration. Subsequent experimental observations validate our theory model construction and simulations, providing evidence that each of sAu, NiFe oxyhydroxide transformed from LDH and LDH itself with interlayer CO32- anions has contributed to the local Au-catalyst interface site and thus the excellent OER activity close to that of ideal electrocatalyst. Importantly, this study may pave new avenues to the exploration and design of highly efficient electrocatalysts for energy conversion applications.

ASSOCIATED CONTENT Supporting Information Details of synthesis, characterization, and computational methods; Figures S1-S18 and Table S1. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *[email protected], [email protected]

Author Contributions §

These authors contributed equally.

Notes The authors declare no competing financial interests.

ACKNOWLEDGMENT This work was financially supported by the National Natural Science Foundation of China (No. 21422104), National key research

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and development program (No. 2016YFB0901600), the Natural Science Foundation of Tianjin City (No. 17JCJQJC44700 and No. 16JCZDJC30600) and the Helmholtz Association (VH-NG-1140).

REFERENCES (1) Liang, L.; Cheng, H.; Lei, F.; Han, J.; Gao, S.; Wang, C.; Sun, Y.; Qamar, S.; Wei, S.; Xie, Y. Angew. Chem. Int. Ed. 2015, 54, 12004. (2) Cheng, F.; Chen, J. Chem. Soc. Rev. 2012, 41, 2172. (3) Meng, F.; Zhong, H.; Bao, D.; Yan, J.; Zhang, X. J. Am. Chem. Soc. 2016, 138, 10226. (4) Xia, B. Y.; Yan, Y.; Li, N.; Wu, H. B.; Lou, X. W.; Wang, X. Nat. Energy 2016, 1, 15006. (5) Zhang, J.; Hu, Y.; Liu, D.; Yu, Y.; Zhang, B. Adv. Sci. 2016, 4, 1600343. (6) Feng, L. L.; Yu, G.; Wu, Y.; Li, G. D.; Li, H.; Sun, Y.; Asefa, T.; Chen, W.; Zou, X. J. Am. Chem. Soc. 2015, 137, 14023. (7) Long, X.; Li, G.; Wang, Z.; Zhu, H.; Zhang, T.; Xiao, S.; Guo, W.; Yang, S. J. Am. Chem. Soc. 2015, 137, 11900. (8) Gao, M.-R.; Xu, Y.-F.; Jiang, J.; Zheng, Y.-R.; Yu, S.-H. J. Am. Chem. Soc. 2012, 134, 2930. (9) Xu, L.; Jiang, Q.; Xiao, Z.; Li, X.; Huo, J.; Wang, S.; Dai, L. Angew. Chem. Int. Ed. 2016, 55, 5277. (10) Qi, J.; Zhang, W.; Xiang, R.; Liu, K.; Wang, H. Y.; Chen, M.; Han, Y.; Cao, R. Adv. Sci. 2015, 2, 1500199. (11) Jung, J.-I.; Risch, M.; Park, S.; Kim, M. G.; Nam, G.; Jeong, H.Y.; Shao-Horn, Y.; Cho, J. Energy Environ. Sci. 2016, 9, 176. (12) Jin, Y.; Wang, H.; Li, J.; Yue, X.; Han, Y.; Shen, P. K.; Cui, Y. Adv. Mater. 2016, 28, 3785. (13) Wang, Y.; Jiang, K.; Zhang, H.; Zhou, T.; Wang, J.; Wei, W.; Yang, Z.; Sun, X.; Cai, W. B.; Zheng, G. Adv. Sci. 2015, 2, 1500003. (14) Guo, Y.; Tong, Y.; Chen, P.; Xu, K.; Zhao, J.; Lin, Y.; Chu, W.; Peng, Z.; Wu, C.; Xie, Y. Adv. Mater. 2015, 27, 5989. (15) Jia, X.; Zhao, Y.; Chen, G.; Shang, L.; Shi, R.; Kang, X.; Waterhouse, G. I. N.; Wu, L.-Z.; Tung, C.-H.; Zhang, T. Adv. Energy Mater. 2016, 6, 1502585. (16) Gao, M.; Sheng, W.; Zhuang, Z.; Fang, Q.; Gu, S.; Jiang, J.; Yan, Y. J. Am. Chem. Soc. 2014, 136, 7077. (17) Liu, W.; Liu, H.; Dang, L.; Zhang, H.; Wu, X.; Yang, B.; Li, Z.; Zhang, X.; Lei, L.; Jin, S. Adv. Funct. Mater. 2017, 27, 1603904. (18) Feng, J.-X.; Xu, H.; Dong, Y.-T.; Ye, S.-H.; Tong, Y.-X.; Li, G.R. Angew. Chem. Int. Ed. 2016, 55, 3694. (19) Ping, J.; Wang, Y.; Lu, Q.; Chen, B.; Chen, J.; Huang, Y.; Ma, Q.; Tan, C.; Yang, J.; Cao, X.; Wang, Z.; Wu, J.; Ying, Y.; Zhang, H. Adv. Mater. 2016, 28, 7640. (20) Fan, K.; Ji, Y.; Zou, H.; Zhang, J.; Zhu, B.; Chen, H.; Daniel, Q.; Luo, Y.; Yu, J.; Sun, L. Angew. Chem. Int. Ed. 2017, 56, 3289. (21) Song, F.; Hu, X. Nat. Commun. 2014, 5, 4477. (22) Gong, M.; Li, Y.; Wang, H.; Liang, Y.; Wu, J. Z.; Zhou, J.; Wang, J.; Regier, T.; Wei, F.; Dai, H. J. Am. Chem. Soc. 2013, 135, 8452. (23) Lu, X.; Zhao, C. Nat. Commun. 2015, 6, 6616. (24) Hou, Y.; Lohe, M. R.; Zhang, J.; Liu, S.; Zhuang, X.; Feng, X. Energy Environ. Sci. 2016, 9, 478. (25) Oliver-Tolentino, M. A.; Vázquez-Samperio, J.; Manzo-Robledo, A.; González-Huerta, R. d. G.; Flores-Moreno, J. L.; Ramírez-Rosales, D.; Guzmán-Vargas, A. J. Phys. Chem. C 2014, 118, 22432. (26) Gorlin, M.; Chernev, P.; Ferreira de Araujo, J.; Reier, T.; Dresp, S.; Paul, B.; Krahnert, R.; Dau, H.; Strasser, P. J. Am. Chem. Soc. 2016, 138, 5603. (27) Ahn, H. S.; Bard, A. J. J. Am. Chem. Soc. 2015, 138, 313. (28) Trotochaud, L.; Young, S. L.; Ranney, J. K.; Boettcher, S. W. J. Am. Chem. Soc. 2014, 136, 6744. (29) Dong, Y.; Zhang, P.; Kou, Y.; Yang, Z.; Li, Y.; Sun, X. Catal. Lett. 2015, 145, 1541. (30) Friebel, D.; Louie, M. W.; Bajdich, M.; Sanwald, K. E.; Cai, Y.; Wise, A. M.; Cheng, M. J.; Sokaras, D.; Weng, T. C.; Alonso-Mori, R.; Davis, R. C.; Bargar, J. R.; Norskov, J. K.; Nilsson, A.; Bell, A. T. J. Am. Chem. Soc. 2015, 137, 1305. (31) Lu, Z.; Xu, W.; Zhu, W.; Yang, Q.; Lei, X.; Liu, J.; Li, Y.; Sun, X.; Duan, X. Chem. Commun. 2014, 50, 6479. (32) Kuo, C.-H.; Li, W.; Pahalagedara, L.; El-Sawy, A. M.; Kriz, D.; Genz, N.; Guild, C.; Ressler, T.; Suib, S. L.; He, J. Angew. Chem. Int. Ed. 2015, 54, 2345.

(33) Zhao, S.; Jin, R.; Abroshan, H.; Zeng, C.; Zhang, H.; House, S. D.; Gottlieb, E.; Kim, H. J.; Yang, J. C.; Jin, R. J. Am. Chem. Soc. 2017, 139, 1077. (34) Ng, J. W. D.; García-Melchor, M.; Bajdich, M.; Chakthranont, P.; Kirk, C.; Vojvodic, A.; Jaramillo, T. F. Nat. Energy 2016, 1, 16053. (35) Ge, X.; Chen, L.; Zhang, L.; Wen, Y.; Hirata, A.; Chen, M. Adv. Mater. 2014, 26, 3100. (36) Qiao, B.; Wang, A.; Yang, X.; Allard, L. F.; Jiang, Z.; Cui, Y.; Liu, J.; Li, J.; Zhang, T. Nat. Chem. 2011, 3, 634. (37) Liu, P.; Zhao, Y.; Qin, R.; Mo, S.; Chen, G.; Gu, L.; Chevrier, D. M.; Zhang, P.; Guo, Q.; Zang, D.; Wu, B.; Fu, G.; Zheng, N. Science 2016, 352, 797. (38) Flytzani-Stephanopoulos, M. Acc. Chem. Res. 2013, 47, 783. (39) Wang, H. Y.; Hung, S. F.; Chen, H. Y.; Chan, T. S.; Chen, H. M.; Liu, B. J. Am. Chem. Soc. 2016, 138, 36. (40) Bajdich, M.; García-Mota, M.; Vojvodic, A.; Nørskov, J. K.; Bell, A. T. J. Am. Chem. Soc. 2013, 135, 13521. (41) Zhang, B.; Zheng, X.; Voznyy, O.; Comin, R.; Bajdich, M.; García-Melchor, M.; Han, L.; Xu, J.; Liu, M.; Zheng, L.; Arquer, F. P. G. d.; Dinh, C. T.; Fan, F.; Yuan, M.; Yassitepe, E.; Chen, N.; Regier, T.; Liu, P.; Li, Y.; Luna, P. D.; Janmohamed, A.; Xin, H. L.; Yang, H.; Vojvodic, A.; Sargent, E. H. Science 2016, 352, 333. (42) Jiao, Y.; Zheng, Y.; Jaroniec, M.; Qiao, S. Z. Chem. Soc. Rev. 2015, 44, 2060. (43) J. Desilvestro; D. A. Corrigan; Weaver, M. l. J. J. Electrochem. Soc. 1988, 135, 885. (44) Man, I. C.; Su, H.-Y.; Calle-Vallejo, F.; Hansen, H. A.; Martínez, J. I.; Inoglu, N. G.; Kitchin, J.; Jaramillo, T. F.; Nørskov, J. K.; Rossmeisl, J. ChemCatChem 2011, 3, 1159. (45) Jiang, N.; You, B.; Sheng, M.; Sun, Y. ChemCatChem 2016, 8, 106.

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