Exploring the evolution of active sites on Fe₂GeO₄–Ni₃Ge₂O₅(OH)₄ interfaces for water oxidation

Abstract

The oxygen evolution reaction (OER) is a pivotal process in electrochemical energy conversion. Herein, we report a computational study-guided experimental work that uncovers the dynamics of active sites in a heterostructure composed of two distinct phases: Brunogeierite (Fe₂GeO₄) and serpentine (Ni₃Ge₂O₅(OH)₄). This heterostructure is synthesized by introducing varying amounts of a nickel precursor into pristine Fe₂GeO₄. When comparing pristine materials, Fe in Fe₂GeO₄ is better for OER as compared with the Ni in Ni₃Ge₂O₅(OH)₄. Interestingly, the Ni becomes more active in the heterostructure following the structural distortion and the induced increased electron transfer, which we proved by ex situ/in situ XAS studies. These findings highlight the dynamic evolution of active sites in the heterostructure, elucidating how the synergy between structural and electronic factors transforms catalytic behavior. The optimized heterostructure as an ideal model reveals enhanced electrocatalytic performance with an overpotential of 325 mV versus RHE to achieve a current density of 100 mA cm^–2, a Tafel slope of 42 mV dec^–1, and long-term stability exceeding 50 h even at high current densities, making it highly promising for a wide range of critical electrolysis applications.

Keywords

active sites / electrochemical oxygen evolution / heterostructure / iron-nickel germanates

References

[1] (a) Stamenkovic VR, Strmcnik D, Lopes PP, Markovic NM. Energy and fuels from electrochemical interfaces. Nat Mater. 2017;161(1):57. (b) Wang J, Kim S-J, Liu J, et al. Redirecting dynamic surface restructuring of a layered transition metal oxide catalyst for superior water oxidation. Nat Catal. 2021;4(3):212.

[2] (a) Wang X, Zhong H, Xi S, et al. Understanding of oxygen redox in the oxygen evolution reaction. Adv Mater. 2022;34(50): e2107956. (b) Boakye FO, Harrath K, Zhang D, et al. Synergistic engineering of dopant and support of Ru oxide catalyst enables ultrahigh performance for acidic oxygen evolution. Adv Funct Mater. 2024;34(48):2408714. (c) Qayum A, Harrath K, Li R, et al. Dynamically reconstructed Fe-CoOOH semi-crystalline electrocatalyst for efficient oxygen evolution reaction. Small. 2025;21:2408854. (e) Rafiq M, Harrath K, Feng M, et al. The XRD peaks of NMB can be indexed to Ni2B (JCPDS No. 48-1222). Energy Mater. 2024;14:2402866.

[3] Mccrory CCL, Jung S, Peters JC, Jaramillo TF. Benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction. J Am Chem Soc. 2013;135(45):16977-16987.

[4] Kibsgaard J, Chorkendorff I. Considerations for the scaling-up of water splitting catalysts. Nat Energy. 2019;4(6):430-433.

[5] (a) Ding H, Liu H, Chu W, Wu C, Xie Y. Structural transformation of heterogeneous materials for electrocatalytic oxygen evolution reaction. Chem Rev. 2021;121(21):13174-13212. (b) Kim JS, Kim B, Kim H, Kang K. Recent Progress on multimetal oxide catalysts for the oxygen evolution reaction. Adv Energy Mater. 2018;8(11):1702774.

[6] (a) Tofik A, Shifa, Wang F, Liu Y, He J. Heterostructures based on 2D materials: a versatile platform for efficient catalysis. Adv Mater. 2019;31:1804828. (b) Zhai P, Xia M, Wu Y, et al. Engineering single-atomic ruthenium catalytic sites on defective nickel-iron layered double hydroxide for overall water splitting. Nat Commun. 2021;12:4587.

[7] (a) Xu Q, Zhang J, Zhang H, et al. Atomic heterointerface engineering overcomes the activity limitation of electrocatalysts and promises highly-efficient alkaline water splitting. Energ Environ Sci. 2021;14(10):5228-5259. (b) Shifa TA, Gradone A, Yusupov K, et al. Interfacing CrOx and CuS for synergistically enhanced water oxidation catalysis. Chem Eng J. 2023;453:139781.

[8] (a) Dionigi F, Strasser P, Dionigi F, Strasser P. NiFe-based (oxy) hydroxide catalysts for oxygen evolution reaction in non-acidic electrolytes. Adv Energy Mater. 2016;6(23):1600621. (b) Ha MA, Alia SM, Norman AG, Miller EM. Fe-doped Ni-based catalysts surpass Ir-baselines for oxygen evolution due to optimal charge-transfer characteristics. ACS Catal. 2024;14(23):17347-17359.

[9] Corrigan DA. The catalysis of the oxygen evolution reaction by iron impurities in thin film nickel oxide electrodes. J Electrochem Soc. 1987;134(2):377-384.

[10] Magnier L, Cossard G, Martin V, et al. Fe–Ni-based alloys as highly active and low-cost oxygen evolution reaction catalyst in alkaline media. Nat Mater. 2024;23(2):252-261.

[11] Friebel D, Louie MW, Bajdich M, et al. Identification of highly active Fe sites in (Ni,Fe)OOH for electrocatalytic water splitting. J Am Chem Soc. 2015;137(3):1305-1313.

[12] Schä H, Sadaf S, Walder L, et al. Stainless steel made to rust: a robust water-splitting catalyst with benchmark characteristics. Energy Environ Sci. 2015;8:2685.

[13] (a) Görlin M, Chernev P, De Araújo JF, et al. Oxygen evolution reaction dynamics, faradaic charge efficiency, and the active metal redox states of Ni–Fe oxide water splitting electrocatalysts. J Am Chem Soc. 2016;138(17):5603-5614. (b) Qiu Z, Tai CW, Niklasson GA, Edvinsson T. Direct observation of active catalyst surface phases and the effect of dynamic self-optimization in NiFe-layered double hydroxides for alkaline water splitting. Energ Environ Sci. 2019;12(2):572-581.

[14] (a) Yoon KY, Park J, Jung M, et al. NiFeOx decorated Ge-hematite/perovskite for an efficient water splitting system. Nat Commun. 2021;12(1):4309. (b) Guo W, Luo H, Jiang Z, et al. Ge-doped cobalt oxide for electrocatalytic and photocatalytic water splitting. ACS Catal. 2022;12(19):12000-12013.

[15] Setkova TV, Spivak AV, Borovikova EY, et al. Synthetic brunogeierite Fe₂GeO₄: XRD, Mössbauer and Raman high-pressure study. Spectrochim Acta Part A Mol Biomol Spectrosc. 2022;267(2):120597.

[16] McBean CL, Liu H, Scofield ME, et al. Generalizable, electroless, template-assisted synthesis and electrocatalytic mechanistic understanding of perovskite LaNiO₃ nanorods as viable, supportless oxygen evolution reaction catalysts in alkaline media. ACS Appl Mater Interfaces. 2017;9(29):24634-24648.

[17] Yamashita T, Hayes P. Analysis of XPS spectra of Fe²⁺ and Fe³⁺ ions in oxide materials. Appl Surf Sci. 2008;254(8):2441-2449.

[18] Fredrick SJ, Prieto AL. Solution synthesis and reactivity of colloidal Fe₂GeS₄: a potential candidate for earth abundant, nanostructured photovoltaics. J Am Chem Soc. 2013;135(49):18256-18259.

[19] Vukašinović J, Rapljenović Ž, Počuča-Nešić M, Ivek T, Branković Z, Branković G. The crucial role of defect structure in understanding the electrical properties of spark plasma sintered antimony doped barium stannate. Mater Res Express. 2023;10(1):15901.

[20] (a) Sun N, Zheng Z, Lai Z, et al. Augmented electrochemical oxygen evolution by d-p orbital electron coupling. Adv Mater. 2024;36:2404772. (b) Yu F, Zhou H, Huang Y, et al. High-performance bifunctional porous non-noble metal phosphide catalyst for overall water splitting. Nat Commun. 2018;91(9):2551.

[21] Perdew JP, Burke K, Ernzerhof M. Generalized gradient approximation made simple. Phys Rev Lett. 1996;77(18):3865-3868.

[22] VASP. Vienna Ab initio Simulation Package. https://www.vasp.at/

[23] (a) Joubert D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys Rev B. 1999;59(3):1758-1775. (b) Blöchl PE. Projector augmented-wave method. Phys Rev B.1994;50(24):17953-17979.

[24] (a) Harrath K, Yao Z, Jiang YF, Wang YG, Li J. Tailoring the active-site spacing of a single-atom catalyst for CH₄-to-CH₃OH conversion: the Co1/UiO-66 MOF as an exemplary model. J Phys Chem C. 2024;128(13):5579-5589. (b) Jiang S, Mushrif SH. Determining surface-specific Hubbard-Ucorrections and identifying key adsorbates on nickel and cobalt oxide catalyst surfaces. Phys Chem Chem Phys. 2023;25(12):8903-8912.

[25] (a) Bahri L, Mbarki F, Harrath K. Understanding the direct methane conversion to oxygenates on graphene-supported single 3D metal atom catalysts. Chem Pap. 2023;77(7):3759-3767. (b) Harrath K, Yao Z, Jiang YF, Wang YG, Li J. Activity origin of the nickel cluster on TiC support for nonoxidative methane conversion. J Phys Chem Lett. 2023;14(17):4033-4041.

[26] (a) Grimme S, Antony J, Ehrlich S, Krieg H. A consistent and accurateab initioparametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J Chem Phys. 2010;132(15):154104. (b) Grimme S. Density functional theory with London dispersion corrections. Wiley Interdiscip Rev Comput Mol Sci. 2011;1(2):211.

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