Iron-regulated NiPS for enhanced oxygen evolution efficiency

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2020-11, Vol.8 (44), p.2358-23589
• Main Authors: Peng, Wenfeng, Li, Junkai, Shen, Kangqi, Zheng, Lirong, Tang, Hu, Gong, Yutong, Zhou, Junshuang, Chen, Ning, Zhao, Shijing, Chen, Mingyang, Gao, Faming, Gou, Huiyang
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Active sites; Electrocatalysts; Energy storage; Iron; Nickel; Oxidation; Oxygen; Oxygen evolution reactions; Photoelectron spectroscopy; Photoelectrons; Pyrite; Raman spectroscopy; Renewable energy; Spectrum analysis; Valence; X ray absorption; X ray photoelectron spectroscopy; X-ray absorption spectroscopy
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta08123j

Development of robust and highly active electrocatalysts for the oxygen evolution reaction (OER) is of significance for next-generation renewable energy storage and conversion. Herein, for the first time, we report pyrite-type iron nickel monophosphosulfide (Ni 1− x Fe x PS, x = 0, 0.1, 0.15, 0.2) electrocatalysts with exceptional OER efficiency and stability under alkaline conditions. Ni 0.85 Fe 0.15 PS/NF exhibits a considerably low overpotential of 251 (314) mV at 10 (100) mA cm −2 with a Tafel slope of 34 mV dec −1 , together with remarkable stability. Moderate Fe regulation in NiPS (Ni 0.85 Fe 0.15 PS) is found to stimulate the activation of high-valence-state Ni/Fe oxyhydroxides during the irreversible surface reconstructions that form disordered MOOH@M x SO y @M x PO y surfaces under OER conditions, as is established by microstructural observations, surface-sensitive X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray absorption spectroscopy. DFT calculations show that the catalytic sites formed by Fe doping are more nucleophilic than the Ni sites and thus more OER active, due to a facile Fe( ii ) → Fe( iii ) oxidation state change for Fe. Meanwhile, overly stable OER surface species are not formed, as Fe in oxidation states higher than Fe( iii ) is not favorable, which leads to a lower barrier for the rate-limiting OER step than that for the Ni site. The present results shed light on the design and development of high-performance electrocatalysts in ternary metal monophosphosulfides, as well as providing a fundamental understanding of their intrinsic active sites. High-purity pyrite iron nickel monophosphosulfides (Ni 1− x Fe x PS, x = 0, 0.1, 0.15, 0.2) were synthesized as efficient OER catalysts for the first time by a clean high-pressure and high-temperature (HPHT) technique.