Compositional alteration of low dimensional nickel sulfides under hydrogen evolution reaction conditions in alkaline media

• Published in: Materials today chemistry Vol. 38; p. 102081
• Main Authors: Solati, Navid, Karakaya, Cüneyt, Şimşek, Kaan, Kaya, Sarp
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2024
• Subjects: Hydrogen evolution reaction; Nickel hydroxide; Nickel sulfide; Raman spectroscopy; Stability; Hydrogen evolution reaction; Stability; Nickel hydroxide; Raman spectroscopy; Nickel sulfide
• ISSN: 2468-5194; 2468-5194
• DOI: 10.1016/j.mtchem.2024.102081

Developing cost-effective electrodes for electrochemical water splitting with minimal kinetic losses remains a primary challenge in water electrolysis. Nickel-based dichalcogenides, particularly sulfides, have emerged as promising candidates for the hydrogen evolution reaction (HER). However, the stability of various nickel sulfide (NixSy) phases under cathodic potentials in alkaline electrolytes is subject to debate. In this study, we investigate the HER activity and durability of both 2-dimensional (2D) and 3-dimensional (3D) NixSy nanostructures with diverse chemical compositions. Through cross-correlation analysis of spectroscopic and electrochemical characterization data, we elucidate the transformation behavior of these materials under operating conditions. Our findings reveal that NiS2 tends to undergo conversion to nickel hydroxide (Ni(OH)2), while Ni-rich phases like Ni3S4 and NiS exhibit greater stability. Furthermore, we demonstrate that in 3D nanostructures, the initial formation of a protective hydroxide layer on the surface inhibits further sulfide transformation. This nickel sulfide/hydroxide composite shows an improved HER activity with lower onset potential (−0.25 V), Tafel slope (105 mV s−1), and charge transfer resistance (17.3 Ω). •2D nanosheets of NiS2 provide a high number of available active sites for HER.•HER activities of 3D NixSy nanospheres gradually improve, S leaching occurs.•Hydroxide and sulfide domains impact HER activity due to enhanced –OH adsorption.