Highly Stable Nickel Sulfoselenide Electrodes for Enhanced Electrochemical Water Splitting

Electrochemical water splitting is garnering increased interest as a method for producing a clean, fossil-fuel alternative energy source, such as gaseous hydrogen. Despite its numerous advantages, water electrolysis requires the use of electrocatalysts to lower the energy barriers associated with the hydrogen (HER) and oxygen (OER) evolution reactions. While some electrode materials exhibit catalytic activity toward only one of these reactions, the development of bifunctional electrocatalysts active in both HER and OER is highly desirable [1]. Among the various classes of catalytic materials, a significant part of research has focused on transition metal sulfides and selenides [2]. Recent studies also suggest that sulfur-selenium-based compounds, known as sulfoselenides, represent a promising new class of bifunctional electrocatalysts for overall water splitting [3]. The present work proposes a simple one-step synthesis of Ni-S-Se electrodes by hydrothermal modification of nickel foam. Special attention was given to investigating the effect of synthesis temperature on the physicochemical and catalytic properties of the obtained materials. The prepared catalysts were comprehensively characterized in terms of morphology and composition using scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and X-ray powder diffraction (XRD). Their electrocatalytic performance toward HER was evaluated in both acidic (0.5 M H 2 SO 4 ) and alkaline (1.0 M KOH) media. Modifications in the morphology and composition of the Ni-S-Se electrodes were found to be key factors in reducing the HER overpotential compared to pure Ni substrate as well as Ni-S and Ni-Se electrodes. Importantly, nickel sulfoselenide electrocatalysts showed excellent long-term stability (50 hours of continuous operation) at a current density of -10 mA cm -2 . Based on these results, the most promising Ni-S-Se material was selected for further evaluation in OER electrocatalysis. [1] S. S. Kumar, H. Lim, Energy Rep., 2022, 8, 13793-13813. [2] U. Shahzad, M. Saeed, H. M. Marwani, J. Y. Al-Humaidi, S. ur Rehman, R. H. Althomali, M. M. Rahman, Int. J. Hydrogen Energy, 2024, 65, 215-224. [3] A. Arulraj, P. K. Murugesan, F. V. Herrera, R. V. Mangalaraja, Int. J. Hydrogen Energy, 2025, 104, 313-323.