Enhancing Water Electrolysis Efficiency with NiSe@CoSe ₂ : A Superior Bifunctional Catalyst for Alkaline and Seawater Electrolytes

Water electrolysis technology is considered one of the most promising methods for producing high-purity hydrogen and oxygen, attracting significant attention. The development of low-cost, efficient, and stable electrocatalysts for water electrolysis is crucial. In this study, we prepared a highly efficient bifunctional electrocatalyst, NiSe@CoSe2, using a hydrothermal method, suitable for both alkaline and seawater electrolytes. The unique semimetallic properties of selenium contribute to the excellent catalytic performance of NiSe@CoSe2. In alkaline electrolyte, at a current density of 10 mA cm–2, the hydrogen evolution reaction (HER) overpotential is −153.7 mV (OER overpotential: 242.3 mV at 10 mA cm–2), and the HER Tafel slope is 140.1 mV dec–1 (OER Tafel slope: 120.4 mV dec–1). In seawater electrolyte, at a current density of 10 mA cm–2, the HER overpotential is −170.7 mV (OER overpotential: 156.5 mV at 30 mA cm–2), with the HER Tafel slope being only 77 mV dec–1 (OER Tafel slope of 104.6 mV dec–1). In both alkaline and seawater environments, the NiSe@CoSe2 electrocatalyst exhibits excellent HER and OER performance. When employed in water splitting, the required voltage for water electrolysis is 1.91 V at 50 mA cm–2 (1.76 V at 30 mA cm–2 for seawater), and the catalyst demonstrates outstanding cyclic stability. Based on these results, NiSe@CoSe2 shows great promise as an efficient bifunctional electrocatalyst for water electrolysis-based hydrogen production.