Demystifying the dual-functional electrocatalytic activity of the 2D Co-doped NbSSe Janus transition metal dichalcogenide for O2 reduction and H2 evolution reactions

Abstract

Developing highly efficient dual-functional electrocatalysts is crucial for advancing energy conversion and storage technologies, particularly for the O2 reduction reaction (ORR) and H2 evolution reaction (HER). Here, we have computationally designed a cobalt-doped Janus 2D monolayer NbSSe (Co_NbSSe) transition metal dichalcogenide (TMD) material and investigated its structural, electronic, and electrocatalytic properties by using density functional theory (DFT). The Co atom plays a crucial role towards both the HER and ORR

and it is emerging as the most promising catalyst for various electrochemical reactions. Our findings reveal that the Co doping in the pristine NbSSe Janus TMD significantly enhances the electrocatalytic activity of the material by activating the inert basal planes and improving electrical conductivity. This material (Co_NbSSe) exhibits remarkable catalytic activity with a low thermodynamic energy barrier of 0.70 eV for ORR, indicative of efficient reaction kinetics. Additionally, its near-optimal hydrogen adsorption energy (ΔGH* ≈ 0.49 eV) enhances HER performance. These insights establish the Janus Co_NbSSe material as a highly promising dual-functional electrocatalyst, offering a strategic design route for next-generation electrocatalysts. The present research work provides insight into the evolution of 2D Janus TMD-based dual-functional electrocatalysts towards HER/ORR and also a deep understanding of the nature of active sites. We hope to provide inspiration for designing state-of-the-art catalysts for future breakthroughs in the electrocatalytic ORR and HER. This journal is © The Royal Society of Chemistry, 2026