Nickel-incorporated MoS₂ nanoflowers as efficient bifunctional electrocatalysts for hydrogen and oxygen evolution...

In this work, we prepared nickel-incorporated MoS₂ nanoflowers (denoted as Ni-MoS₂) via a combined hydrothermal and wet chemical reduction approach. The as-prepared catalyst exhibits a three-dimensional hierarchical nanoflower architecture composed of interconnected ultrathin nanosheets, providing abundant exposed active sites and enhanced electrolyte accessibility. Comprehensive structural and spectroscopic analyses, including synchrotron-based X-ray absorption spectroscopy (XAS), confirm successful Ni incorporation and reveal strong interfacial electronic coupling between Ni species and the MoS₂ framework. As-prepared material demonstrates excellent hydrogen and oxygen evolution reaction performances in alkaline medium (1.0 KOH). Of special relevance, Ni-MoS₂ initiates the hydrogen evolution reaction (HER) at a low onset potential of 66 mV and achieves low overpotential (η) of 185 mV (at the cathodic current density of 10 mAcm^-2) along with low Tafel slope of 145 mVdec^-1. Moreover, Ni-MoS₂ retains 92% of its original performance in chronoamperometric (CA) stability test up to 13 h. More interestingly, the Ni-MoS₂ outperforms the noble metal-based catalysts in the alkaline oxygen evolution reaction (OER) with a remarkably lower overpotential of 285 mV at the anodic current density of 10 mAcm^-2 and Tafel slope of 125 mVdec^-1. Of utmost importance, Ni-MoS₂ exhibits excellent electrochemical durability after 1000 CV cycles. Importantly, the catalyst achieves overall water splitting at approximately 1.60 V in a two-electrode configuration, highlighting its practical bifunctional capability. The improved catalytic performance is attributed to the strong interfacial electronic coupling between Ni and MoS₂, enhanced electrochemically accessible active surface area, and improved charge-transfer kinetics. Furthermore, the coexistence of conductive 1T and catalytically active 2 H phases synergistically facilitates electron transport and electrochemical reaction kinetics. This study highlights the potential of Ni-MoS₂ nanostructures as efficient and durable bifunctional electrocatalysts for alkaline water splitting.