Biphasic Ni-MXene Quantum-Confined Nanostructures: A Versatile Janus Platform for Advanced Energy Storage and Catalytic Oxidations

The demand for sustainable energy storage and ecofriendly catalysts has intensified the search for advanced multifunctional materials. Herein, this work presents the synthesis and characterization of Janus Ni-MXene quantum dot (Ni-MJQD), a novel material architecture that exhibits high performance in supercapacitor and catalytic applications. A Ni-MJQD cathode delivers an impressive gravimetric specific capacity of 168.75 mAh g⁻¹ at 3 A g⁻¹, and its Janus structure optimizes the balance between capacity and ion diffusion. In an asymmetric hybrid supercapacitor (AHSC) with a porous activated carbon (PAC) anode, it achieves an energy density of 54.22 Wh kg⁻¹, a power density of 1599 W kg⁻¹, and 88% capacity retention over 20 000 cycles. As a catalyst, the Ni-MJQD also exhibits high activity in benzyl alcohol oxidation, reaching 95% conversion and 98.4% selectivity for benzaldehyde, with the largest turnover frequency of 8.8825 × 10⁻³ moles g⁻¹ h⁻¹ using peroxymonosulfate (PMS) as an oxidant. Mechanistic analysis reveals contributions from both radical and nonradical pathways. These findings emphasize the unique potential of the Ni-MJQD electrodes for sustainable energy storage and green synthesis applications.