Synergistically self-assembled in situ growth of MXene@MOF derived sodium alginate hydrogel 3D frameworks as next-generation electrocatalysts for oxygen and hydrogen evolution

Abstract

The need to minimize carbon emissions and improve sustainable energy systems has stimulated significant research into multifunctional materials. This work presents a unique MXene@MOF and sodium alginate hydrogel composite as an electrocatalyst in energy storage and conversion. The Max-phase titanium niobium aluminum carbide (TiNbAlC) was etched to remove Al layers, producing MXene (TiNbCTx). The MXene nanosheets were dispersed in methanol, ultrasonicated, and mixed with polyvinylpyrrolidone (PVP). Subsequently, Zn(NO₃)₂·6H₂O and Co(NO₃)₂·6H₂O were added, followed by 2-methylimidazole, and stirred for 2 h. After 4 h, centrifugation, washing, and freeze-drying produced TiNbC@MOF. This composite was further incorporated into a sodium alginate hydrogel to construct TiNbC/MOF@SA-H. Besides, the characterization included SEM, EDX, XRD, FTIR, AFM, TGA, and XPS analysis. The performance of the electrocatalyst was assessed for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline medium (1 M KOH). TiNbC/MOF@SA-H demonstrated excellent capacitance, high rate capability, and stability over 1000 cycles. TiNbC/MOF@SA-H demonstrates enhanced OER electrocatalytic performance relative to the reference IrO₂ and the composite TiNbC/MOF, exhibiting low overpotentials of 185, 188 and 204 mV at current densities of 10, 20 and 50 mA cm⁻², respectively. Additionally, it shows superior HER catalytic activity compared to other prepared samples, requiring only 17, 79 and 325 mV to achieve current densities of 10, 50 and 100 mA cm⁻², respectively. The material achieved an OER Tafel slope of 84 mV dec⁻¹ and a HER Tafel slope of 61.8 mV dec⁻¹ at a 1 V s⁻¹ scan rate.