Tailoring a Manganese-Based Metal–Organic Framework for High-Performance Water Splitting Applications

Abstract The synthesis of a manganese-based MOF (Mn-MOF) was accomplished via a sonochemical approach and directly coated onto a platinum electrode to construct a binder-free electrocatalyst for hydrogen and oxygen evolution in alkaline solution. FT-IR analysis confirmed the bidentate coordination of the carboxylate groups to Mn 2+ through the asymmetric (1604 cm - ¹) and symmetric (1426 cm - ¹) stretching vibrations, while PXRD patterns indicated high crystallinity. The Mn–O bond was detected at 661 cm - ¹. BET analysis revealed a large surface area of 1106.65 m 2 g - ¹ and a pore size of 3.27 nm, confirming its mesoporous structure. SEM analyses demonstrated uniformly distributed nanosheets (14–21 nm), while TGA confirmed good thermal stability up to 347 °C. In 1.0 M NaOH, the Mn-MOF/Pt electrode revealed impressive HER activity with an overpotential of 83 mV at 10 mA·cm -2 and a Tafel slope of 70 mV·dec - ¹, following a Volmer–Tafel mechanism. For OER, it required an overpotential of 593 mV at 10 mA·cm -2 , with a Tafel slope of 196 mV·dec - ¹. EIS results revealed low charge transfer resistances (67.7 Ω for HER, 970.9 Ω for OER), indicating efficient charge transport. The catalyst exhibited outstanding durability over 54,000 s for both HER and OER, maintaining stable current density. These results demonstrate that the Mn-MOF’s high porosity, large active surface area, and redox-active Mn sites collectively contribute to its superior bifunctional electrocatalytic activity and stability, establishing it as a Potential candidate for sustainable water-splitting applications.