## 3 Results
This clearly indicates that robust hybrid coupling between the nanoparticles and carbon nanotubes plays a crucial role in enhancing ORR catalysis. [54, 55]. To delve deeper into the pronounced ORR activity of the MnCo\({}_{2}\)O\({}_{4}\)-CNTs nanocomposite, linear sweep voltammetry (LSV) curves at various rotation rates ranging from 400 to 2000 rpm are depicted in Figure 4c. In these curves, the broad current plateaus indicative of the diffusion-limiting current density are readily apparent, with the limiting current density escalating and the rotation rate increasing, attributed to the reduced diffusion distance at higher rates. Additionally, the Koutecky-Levich (K-L) analysis, portrayed in Figure 4d at varying potentials from 0.20 to 0.55 V vs. RHE across rotation speeds from 400 to 2000 rpm, is performed to elucidate the underlying reaction mechanism of the MnCo\({}_{2}\)O\({}_{4}\)-CNTs catalyst. The impeccable linearity and nearly uniform slope across these plots corroborate the first-order reaction kinetics. Moreover, the calculated average number of electrons  
Figure 4: (**a**) CV curves of as-prepared samples (solid line for O\({}_{2}\)-saturated, dashed line for N\({}_{2}\)-saturated); (**b**) ORR polarization curves of MnCo\({}_{2}\)O\({}_{4}\), MnCo\({}_{2}\)O\({}_{4}\)-CNTs, CoMn\({}_{2}\)O\({}_{4}\), CoMn\({}_{2}\)O\({}_{4}\)-CNTs, and commercial Pt/C catalyst with the rotation of 1600 rpm; (**c**) LSV curves of MnCo\({}_{2}\)O\({}_{4}\)-CNTs nanocomposites in O\({}_{2}\)-saturated 0.1 M KOH electrolyte from 400 to 2000 rpm; (**d**) linear fitting of the Koutecky–Levich model at different potentials of MnCo\({}_{2}\)O\({}_{4}\)-CNTs nanocomposites. transferred (n) is approximately 3.95, indicating that the MnCo\({}_{2}\)O\({}_{4}\)-CNTs catalyst predominantly follows a quasi-four-electron (quasi-4e\({}^{-}\)) pathway for ORR, underscoring its efficient electron transfer mechanism. The long-term durability of a catalyst is a critical factor for its practical application. Chronoamperometric tests for MnCo\({}_{2}\)O\({}_{4}\)-CNTs composites, MnCo\({}_{2}\)O\({}_{4}\) + CNTs physical mixtures, and commercial Pt/C were performed at 0.7 V vs. RHE in an O\({}_{2}\)-saturated 0.1 M KOH environment. As illustrated in Figure S4, the current density of the MnCo\({}_{2}\)O\({}_{4}\)-CNTs composites exhibited a mere 4.24% decline following 10,000 s of continuous operation, in stark contrast to the 13.79% and 12.89% reductions observed in the MnCo\({}_{2}\)O\({}_{4}\) + CNTs mixtures and Pt/C, respectively. Notably, the endurance of the nanocomposites surpasses that of the physical blends of MnCo\({}_{2}\)O\({}_{4}\) and CNTs. This considerable enhancement in stability is largely ascribed to the robust chemical hybrid coupling between MnCo\({}_{2}\)O\({}_{4}\) and CNTs, as substantiated via X-ray photoelectron spectroscopy (XPS) analysis. Consequently, the MnCo\({}_{2}\)O\({}_{4}\)-CNTs nanocomposites not only demonstrate competitive ORR activity but also superior durability compared to commercial Pt/C catalysts, positioning them as a viable alternative to platinum-based catalysts. To explore the broader applications of manganese-cobalt nanoparticles-CNTs composites in electrochemical catalysis, oxygen evolution reaction (OER) experiments were carried out in a 0.1 M KOH solution. Displayed in Figure S5, the RDE polarization curves for MnCo\({}_{2}\)O\({}_{4}\)-CNTs, CoMn\({}_{2}\)O\({}_{4}\)-CNTs, and commercial Pt/C catalysts reveal significant findings. The OER onset potential for both MnCo\({}_{2}\)O\({}_{4}\)-CNTs and CoMn\({}_{2}\)O\({}_{4}\)-CNTs composites is approximately 1.53 V vs. RHE, showcasing a marked improvement over the Pt/C catalyst. Despite being slightly less efficient than elite precious metal oxides like RuO\({}_{2}\) and IrO\({}_{2}\), which currently represent the pinnacle of OER catalysts, these manganese-cobalt nanoparticles-CNTs nanocomposites emerge as promising candidates in active OER electrocatalysis.