## 3 Results
Through Gaussian fitting, the primary Mn 2p spin-orbit peaks, Mn 2p\({}_{1/2}\) at approximately 653.1 eV and Mn 2p\({}_{3/2}\) at about 641.5 eV, were deconstructed into four distinct peak components. The binding energies at approximately 641.2 and 652.6 eV, as seen in Figure 3b, are indicative of Mn\({}^{2+}\), while the peaks at around 643.0 and 653.9 eV can be ascribed to Mn\({}^{3+}\)[47]. Likewise, the Co 2p spectrum, illustrated in Figure 3c, was optimally fitted assuming eight variants, including two pairs of spin-orbit doublets representative of Co\({}^{2+}\) and Co\({}^{3+}\) states, along with their respective four shakeup satellites (denoted Sat.) [47; 48]. Thus, it is reasonable to conclude that the mixed-valence metal cations (Mn\({}^{2+}\), Mn\({}^{3+}\), Co\({}^{2+}\) and Co\({}^{3+}\)) co-exist in both MnCo\({}_{2}\)O\({}_{4}\)-CNTs and CoMn\({}_{2}\)O\({}_{4}\)-CNTs nanocomposites at octahedral and tetrahedral stacking interstices [46]. It is significant  
Figure 1: XRD patterns of (**a**) MnCo\({}_{2}\)O\({}_{4}\) and MnCo\({}_{2}\)O\({}_{4}\)-CNTs and (**b**) CoMn\({}_{2}\)O\({}_{4}\) and CoMn\({}_{2}\)O\({}_{4}\)-CNTs. to note that these fluctuating valence states of the metal cations are likely to augment the electrochemical performance of the materials [49]. As depicted in Figure 3d, the C 1s spectra exhibit a predominant peak at 284.3 eV, attributable to the C=C bonds within the CNTs, and two subsidiary peaks corresponding to oxidized carbon forms, such as C-O and C=O, underscoring the robust interactions between the manganese-cobalt nanoparticles and the CNTs [50; 51]. The electrocatalytic efficacies of the synthesized catalysts for the oxygen reduction reaction (ORR) were initially evaluated using cyclic voltammetry (CV) in a 0.1 M KOH solution with a glassy carbon electrode. As depicted in Figure 4a, all O\({}_{2}\)-saturated curves displayed pronounced reduction current peaks compared to those recorded in N\({}_{2}\)-saturated electrolytes, thereby indicating the ORR catalytic capabilities of the manganese-cobalt  
Figure 3: XPS spectra of MnCo\({}_{2}\)O\({}_{4}\)-CNTs and MnCo\({}_{2}\)O\({}_{4}\)-CNTs. (**a**) Survey spectrum, (**b**) Mn 2p, (**c**) Co 2p, and (**d**) C 1s. Figure 2: TEM images of (**a**–**c**) MnCo\({}_{2}\)O\({}_{4}\) nanoparticles and (**d**–**f**) MnCo\({}_{2}\)O\({}_{4}\)-CNTs nanocomposites. spinel nanoparticles and their composites. Additionally, the results of the rotating disk electrode (RDE) linear sweep voltammetry (LSV) assays conducted in O\({}_{2}\)-saturated 0.1 M KOH solution at a rotation speed of 1600 rpm are showcased in Figure 4b. Notably, the MnCo\({}_{2}\)O\({}_{4}\)-CNTs and CoMn\({}_{2}\)O\({}_{4}\)-CNTs composite catalysts demonstrated superior catalytic performance relative to their individual constituents. This enhanced efficiency is credited to the CNTs' hybridization of chemical bonds, which bolsters the electronic conductivity of the manganese-cobalt oxides [52]. Remarkably, the MnCo\({}_{2}\)O\({}_{4}\)-CNTs nanocomposites exhibited the most proficient catalytic activity for ORR, outstripping other catalysts in terms of onset potential and current density. The onset and half-wave potentials of the MnCo\({}_{2}\)O\({}_{4}\)-CNTs were measured at 1.03 and 0.73 V vs. RHE, respectively, rivaling the performance of commercial Pt/C catalysts, and also exhibited a substantial current density. The Co\({}^{3+}\) at octahedral sites is known to be the catalytic sites for the ORR. [18] In the case of MnCo\({}_{2}\)O\({}_{4}\)-CNTs, Co\({}^{3+}\) and Mn\({}^{2+}\) are the dominant component in octahedral and tetrahedral interstices, thus favoring MnCo\({}_{2}\)O\({}_{4}\)-CNTs to exhibit a superior ORR catalytic activity [53]. Furthermore, the ORR performance of the MnCo\({}_{2}\)O\({}_{4}\)-CNTs composite catalyst significantly surpasses that of mere physical mixtures of MnCo\({}_{2}\)O\({}_{4}\) and CNTs, as illustrated in Figure S2.