The high-resolution XPS spectrum in Figure shows the Mo 3d and S 2s regions of MoS 2 QDs and the Mo dopants. The peaks at 231.62 eV (Mo 3d 5/2 ) and 235.7 eV (Mo 3d 3/2 ) correspond to the Mo 6+ oxidation state. The peaks at 229.01 and 233 eV are indicative of Mo 3d 5/2 and Mo 3d 3/2 , respectively, and suggest that the deposited MoS 2 QDs exist in the 2H phase. Furthermore, the comparison of high-resolution XPS spectra before and after extended electrocatalysis reveals a minor shift in the Mo peaks, which are located at 230.96 eV (Mo 3d 5/2 ) and 234.72 eV (Mo 3d 3/2 ) for Mo 6+ (Figure and). This demonstrates that the Mo dopants and the deposited MoS 2 QDs are highly durable under electrocatalytic conditions. However, the peak position of MoS 2 QDs in the XPS spectrum Mo 3d shifts to 228.54 and 232.12 eV, suggesting that MoS 2 QDs may transform from the 2H to the 1T' phase during electrocatalysis (Figure ). This QD-induced shift has previously been correlated with increased electrical conductivity of the electrode and higher density of electrocatalytic active sites. The S 2p high-resolution XPS spectrum after electrocatalytic activity reveals distinct peaks at 160.49 and 163.63 eV, which correspond to the S 2p 3/2 and S 2p 1/2 binding energies of S 2-in MoS 2 QDs, respectively (Figure ). The observed S 2p XPS peak positions indicate that the MoS 2 QDs undergo a phase transition from the 2H phase to the 1T' phase during extended electrocatalysis. The O 1s XPS spectrum (Figure ) can be split into three subpeaks at 529.13, 531.69, and 534.26 eV. These correspond to the metal-oxygen bonds, defect sites with low oxygen coordination, and adsorbed OH or H 2 O, respectively. The O 1s XPS peaks of MoS 2 @NiFeCo-Mo(doped)-LDH exhibit a minor shift towards more negative energies after prolonged electrocatalysis, which highlights the high stability of the catalyst (Figure ). The high-resolution XPS spectrum of MoS 2 @NiFeCo-Mo(doped)-LDH following extended electrocatalysis exhibits minor alterations in peak positions for all elements, and further confirms the high durability of the hierarchical MoS 2 @NiFeCo-Mo(doped)-LDH heterostructure.