The local electronic structures and coordination environments of CoSe2 materials were analyzed through ex situ XAS characterizations (Figure ,e and Figure ). Corresponding ex situ Co K-edge X-ray absorption near-edge structure (XANES) spectra shown in Figure unravel a similar line shape in the rising absorption edge of CoSe2 materials, indicating comparable local coordination geometries of Co centers coordinated by Se atoms. A close examination of the Co K-edge XANES spectra (~7725 eV) highlights prominent white line features of o-CoSe2 compared to c-CoSe2 and c-S-CoSe2. This infers that surface oxidation is more accessible for the as-prepared o-CoSe2 than for the other phase samples. Co K-edge Fourier-transform extended X-ray absorption fine structure (FT-EXAFS) characterizations were further conducted to identify the local coordination environments of Co centers of the investigated samples. The results show (Figure ) that all CoSe2 samples feature only one intense peak within the interval of R+ΔR = 1 to 3 Å, corresponding to the backscattering of Co-Se/S pairs. Notably, the observed backscattering signal of c-S-CoSe2 exhibits a distinct negative position shift compared to c-CoSe2 and c-S-CoSe2, due to the shorter interatomic distance of the Co-S bond relative to the Co-Se bond, as supported by the fitting results of Co K-edge EXAFS spectra (Table ). Precise identification of the local coordination environments of Co centers in o-CoSe2 and c-CoSe2 is challenging because both feature similar [CoSe6] octahedra motifs (Figure ). However, the interatomic distance of the characteristic Se-Se pairs in o-CoSe2 is slightly larger than the one in c-CoSe2. Such a difference can be monitored by the Raman spectra due to its sensitivity to the librational vibrations of characteristic Se-Se pairs (Figure and Figure ). As expected, o-CoSe2 features its characteristic Se-Se librational vibration at ca. 174 cm -1 , which undergoes a positive Raman shift to ca. 187 cm -1 when the c-CoSe2 phase is present. Partial S incorporation into c-CoSe2 leads to the construction of S-Se pairs with a further decrease in the interatomic distance, and the characteristic Raman signals shift to a higher wavenumber at ca. 203 cm -1 accordingly. It is also noteworthy that partial S incorporation produces newly formed Raman signatures at ca. 299 and 490 cm -1 , which can be assigned to the stretching vibrations of S-Se and Co-S/Se pairs, respectively.