A catalyst of the oxygen evolution reaction (OER) that is viable, affordable, and active for effective water-splitting applications is critical. A variety of electrocatalysts have been discovered to replace noble metal-based catalysts. Of these, transition metal-based sulfides are essential for incorporating carbonaceous materials to improve electrical conductivity, resulting in better electrocatalytic performance. Our study illustrates the synthesis of Cu 2 MnS 2 (CMS) nanoflakes and their different rGO composites (10 to 40 wt %) via a hydrothermal technique for an effective water oxidation reaction. The X-ray diffraction pattern reveals that the prepared Cu 2 MnS 2 nanoflakes exhibit a cubic crystal structure. The high-resolution scanning electron microscopy and the high resolution transmission electron microscopy images corroborate the formation of the nanoflake-like morphology of Cu 2 MnS 2 with the strong interaction of rGO. The selected area electron diffraction analysis pattern reveals a polycrystalline nature. The Fourier transform infrared spectrum shows the existence of a metal sulfur vibrational band at 590 cm −1 , and Raman analysis infers the presence of rGO. The X-ray photoelectron spectroscopy spectra reveal the oxidation states of the elements present in the samples. Using Brunauer−Emmett−Teller analysis, the surface area of CMS-20 is found to be 117.04 m 2 /g. The measured OER overpotentials using linear sweep volammetry and the values are 380, 370, 340, 376, and 400 mV at 10 mA/cm 2 for CMS, CMS-10, CMS-20, CMS-30, and CMS-40, respectively, and the corresponding Tafel slope values are 179, 158, 149, 206, and 240 mV/decade, respectively. The electrochemical active surface area is estimated using cyclic voltammetry for all of the catalysts, where CMS-20 showed a larger surface area. Also, the same catalyst exhibits good stability for ∼24 h at a constant potential, which is confirmed via chronoamperometry. Thus, combining transition metal-based sulfides with carbonaceous materials indicates improved catalytic behavior for the preparation of high-performance OER electrocatalysts. Overall, the prepared CMS-20 performed as an efficient OER electrocatalyst and can be utilized for practical applications in energy conversion.
