Figure 2. Comparison of MoSe2-I-36h after Pt decoration. a ) X-ray diffraction (XRD) spectra; green sphere and grey diamond indicate MoSe2 1T/2H and carbon paper, b) Raman spectra of MoSe2-I-36h; Magenta diamond, blue reverse triangle, and red diamond denote MoOx, MoSe2-2H, and MoSe2-1T.
Figure 2 (a) displays XRD spectra of MoSe2-I-36h before and after Pt cluster decoration. Similar to MoSe2-P 36h case, MoSe2-I-36h was composed of mixed phases of 1T/2H MoSe2. After Pt decoration on the MoSe2, the peaks matching to 1T/2H phases of MoSe2 remained unchanged while Pt XRD peaks were not detected due to low concentration. From the Raman spectra inFigure 2 (b), the intensity of the A1g peak (2H phase) was decreased, whereas those of J1, J2, J3, and E12g (1T phase peaks) increased significantly after the Pt decoration, indicating the conversion of 2H MoSe2 to 1T MoSe2 during the Pt electrodeposition process. Figure S11(a) , shows the XPS analysis of the MoSe2-I-36h-Pt sample where the presence of Pt element was clearly confirmed compared to the pristine MoSe2-I-36h. Furthermore, the intensities of the peaks (229.3, 232.9 eV for Mo 3d and 54.7 and 55.7 eV for Se 3d, which were related to 2H-MoSe2, were decreased while increase in relative intensities of the 1T-MoSe2 were observed after the Pt electrodeposition process, as depicted in Figures S11 (b) and (c) which is in good agreement with the Raman analysis.Figures S11 (d) exhibit Pt 4f spectra, the peaks located at 72.5 and 75.6 eV corresponding to Pt0 were observed, while the peaks located at 73.6 and 76.8 eV corresponding to Pt2+ might be attributed to the oxidation of Pt nanoparticles during the electrochemical reaction process.[18]