Electrochemical Hydrogen Evolution over Hydrothermally Synthesized Re-Doped MoS2 Flower-Like Microspheres

Abstract

In this research, we report a simple hydrothermal synthesis to prepare rhenium (Re)- doped MoS2 flower-like microspheres and the tuning of their structural, electronic, and electrocatalytic properties by modulating the insertion of Re. The obtained compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Structural, morphological, and chemical analyses confirmed the synthesis of poorly crystalline Re-doped MoS2 flower-like microspheres composed of few stacked layers. They exhibit enhanced hydrogen evolution reaction (HER) performance with low overpotential of 210 mV at current density of 10 mA/cm2, with a small Tafel slope of 78 mV/dec. The enhanced catalytic HER performance can be ascribed to activation of MoS2 basal planes and by reduction in charge transfer resistance during HER upon doping.

Intercalation leads to inverse layer dependence of friction on chemically doped MoS2

“…with less than 10 layers) and bulk flakes of undoped and Re-doped MoS 2 , the results of which are summarized in figure 3. The main conclusions from these measurements can be described as follows: (i) the separation in frequency between the E 2g and A 1g modes (19 cm −1 , 23 cm −1 , and 25 cm −1 for single-layer, few-layer and bulk MoS 2 regions, respectively) decreases with decreasing thickness in accordance with the literature [22]; (ii) the spectra of Re-doped MoS 2 are devoid of peaks associated with the formation of ReS 2 (an E 2g peak at 163 cm −1 and an A 1g -like peak at 213 cm −1 ), ruling out phase segregation as a result of Re doping [23]; (iii) there is a significant decrease in the intensity of the E 2g and A 1g peaks for all Re-doped samples (calibrated against the intensity of the reference Si peak at 521 cm −1 ) when compared with the undoped ones; and (iv) the two predominant Raman-active modes of MoS 2 (the E 2g mode, which arises from the in-plane opposite vibration of two S atoms against a Mo atom, and the A 1g mode, which corresponds to the out-of-plane vibrations of S atoms in opposite directions) [24] are observed in all samples, with small red shifts in the few-and many-layer cases.…”

Cobalt-Doped MoS2-Integrated Hollow Structured Covalent Organic Framework Nanospheres for the Effective Photoreduction of CO2 under Visible Light

“…Intercalated ions, possibly attributable to the doped cobalt (Co) atoms, may account for the observed interlayer expansion. 42,58 No obvious diffraction peaks of Co-1T-MoS 2 are detected in the XRD pattern of the hybrid, which may be due to their low concentration or less crystalline quality in the composite structure.…”

“…This could be due to the increased interlayer distance in 1T phase MoS 2 , indicating the successful formation of TpPa-1/Co-1T-MoS 2 composite and the effectiveness of the developed synthesis method. Intercalated ions, possibly attributable to the doped cobalt (Co) atoms, may account for the observed interlayer expansion. , No obvious diffraction peaks of Co-1T-MoS 2 are detected in the XRD pattern of the hybrid, which may be due to their low concentration or less crystalline quality in the composite structure.…”

Toward low-cost and sustainable SERS substrate: novel ultrasensitive AMS5 nanoflowers

“…AMS 5 has a smaller charge transfer resistance and a higher current density, indicating that doping Ag is conducive to charge transfer between substrates and molecules. 20,[37][38][39][40][41] Based on the above results, the enhancement mechanism of AMS 5 is analyzed in Fig. 5e, showing certain feasible CT processes: (1) the electrons in AMS 5 are excited from the VB to CB; (2) then, electron excitation from the CB of AMS 5 transfers to the HUMO level; (3) similarly, electron excitation in R6G from the HOMO to LUMO; (4) the excited electron transfer from the R6G (LOMO) to the CB of AMS 5 .…”