Defect Engineering of MoS₂ and Its Impacts on Electrocatalytic and Photocatalytic Behavior in Hydrogen Evolution Reactions

Abstract

Molybdenum disulfide (MoS2) has been regarded as a favorable photocatalytic co‐catalyst and efficient hydrogen evolution reaction (HER) electrocatalyst alternative to expensive noble‐metals catalysts, owing to earth‐abundance, proper band gap, high surface area, and fast electron transfer ability. In order to achieve a higher catalytic efficiency, defects strategies such as phase engineering and vacancy introduction are considered as promising methods for natural 2H‐MoS2 to increase its active sites and promote electron transfer rate. In this study, we report a new two‐step defect engineering process to generate vacancies‐rich hybrid‐phase MoS2 and to introduce Ru particles at the same time, which includes hydrothermal reaction and a subsequent hydrogen reduction. Compositional and structural properties of the synthesized defects‐rich MoS2 are investigated by XRD, XPS, XAFS and Raman measurements, and the electrochemical hydrogen evolution reaction performance, as well as photocatalytic hydrogen evolution performance in the ammonia borane dehydrogenation are evaluated. Both catalytic activities are boosted with the increase of defects concentrations in MoS2, which ascertains that the defects engineering is a promising route to promote catalytic performance of MoS2.

Construction of Hybrid MoS2 Phase Coupled with SiC Heterojunctions with Promoted Photocatalytic Activity for 4-Nitrophenol Degradation

“…38 TG/DTA (Figure 2b) from 150 to 250 °C shows a broad endothermic peak on DTA without obvious mass loss, which corresponds to the transition from the 1T phase to the 2H phase, respectively. 7,37 As solitary, the 1T-MoS 37,43−46 S 2p spectra also showed a similar result, as shown in Figure S1. X-ray absorption fine structure (XAFS) spectroscopy can also provide evidence for the formation of the 1T/2H hybrid structure.…”

“…The hybrid 1T/2H-MoS 2 phase was synthesized by the hydrothermal method with the insertion of the guest ion of NH 4 + according to our previous work. 7 Figure 1 shows the XRD and TG of the synthesized 1T/2H-MoS 2 . The XRD patterns (Figure 1a, down) of the 2H-MoS 2 exactly matched with the standard card of MoS 2 (JCPDS 65-1951), while the 1T/2H-MoS 2 pattern (Figure 1a, up) lost some peaks due to poor crystallinity.…”

“…8,9 On the other hand, the 1T-MoS 2 has been proven to obtain more catalytically active sites than the 2H-MoS 2 because its basal plane can also act as active sites while the 2H-MoS 2 is only active on edge sites. 1,7,10,11 However, the 1T-MoS 2 is metastable, easily converts to the 2H phase spontaneously, and also suffers from extremely harsh synthesis conditions, which strictly limits the application of the 1T-MoS 2 . Meanwhile, the superior properties of the 1T-MoS 2 are so attractive that researchers are trying to solve the challenges that the 1T-MoS 2 is facing.…”

“…and reduction from hydrogen species are two important processes in a 4-NP reduction process, 21,32,33 MoS 2 /SiC suspects to have potential in this reaction because of its ability to react with BH 3 δ− through photogenerated holes and excellent binding ability of hydrogen intermediate. 7,34 Herein, we report a hybrid 1T/2H phase MoS 2 synthesized by the hydrothermal method, which was combined with SiC to form a heterojunction catalyst for the 4-NP degradation. In this reaction, defect sites in MoS 2 act as active sites for the first step of degradation, which allows the MoS 2 /SiC heterojunction catalyst to complete this reaction through the photocatalytic pathway.…”

Recent advances in two‐dimensional transition metal dichalcogenides as photoelectrocatalyst for hydrogen evolution reaction

“…82 Consequently, the active sites of the 1T-phase 2D-TMDs are on the basal plane instead of the edge sites, as seen in the 2H-phase 2D-TMDs. Moreover, the catalytic activity of 2D-TMDs toward the HER can also be improved through phase engineering, 83,84 defect engineering, 85,86 metal doping, 87,88 and composition engineering. [89][90][91] IMPROVEMENT OF THE CATALYTIC PERFORMANCE OF TMDS 2D-TMDs/p-Si p-n junction for PEC-HER P-type silicon (p-Si) is a well-known semiconductor with a low bandgap of 1.1 eV; it is able to absorb a wide range of UVvisible light for generating electron-hole pairs for use in various photovoltaic devices, such as solar cells or photodiodes.…”