Single atom Ru doping 2H-MoS2 as highly efficient hydrogen evolution reaction electrocatalyst in a wide pH range

Elucidating the Critical Role of Ruthenium Single Atom Sites in Water Dissociation and Dehydrogenation Behaviors for Robust Hydrazine Oxidation‐Boosted Alkaline Hydrogen Evolution

“…[39] Compared with CC@WS 2 , the S 2p XPS spectra of CC@WS 2 /Ru-450 also show a negative shift (≈0.10 eV), which mainly because of the same combined effect as those of in W 4f spectra (Figure 3b). [30] Figure 3d presents three typical characteristic peaks at 286.2, 284.6, and 282.0 eV which are assigned to the CO, CC (partially overlapping with the Ru 3d 3/2 ) species in C 1s orbital, and Ru δ+ with oxidation state in Ru 3d 5/2 signal for CC@WS 2 /Ru-450, respectively. [40,41] Moreover, high-resolution XPS spectrum of Ru 3p signal for CC@WS 2 /Ru-450 was performed to further support the atomic scale of Ru in CC@WS 2 /Ru-450.…”

“…After the galvanostatic deposition of Ru on the Sv of WS 2 , the CC@WS 2 /Ru-450 (the deposition time of Ru SAs is 450 s as noted) have similar structures with individual WS 2 NSs, and no stacking phenomenon between layers of the WS 2 nanosheet structure is observed, indicating the deposition of Ru on WS 2 does not affect the morphology of WS 2 (Figure 1f,g). [30] It is noted that the morphological changes during the high-temperature sulfidation process is attributed to the structural property of WS 2 . [27] As shown in Figure 1h, with the sulfidation reaction temperature rising, sublimed sulfur vapor reacts with surface WO 3 to form SWS bonds, and small size of WS 2 nanosheets form at the first reaction stage, as evidenced by the SEM images in Figure S1 of the Supporting Information, in which nanowires and nanosheets are coexistence in CC@WS 2 at the sulfidation time of 0.5 h. Subsequently, the sublimed sulfur vapor further reacts with more WO 3 nanowires and breaks the WO bonds, the WS 2 nanosheets gradually grow large and stack perpendicular because of the formed lattice layers induced by weak van der Waals gap.…”

“…The WS 2 /Ru-450 displays a similar structure with WS 2 , demonstrating the deposition of Ru in WS 2 does not change the inherent morphology of WS 2 (Figure S3, Supporting Information). [30] The microscopic atomic arrangement of Ru SAs in WS 2 was further characterized by the spherical aberration correction (AC) HAADF-STEM, as shown in Figure 2i. The hexagonal structure can be clearly observed in the 2H phase of WS 2 where the yellow and blue balls represent S and W atoms, respectively.…”

“…[38] Compared with CC@WS 2 , W 4f spectrum of CC@WS 2 /Ru-450 exhibits a shift of 0.15 eV toward lower binding energy, which may due to the combined effect of the work function change and electron configuration of W and S in CC@WS 2 / Ru-450. [30] Another two peaks at 35.8 and 37.9 eV are W 6+ species resulting from the partial surface oxidation of CC@WS 2 /Ru-450. The XPS spectra in Figure 3c shows an S 2p 3/2 S 2p 1/2 doublet peaks at 162.4 and 163.6 eV, respectively, are characteristic peaks of S 2− species in WS 2 .…”

“…As shown in Figure S9 of the Supporting Information, the peaks located at 463.1 eV (Ru 3p 3/2 ) and 485.4 eV (Ru 3p 1/2 ) are ascribed to the form of Ru δ+ rather than metallic Ru, further indicating the atomic scale of Ru in the CC@WS 2 /Ru-450. [30,42] Compared with CC@WS 2 @Ru NPs, no peaks appear at 280.7 eV of Ru 0 in CC@WS 2 /Ru-450, indicating the absence of metallic Ru and leading to strong interaction between Ru SAs and WS 2 , which modulates the charge density of the Ru SAs. [43] However, the Ru SAs tends to aggregate to nanoclusters when the deposition higher than 450 s as evidenced by the Ru 3d signal for CC@WS 2 /Ru SAs with different deposition time (110, 225, 450, 900, and 1800 s) (Figure S10, Supporting Information), where the Ru 0 signal appears at the deposition time of 900 and 1800 s. The Raman spectroscopies are also conducted to analyze the influences of Ru-doping on the bonding natures of 2H-WS 2 .…”