Defective molybdenum sulfide quantum dots as highly active hydrogen evolution electrocatalysts

Advanced Electrode Materials Comprising of Structure‐Engineered Quantum Dots for High‐Performance Asymmetric Micro‐Supercapacitors

“…The high‐resolution Mo 3d spectrum (Figure g) shows three major peaks at 229.7, 232.9, and 236.1 eV, corresponding to Mo 3d5/2, Mo 3d3/2, and Mo 3d3/2, respectively. This reveals the dominance of the Mo +4 valence state in the product with the coexistence of the Mo +5 and Mo +6 valence states, indicating that there is a slight oxidation of the Mo +4 ions during the solvothermal reaction . Meanwhile, the binding energy of S 2s (Figure h) slightly shifts from 227 to 226.6 eV, demonstrating that the S valence state in MoS 2 has been affected by the change of Mo valence state.…”

“…Moreover, X‐ray diffraction (XRD) and Raman spectra are performed to evaluate the crystallinity and structure evolution of the MoS 2 ‐QDs as compared to bulk MoS 2 . It is noted that the weak (002) diffraction peak and the disappearance of other representative peaks in MoS 2 ‐QDs diffraction pattern indicate that there are no long‐range ordered crystal face and a limited portion of the crystalline lattice involved in diffraction, implying the as‐prepared MoS 2 ‐QDs with ultrafine size and monolayer or few‐layer structure (Figure S4, Supporting Information) . Furthermore, the Raman peaks of MoS 2 ‐QDs (Figure S5, Supporting Information) at 380.3 and 405.4 cm −1 are assigned to E 1 2g and A 1 g , respectively, and exhibit an apparent blueshift compared to those of bulk MoS 2 .…”

“…Moreover, the S 2p spectrum confirms that the existing valence states of S in MoS 2 ‐QDs are S −2 and S +6 , indicating its small partial oxidization. Notably, the O 1s spectrum (Figure i) is divided into three peaks, which are attributed to the MoO bond, the surface‐adsorbed species (OH, O, or oxygen vacancies), and the adsorbed water, implying a partial oxidation of MoS 2 ‐QDs . Such partial oxidation of MoS 2 ‐QDs can introduce rich defects, thus modify the electronic properties of MoS 2 ‐QDs and produce more active surface area, which benefits to the enhancement of electrochemical performance.…”

Properties, Preparation and Applications of Low Dimensional Transition Metal Dichalcogenides

“…The excellent catalytic activity might result from two factors: (1) The QDs might possess unique defect-rich structure that could bring in more active edge sites; (2) the efficiency of electrons transferred between the active edge sites and electrode was enhanced due to the random or disordered stacking of the exfoliated nanosheets on the surface of glass carbon electrode. Recently, Li’s group successfully fabricated MoS 2 QDs of about 2 nm diameter by using a facile and general ultrafast laser ablation method [ 188 ]. The as-prepared MoS 2 QDs showed significant lattice deformation and high amounts of surface defects.…”

Defective NiFe2O4 Nanoparticles for Efficient Urea Electro‐oxidation

“…[18] In order to prepareh igh-performance urea electro-oxidation catalysts, many methods have been developed, including preparing 2D nanosheets, [7,10,21] synthesizing heterostructures, [18,22,23] and growing on conductive substrates. [4,24] In recent years, defect engineering strategy was widelya dopted for optimizing the catalytic property of various catalysts in manya reas, including photocatalytic hydrogen evolution [25][26][27] and electrocatalytic hydrogen evolution, [28][29][30][31][32][33][34][35] oxygen evolution [36][37][38][39] as wella so xygen reduction. [40][41][42] Actually,s ignificantly enhanced catalytic performances were found by researchers mainly owing to the increased numberso f active sites.…”