Quantum‐Dot‐Mediated Controlled Synthesis of Dual Oxides of Molybdenum from MoS₂: Quantification of Supercapacitor Efficacy

Abstract

The versatile technological applications of molybdenum oxides requires the efficient synthesis of various stoichiometric molybdenum oxides. Thus, herein, a controlled method to synthesize both MoO and MoO from MoS via quantum dot intermediates is reported. Microscopic, spectroscopic, and X-ray studies corroborate the formation of orthorhombic α-MoO with a microbelt structure and monoclinic MoO nanoparticles that self-assemble into hollow tubes. Quantitative investigations into charge-storage kinetics reveal that MoO exhibits an excellent pseudocapacitive response up to a mass loading of 5 mg cm with an areal capacity of 327.2 mC cm at 5 mV s , with 41.9 % retention at 100 mV s . In contrast, above a mass loading of 0.5 mg cm , the charge-storage nature of MoO electrodes switches from that of a supercapacitor to battery type. At a sweep rate of 50 mV s , 87.2 % of the total charge is contributed by a capacitive response in a 1 mg cm MoO electrode. The charge-storage kinetics of MoO and MoO reflect on the respective asymmetric supercapacitors. A MoO //graphite asymmetric supercapacitor holds an outstanding energy density of 341 mW h m at a power density of 4949 mW m and delivers an ultrahigh power density of 28140 mW m with an energy density 142 mW h m and energy efficiency of 87 %.

Efficient and Facile Synthetic Route of MoO3:MoS2 Hybrid Thin Layer via Oxidative Reaction of MoS2 Nanoflakes

“…The reaction mechanism of MoS2 oxidation is generally described through the reaction of a free hydroxyl radical coming from H2O2, involved in Mo-S breaking and oxidation of S 2-and Mo 4+ leading to the formation of MoO3 [10,36]. However, the oxidation of Mo 4+ may not be totally achieved since the decomposition of the Mo3d peaks reveals the presence of an intermediate product in the hybrid layer that corresponds to the oxidation state of Mo 5+; as reported by S. Shin et al, this intermediate corresponds to MoOxSy named molybdenum oxysulfide, which is related to the incomplete substitution of sulfur by oxygen [37,38].To discuss the reaction process, S 2p and O1s spectra of the hybrid thin film are illustrated in Figure 7; it can be seen in the S2p spectrum that there is a spin-orbit doublet at the binding energy of 161 eV and 163 eV corresponding to the oxidation state The reaction mechanism of MoS 2 oxidation is generally described through the reaction of a free hydroxyl radical coming from H 2 O 2 , involved in Mo-S breaking and oxidation of S 2− and Mo 4+ leading to the formation of MoO 3 [10,36]. However, the oxidation of Mo 4+ may not be totally achieved since the decomposition of the Mo3d peaks reveals the presence of an intermediate product in the hybrid layer that corresponds to the oxidation state of Mo 5+ ; as reported by S. Shin et al, this intermediate corresponds to MoOxSy named molybdenum oxysulfide, which is related to the incomplete substitution of sulfur by oxygen [37,38].…”

Hierarchical Transition Metal Oxide Arrays Grown on Graphene‐Based Fibers with Enhanced Interface by Thin Layer of Carbon toward Solid‐State Asymmetric Supercapacitors

“…The log i and log v values of GCF@NC@NCO electrode for anodic potential of 0.05, 0.15, 0.25 and 0.35 V vs Hg/HgO are calculated and represented in Figure S7. To minimize the effect of Ohmic losses and overpotentials at faster sweep rates, the current at particular peak potential, 0.25 V, is trapped as a function of sweep rate . The measured “b” values are 0.88, 0.96, 0.84 and 0.81 for the respective potentials, respectively, i. e. close to 1.…”

Synthesis of Stable and Efficient Electrocatalysts for Hydrogen Evolution: Hierarchical NiMo-Based Hollow Nanotubes

“…Recently, some metal-metal oxide-based heterostructures (Pt-Ni(OH) 2 , Ru-O-Mo, and MoNi-Ni(OH) 2 ) have been reported to demonstrate bifunctional effects in improving the catalytic behavior of HER [26][27][28][29]. Further, the intrinsic activity of electrocatalysts can be tuned using several approaches, including tuning electronic conductivity, controlling the dimensions of nanostructured materials (0 to 3 D), and creating porous/ hollow/hierarchical structures [14,15,[30][31][32][33]. Typical hierarchical hollow nanotubular structured materials represent a novel class of materials with unique structural dimensions [16,17,[34][35][36][37][38].…”