“Simple-Stir” Heterolayered MoS₂/Graphene Nanosheets for Zn–Air Batteries

Abstract

A facile, one-pot, top-down, protein-assisted, simply-stir method to produce aqueous suspensions of MoS 2 /graphene hybrid (MoS 2 /Gr) nanoplatelets of up to 14 mg mL −1 for applications in sustainable, next-generation batteries is reported here. Bovine serum albumin (BSA) served as the exfoliant to rapidly produce high concentrations of the hybrid by simply stirring on a desk top stirrer without any specialized equipment. The reactor is amenable for continuous flow, allowing for scale-up to produce large quantities, 24/7, with minimal human intervention. Raman spectroscopy, X-ray diffraction, ultraviolet−visible spectroscopy, and energy-dispersive X-ray spectroscopy indicated the coexistence of both MoS 2 and graphene nanosheets in a majority of flakes. The Raman spectra indicated low defect, 3−4 layer graphene sheets with very low oxidation levels, as well as 4−8 layer MoS 2 flakes. The exfoliation mechanism was studied as a function of the concentrations of bulk MoS 2 , graphite, protein, as well as the stirring speed, pH, and temperature. The reaction orders with respect to these parameters were determined. Temperature dependence data indicated a thermal energy barrier of 19.1 kJ/mol, but the rpm dependence gave an extremely low shear energy barrier of 22.2 nJ/mol. One unique insight gained here is that the lateral destacking of the platelets via translational excitation induced by stirring populates higher translational states in the direction along the solvent flow. Thus, stirring is very efficient in destacking the platelets at a low energy cost, a mechanism for efficient exfoliation of two-dimensional materials. The cyclic voltammograms of the MoS 2 /Gr hybrid with a 1:13 mole ratio showed enhanced oxygen reduction activities, nearly double that of Gr nanosheets or ∼25-fold that of MoS 2 nanosheets, and vastly higher than those of both the bulk phases. The hybrid with a 1:13 mole ratio was used to fabricate flexible, functional, and bioabsorbable/biodegradable Zn−air batteries with high open circuit voltages (1.4 V) and high specific energy of up to 130 W h kg −1 , establishing practical applications of the hybrids over the individual nanosheets.

Gelatin-assisted co-exfoliation of graphene nanoplatelets/MoS2for high-performance supercapacitors

“…This preparation method to procure electro-active materials is highly prominent compared to other reported articles. 20,44 The formation of co-exfoliated GNP/MoS 2 hybrid nanosheets is further conrmed by UV-visible spectroscopy, Raman spectroscopy, uorescence spectroscopy, zeta-potential, PXRD, XPS, SEM, and HR-TEM.…”

“…This preparation method to procure electro-active materials is highly prominent compared to other reported articles. 20,44…”

“…[16][17][18] The synthesis of G/MoS 2 heterostructure composites undergoes several steps under harsh conditions and is time and energy-consuming. 19,20 For mass production, the preparation process of G/MoS 2 is inappropriate and unsatisfactory. Therefore, to overcome these restrictions, a novel strategy for scalable, cost-effective, and sustainable methods must be developed for the synthesis of the G/MoS 2 hybrid.…”

Manganese Molybdate Cathodes with Dual-Redox Centers for Aqueous Zinc-Ion Batteries: Impact of Electrolyte on Electrochemistry

“…To date, research efforts on cathode materials for aqueous zinc-ion batteries have been dominated by manganese oxides, vanadium oxides, and Prussian blue analogs, similar to magnesium-ion battery systems . However, recently, molybdenum-based sulfides and oxides, such as MoS 2 , Mo 6 S 8 , and MoO 3 , have gained traction as cathode materials for aqueous zinc-ion batteries. − These materials have shown promise as potential cathode candidates due to their high theoretical capacities originated from the Mo 6+ /Mo 4+ redox, as well as excellent rate capabilities and cycling performances. Additionally, molybdates, such as CoMoO 4 , and NiMoO 4 , have be employed as cathode materials in alkaline-based aqueous rechargeable zinc-ion batteries. − However, alkaline-based systems suffer from severe dendrite formation on the zinc metal anode.…”

Stable Solid Electrolyte Interface Achieved by Separator Surface Modification for High-Performance Anode-free Potassium Metal Batteries

“…Without a complex synthesis and multiple fabrication process, reduced graphene oxide (rGO) has high electrical conductivity, flexibility, mechanical strength, and excellent chemical corrosion resistance. 41 The monolayer rGO film can be easily transferred onto the separator, without an effect on the weight and thickness. In addition, through an in situ electrochemical reaction and construction of a "potassium-philic" interface, the realization of being anodefree and highly stable anodes has been obtained for KMBs.…”