Coupling MnS and CoS Nanocrystals on Self-Supported Porous N-doped Carbon Nanofibers to Enhance Oxygen Electrocatalytic Performance for Flexible Zn-Air Batteries

Abstract

Seeking highly efficient, stable, and cost-effective bifunctional electrocatalysts of rechargeable Zn–air batteries (ZABs) is the top-priority for developing new generation portable electronic devices. For this, the rational and effective structural design, interface engineering, and electron recombination on electrocatalysts should be taken into account to reduce the reaction overpotential and expedite the kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we construct a MnCo-based metal organic framework-derived heterogeneous MnS–CoS nanocrystals, which are anchored on free-standing porous N-doped carbon fibers (PNCFs) by the in situ growth method and vulcanization process. Benefiting from the abundant vacancies and active sites, strong interfacial coupling as well as favorable conductivity, the MnS–CoS/PNCFs composite electrode delivers a mentionable oxygen electrocatalytic activity and stability with a half-wave potential of 0.81 V for ORR and an overpotential of 350 mV for OER in the alkaline medium. Of note, the flexible rechargeable ZAB using MnS–CoS/PNCFs as binder-free air cathode offers high power density of 86.7 mW cm–2, large specific capacity of 563 mA h g–1, and adapts to different bending degree of operation. In addition, the density functional theory calculation clarifies that the heterogeneous MnS–CoS nanocrystals reduces the reaction barrier and enhances the conductivity of the catalyst and the adsorption capacity of the intermediates during the ORR and OER process. This study opens up a new insight to the design of the self-supported air cathode for flexible electronic devices.

Sulfidation of CoCuOx Supported on Nickel Foam to Form a Heterostructure and Oxygen Vacancies for a High-Performance Anion-Exchange Membrane Water Electrolyzer

“…In Figure a, the full survey spectra of CoCuO x /NF indicate the presence of Co, Cu, and O, while that of S-CoCuO x /NF show the presence of Ni and S. The high-resolution XPS spectra of Co, Cu, O, Ni, and S are shown in Figure b–f. Figure b reveals the presence of Co 2p 2/3 and Co 2p 1/2 peaks at 781 and 795 eV, for both CoCuO x /NF and S-CoCuO x /NF, respectively. , Compared to the Co 2p spectra of CoCuO x /NF, that of S-CoCuO x /NF shows much higher intensity satellite peaks at 786.22 and 804.94 eV, indicating the increase in the content of Co 2+ caused by the reduction of Co 3+ . The concentration of oxygen vacancies, according to the previous report, ,,, is positively correlated with the Co 2+ /Co 3+ ratio, demonstrating the increase in the density of oxygen vacancy.…”

Transition metal sulfide nanostructures: synthesis and application in metal-air batteries

“…It also avoids high power utilization and does not release any toxic gases. The MnCo-based metal-organic framework was prepared by He and coworkers [82]. The heterogeneous MnS-CoS nanocrystals were anchored to free-standing porous N-doped carbon fibers (PNCFs) using in situ growth and vulcanization.…”

“…The advantages of this study include its self-activation and selfsupported fabrication (binder-free) method, low power consumption, avoidance of toxic gas release, lack of the use of hazardous reducing agents and organic solvents, the distinctive surface morphology of FeCoS nanoclusters/nanosheet-based heterostructures, more stable FeCoS nanoclusters under alkaline conditions during electrochemical OER processes, and the format-facilitating effects of Fe and CoS. Various other TMSsbased nanocrystals (CoS/NC, CoS/PNCFs, MnS-CoS/NC, and MnS-CoS/PNCFs) were developed using a situ growth and vulcanization method for improved ORR/OER in 1.0 M KOH [82]. Among the developed TMS nanocrystals, the MnS-CoS/PNCFs nanomaterials delivered the greatest ORR/OER activity, when compared to other electrodes (figure 10).…”

Efficient Bifunctional NiFe-LDH@Co9S8 Nanoflower Electrocatalysts Anchored with Pt Nanocrystal for Flexible Quasi-solid Rechargeable Zinc Air Battery

“…To alleviate the energy crisis, innovative battery energy storage systems are of great demand to store renewable intermittent sources of energy, including solar and wind. , Rechargeable zinc–air batteries (RZABs) have the advantages of an economic price, a high theoretical specific energy (1218 Wh kg –1 ), and a harmless aqueous electrolyte and have emerged as promising candidates for ideal grid-scale energy storage. − RZABs are composed of air cathodes, aqueous electrolytes, electrically insulating separators, and Zn anodes . However, RZABs still confront the bottlenecks of limited discharge and recharge performance due to sluggish kinetics oxygen reaction at the air cathode, resulting in requiring both efficient bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts. − Normally, RZABs adopt Pt/C and RuO 2 (or IrO 2 ) as ORR and OER catalysts, but the high price of the noble-metal material hinders their wide application. − …”