ORR in Non-Aqueous Solvent for Li-Air Batteries: The Influence of Doped MnO2-Nanoelectrocatalyst

Abstract

One of the major drawbacks in Lithium-air batteries is the sluggish kinetics of the oxygen reduction reaction (ORR). In this context, better performances can be achieved by adopting a suitable electrocatalyst, such as MnO2. Herein, we tried to design nano-MnO2 tuning the final ORR electroactivity by tailoring the doping agent (Co or Fe) and its content (2% or 5% molar ratios). Staircase-linear sweep voltammetries (S-LSV) were performed to investigate the nanopowders electrocatalytic behavior in organic solvent (propylene carbonate, PC and 0.15 M LiNO3 as electrolyte). Two percent Co-doped MnO2 revealed to be the best-performing sample in terms of ORR onset shift (of ~130 mV with respect to bare glassy carbon electrode), due to its great lattice defectivity and presence of the highly electroactive γ polymorph (by X-ray diffraction analyses, XRPD and infrared spectroscopy, FTIR). 5% Co together with 2% Fe could also be promising, since they exhibited fewer diffusive limitations, mainly due to their peculiar pore distribution (by Brunauer–Emmett-Teller, BET) that disfavored the cathode clogging. Particularly, a too-high Fe content led to iron segregation (by energy dispersive X-ray spectroscopy, EDX, X-ray photoelectron spectroscopy, XPS and FTIR) provoking a decrease of the electroactive sites, with negative consequences for the ORR.

N-doped carbon nanotubes encapsulated with FeNi nanoparticles derived from defect-rich, molecule-doped 3D g-C3N4 as an efficient bifunctional electrocatalyst for rechargeable zinc–air batteries

“…The highest catalytic activity of FeNi/N-CNT should be attributed to the tubular structure of nanometer grade, together with the highest SSA that ensured the "exposure" level of active sites. [52][53][54] Furthermore, the incorporation of Fe and Ni metals into D-g-C 3 N 4 could help the generation of Fe-N x and Ni-N x and new FeNi alloy active sites. [55][56][57] For the same reason, Fe/N-C and Ni/N-C exhibited higher activity than the N-C electrocatalyst.…”

Enhancing Interaction between Lanthanum Manganese Cobalt Oxide and Carbon Black through Different Approaches for Primary Zn–Air Batteries

“…The peaks at 532.0 and 534.0 eV are associated with the C-O and C=O species of the carbon material, respectively [67]. Finally, the peak at around 533.0 eV is associated with the M-O-C species [27,68]. Additionally, differences are observed in the contribution of the C-O and M-O-C species.…”

Advanced nano-bifunctional electrocatalysts in Li–air batteries for high coulombic efficiency

“…69,70 In addition, transition metal elements possess multiple valence states, which are beneficial for the creation of oxides with different crystal structures. 71,72 In this section, two types of TMO nanomaterials are discussed based on their syntheses and structures, namely, Mn and Co-oxide based bifunctional catalysts.…”