Atomic Modulation of FeCo–Nitrogen–Carbon Bifunctional Oxygen Electrodes for Rechargeable and Flexible All‐Solid‐State Zinc–Air Battery

Abstract

Rational design and exploration of robust and low‐cost bifunctional oxygen reduction/evolution electrocatalysts are greatly desired for metal–air batteries. Herein, a novel high‐performance oxygen electrode catalyst is developed based on bimetal FeCo nanoparticles encapsulated in in situ grown nitrogen‐doped graphitic carbon nanotubes with bamboo‐like structure. The obtained catalyst exhibits a positive half‐wave potential of 0.92 V (vs the reversible hydrogen electrode, RHE) for oxygen reduction reaction, and a low operating potential of 1.73 V to achieve a 10 mA cm−2 current density for oxygen evolution reaction. The reversible oxygen electrode index is 0.81 V, surpassing that of most highly active bifunctional catalysts reported to date. By combining experimental and simulation studies, a strong synergetic coupling between FeCo alloy and N‐doped carbon nanotubes is proposed in producing a favorable local coordination environment and electronic structure, which affords the pyridinic N‐rich catalyst surface promoting the reversible oxygen reactions. Impressively, the assembled zinc–air batteries using liquid electrolytes and the all‐solid‐state batteries with the synthesized bifunctional catalyst as the air electrode demonstrate superior charging–discharging performance, long lifetime, and high flexibility, holding great potential in practical implementation of new‐generation powerful rechargeable batteries with portable or even wearable characteristic.

In Situ Coupling Strategy for the Preparation of FeCo Alloys and Co4N Hybrid for Highly Efficient Oxygen Evolution

“…The surface Co/Fe element distribution of FeCo-Co 4 N/N-C is further disclosed by electron energy loss spectroscopy mapping (EELS, Figure 1c). [31] N-doped sites with a total amount of 1.5 at% (Table S1, Supporting Information) was supported by the XPS N 1s spectrum as well ( Figure S7, Supporting Information). We therefore employed highresolution X-ray photoelectron spectroscopy (XPS) analysis for Fe 2p and Co 2p to study the surface chemistry of FeCo-Co 4 N/N-C ( Figure S7, Supporting Information).…”

“…[30] These results clearly indicate that diverse Co-based active sites could be simultaneously generated through this facile in situ coupling approach, thus, suggesting great potential for the OER application. [31] Ionic state (781.6 and 796.4 eV) cobalt with shakeup satellites (785.2 and 802.7 eV) were also observed. Based on the ICP-OES results, 2.6 and 3.6 wt% of Co and Fe were detected, respectively.…”

“…Compared to conventional Co-based electrocatalysts prepared using phthalocyanine-like rings as templates, [26,27] high-temperature pyrolysis may play a crucial role in formatting of Co 4 N, rather than other Co-based materials. [31][32][33] Two peaks at 710.2 and 714.0 eV can be assigned to the binding energies of the 2p 3/2 orbitals of Fe 2+ and Fe 3+ species, respectively. [30] These results clearly indicate that diverse Co-based active sites could be simultaneously generated through this facile in situ coupling approach, thus, suggesting great potential for the OER application.…”

CuCo2S4 Nanosheets@N‐Doped Carbon Nanofibers by Sulfurization at Room Temperature as Bifunctional Electrocatalysts in Flexible Quasi‐Solid‐State Zn–Air Batteries

“…[1][2][3][4][5][6][7][8] In principle, the advancement of flexible ZABs is critically dependent on the availability of desired air electrodes with excellent bifunctional electrocatalysis for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), together with robust flexibility and mechanical strength. [19][20][21][22][23][24][25][26][27] For example, CuCo 2 O 4 quantum dots attached on N-doped carbon nanotubes (CuCo 2 O 4 @NCNTs) were shown to be an impressively bifunctional electrocatalyst including a good positive half-wave potential (0.80 V) for ORR and a low overpotential (467 mV@10 mA cm −2 ) for OER, which can contribute to an energy density of 659 W h kg −1 (in liquid state) for ZAB. Bimetallic oxides (BOs)@heteroatom-doped carbon hybrids have drawn considerable attentions, because of their high catalytic efficiency, derived from the synergetic effects between the nanostructured BOs (for OER) and N-doping in carbon materials (for ORR).…”

N,S Co-Doped Carbon Nanofibers Derived from Bacterial Cellulose/Poly(Methylene blue) Hybrids: Efficient Electrocatalyst for Oxygen Reduction Reaction

“…In these devices, the oxygen reduction reaction (ORR) on the cathode is very slow kinetically, and thus requires platinum (Pt) as electrocatalyst. As the high price and unsatisfactory methanol tolerance of Pt have become a bottleneck of its extensive application in the fuel cells and metal-air batteries, the development of cheap and steady non-platinum catalysts is a practical and urgent issue [5][6][7][8]. In such conditions, To identify the formation of PMB on the surface of BC, the samples of BC, BC/MB and BC/PMB were characterized.…”