Ultrathin Co(OH)₂ Nanosheets@Nitrogen‐Doped Carbon Nanoflake Arrays as Efficient Air Cathodes for Rechargeable Zn–Air Batteries

Abstract

Developing highly active, cost‐effective, and durable bifunctional oxygen electrocatalysts is an important step for the advancement of rechargeable Zn–air batteries (ZABs). Herein, an efficient bifunctional oxygen electrocatalyst of ultrathin Co(OH)2 nanosheets supported on nitrogen‐doped carbon nanoflake arrays (named as Co(OH)2@NC), is reported, which yields excellent bifunctional activity, i.e., a low overpotential of 285 mV to reach 10 mA cm−2 for oxygen evolution reaction (OER), a high half‐wave potential (0.83 V) for oxygen reduction reaction (ORR), and a low potential gap (ΔE) of 0.69 V. The excellent bifunctional catalytic performance can be ascribed to the concerted efforts of cobalt hydroxide toward OER and nitrogen‐doped carbon for ORR. The Co(OH)2@NC nanoflake arrays is further used as binder‐free air cathodes for rechargeable Zn–air batteries, exhibiting a high specific capacity of 798.3 mAh gZn−1, improved stability (a working life of >70 h at 5 mA cm−2), as well as a reduced long‐term charging voltage, which outperforms the counterparts of NC nanoflake arrays and Pt/C‐based air cathodes. One step further, the Co(OH)2@NC nanoflake arrays on carbon cloth are directly used as binder‐free air cathodes for flexible, solid‐state ZABs, showing excellent performance under deformation as well.

Hollow Carbon Sphere and Polyhedral Carbon Composites Supported Iron Nanoparticles as Excellent Bifunctional Electrocatalysts of Zn–Air Battery

“…This means that nitrogen species exist in a more stable form after high‐temperature pyrolysis. [ 58–60 ] The presence of pyridinic N and graphitic N indicates that nitrogen is in situ doped into carbon‐based materials. The successful doping of nitrogen can greatly improve the electrocatalytic performance of the catalyst, as graphitic N, pyridinic N, pyrrolic N, and M–N x can provide more active sites.…”

“…[ 66 ] In the C 1 s spectrum (Figure 6d), the peak can be deconvoluted into four entities, which are M–C x , C–C, C–N, and C═O, with binding energies of 284.4, 284.9, 285.9, and 289.8 eV, respectively. [ 28,58 ] This indicates that nitrogen is successfully doped into the carbon framework and forms a small number of metal carbides.…”

Electrostatics and Chemistry Combination Divalent Cobalt Ions and Alkali-Treated MXene for High-Performance Lithium-Ion Batteries

“…The binding energies of Co@MXene C 1s (Figure h) are located at 286.30, 283.51, and 282.34 eV, corresponding to three bonding states C–O, C–C, and C–Ti–T x , respectively. To further understand the Co@MXene after alkali treatment, the high-resolution spectra of O 1s (Figure i) are analyzed and there are two fitted peaks located at 529.35 and 530.71 eV, which are compatible with the presence of −OH bonds and the combination of Co 2+ with −OH. , It is presumed that some of the −F end groups in the composites are substituted by −OH. This result further revealed that the alkali treatment could change the surface morphology of the composites and facilitate the formation of hydrogen bonds between MXene and Co 2+ , thereby improving the stability of the structure.…”

Frontiers and Structural Engineering for Building Flexible Zinc–Air Batteries

“…[71,72] Currently, flexible ZABs are restricted by the troubling issues of ZABs themselves and the immature technology for device deformability. [73][74][75][76] The overall battery properties come from each component, and the flexibility of these critical parts will be discussed in the next section.…”