Strongly Coupled NiCo₂O₄ Nanocrystal/MXene Hybrid through In Situ Ni/Co–F Bonds for Efficient Wearable Zn–Air Batteries

Abstract

Recently, owing to the high energy density and excellent security, wearable Zn−air batteries (ZABs) have been known as one of the most prominent wearable energy storage devices. However, sluggish oxygen reaction kinetics of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in the air-breathe cathode seriously has limited further practical applications. In this work, we synthesize a NiCo 2 O 4 nanocrystal/ MXene hybrid with strong Ni/Co−F bonds. The prepared MXene-based hybrid composites show remarkable ORR and OER electrocatalytic activity, which results in the fabricated solid-state ZAB device to achieve an open-circuit voltage of 1.40 V, peak power density of 55.1 mW cm −2 , and energy efficiency of 66.1% at 1.0 mA cm −2 ; to the best of our knowledge, this is the record performance among all reported flexible ZABs with MXene-based air cathodes and comparable with some noble metal catalysts. Moreover, even after cutting and suturing, our flexible solid-state ZAB devices are tailorable with high rate of performance.

A comprehensive review of MXenes as catalyst supports for the oxygen reduction reaction in fuel cells

“…Recently, new bottom-up MXene synthesis methods were developed, including chemical vapor deposition (CVD), 134,135 template methods, 114,136 and plasmaenhanced pulsed laser deposition. 137 Figure 3E,F show a schematic of the CVD growth process and the resulting Mo 2 C produced.…”

Air Electrodes for Flexible and Rechargeable Zn−Air Batteries

“…[ 30,66 ] Mai and his co‐workers reported a strongly coupled NiCo 2 O 4 nanocrystal/MXene hybrid for efficient bifunctional catalysts in solid‐state wearable ZABs. [ 67 ] NiCo 2 O 4 played the role as active substances in the hybrid, and the MXene nanosheets worked as conductive supports and prevented NiCo 2 O 4 NPs from aggregating. Figure 4o shows the synthetic process of NiCo 2 O 4 /MXene.…”

Recent Advances on MXene‐Based Electrocatalysts toward Oxygen Reduction Reaction: A Focused Review

“…The fabricated catalyst exhibited considerably low ORR activity (onset potential of 0.89 V) compared to that of the Fe-and Co-based MXene catalysts, with the lowest number of electrons referred per O 2 being as low as 3.4; it is to be noted that there was no second carbon component in this catalyst. Lei et al [132] synthesized strongly coupled, ultrasmall NiCo 2 O 4 -on-Ti 3 C 2 F x (OH) x as an ORR catalyst. Co and Ni were noted to be strongly coupled with the F terminations of the MXene via CoF and NiF bonds, which was believed to facilitate charge transport and generate a high electrocatalytic activity.…”

“…Reproduced with permission. [ 132 ] Copyright 2020, American Chemical Society. m) Differential charge density mapping of N–CoSe 2 /3D MXene.…”

“…Lei et al. [ 132 ] synthesized strongly coupled, ultrasmall NiCo 2 O 4 ‐on‐Ti 3 C 2 F x (OH) x as an ORR catalyst. Co and Ni were noted to be strongly coupled with the F terminations of the MXene via CoF and NiF bonds, which was believed to facilitate charge transport and generate a high electrocatalytic activity.…”