In situ produced Co9S8 nanoclusters/Co/Mn-S, N multi-doped 3D porous carbon derived from eriochrome black T as an effective bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Construction of high-efficiency, low cost and stable non-noble metal catalyst on air cathode is of great importance for design and assembly of rechargeable Zn-air battery. Eriochrome black T (EBT) has phenolic hydroxyl and -N=Ν- groups, which provides multiple coordination sites for metal ions. Herein, Co₉S₈ nanoclusters implanted in Co/Mn-S,N multi-doped porous carbon (Co₉S₈@Co/Mn-S,N-PC) are fabricated with the mixture (i.e. EBT, metal precursors and dicyandiamide) by a coordination regulated pyrolysis strategy. Specifically, EBT effectively chelates with the Co and Mn ions, resulting in multiple incorporation and fine modulation of the carbon electronic structures. Meanwhile, its sulfonic acid groups are reduced at such high temperature, accompanied by simultaneously embedding S element in the carbon, ultimately in situ forming Co₉S₈ nanoclusters. The Co₉S₈@Co/Mn-S,N-PC performs as an effective bifunctional oxygen catalyst, displaying a positive half-wave potential of 0.85 V and a large limiting current density of 5.89 mA cm^-2 for oxygen reduction reaction (ORR) in alkaline media, coupled with a small overpotential of 320 mV at 10 mA cm^-2 towards oxygen evolution reaction (OER), outperforming commercial Pt/C and RuO₂ catalysts, respectively. Furthermore, the assembled rechargeable Zn-air battery with Co₉S₈@Co/Mn-S,N-PC exhibits the much better charge/discharge performance and long-term durability (210 h, 630 cycles). This research opens an instructive avenue to develop high-efficient and stable bifunctional oxygen electrocatalysts in energy transformation and storage devices.

Hydrophobic POM Electrocatalyst Achieves Low Voltage "Charge" in Zn-Air Battery Coupled with Bisphenol A Degradation

Zn-air batteriesare a perspective power source for grid-storage. But, after they are discharged at1.1 to 1.2 V, large overpotential is required for their charging (usually 2.5 V). This is due to a sluggish oxygen evolution reaction (OER). Incorporating organic pollutants into the cathode electrolyte is a feasible strategy for lowering the required charging potential. In the discharge process, the related oxygen reduction reaction, hydrophobic electrocatalysts are more popular than hydrophilic ones. Here, a hydrophobic bifunctional polyoxometalate electrocatalyst is synthesized by precise structural design. It shows excellent activities in both bisphenol A degradation and oxygen reduction reactions. In bisphenol A containing electrolyte, to achieve 100 mA ⋅ cm^-2 , its potential is only 1.32 V, which is 0.34 V lower than oxygen evolution reaction. In the oxygen reduction reaction, this electrocatalyst follows the four-electron mechanism. In both bisphenol A degradation and oxygen reduction reactions, it shows excellent stability. With this electrocatalyst as cathode material and bisphenol A containing KOH as electrolyte, a Zn-air battery was assembled. When "charged" at 85 mA ⋅ cm^-2 , it only requires 1.98 V. Peak power density of this Zn-air battery reaches 120.5 mW ⋅ cm^-2 . More importantly, in the "charge" process, bisphenol A is degraded, which achieves energy saving and pollutant removal simultaneously in one Zn-air battery.

A rationally designed bifunctional oxygen electrocatalyst based on Co2P nanoparticles for Zn–air batteries

A highly-efficient Co₂P-based bifunctional oxygen catalyst has been developed though an enhanced coupling with N,P co-doped carbon nanoparticles and 3D carbon networks, which exhibits better bi-catalytic performance than benchmark noble metal-based counterparts.