Enriched sp²-Hybridized C Atoms toward the Tradeoff between Activity, Conductivity and Stability of Spherical Porous Metal–Nitrogen–Carbon Catalysts for Rechargeable Zinc–Air Batteries

Abstract

Advances in high-performance transition-metal–nitrogen–carbon catalysts (M–N–Cs) for the oxygen reduction reactions (ORR) are high-profile efforts to realize the large-scale implementations of rechargeable zinc–air batteries. However, it is extremely desirable but challenging to achieve stable active sites and excellent electron transport capability for M–N–C catalysts. Herein, spherical porous M–N–Cs (denoted as NPCS-Fc) with tailoring of the sp2-C/sp3-C ratio in carbon shell were prepared from low-cost coal tar pitch (CTP) via an acid-treatment-introduced defect-assisted one-step pyrolysis strategy. Due to the tradeoff among activity, conductivity, and stability, NPCS-Fc exhibits excellent ORR performance with a half-wave potential (E 1/2) of 0.863 V, a low Tafel slope of 59 mV dec–1, and long-cycle durability in alkaline media. As the air cathode, the assembled rechargeable zinc–air battery delivers a high OCV of 1.538 V and a specific capacity of 870 mAh gzn–1. The enriched sp2-C atom strategy to give M–N–C materials opens up a facile way for developing high-performance catalysts in flexible, rechargeable zinc–air batteries.

Advanced design strategies for Fe-based metal–organic framework-derived electrocatalysts toward high-performance Zn–air batteries

“…The presence of pyridine nitrogen can enhance the wettability of the catalyst surface and increase E on . 74,75 Graphite nitrogen not only improves diffusion performance but also controls the limiting current density, and further accelerates electron transfer. 76,77 The larger electronegativity of the N element will effectively adjust the electronic distribution and charge density of carbon materials.…”

A Long‐Overlooked Pitfall in Rechargeable Zinc–Air Batteries: Proper Electrode Balancing

“…Numerous studies have calculated the specific discharge capacity on the basis of the so called "consumed zinc" instead of using the total mass of the installed zinc plate when using stack cell, as it is common practice in battery research. [54,[105][106][107][108][109][110][111][112][113][114][115] The discharge capacity in the "consumed zinc"-approximation is not determined by battery cyclization but by discharging the cell once. The capacity obtained can be taken from the discharge curve, which is shown schematically in Figure 5.…”