A Porous Nano-Micro-Composite as a High-Performance Bi-Functional Air Electrode with Remarkable Stability for Rechargeable Zinc–Air Batteries

Abstract

The development of bi-functional electrocatalyst with high catalytic activity and stable performance for both oxygen evolution/reduction reactions (OER/ORR) in aqueous alkaline solution is key to realize practical application of zinc–air batteries (ZABs). In this study, we reported a new porous nano-micro-composite as a bi-functional electrocatalyst for ZABs, devised by the in situ growth of metal–organic framework (MOF) nanocrystals onto the micrometer-sized Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF) perovskite oxide. Upon carbonization, MOF was converted to porous nitrogen-doped carbon nanocages and ultrafine cobalt oxides and CoN4 nanoparticles dispersing inside the carbon nanocages, which further anchored on the surface of BSCF oxide. We homogeneously dispersed BSCF perovskite particles in the surfactant; subsequently, ZIF-67 nanocrystals were grown onto the BSCF particles. In this way, leaching of metallic or organic species in MOFs and the aggregation of BSCF were effectively suppressed, thus maximizing the number of active sites for improving OER. The BSCF in turn acted as catalyst to promote the graphitization of carbon during pyrolysis, as well as to optimize the transition metal-to-carbon ratio, thus enhancing the ORR catalytic activity. A ZAB fabricated from such air electrode showed outstanding performance with a potential gap of only 0.83 V at 5 mA cm−2 for OER/ORR. Notably, no obvious performance degradation was observed for the continuous charge–discharge operation for 1800 cycles over an extended period of 300 h.

2D Heterojunction Between Double Perovskite Oxide Nanosheet and Layered Double Hydroxide to Promote Rechargeable Zinc‐Air Battery Performance

“…In comparison, pristine PBMNC‐0.1 NS cathode degrades within an hour whereas Pt/C‐RuO 2 couple lasts up to 15 h. Moreover, the long‐term cyclic stability test for PBMNC/LDH‐20 cathode shows only 0.46 V increase in charge‐discharge voltage gap after 100 h (Figure 4d). The cathodic performance of PBMNC/LDH‐20 is at par with the recent reports on similar composite systems (Table S5) [14,20,34,37–40] …”

Facilitating Oxygen Redox on Manganese Oxide Nanosheets by Tuning Active Species and Oxygen Defects for Zinc‐Air Batteries

“…The Co−MnO 2 also presented an electron transfer number ( n ) of 3.96, which is close to 4 (Figure S3). This result indicates that most of the oxygen undergoes a four‐electron reduction process, which leads to a high selectivity for the OH − production [57–59] . In Figure 2b, Co−MnO 2 and Ni‐MnO 2 presented improved OER catalysis, which could be highly associated with the introduced Co and Ni and the oxygen defects.…”

A Function‐Separated Design of Electrode for Realizing High‐Performance Hybrid Zinc Battery

“…The transfer number of ≈4 indicates the predominant 4‐electron transfer process for OH − yielding. [ 51–53 ] MnS also shows a fair OER activity with a potential of 1.813 V at 10 mA cm −2 ( E j =10 ). While the ORR activity of Ni x Co 1− x S 2 ( E 1/2 = 0.710 V) is inferior to MnS, Ni x Co 1− x S 2 material shows a more favorable OER activity indicated by a E j =10 of 1.610 V. It suggests that the introduction of Ni x Co 1− x S 2 into the MnS will realize a significant improvement of the OER activity.…”