CHEMICAL SCIENCE

Modulating iron/cobalt single-atom synergistic catalysts to realize high-performance zinc-air batteries


Rechargeable zinc-air ion batteries have the advantages of safety, zero pollution, high energy, high power, low cost and material reproducibility, of which the oxygen electrocatalyst in the air electrode is the key to the technology.

Recently, the research group of Zhao Wei of Shenzhen University reported a method of using atom-interface regulation to synthesize a nitrogen/sulfur-doped porous carbon-borne iron/cobalt single atom synergistic double catalyst, which was used as an air electrode material to achieve excellent zinc-air battery cyclic charge and discharge performance. Through a variety of experimental characterization techniques combined with theoretical calculations, the Fe-(N2S) and Co-(N2S) structures of asymmetric coordination were determined, which improved the charge transfer efficiency, reduced the reaction energy barrier, and improved the ORR and OER reaction performance.

On January 30, 2023, the study was published as “Simultaneously Engineering the Synergistic-Effects and Coordination-Environment of Dual-Single-Atomic Iron/Cobalt-sites as a Bifunctional Oxygen Electrocatalyst.” for Rechargeable Zinc-Air Batteries, published online in the journal ACS Catalysis.

Researcher Wei Zhao of the Institute for Advanced Study of Shenzhen University is the only corresponding author of the paper, and the first author is Ghulam Yasin, a postdoctoral fellow at the Institute for Advanced Study of Shenzhen University.

The researchers successfully prepared nitrogen/sulfur-doped porous carbon-borne Fe/Co two-point single-atom catalyst Fe, Co/DSA-NSC, and characterized the catalyst materials with SEM, HRTEM, XRD, HAADF-STEM, XAS, etc. 1)。

Fig. 1. (a) Schematic-sketch of the fabrication of the atomically-dispersed dual-metal active-sites in nitrogen/sulfur doped carbon-nanosheets. SEM-image (b) TEM image (c) and the HRTEM image (d) of the Fe,Co/DSA-NSC catalyst. (e) HAADF-STEM image of the Fe,Co/DSA-NSC and the subsequent elemental mappings of Fe, Co, N, S and C components. (f) XRD pattern (g) and the Raman spectra of NSC and Fe,Co/DSA-NSC catalysts.

Electrochemical test of catalyst Fe, Co/DSA-NSC: the half-wave potential of ORR is 879 mV, and the overpotential of OER is 210 mV (j=10 mA/cm2); ORR half-cell test, after 10,000 CV cycles, the half-wave potential dropped by only 6 mV; In the OER stability test, the overpotential increased by only 0.1% after 20 hours of continuous operation at a current density of 10 mA/cm2. Subsequently, the research group tried the application and used Fe,Co/DSA-NSC catalyst as an air electrode to make a rechargeable zinc-air battery, and found that it has good charge-discharge performance and excellent cycle stability: the open-circuit voltage VOC is 1.52 V, and the peak power density is 240 mW/cm2, which is better than the commonly used reference benchmark commercial Zinc-air battery (1.41 V&189 mW/cm2) with Pt/C & IrO2 as the air electrode. The specific capacitance (specific-capacity) at a current density of 10 mA/cm2 is 748 mA h gZn−1, which is also better than the zinc-air battery with Pt/C & IrO2 (621 mA h gZn−1). In order to deeply understand the internal reasons for the excellent performance of the catalyst, the research group made DFT theoretical calculations, studied the electronic structure of the catalyst material and the OER/ORR reaction mechanism, and determined that the Fe-(N2S) and Co-(N2S) structures of asymmetric coordination were the active sites, and Fe-(N2S) had higher activity for ORR, while Co- (N2S) had higher activity for OER. The Fe/Co dual catalytic active site greatly reduces the ORR and OER reaction barriers, improves the charge transfer efficiency, thereby improving the ORR and OER performance, and the corresponding charge and discharge performance of zinc-air batteries, please refer to the article (Fig. 2、Fig. 3)。

Fig. 2. ORR linear-scan voltammogram (LSV) curves of NSC, Fe/SA-NSC, Co/SA-NSC, Fe,Co/DSA-NSC and Pt/C catalysts (a) and the consequential ORR-half-wave potentials (b). (c) LSV-curves of the Fe,Co/DSA-NSC sample at different rotations. OER LSV-curves (d), the resulting overpotentials at 10 mA/cm2 (e) and the Tafel plots (f) of NSC, Co/SA-NSC, Fe/SA-NSC, Fe,Co/DSA-NSC and IrO2 catalysts. (g) The ORR-LSV curves of the Fe,Co/DSA-NSC before and after 10,000 cycles. (i) The OER-LSV curves of the Fe,Co/DSA-NSC before and after 1000 cycles. (h) Graphical depiction of ORR/OER catalytic performance before and after stability test.

Fig. 3. (a) Oxygen-activity obtained from the ORR (E1/2) and OER (Ej=10) of NSC, Fe/SA-NSC, Co/SA-NSC, Fe,Co/DSA-NSC and Pt/C&IrO2 catalysts. (b) A graphic design of a zinc-air battery with the Fe,Co/DSA-NSC catalyst as the air-electrode. (c) Discharge-polarization and correspondent peak-power density curves of Fe,Co/DSA-NSC and Pt/C&IrO2 catalysts (d) Charging/Discharge-voltage curves. (e) Discharging-curves at 10 mA/cm2. (f) Galvanostatic discharging-profile at different current densities. (g) Charge/Discharge-cycling performance at 10 mA/cm2. (h) Bloated cycling potential gap at 10 mA/cm2.

This research was supported by the National Natural Science Foundation of China and the Shenzhen Municipal Project, with Shenzhen University as the first completion unit. (Source: Science Network)

Related paper information:https://doi.org/10.1021/acscatal.2c05654



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