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New Findings on Highly-efficient Bifunctional Oxygen Electrocatalyst

Yawen Tang’s research team reported a highly-efficient bifunctional oxygen electrocatalyst, Ni3FeN microspheres with hierarchically porous structure. This novel Ni3FeN catalyst was synthesized via thermal ammonolysis of NiFe LDH microspheres that are formed via a simple yet efficient arginine derived self-assembly methodology.

(a) Schematic illustration of the formation of the porous Ni3FeN hierarchical microspheres;
(b) Schematic interaction between arginine and metal ions; (c) Schematic interaction between arginine molecules.

 

The researchers of the research team led by Yawen Tang are from the School of Chemistry and Material Science, Nanjing Normal University. The related research results are published on the Nano Energy online (2017, DOI: org/10.1016/j.nanoen.2017.06.029) entitled as “Hierarchically mesoporous nickel-iron nitride as a cost-efficient and highly durable electrocatalyst for Zn-air battery.” Nano Energy is a top journal in the field of nano energy research whose impact factor reaches 12.343 in 2017. The first author of this paper is Gengtao Fu, a doctor of the School of Chemistry and Material Science.

(a-c) SEM images of the NiFe LDH hierarchical microspheres at different magnification; (d-f) SEM images of the porous Ni3FeN hierarchical microspheres at different magnification; (g) N2 adsorption–desorption isotherms and (h) XRD pattern of the porous Ni3FeN hierarchical microspheres. The inset in (g) shows the corresponding pore distribution curve; (i) Atomic structure model of the Ni3FeN (Ni atoms at the face centers, Fe atoms at the corners and N atoms in the center).

“Rechargeable Zn-air battery is largely limited by the lack of low-cost and highly efficient bifunctional oxygen catalysts for both oxygen evolution and reduction reactions (OER and ORR). Therefore, Yawen Tang’s research group discoverd a promising bifunctional electrocatalyst, mesoporous nickel-iron nitride (Ni3FeN), which was synthezied by thermal ammonalysis of hierarchal NiFe layered double hydroxide microspheres.”

“Different with the widely studied carbon /oxide composite catalysts, this metallic nitride does not need carbon as a conducting support, thus avoiding the issue of carbon corrosion at high potertials.”

The obtained Ni3FeN microspheres display an outstanding activity and stability in catalyzing the alkaline OER and ORR greater than those of other NiFe derivatives. Moreover, Ni3FeN microsphere as an air-cathode exhibits a low voltage gap between charge and discharge and a long lifetime in a home-made rechargeable Zn–air battery, further demonstrating their excellent activity and stability.

(a) STEM image and corresponding EDX mappings of Ni (red), Fe (green) and N (yellow) elements distributed at the Ni3FeN hierarchical microspheres; (b) EDX spectrum and (c) XPS survey scan spectrum of the Ni3FeN hierarchical microspheres; (d) High-resolution Ni 2p and Fe 2p XPS spectra for the Ni3FeN (black) and NiFe LDH (red).

The catalysts provide outstanding bifunctional performance with a low overpotential (0.355 V) at 10 mA cm-2, a low Tafel slope (70 mV dec-1) for OER, and a positive half-wave potential (0.78 V) for ORR under alkaline solution. More importantly, it delivers a lower voltage gap between charge and discharge and a better stability over 300 cycles compared to that of the more costly RuO2 air-cathode.

Gengtao Fu is a Ph.D graduate in 2017. When he was a graduate student, he had already yielded abundant academic achievements. He published 31 SCI papers in total on Nano Letters (IF: 13.779), Advanced Energy Materials (IF: 16.721), Nano Energy (IF: 12.343) and Chemical Science (IF: 9.144) whose total impact factor and cites reach 245 and 900 respectively. Among all the papers, six are SCI-TOP, six are highly cited, two are Cover Papers, two are introduced by the American Association for the Advancement of Science as highlights and one is introduced as highlight in the X-MOL chemistry platform.

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