Singapore Institute of Technology

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Milk powder-derived bifunctional oxygen electrocatalysts for rechargeable Zn-air battery

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posted on 2024-02-19, 05:26 authored by Xuncai Chen, Li Wei, Yanqing Wang, Shengli Zhai, Zibin Chen, Songwen Tan, Zheng Zhou, Andrew Keong NgAndrew Keong Ng, Xiaozhou Liao, Yuan Chen

Sustainable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysts are desirable for many energy storage and conversion systems. Australian dairy industry generates a large amount of expired milk powders every year, which are often dumped as food wastes. Here, we report a highly efficient bifunctional O2 electrocatalyst by incorporating mixed metal oxide (NiFeOx) nanoparticles into N (8.5 at%) and P (1.9 at%) dually doped carbon materials derived from milk powders. This catalyst demonstrates an onset potential of 0.90 V vs. reversible hydrogen electrode (RHE), a kinetic limiting current density of 12.9 mA cm−2 at 0.4 V vs. RHE, and an electron transfer number of 3.86 for ORR, it also shows an onset potential of 1.48 V vs. RHE, an overpotential of 0.32 V at 10 mA cm−2, a Tafel slope of 59.03 mV/dec in 1.0 M KOH for OER. Its catalytic performance is comparable to that of the best metal-free carbon-based ORR electrocatalysts and OER electrocatalysts based on hybrids of metal oxides and carbon materials. Rechargeable Zn-air batteries were also fabricated using air electrodes made of this catalyst, demonstrating an open-circuit potential of 1.39 V, a specific capacity of 688 mAh g−1 (corresponding to an energy density of 853 Wh kgZn−1), and excellent rechargeability over 150 cycles with a small performance loss. The milk powder-derived carbon materials can be used to produce eco-friendly and high value-added electrocatalysts for energy conversion and storage applications while reducing food wastage.


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Energy Storage Materials

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