Conversion of maize straw into nitrogen-doped porous graphitized carbon with ultra-high surface area as excellent oxygen reduction electrocatalyst for flexible zinc-air batteries

作者：Hao, Xiaoqiong; Chen, Weiheng; Jiang, Zhongqing^*; Tian, Xiaoning; Hao, Xiaogang; Maiyalagan, Thandavarayan; Jiang, Zhong-Jie

来源：Electrochimica Acta, 2020, 362: 137143.

DOI：10.1016/j.electacta.2020.137143

• Maize straw
• Nitrogen-doped porous graphitized carbon
• Oxygen reduction reaction
• Flexible zinc-air batteries
• Agricultural waste reuse

Rational design and preparation of waste biomass derived carbon as air electrode catalysts are pivotal for large-scale sustainable development of Zn-air battery, simultaneously promoting waste resource reuse. Herein, a three-dimensional nitrogen-doped porous graphitized carbon (MS-NPC) is designed by employing maize straw as carbon precursors. The N-doping can cause increased active sites for oxygen reduction reaction (ORR), and the FeCl3 activated porous graphitized structure provides an efficient O-2 and electrolyte pathway toward easily access to active sites. The resultant N-doped porous graphitized maize straw carbon (MS-NPC) surprisingly exhibits high specific surface area (1483 m(2) g(-)(1)), high nitrogen content (4.70%), a rather positive onset potential (0.985 V vs. RHE) and large limiting current density (5.8 mA cm(-2)), which is even better than most reported leading results based on biomass-derived carbon. Density-functional-theory computations confirm the synergetic effect between N-doping and FeCl3 activated porous graphitized structure are promising to accelerate ORR process which is the essential reason for high ORR catalytic performance of MS-NPC. Furthermore, a primary Zn-air battery (ZAB) designed with MS-NPC electrode displays a maximum power density (127.9 mW cm(-2)), super specific-dischargecapacity (794 mAh gm(-1) at 300 mA cm(-2)), longtime stability, ZnO immunity and flexible properties. Practical testing verifies that the home-made ZAB can easily power LEDs and electric fans, thereby presenting a promising strategy for the development of economical and highly active carbon as excellent ORR electrocatalyst from waste biomass.