Waste Tire Derived Carbon Support for Non-Platinum-Group Metal Catalyst Materials for Oxygen Reduction Reaction in Alkaline Medium

Abstract

Extensive use of non-renewable energy sources and excessive accumulation of hard-to-recycle waste, such as end-of-life tires, are among the most significant environmental problems today. For a more sustainable future, it is essential to find alternative solutions to energy and special waste management. For example, waste tires can be used to synthesize high-tech porous carbon materials, which can be used as a carbon support in fuel cell catalysts. [1] While fuel cells offer a promising alternative to some fossil fuel-based technologies, low temperature fuel cell catalysts rely on expensive platinum. Non-platinum-group metal (NPGM) catalysts, such as iron and nitrogen co-doped carbon materials are good contenders to platinum-based catalysts for the oxygen reduction reaction. Synthesizing porous carbon materials for more economically viable NPGM fuel cell catalysts could provide one way to use waste tires more sustainably and lower the cost of efficient fuel cell catalysts.For this work, a carbon material was synthesized by pyrolyzing tire granules (Imdex A/S) at 1000 °C for three hours in Ar [2]. Based on this carbon material, several iron and nitrogen co-doped catalyst materials were synthesized using Fe(NO3)3 as the iron source, dicyandiamide or guanidine as the nitrogen source, and ZnCl2 as a pore modifier. All synthesized materials were acid washed overnight to remove redundant elements such as Zn from the pore modifier and various impurities originating from the tire granules (mainly Si, S, Ca, and Zn). Finally, the materials pyrolyzed for a second time. The pyrolysis temperature, choice of nitrogen compound, and precursor ratios were varied for the syntheses described in this work.The NPGM catalyst materials were characterized by various physical and electrochemical methods to describe the relationship between the catalyst structure and the activity of the oxygen reduction reaction. SEM and SEM-EDX were used to evaluate the morphology and composition of the catalyst materials. N2 sorption data suggested that the specific surface area ranged from 77 to 194 m2 g-1 for all materials. Electrochemical characterization was performed in 0.1M KOH solution using the rotating disk electrode method. The highest onset potential (Eon = 920 mV vs RHE) was reached by a material using guanidine as the nitrogen source pyrolyzed at 900 °C, which is comparable to other recently described NPGM materials [3], including waste-tire derived NPGM catalysts [4]. Acknowledgements: This work was supported by the following projects: PRG676 “ Development of express analysis methods for micro-mesoporous materials for Estonian peat derived carbon supercapacitors” (1.01.2020- 31.12.2024)"Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” (TK141) (1.01.2016−1.03.2023) References [1] J. S. Gnanaraj et al., Sustainability 10(8), 2840 (2018)[2] J. Laanemäe, R. Jäger, P. Teppor, O. Volobujeva, and Enn Lust, ECS Transactions, 108, p. 39 (2022)[3] R. Gutru et al., International Journal of Hydrogen Energy, 47 (2022)[4] M. Muhyuddin et al., Electrochemica Acta, 433, 141254 (2022)