Valorization of Naturally Abundant Low-Value Peat into Highly Active Non-Platinum Group Metal Oxygen Reduction Catalysts

Abstract

As society continues to adopt an increasingly eco-friendly stance, the efficient usage of natural resources needs to be maximised. For instance, energy obtained from biomass covers roughly a tenth of the global demand. This biomass can instead be used as a carbon source to produce value-added materials such as tnon-platinum group metal (NPGM) oxygen reduction catalysts, which are desperately sought after as global demand for fuel cells continues to rise [1,2]. For example, peat is an extremely abundant biomass material in Estonia covering roughly 20% of the country [3]. Herein, the viability of using peat-based catalysts as oxygen reduction catalysts in alkaline media was investigated. The peat sourced from a local peatland was processed and modified with inexpensive iron and nitrogen precursors through the common double-pyrolysis and acid washing synthesis procedure into peat-based NPGM catalysts. Additionally, zinc chloride was used as a pore forming agent. The influence of several principal synthesis parameters, e.g. precursor compound type and amount, on the physical and electrochemical properties of these materials was investigated using various characterization methods. The NPGM catalysts obtained from naturally abundant peat were highly microporous systems due to the inclusion of zinc chloride in the synthesis mixture. High onset (~0.93 V vs RHE) and half-wave potential (~0.83 V vs RHE) values were obtained for most of the materials in activity screening experiments conducted with a rotating disc electrode setup using 0.1 M KOH. However, using an excessive amount of the nitrogen precursor in the synthesis proved to be detrimental to the obtained activity. The high activity of the obtained peat-derived catalysts was further investigated in a rotating ring disc electrode setup where the influence of the studied synthesis parameters on the oxygen reduction reaction selectivity was more evident. Acknowledgments This work was supported by the EU through the European Regional Development Fund under projects TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), NAMUR “Nanomaterials - research and applications” (3.2.0304.12-0397), NAMUR+ core facility funded by the Estonian Research Council (TT 13), PRG676 “Development of express analysis methods for micro-mesoporous materials for Estonian peat derived carbon supercapacitors” (01.01.2020–31.12.2024) and PUT1581 (1.01.2017–31.12.2020). References F. Jaouen, D. Jones, N. Coutard, V. Artero, P. Strasser, A. Kucernak, Johns. Matthey Technol Rev. 2018, 62, 231. E4tech, 2022, The Fuel Cell Industry Review 2021 . M. Orru, H. Orru, Est. J. Earth Sci. 2008, 57, 87.