Abstract
Biomass from agricultural by-products is gaining increasing interest as cheap and abundant precursor in the development of active materials for efficient and environmentally friendly devices like fuel cells. Herein, we investigated iron and nitrogen co-doped nanoporous carbons derived from aronia, peach stones and coal tar pitch/furfural as electrocatalysts for the electrochemical oxygen reduction reaction (ORR) in alkaline media. Urea was used as nitrogen precursor and two annealing steps with intermediate acid leaching served to activate the catalysts. Within the series, the peach stone-derived catalyst exhibited a catalytic activity for the ORR close to the benchmark Pt/C, with a 60 mV dec−1 Tafel slope upon the incorporation of 0.57 wt% Fe and proper combination of N-Fe species (20%) with pyridinic/pyridonic moieties (49%). We concluded that the microporosity and a certain content of meso/macro-pores of the activated carbon, together with the creation of graphitic domains result in a high relative amount of Fe-N4 and nitrogen functionalities, which determine the electrocatalytic performance.
Highlights
Polymer electrolyte fuel cells (PEFC) are considered ideal power sources in a sustainable energy scenario due to their high power density and quasi-zero emissions [1,2]
The activated carbons denoted as PS and AR were produced from peach stones and dried aronia residues, respectively, by carbonization of 150 g raw material in nitrogen atmosphere at 550 °C for 30 min. 85 g of the obtained product were subjected to activation with water vapour for 1 h at 750 °C and 700 °C, respectively
An effective strategy for the preparation of active oxygen reduction reaction (ORR) catalysts from biomass, urea and iron nitrate is presented as non-critical raw alternative material catalyst for PEFC cathodes
Summary
Polymer electrolyte fuel cells (PEFC) are considered ideal power sources in a sustainable energy scenario due to their high power density and quasi-zero emissions [1,2]. Electrocatalysts based on platinum or platinum group metals (PGM) present a high activity toward the ORR and an adequate long-term stability [1] These metals are expensive and not abundant, making them not suitable for the widespread commercialization of PEFC in a sustainable situation where non critical raw materials are required. Besides to micropores to anchor the active phase, the presence of mesopores is required to facilitate a fast transport of oxygen in the porous framework [41] In this regard, a high activity for the ORR has been reported for biomass-derived hierarchical porous carbon materials doped with nitrogen and/or transition metals by different synthesis routes [32,45,46,47,48,49,50]. The performance of the catalysts is discussed with regard to their physico-chemical properties, aimed to gather further insights on the desired characteristics of bioresources to promote their valorization into useful catalysts for energy devices
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