Síntese de um eletrocatalisador bifuncional baseado na dopagem de óxido de grafeno reduzido com nitrogênio

Abstract

The development of efficient and low-cost bifunctional catalysts for oxygen reduction (RRO) and oxygen evolution (REO) reactions is essential for the advancement of fuel cell technologies. In this sense, the present work presents a study carried out to develop a bifunctional catalyst using phenanthroline as N-precursor for the doping of reduced graphene oxide (rGO). The catalyst prepared under optimized conditions through a multivariate statistical study, using parameters such as time (0.3 at 3.7 h), pyrolysis temperature (631.8 at 968.2 °C) and catalyst mass (59.8 a 110.2 mg), exhibited considerable electrocatalytic activity against RRO, with the involvement of 4 (four) electrons. Furthermore, the recorded Tafel slope (~150 mV dec-1 ) indicated the first electron transfer as the determining step of the reaction. Morphological and physicochemical characterizations provided information about the structure of the material, correlating the stability and catalytic performance observed with the temperature and pyrolysis time. Notably, this study also showed that under optimized conditions, the same precursor can produce diverse results. In this sense, the optimized catalyst showed electrocatalytic activities ORR / OER (ΔE = 1,05 V) in alkaline media, with competitive performance compared to commercial Pt/C catalysts and metal-free catalysts reported in the literature. The activity for REO was evaluated by polarization curves, demonstrating the bifunctional performance of the event.