Insights into Bimetallic CoFe Nanoparticles Incorporated on N-Doped Carbon Nanosheets toward Acidic Oxygen Reduction Reaction

Transition metal materials are actively being studied as scalable alternatives to platinum group metal-based catalysts (PGMs) for the oxygen reduction reaction (ORR). However, a comprehensive understanding of the ORR mechanistic pathways on non-PGM catalyst surfaces is needed, particularly under the acidic conditions under which most fuel cells operate. Accordingly, this work investigates the ORR activity and mechanisms of iron (Fe), cobalt (Co), and bimetallic cobalt–iron alloy nanoparticles (CoFe NPs) incorporated on N-doped carbon nanosheet (NC) scaffolds. We find that the CoFe NPs outperform their monometallic counterparts through rotating ring-disk electrode (RRDE) experiments. Through O2-temperature-programmed desorption (TPD) analysis, we note that CoFeNC exhibited intermediate O2 binding energies. Finally, in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy measurements point to differing populations of reaction intermediates under ORR-relevant potentials. The above findings aid in constructing an ORR reaction pathway on the CoFeNC catalyst surface and developing a rationale behind the superior performance of the CoFeNC NPs. In all, this work advances the community's efforts in emerging strategies toward the development of high-performance and acid-stable non-PGM catalysts.