Nanowires-based MnO 2 -Ru/rGO: An efficient oxygen reduction reaction electrocatalyst

Oxygen Reduction Reaction (ORR) for clean energy is hindered by expensive Pt-based electrocatalysts, prompting efforts to replace it with alternative electrocatalysts. Thus, we started by synthesizing MnO 2 nanowires through a hydrothermal approach, followed by the growth of ruthenium nanoparticles (Ru NPs) without surface modification, using just 2.0 wt% of the noble metal (MnO 2 -Ru). However, to further enhance the electrocatalyst's performance and reduce costs, we combined different ratios of reduced graphene oxide (rGO) with the electrocatalyst. X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy were employed to characterize the chemical composition and morphological properties of MnO 2 -Ru. These analyses identified the presence of the compounds during synthesis and confirmed the deposition of Ru NPs on the surface of MnO 2 nanowires. The optimized MnO 2 -Ru/rGO demonstrated superior ORR activity than rGO, MnO 2, and MnO 2 -Ru individually, with more positive onset potential (−0.054 V) and half-wave potential of −0.173 V. Notably, MnO 2 -Ru/rGO reduced oxygen via the four-electron transfer pathway. Furthermore, the higher stability and excellent methanol tolerance of MnO 2 -Ru/rGO compared to the commercial 20 wt% Pt/C indicates its suitability for fuel cells, maintaining approximately 70 % of its initial current after 8000 s.