Single-atom cobalt on N-doped reduced graphene oxide pushes the oxygen reduction reaction toward 4-electron pathway

We present a cobalt-based single-atom catalyst (SAC) anchored on nitrogen-doped reduced graphene oxide (Co-N-rGO), synthesized via a rapid, one-pot microwave-assisted method. Comprehensive characterization by FESEM, TEM, Raman spectroscopy, and X-ray photoelectron spectroscopy confirms the successful formation of atomically dispersed Co(II) centers, coordinated to oxygen-containing functional groups within the graphene matrix, with no evidence of metallic clusters or oxide nanoparticles. The atomically dispersed Co sites act as highly active centers for the oxygen reduction reaction (ORR) in alkaline media, achieving an onset potential of ~0.9 V vs. RHE, an average electron transfer number of ~3.9, and a low peroxide yield of ~6%, delivering near four-electron transfer efficiency, and outstanding durability that surpasses commercial Pt/C catalysts. First-principles density functional theory (DFT) calculations corroborate the XPS findings and reveal the electronic structure of the Co–O coordination environment, offering atomistic insight into the catalytic mechanism. The synergy between precise site isolation, optimized local coordination, and electronic modulation enables the superior electrocatalytic performance of this Co SAC. This study establishes a versatile and scalable framework for engineering high-performance ORR catalysts featuring non-noble metal single-atom active sites.