Co(O)₄(N)‐type single‐atom‐based catalysts and ligand‐driven modulation of electrocatalytic properties for reducing oxygen molecules

Abstract

Single‐atom‐based catalysts are intriguing electrocatalytic platforms that combine the advantages of molecular catalysts and conductive carbon‐based materials. In this work, hybrids (Co‐NrGO‐1 and Co‐NrGO‐2) were generated by wet‐reactions between organometallic complexes (Co(CH3COO)2 and Co[CH3(CH2)3CH(C2H5)COO]2, respectively) and N‐doped reduced graphene oxide at 25°C. Various characterizations revealed the formation of atomically dispersed Co(O)4(N) species in Co‐NrGO‐2. Density functional theory (DFT) calculations explained the effect of the aliphatic C7 group in Co2 on the formation processes. The Co‐NrGO‐2 hybrid showed excellent catalytic performance, such as onset (0.94 V) and half‐wave (0.83 V) potentials, for electrochemical oxygen reduction reaction (ORR). Co‐NrGO‐2 outperformed Co‐NrGO‐1, which was explained by more back donation to the antibonding orbitals of O2 from electron‐rich aliphatic groups. DFT calculations support this feature, with mechanistic investigations showing favored ORR reactions and facile breakage of double bonds in O2.