Hetero-N-Coordinated Co Single Sites with High Turnover Frequency for Efficient Electrocatalytic Oxygen Evolution in an Acidic Medium

The development of noble-metal-free, acid-compatible oxygen electrocatalysts and monitoring their active sites' evolution under working conditions are crucial for global renewable energy storage and conversion. Here, we present a new type of hetero-N-coordinated Co (HNC-Co) single sites, with Co active centers bonding to hetero pyridinic- and amino-N ligands, as an efficient oxygen evolution reaction (OER) electrocatalyst in an acidic medium. The atomically dispersed HNC-Co electrocatalyst could effectively oxidize water at a quite low overpotential of 265 mV at 10 mA cm(-2) in 0.5 M H2SO4 solution with an ultrahigh turnover frequency of 2.8 s(-1) and a huge mass activity of 7.6 A mg(-1), similar to 80-240 times that of commercial IrO2. By using operando synchrotron infrared spectroscopy, a potential-driven active site evolution of H2N-(*O-Co)-N-4 is observed for the first time during the OER process, which greatly promotes the surface oxo-species transformation for efficient acidic OER catalysis.