Iron single-atom catalysts confined in covalent organic frameworks for efficient oxygen evolution reaction

The exploration of environmentally friendly and highly efficient oxygen evolution reaction (OER) catalysts is vital to large-scale, electrochemical renewable-fuels generation. Here, we report an iron single-atom catalyst (SAC) confined in a covalent organic framework (Fe-SAC@COF), which constitutes an unusual Fe-NO coordination in the skeleton. The as-prepared Fe-SAC@COF exhibits a high mass activity of 9.20 A mg(-1), which is 1.95 times higher than Ni species of the same coordination and 5.05 times higher than nanoparticulate Fe counterpart. Moreover, it shows, to the best of our knowledge, a record-low overpotential (290 mV) and Tafel slope (40 mV dec(-1)) among the reported atomically dispersed Fe-based catalysts and surpasses the benchmark Ir/C catalyst. The density functional theory calculation shows that the Fe-NO coordination exhibits low binding energy of oxygenated intermediates, which leads to an outstanding electrocatalytic OER performance. This work provides design strategies toward unusually coordinated SACs by prudent COF confinement for advanced electrocatalysis.