Evidences of LOER in Fe-LNO and LNO. (a) The rainbow map contains current density, voltage, and pH of LNO. (b) Specific OER catalytic activity at 1.55 V and 1.60 V versus RHE as a function of pH. (c) Two oxidation mechanisms of LNO and NiOOH. (d) Cyclic voltammograms in 0.1 mol/l Li18OH and LiOH of catalysts. (e) Illustration of the mechanism of 18O labeled TOF-SIMS. (f) The 18O signal in LNO and Fe-LNO (the intensity has been normalized by 16O signal).