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Stabilizing atomically dispersed single atoms (SAs) on Si photoanodes for photoelectrochemical-oxygen evolution reaction is still challenging due to the scarcity of anchoring sites. Here, we elaborately demonstrate the decoration of Ir SAs on Si photoanodes and assess the role of SAs on the separation and transfer of photogenerated charge carriers. NiO/Ni thin film, an active and highly stable catalyst, is capable of embedding the Ir SAs in its lattices by locally modifying the electronic structure. The isolated Ir SAs enable the effective photogenerated charge transport by suppressing the charge recombination and lower the thermodynamic energy barrier in the potential-determining step. The Ir SAs/NiO/Ni/ZrO2/n-Si photoanode exhibits a benchmarking photoelectrochemical performance with a high photocurrent density of 27.7 mA cm− 2 at 1.23 VRHE and 130 h stability. This study proposes the rational design of SAs on Si photoelectrodes and reveals the potential of the Ir SAs to boost photogenerated charge carrier kinetics.