The development of low overpotential, non-precious metal oxide electrocatalysts is important for sustainable water oxidation using renewable energy. Here we report the fabrication of nano-interfaces between MnOx nanoscale islands and NiFe layered double hydroxide (LDH) nanosheets, which were chosen as baseline electrocatalysts for OER activity tuning. The MnOx nano-islands were grown on the surfaces of NiFe-LDH nanosheets by atomic layer deposition (ALD). Morphological and structural characterization indicated that the MnOx formed flat nanoscale islands which uniformly covered the surfaces of NiFe-LDH nanosheets, giving rise to a large density of threedimensional nano-interfaces at the NiFe-LDH/MnOx/electrolyte multi-phase boundaries. We showed by X-ray spectroscopic characterization that these nano-interfaces induced electronic interactions between NiFe-LDH nanosheets and MnOx nano-islands. Through such modifications, the Fermi level of the original NiFe-LDHwas lowered by donating electrons to the MnOx nano-islands, dramatically boosting the OER performance of these electron-deficient NiFe-LDH catalysts. Using only 10 cycles of ALD MnOx, the MnOx/NiFe-LDH nanocomposites exhibited remarkable and enhanced electrocatalytic activity with an overpotential of 174 mV at 10 mA cm(-2). This work demonstrates a promising pathway for tuning transition metal electrocatalysts via a generic ALD surface modification technique.