Graphene hybrids comprised of diverse functional materials have shown exceptional performance. However, only 2D composites were widely studied, the understanding of graphene hybridization behavior with complex 3D nanostructures remains unclear. In this work, we investigate how the graphene hybridization is affected by the presence of 3D nanovoids, and the corresponding influence on the electrocatalysis of hydrogen peroxide reduction. The 3D nanovoids of the cobalt manganese oxide (CMO) increase the amount of graphene captured in the composites for the higher surface areas, uniform porosity, and improved electrocatalytic activities. The formation of graphene/CMO interfaces contributes to the efficient H2O2 reduction at the more positive onset potentials than graphene or CMO material alone. Controls of the inhomogeneous distribution and void-filling behavior of graphene on CMO surface are critical to achieve optimal, synergistic electrocatalysis. The graphene/CMO hybrids with full graphene coverage exhibit the greatly enhanced H2O2 sensitivity by 2900 and 48 times greater than commercial products and bare CMO, respectively. (C) 2015 Elsevier Ltd. All rights reserved.