Three-dimensional (3D) hierarchical hollow urchin-like NiO/NiCo2O4 heterostructures have been prepared via a facile one-pot hydrothermal method. The 3D urchin-like structure brings about high specific surface area of 40.2 m(2) g(-1). The NiO/NiCo(2)O(4 )heterostructures are composed of 59 wt% of NiO and 41 wt% of NiCo2O4 and enriched with NiO/NiCo2O4 phase boundaries. When used as catalysts for styrene oxidation reaction (SOR), the NiO/NiCo(2)O(4 )heterostructures present a markedly high selectivity of 90.8% to styrene oxide (SO) and a high SO yield of 81.4%. The high catalytic performance of the NiO/NiCo2O4 heterostructures can be attributed to the high specific surface area and the abundant NiO/NiCo2O4 phase boundaries, both of which contribute to the numerous active sites. (C) 2018 Elsevier Inc. All rights reserved.