The development of cost-effective and highly efficient electrocatalysts for oxygen evolution reaction (OER) is a grave challenge in water splitting catalysis for the clean and viable production of molecular hydrogen (H-2). Herein, we report the fabrication of higher-dimensional thin film CuO nanostructures with controlled morphologies i.e., nanosheets, nanocubes, nanoflowers, and nanoleaves and their relative performance for water oxidation catalysis. Among these nanostructures, CuO nanoflowers exhibit high catalytic activity with an onset potential of 1.48 V and a Tafel slope of 84 mVdec(-1) in 1 M KOH solution. Moreover, an overpotential of 270 mV and 400 mV is needed to attain a current density of 10 mAcm(-2) and 100 mAcm(-2) respectively with high Faradaic efficiency. More promisingly, the catalytic performance was found highly dependent upon the nanoscale features and subsequently the improved electrochemically active surface area (ECSA). Such morphology dependent OER performance and binder-free nature of catalyst may provide the high-speed track for electrons transport owing to the inherent catalyst-substrate electronic interconnection and thus making it more promising and high-performance electrocatalyst for OER. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.