The compound semiconductor Zn1-xCoxO (x = 0.42; ZnO:Co) has recently gained interest as a highly active electrocatalyst material for water oxidation (WOCs). We report on the significant structural and electronic transformations under anodic oxygen evolution reaction conditions of a novel, large area scalable sputtered ZnO:Co electrocatalyst. ZnO:Co sputtered films showed the transition of the polycrystalline ZnO:Co electrocatalyst material to a partially amorphous nanocomposite (ZnO:Co/Co(OH)(2)/CoOOH). A high reactivity of the electrocatalyst material compensates effectively the low specific surface area of sputtered electrocatalyst thin films. The aim of this work is to examine the polycystral morphology of sputtered electrocatalyst thin film material, which can be also produced industrially on large areas and has a high WOC performance. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.