Realizing the synthesis of highly efficient electrocatalysts for water splitting is generally regarded as a significant section in the field of renewable energy conversion and storage but still an intriguing challenge. Here, a series of transition metal oxyphosphides with ultrafine nanosheet structure have been successfully created as high-performance electrocatalysts for oxygen evolution reaction (OER). Taking advantages of the abundant surface defects, modified electronic effects, as well as the high surface active areas, we herein successfully construct a novel class of highly-efficient electrocatalysts, and the resultant NiZn oxyphosphide nanosheets (NiZnP NSs) can exhibit relatively low overpotentials of 290 and 332 mV to achieve the current densities of 10 and 50 mA cm(-2) for OER, respectively, outperforming most of non noble metal electrocatalysts. More impressively, such NiZnP NSs can also retain high catalytic activity with negligible composition and structure variations after long-term electrochemical test. This work provides prospects to construct highly efficient, earth abundant, and ultra-durable two-dimensional (2D) electrocatalysts for water splitting. (C) 2018 Elsevier Inc. All rights reserved.