The development of clean and renewable energy technologies is seen as the key to addressing energy and environmental issues.Oxygen evolution reaction (OER) plays key roles in storage intermittent energy,such as solar and wind,from water splitting.Recently, OER under neutral conditions receives considerable interests due to its environmental friendliness.However,the efficiency of OER under neutral environment is far below that under alkaline or acidic condition.In this review,the current researchers' understanding of the mechanism of OER under mild pH conditions is firstly outlined.Thereafter,several important characterisation techniques for in situ tracking of the electrocatalytic process of OER are presented,which is crucial to reveal the OER mechanism under neutral conditions.Moreover,an overview over catalytic materials towards neutral OER,including Co?,Ni?,and Mn?based catalysts,is provided.Finally,a brief outlook on the remaining challenges and possible strategies for promoting neutral OER is given.