NiFe-layered double hydroxides (NiFe-LDH) have emerged as promising oxygen evolution reaction (OER) catalysts in alkaline medium, but their commercial applications are limited due to the decrease in their activity as the electrolyte becomes less alkaline. Thus, a comprehensive understanding of the OER mechanism of NiFe-LDH in alkaline medium is desirable for the rational design of new catalysts with improved performances. Especially, their spin-related factors have rarely been systematically investigated during the OER (diamagnetic H