Oxygen evolution reaction (OER) is an important half reaction in many energy conversion and storage techniques. However, the development of a low‐cost easy‐prepared OER electrocatalyst with high mass activity and rapid kinetics is still challenging. Here, we report the facile deposition of tannin‐NiFe (TANF) complex film on carbon fiber paper (CP) as a highly efficient OER electrocatalyst. TANF performs rapid OER reaction kinetics with a very small Tafel slope of 28 mV dec‐1. And the mass activity of TANF reaches as high as 9.17×103 A g‐1 at the overpotential of 300 mV, which is nearly 200 times larger than that of NiFe double layered hydroxide. Furthermore, tannic acid in TANF can be electrochemically extracted under anodic potential, leaving the inorganic composite NixFe1‐xOyHz as the OER‐active species. This work may provide a guideline for probing the electrochemical transformation process and investigating the reactive species of other metal‐organic com
plexes as heterogeneous electrocatalysts.
