▎ 摘　　要

The fabrication of a carbon (C)-based, metal-free, efficient, and stable electrocatalyst at high oxygen evolution reaction (OER) overpotential is essential to advance the field of water splitting and air-battery related energy systems. For this purpose, we here synthesize a stacked nanofilm (G-BNG) of pure graphene (G) on boron and nitrogen (BN)-codoped graphene (BNG) with a total thickness of about 2-3 nm and 87% transparency at 550 nm that shows an efficient OER performance, better than that of a stacked G-G layer, G-BG film, or G-NG film in an alkaline electrolyte. The G-BNG film performs OER with the highest reaction kinetics (lowest Tafel slope similar to 143.22 mV/dec) and a small overpotential (0.58 V) along with 81.6% retention of the current density at 1.8 V (vs reversible hydrogen electrode) even after 50000 s of operation. Experimental analysis reveals that the doped B and N atoms in the bottom layer influence the p-bonding environment in the top G layer, facilitating the effective electron/charge transfer for OER electrocatalysis. Furthermore, the demonstrated OER performance is comparable or even superior to that of other reported C-based electrocatalysts with at least 400-700 times lower catalyst loading, making the G-BNG film promising for advanced renewable energy conversion systems, such as various kinds of transparent air batteries and water electrolyzers.