A carbon dot-based total green and self-recoverable solid-state electrochemical cell fully utilizing O2/H2O redox couple

Electrochemical cell can overcome the inherent intermittence of the renewable energy sources, thus showing great potentials in applications ranging from electrical energy storage to future smart grid. However, the current electrochemical cells could not achieve the “total green” feature by fully utilizing the clean and abundant O 2 /H 2 O redox couples due to the enormous overpotentials for both oxygen reduction reaction (ORR) and oxygen release reaction (OER). Herein, we report a “total green” electrochemical composite film cell based on carbon dots (CDots), which can realize both ORR and OER in the acid environment. The in-air voltage generation (0.95 V, with a maximum power of 5.3 μW) relies on the multiple-electron-transfer redox chemical reaction between the two active components inside the composite film, that is, ORR/OER of CDots and the redox reaction of polyaniline (PANI) on the electrode and the resulting proton concentration gradient. Interestingly, the cell can be self-recovered at low load, recharged by adding H 2 O 2 , or electrocharged at high load. We anticipate that current study may open up new opportunities for designing and developing total-green energy storage and conversion systems for diverse applications.