Crown ether as a bifunctional booster in electrochemical water splitting

Abstract

Electrochemical water splitting using renewable energy is considered a key technology to mitigate global warming and to realize the hydrogen economy. Extensive efforts have been devoted to finding high-performance electrode catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) involved in electrochemical water splitting, whereas the research on added components in the electrolyte to boost HER and/or OER is very limited. In this work, we report the use of 18-crown ether-6 (18C6) in the electrolyte as a bifunctional booster in water splitting. The addition of 18C6 in alkaline electrolyte drastically boosts HER current density from −50 to −300 mA cm−2 at −0.3 V vs. RHE and OER current density from 25 to 250 mA cm−2 at 1.7 V vs. RHE on the Ni foam electrode. Combing DFT calculations and experimental characterizations, the functions of 18C6 in boosting HER and OER on nickel electrodes under the alkaline condition are revealed. This research demonstrates the potential of macrocycle molecules as electrolyte additives and opens up new opportunities for boosting the performance of water splitting.