Biological nicotinamide cofactor as a redox active motif for reversible electrochemical energy storage

Abstract

Exploiting organic materials participating in the energy transduction processes in biological system can inspire the discovery of new electrode chemistry for rechargeable batteries, considering the analogy in their electrochemical reactions involving the redox activity. Nicotinamide adenine dinucleotide ($NAD^+$) is one of the most well-known redox cofactors carrying electrons in photosynthesis and the cellular respiration process by virtue of redox active $NAD^+$ motif. Herein, we firstly report that intrinsically charged NAD+ motif can serve as an active electrode in electrochemical lithium cells. Through anchoring $NAD^+$ motif by the anion-incorporation, redox activity of the $NAD^+$ is successfully implemented in conventional lithium batteries, exhibiting the average voltage of 2.3 V vs. $Li^+$/Li. We also show that the operating voltage and capacity are tunable by altering the anchoring anion species without modifying the redox center itself. This work not only demonstrates the redox capability of $NAD^+$, the most well-known redox cofactor, as electrodes, but also suggests that anchoring the charged biological cofactors with anion-incorporation is a viable new approach to exploit various charged biological cofactors in conventional rechargeable battery systems.