Proton coordination chemistry in pyrene-based anodes for ultralong-life aqueous proton batteries†

Abstract

Sustainable and safe aqueous proton batteries (APBs) have attracted significant attention owing to their unique “Grotthuss mechanism”. Although organic small molecules with stable and adjustable frameworks are promising electrode materials, their easy dissolution in electrolytes and unsatisfactory intrinsic conductivity hinder their broad application in APB devices. Herein, 2,7-diammonio-4,5,9,10-tetraone (PTO-NH₃⁺) with stable intermolecular hydrogen-bond networks was designed via an in situ electrochemical reduction strategy. The optimized molecule structure endows low charge transport barriers, high chemical reactivity, and prominent charge affinity. The fast kinetics of proton coordination/de-coordination behavior in PTO-NH₃⁺ electrodes is corroborated by ex situ characterization techniques and theoretical calculations. As a result, the robust four-step 4e⁻ H⁺ coordination with PTO-NH₃⁺ electrode achieves an excellent rate performance (214.3 mA h g⁻¹ at 0.05 A g⁻¹ and112.9 mA h g⁻¹ at 40 A g⁻¹), along with a long lifespan (10 000 cycles). These findings shed light on further avenues towards advanced proton batteries.