Optimized Charge Storage in Aza-Based Covalent Organic Frameworks by Tuning Electrolyte Proton Activity

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Proton activity in electrolytes is key to aqueous battery performance.
• High proton redox activity enhances capacity and rate, but can cause hydrogen evolution reactions (HER), limiting potential and stability.

Purpose of the Study:

• To investigate the effect of electrolyte proton activity on the electrochemical performance of aza-based covalent organic frameworks (COFs).
• To understand the tradeoff between proton redox reactions and HER in COF hosts.
• To elucidate the origin of proton activity in near-neutral electrolytes.

Main Methods:

• Utilized an aza-based covalent organic framework (COF) as a host material.
• Studied performance in various electrolytes to vary proton activity.
• Employed in situ and ex situ characterizations to analyze charge storage and reaction mechanisms.

Main Results:

• Revealed a tradeoff between proton redox reactions and HER in the COF host.
• Identified hydrated water molecules in the first solvation shell as the origin of proton activity in near-neutral electrolytes.
• Presented a detailed analysis of the charge storage process in COFs.

Conclusions:

• Electrolyte proton activity significantly impacts aqueous battery performance.
• Understanding and controlling proton activity is crucial for designing high-energy aqueous batteries.
• Hydration shells play a vital role in proton activity in near-neutral electrolytes.