Realizing Two-Electron Transfer in Ni(OH)₂ Nanosheets for Energy Storage

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Electrode material capacity is limited by electron transfer per redox center.
• Multi-electron transfer offers higher capacity but is kinetically and thermodynamically challenging.
• Traditional multilayer Ni(OH)₂ exhibits one-electron transfer.

Purpose of the Study:

• To investigate multi-electron transfer in monolayer Ni(OH)₂ nanosheets.
• To understand the mechanism hindering/enabling multi-electron transfer.
• To explore the potential for enhanced energy storage capacity.

Main Methods:

• First-principles calculations to predict redox processes.
• Experimental synthesis of monolayer Ni(OH)₂ nanosheets.
• In situ experiments to observe electrochemical transformations.

Main Results:

• Monolayer Ni(OH)₂ facilitates two-electron transfer (Ni²⁺ → Ni⁴⁺).
• Calculations show hindered second electron transfer in multilayer due to hydrogen bonds and Jahn-Teller distortion.
• Experimental capacity of ∼576 mA h/g achieved, nearly double that of one-electron processes.
• In situ studies confirm two-electron transfer and Ni⁴⁺ formation in monolayers.

Conclusions:

• Atomically thin Ni(OH)₂ enables a novel two-electron redox mechanism.
• Monolayer structure overcomes limitations of bulk materials for multi-electron transfer.
• This work provides a strategy to multiply energy storage capacity by tuning electron transfer numbers.