Hydrogen‐Bond Network‐Activated O 2 in ChCl‐Based Deep Eutectic Solvent Lowers the Overpotential of Oxygen Reduction Reaction on Carbon Electrode

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Abstract
The oxygen reduction reaction (ORR) constitutes a central process in electrochemical energy conversion technologies such as fuel cells and metal‐air batteries, yet it is severely limited by sluggish kinetics and large overpotentials. Beyond catalyst design, electrolyte regulation plays a critical role in determining ORR activity. In this study, through a combination of kinetic measurements, spectroscopic analyses, and theoretical calculations, we demonstrate that ORR in the choline chloride (ChCl)‐based deep eutectic solvent (DES) Ethaline is thermodynamically more favorable but kinetically more constrained than in ionic liquids. The introduction of O 2 is found to substantially perturb the intrinsic hydrogen‐bond network of the DES, while the hydrogen‐bonded environment in turn facilitates the activation of O 2 toward reduction. On this basis, we propose a novel “hydrogen‐bond network‐activated O 2 ” mechanism for ORR in DESs, which can be classified as a CEC pathway, wherein O 2 undergoes a solvent‐induced activation step prior to electron transfer in electrolytes featuring complex hydrogen‐bond networks such as Ethaline. This mechanism provides new insights into electrolyte regulation of ORR and opens new avenues for the design of efficient electrocatalytic systems.
Funding Information
  • National Natural Science Foundation of China (22372140)
  • National Natural Science Foundation of China (22372072)
  • National Natural Science Foundation of China (22574135)
  • National Natural Science Foundation of China (92372124)

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