The first thing we learn in chemistry is the periodic table. The group 1 consists of lithium, sodium, potassium, and cesium, which are known as alkali metals, existing primarily as the cation forms in nature. Representative example is the salt in seawater. 

These ions have been assumed to be chemically inert as they are surrounded by water molecules, which does not react readily but exhibits a very stable state. In this regards, alkali metal ions are known as ‘spectator ions’ in the textbook, and merely serve as ionic conductors in aqueous electrochemical environments.

In this study, we disclose the counterintuitive discovery that contradicts the textbook knowledge, which the catalytic role of alkali metal cations can actively form chemical bonds with reaction intermediates and control the reaction kinetics. Using the advanced in situ analyses, we decipher the spectroscopic fingerprint of alkali metal cations-associated reaction intermediate as sodium superoxide(NaO2). This finding lead us to conclude the catalytic role of alkali metal cations in mediating the reaction in aqueous electrolytes.

Prof. Choi stated “To maximize the efficiency of numerous electrochemical reactions, insightful research in considering the characteristics of both electrode and electrolyte is necessary.” Also, “With this understanding, we are planning to conduct additional research that can be applied to commerically viable electrochemical systems.” Prof. Choi said.

Proposed mechanism of alkali ions acting as the catalyst in mediating the reaction 

[Reference] Ji, S. G. et al., (2024) “Alkali metal cations act as homogeneous cocatalysts for the oxygen reduction reaction in aqueous electrolytes.” Nature Catalysis

[Main Author] Sang Gu Ji (Pohang University of Science and Technology), Minho M. Kim (Korea Advanced Institute of Science and Technology), Man Ho Han (Korea Institute of Science and Technology), Hyung-Suk Oh (Korea Institute of Science and Technology), Hyungjun Kim (Korea Advanced Institute of Science and Technology), and Chang Hyuck Choi (Pohang University of Science and Technology)

* Contact email : Professor Chang Hyuck Choi (chchoi@postech.ac.kr)