Dynamic Evolution of Solid–Liquid Electrochemical Interfaces over Single-Atom Active Sites

Abstract

The structural dynamics of the solid–liquid interfaces (SLEIs) determines the chemistry in all electrochemical processes. Here, by combining multiple operando synchrotron spectroscopies, we identify at the atomic level a general evolution of single-atom Ni at SLEIs into a near-free atom state in the electrochemical oxygen reduction reaction (ORR). We uncover that the single-atom Ni at SLEIs tends to be dynamically released from the nitrogen–carbon substrate and then forms a near-free, isolated-zigzag active site (Ni₁^(2-δ)+N₂) during the reaction. This isolated-zigzag Ni₁^(2-δ)+N₂ active site facilitates the adsorption and dissociation of O₂ into a crucial *O intermediate within the electrical double layers, realizing a highly efficient single-atom catalyst with the best ORR performance in alkaline solutions reported thus far. These findings may pave a general way for dissecting other important structural dynamic processes at SLEIs, such as hydrogen evolution, oxygen evolution, and CO₂ reduction reactions.