Single-Atom Co–N₄ Electrocatalyst Enabling Four-Electron Oxygen Reduction with Enhanced Hydrogen Peroxide Tolerance for Selective Sensing

Abstract

Electrocatalysis of the four-electron oxygen reduction reaction (ORR) provides a promising approach for energy conversion, storage, and oxygen monitoring. However, it is always accompanied by the reduction of hydrogen peroxide (H2O2) on most employed catalysts, which brings down the electrocatalytic selectivity. Here, we report a single-atom Co–N4 electrocatalyst for the four-electron ORR at an onset potential of 0.68 V (vs RHE) in neutral media while with high H2O2 tolerance, outperforming commercial Pt electrocatalysts. Electrochemical kinetic analysis confirms that the Co–N4 catalytic sites dominantly promote the direct four-electron pathway of the ORR rather than the two sequential two-electron reduction pathways with H2O2 as the intermediate. Density functional theory calculations reveal that H2O2 reduction is hampered by the weak adsorption of H2O2 on the porphyrin-like Co centers. This endows the electrocatalyst with improved resistance to current interference from H2O2, enabling highly selective O2 sensing as validated by the reliable sensing performance in vivo. Our study demonstrates the intriguing advantage of single-atom catalysts with high capacity for tailoring metal–adsorbate interactions, broadening their applications in environmental and life monitoring.

Selectively Probing Neurochemicals in Living Animals with Electrochemical Systems

“…One appealing approach is to modify the electrode interface with inorganic/organic electrocatalyst to improve the electron transfer of the analyte at the interface, thus eliminating the interference from potential over‐lapping endogenous chemicals. With the continuous invention of new materials, such as graphdiyne, [18a–c,67] single‐atom catalyst, [22a,68] quantum dots, [69] metal‐organic frames (MOFs), [70] etc., the development of superior eletrocatalyst base electrochemical sensors will meet new opportunities in sensing applications. Alternatively, the role of advanced in vitro aptamer screening [71] and protein engineering techniques [72] in the development of selective neurochemical sensors cannot be ignored.…”

How to select effective electrocatalysts: Nano or single atom?

“…immobilized cobalt single atom in N‐doped hollow carbon spheres to prepare Co‐N 4 /C SAC. [ 119 ] XAFS test proves that Co‐N 4 /C ingle atom site electrocatalyst has Co‐N 4 coordination structure. Electrochemical analysis shows that the Co‐N 4 structure is the active site of the four‐electron path in the ORR reaction, not the active site of the two‐electron path.…”

Porous Carbon Architecture Assembled by Cross-Linked Carbon Leaves with Implanted Atomic Cobalt for High-Performance Li–S Batteries

“…2j and Table S1. The best fitting result for the first shell indicates that each Co atom is likely coordinated by four nitrogen atoms, suggesting a Co-N 4 configuration for the Co-N bonding [39,40]. The pore str ucture of samples was investigated by nitrogen sorption isotherms.…”