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.
Hydrogen sulfide (H 2 S) is recognized as a gasotransmitter and multifunctional signaling molecule in the central nervous system. Despite its essential neurofunctions, the chemical dynamics of H 2 S during physiological and pathological processes remains poorly understood, emphasizing the significance of H 2 S sensor development. However, the broadly utilized electrochemical H 2 S sensors suffer from low stability and sensitivity loss in vivo due to sulfur poisoning-caused electrode passivation. Herein, we report a high-performance H 2 S sensor that combines single-atom catalyst strategy and galvanic redox potentiometry to overcome the issue. Atomically dispersed NiN 4 active sites on the sensing interface promote electrochemical H 2 S oxidation at an extremely low potential to drive spontaneous bipolarization of a single carbon fiber. Bias-free potentiometric sensing at open-circuit condition minimizes sulfur accumulation on the electrode surface, thus significantly enhancing the stability and sensitivity. The resulting sensor displays high selectivity to H 2 S against physiological interferents and enables real-time accurate quantification of H 2 S-releasing behavior in the living mouse brain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.