Highly Stable and Selective Sensing of Hydrogen Sulfide in Living Mouse Brain with NiN 4 Single-Atom Catalyst-Based Galvanic Redox Potentiometry

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.