Heterogeneous metal substitution–driven selectivity enhancement in single-phase spinel oxides for interference-free electrochemical hydrogen sulfide detection

Nanomaterial-based electrochemical sensors are promising tools in atmospheric chemistry, offering reliable detection of toxic gases. Here, we report a single-phase tetrametallic spinel oxide, (Mn0.56Cr0.77Rh0.77Ni0.90)O4 (MCRN-O), as an electrode material for amperometric H2S sensing. Synergistic interactions among multiple cations within the spinel framework enabled homogeneous integration, imparting distinctive physicochemical properties and superior electrochemical performance. In deaerated phosphate-buffered saline solution (0.05 M), MCRN-O delivered high sensitivity (0.0084 µA µM–1) and a low detection limit (0.058 µM), markedly outperforming the comparison samples MCN-O and MC-O. It also exhibited excellent selectivity, with coefficient values below − 2 for CO and NO, while achieving performance comparable to or better than previously reported electrochemical H2S sensors.