Designing Cu2+ as a Partial Substitution of Protons in Polyaniline Emeraldine Salt: Room-Temperature-Recoverable H2S Sensing Properties and Mechanism Study

Hydrogen sulfide (H 2 S) sensors are in urgent demand in the field of hermetic environment detection and metabolic disease diagnosis. However, most of the reported room-temperature (RT) H 2 S sensors based on transition metal oxides/salts unavoidably suffer from the poisoning effect, resulting in the unrecoverable behavior to restrain their application. Herein, copper(II) chloride-doped polyaniline emeraldine salt (PANI-CuCl 2 ) was devised for RT-recoverable H 2 S detection, where the copper ion (Cu 2+ ) was designed as a partial substitution of protons (H + ) in PANI. The prepared gas sensor exhibited full recovery capability toward 0.25–10 ppm H 2 S, good repeatability, and long-term stability under 80% RH. Meanwhile, the changes of the PANI-CuCl 2 during the H 2 S sensing period were analyzed via multiple analytical methods to reveal the reversible sensing behavior. Results showed that doping of Cu 2+ not only promoted the PANI’s response through the formation of conductive copper sulfide (CuS) and following H + redoping in the PANI but also facilitated the sensor’s recovery behavior because of the Cu 2+ regeneration under the H + /oxygen environment. This work not only proves the changes of the interaction between the PANI and Cu 2+ during the H 2 S sensing period but also sheds light on designing recoverable H 2 S sensors based on transition metal salts.