Z‑Scheme cathodic photoelectrochemical sensors for detection of hydrogen sulfide based on AgCl-Ag coupled with porous carbon nitride

In this study, we report the development of indirect Z-scheme heterojunction to construct a cathodic photoelectrochemical (PEC) sensor for highly-selective detection of endogenous H2S using AgCl-Ag core–shell nanostructures coupled with porous carbon nitride (PCN) as cathode materials. As an electron mediator, Ag on the Z-scheme heterojunction transformed to Ag2S in the presence of H2S, resulting in the destruction of original charge-carrier migration pathway. Meanwhile, photo-induced charges on the then formed AgCl-Ag2S/PCN cannot be as effectively separated as they are on AgCl-Ag/PCN due to the straddling energy band alignments. A decrease in cathodic signal may be expected. Consequently, the H2S concentration could be quantitated by such corresponding decrease, which thus underlines a novel signal-off cathodic PEC bioanalysis strategy. More importantly, the ‘Z-scheme’ PEC sensor based on AgCl-Ag/PCN exhibits analytical performance with high sensitivity, showing its potential to be applied to the areas of biomedical and health care etc.