Single-Atom Iron Boosts Interfacial Oxygen Reduction for Self-Powered Photoelectrochemical Biosensing.

The sluggish interfacial reaction of the photocathode seriously hinders the application of self-powered photoelectrochemical (PEC) systems. In order to solve the above problem, iron single-atom catalysts (Fe SACs) were used to accelerate the oxygen reduction reaction (ORR) at the photocathode interface. It made dissolved oxygen and water circulate efficiently between the photoanode Bi2S3 and the photocathode Cu2O/Cu3SnS4 interface, inhibited photogenerated carrier recombination, and greatly enhanced the cathodic photocurrent. Furthermore, the excellent conductivity of Fe SACs could further accelerate interface electron transfer and improve the efficiency of the self-powered PEC system. As a proof-of-concept application, a self-powered PEC biosensor with Fe SAC interface regulation was developed to detect microcystin-LR (MC-LR). MC-LR bound to its aptamer for the quantitative release of mesoporous silicon-encapsulated l-cysteine (l-Cys). At this stage, Fe SACs would react with the sulfhydryl group of l-Cys to form a complex, blocking the active sites of Fe SACs and significantly reducing the cathodic photocurrent to achieve sensitive detection of MC-LR. In summary, this work used SACs to accelerate interfacial redox reactions, significantly improve the efficiency of a self-powered PEC system, and open up a path for the detection of water pollutants.