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.