Bifunctional Single‐Atom Iron Cocatalysts Enable an Efficient Photoelectrochemical Fuel Cell for Sensitive Biosensing

Abstract Semiconductor‐based photoelectrochemical (PEC) fuel cells offer a feasible solution for sustainable and environmentally friendly energy production by converting solar and chemical energy into electrical energy. However, the low PEC activities of PEC fuel cells have hindered their practical application due to rapid electron‐hole recombination and slow interfacial reaction kinetics. To address this issue, a unique PEC fuel cell composed of dual photoelectrodes utilizing low‐cost biomass, ascorbic acid, as an organic fuel is reported. Significantly, the integration of bifunctional iron single‐atom catalysts (Fe SACs) and photoactive materials has effectively constructed a bridge for charge carrier transfer, boosting interfacial reaction kinetics and photoelectric conversion efficiency. Notably, the optimal dual‐photoelectrode PEC fuel cell decorated with Fe SACs exhibits superior performance, delivering a maximum power density of 82.82 µW cm⁻². Taking advantage of the peroxidase‐like activity of Fe SACs, the resultant self‐powered PEC fuel cells are explored for sensitively detecting actual uric acid samples. This study provides a promising avenue to boost the energy conversion efficiency of PEC fuel cells for sensitive self‐powered biosensing.