Charge transfer catalysis at solid/liquid interface in photoelectrochemical processes: Enhancement of polycrystalline film electrode stability and performance

摘要

Photovoltaics (PVs) show high conversion efficiency in renewable energy. However, PV systems demand advanced preparations and relatively large amounts of staring materials. Photoelectrochemical (PEC) systems, with monolithic semiconductor (SC) electrode/Redox couple interface, emerged, but still demand special preparation conditions and relatively large amounts of starting materials. Polycrystalline film electrodes, are studied as replacement for monolithic SC electrodes, both theoretically and experimentally. Examples are dye-sensitized solar cells (DSSCs) and metal chalcogenides. With narrow-to-medium band gaps, metal chalcogenides are suitable for the abundant visible solar light. However, polycrystalline film electrodes suffer major shortcomings. Pristine films show low conversion efficiency. Being polycrystalline, they have low carrier mobility. They are also unstable to photo-corrosion, due to charge build-up in the space charge layer (SCL). Enhancement of polycrystalline film electrode PEC performance and stability was reported using different methods. Among those, charge transfer catalysis at the film electrode surface, is focused here. The modification involves attaching electroactive species to the electrode surface. Ability of electroactive species to behave as charge transfer catalysts at the solid/liquid interface is discussed. By such behavior, the catalysts speed up charge transfer and consequently increase photocurrent. Moreover, charge build-up in the SCL is prevented by quick charge transfer, which protects the electrode surface from photo-corrosion. Ability of charged electroactive species to shift flat band edge position, with its consequences, is also described. Recommended features of an effective catalyst species for PEC systems are described together with recommendations for more future research in the field.