Photon, Electron, and Ion Management in Artificial Photosynthesis: Realizing Efficient Renewable Energy to Fuel Conversion

Direct production of fuels from sunlight, air (N₂ or CO₂), and water that can be stored, transported, and later converted into hydrogen or electricity to provide power for transportation and distributed energy generation, have received recent attentions worldwide. This technology could also provide chemicals as synthetic precursors or realize grid-level storage of intermittent solar energy. In artificial photosynthesis based on semiconductor photoelectrochemistry, production of chemical fuels generally requires the coupling of separated electrical charges with electrocatalysts for multi-electron chemical reactions. Meanwhile, the development of integrated, efficient and stable photoelectrochemical (PEC) systems requires the pairing of light-absorbing materials with an optimum bandgap combination. The development of such systems has been hindered in part by the lack of semiconducting materials that can simultaneously provide efficiency and stability in a corrosive aqueous electrolyte, typically strong acid or base. In this talk, I will present our recent progress in the development of efficient and stable PEC devices for H2 production from solar-driven water splitting. First, I will summarize some recent development of photon management in PEC devices and module designs from modeling to experiment. Then, I will discuss methods for heterogeneous interfacial energetic modification on covalence-bond semiconductors for efficient free carriers (electrons/holes) separation. Finally, I will present a novel approach to managing the ionic environment for creating a defect-tolerant condition, which leads to a record-setting solar water-splitting prototype.