Photon, electron, and ion management in artificial photosynthesis: Realizing efficient and stable renewable energy to fuel conversion

Abstract

Direct prodn. of fuels from sunlight, air (N_2 or CO_2), 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 technol. could also in principle provide chems. as synthetic precursors or realize grid-level storage of intermittent solar energy. In artificial photosynthesis based on semiconductor photoelectrochem., the prodn. of chem. fuels generally requires the coupling of semiconductors with electrocatalysts where elec. charges are generated, sepd. and transferred for multi-electron chem. reactions, as well as the pairing of light-absorbing materials with optimum bandgap combinations. The development of such systems has been hindered in part by the lack of semiconducting materials that can provide efficiency and stability simultaneously in a corrosive environment, typically either strong acid or base. In this talk, I will present our efforts to fill this knowledge gap in the development of efficient and stable renewable energy to fuel conversion through the rational management of photons, electrons and ions in the coupled optoelec. and electrochem. process. First, I will summarize recent developments of photon management in PEC devices and modules from modeling to expt. Then, I will discuss methods for heterogeneous interfacial energetic modification on covalence-bond semiconductors for the efficient sepn. of free carriers (electrons/holes). Finally, I will present a novel concept for ion management in integrated PEC devices, which creates a defect-tolerant condition for unstable materials and leads to the demonstration of a record-setting solar water-splitting prototype.