The sustained use of solar energy is plagued by the intermittency of sunlight. If the energy from fleeting solar photons can be stored in chemical bonds through electrochemical reactions, this intermittency can be levelized to power demands. Although water is often proposed as the electron source for these reactions, myriad electron sources exist that may be better matched to the voltage output of existing photovoltaics. In light of this, peeled silicon microrod arrays, partially embedded in a Nafion proton-exchange membrane, were used to drive solar hydroiodic-acid splitting (i.e. HI --> H2 + I3�).Open-circuit photovoltages measured for p-type and n-type microrod arrays driving aqueous H2 evolution and iodide oxidation, respectively, were 450 � 500 mV. Corrosion of Si was attenuated through methylation of Si atop sites via a two-step chlorination�alkylation surface chemistry procedure. This resulted in stable iodide oxidation under continuous simulated sunlight illumination for weeks. Amorphous MoSx, Pt, or PEDOT:PSS electrocatalysts were deposited on the microrods to catalyze H2 evolution and iodide oxidation. Si microrod arrays were partially embedded in Nafion and mechanically removed from the Si substrate to yield free-standing, flexible devices. Solar-to-hydrogen efficiencies and faradaic yields for product formation were quantified. These systems are sustainable because the HI fuel precursor is inorganic, thus not capable of liberating CO2, and HI can be regenerated in a flow battery or fuel cell as H2 + I3�/I2.

Demonstration of artificial photosynthesis with peeled silicon microrod arrays

246th National Meeting (2013)

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