Photoelectrochemical cell (PEC) has been explored extensively as one of the popular approaches to produce hydrogen from water for solar energy conversion. One of the key challenges is to overcome the energetic barriers for electron transfer at multiple interfaces. Increasing temperature is a promising way to address this problem. For example, even state-of-the-art electro-catalysts RuO2 and Pt require an overpotential of >0.2V at room temperature to drive oxygen-evolution and hydrogen-evolution reactions at rates matching the incident solar flux. Simply by increasing the temperature to 600ºC, the rate of a reaction with a 0.3eV activation barrier increases by a colossal 2,700x.
We are designing and fabricating a new class of PECs that will operate at temperatures significantly above room-temperature. Through careful interface engineering, the solar-to-fuel efficiency increases, rather than decreases with temperature. Therefore, thermal and photon energy are harvested simultaneously.