21st-Century Energy: Solar Storage in Hydrogen Gas

Energy supply and security are likely to be major drivers in the development of human civilization in the next 100 years. There is broad consensus that transitioning from fossil fuel sources to renewables in the next 5-50 years is a requirement for bringing about sustainable societies. Solar energy is by far the most plentiful renewable energy source, but existing solar capture technologies do not allow for the large-scale or long-term storage of solar energy; this severely limits the maximum possible utilization of the solar resource. Thus we are seeking to develop a new mode of solar energy capture, broadly called artificial photosynthesis, involving the direct conversion of light energy to chemical energy using semiconductor light absorbers and heterogeneous catalysts.

This talk will focus on the development of one absorber, silicon (Si), and one catalyst, nickel-molybdenum (Ni—Mo) alloy, which have been studied heavily in the Lewis and Gray groups in the last 5 years. When combined, this absorber and catalyst pair are capable of storing solar energy in chemical bonds by generating hydrogen gas from aqueous solution when illuminated with white light. I will describe how we design, fabricate, and evaluate assemblies incorporating these two components. I will also explain how recent developments in studying Si/Ni—Mo assemblies point toward new materials and device designs that promise much higher energy storage efficiencies than are currently attainable.