Harold Hwang, applied physics/photon science

The solar water-splitting reaction to hydrogen and oxygen has potential to greatly reduce the production of greenhouse gases. The generated hydrogen can be used in fuel cells or as feedstock for ammonia and industrial chemical synthesis, thereby reducing fossil-fuel-derived hydrogen.

Three principal factors limiting the practical
implementation of solar water splitting are: i) inefficient charge 
separation, ii) slow chemical reaction rate at the catalyst surface 
and iii) ineffective use of the solar spectrum in the visible range.
 Although there are many efforts to address these challenges, the
 vast majority of experimental activities use polycrystalline
materials. The effects of surface crystalline orientation, particle size,
doping and surface modifications are typically not isolated, with experiments simultaneously varying multiple relevant parameters. Thus there is great difficulty in developing a fundamental understanding necessary for significant progress.

Here we propose that single crystalline oxide heterostructures, grown with atomic precision, can provide the experimental platform to develop this understanding and the design principles that can enhance conversion efficiency.