Understanding the science of solar-based energy: more researchers are better than one

Drawing of a dual photoelectrode assembly proposed by Caltech's "Powering the Planet" Chemical Bonding Center project. The assembly's cell is designed such that the photoanode will absorb high energy blue light (blue arrow) but not low energy red light (red arrow). The low energy light passes through the photoanode material and is absorbed by the photocathode material. When sunlight strikes the photocathode in the assembly, the nanorods produce negatively charged electrons (e-) and positively charged holes. The electrons move to the hydrogen (H2) catalyst on the surface of the rods, where hydrogen is produced from the electrons and positively charged hydrogen ions or protons (H+). The positively charged holes flow through the photocathode rods into the photoanode where they migrate to the oxygen (O2) catalyst on the surface. The holes are used to produce oxygen and protons from water (H2O). The protons pass through the membrane to maintain charge balance. Credit: Elizabeth Santori and Nathan S. Lewis, California Institute of Technology