Multiple views of NIST's photoelectrochemical hydrogen cell. Side schematic [A] shows princial components of the cell. Electrodes on the top are titanium toped with platinum. An incoming photon generates a electron (e) and hole (h). Microscope image [B] shows top of the cell surface with cylinderical electrodes and scanning laser beam. Photo-current scan [C] shows relatively high current around the base of the electrodes, while the electrochemical scan [D] shows a complex pattern of hydrogen generation on and around the electrode.