Scheme 1.

Schematics of three electrochemical systems that facilitate mass transport between the photoelectrodes and the counter electrodes, where υ_conv. illustrates convective mass transport by rapid stirring, υ_diff. illustrates diffusive mass transport in solution, and illustrates diffusive mass transport within microporous photoelectrodes. Scheme 1A depicts a two-electrode thin-layer configuration that exploits effective diffusive transport. Scheme 1B shows a conventional three-electrode configuration that uses rapid convective stirring. Scheme 1C illustrates a stand-alone, two-terminal photoelectrochemical solar cell configuration that uses a deeply embedded Ag film as the counter electrode. The typical direction of illumination was normal to the working electrode.