Composite photoanodes

A method of forming a composite photoanode, comprising photoelectrodepositing a solid conformal layer of an electrocatalyst from an electrolyte solution on a surface of a semiconductor submerged in the electrolyte solution by simultaneously:

• (1) impinging the surface of the semiconductor with electromagnetic radiation having a first wavelength and a first irradiance, to provide a first photoenergy that is sufficient to excite an electronic transition of the semiconductor;
• and
• (2) applying a first electric bias to the semiconductor, wherein the first electric bias is less than an electrochemical deposition bias, said electrochemical deposition bias being the minimum voltage required to electrodeposit the electrocatalyst onto the surface of the semiconductor without impinging the surface of the semiconductor with electromagnetic radiation having the first photoenergy;
• wherein the combination of the first photoenergy and the first electric bias are sufficient to deposit catalyst components from the electrolyte to form the solid conformal layer of the electrocatalyst.