Photopotentials on Copper and Copper Alloy Electrodes

Abstract

The effect of white light illumination on the current‐potential relationships of pure copper and of Cu‐Ni and Cu‐Al alloys in neutral solutions was examined, both under galvanostatic and potentiostatic conditions. The results obtained show that the photoresponse is only weakly affected by the addition of alloying elements to copper, but that it is influenced by the method of formation of the oxide film on the metal surface. Depending on whether or not the film was formed by reaction with a copper solution, the amplitude of the signal response could be strongly affected and the sign of the photopotential at open circuit reversed, indicating a change in the nature of the majority carriers. Polarization of the electrode can also vary the photoresponse, but its rapid following of the potential does not support the view that the structure of the oxide film is altered. Impedance measurements on electrodes under illumination and in the dark indicate that the charge‐transfer reactions, rather than the resistivity of the oxide film, are affected by light.