Nickel interlayer enables indirect corrosion protection of magnesium alloy by photoelectrochemical cathodic protection

As a green and sustainable corrosion protection technology, photoelectrochemical cathodic protection (PECCP) cannot be applied to protect metals having low corrosion potential (Ec) due to the insufficient negative conduction band (CB) potential of the present semiconductor materials. Herein, for the first time, PECCP is reported to indirectly protect metals with low Ec from corrosion by introduction of an interlayer with high Ec between the substrate and semiconductor. As an example, a nickel interlayer was firstly deposited on magnesium alloy substrate by chemical deposition and electrodeposition to provide the high Ec, followed by electrodeposition of Cu2O semiconductor layer on the nickel layer. A series of characterizations, including high-resolution transmission electron microscope and X-ray photoelectron spectroscopy, indicate that the resultant Cu2O semiconductor has an octahedral structure and an edge length of ca. 514 nm. The n-type property of the semiconductor is determined by the Mott-Schottky curve, and the photo-response behavior, such as obvious photo-induced potential drop and stable photocurrent density as high as 747 mu A cm-2 under visible light illumination, is confirmed by electrochemical and photoelectrochemical measurements. The new proposed methodology described in this study is not limited to magnesium alloy but also can be possibly applied in other structural metals having low Ec.