The Mg-6%Al-3%Zn and Mg-6%Al-3%Zn-(1%, 1.5%, 2%)In alloys were prepared by melting and casting. Their microstructures were investigated via metallographic and energy-dispersive X-ray spectroscopy (EDS) analysis. Moreover, hydrogen evolution and electrochemical tests were carried out in 3.5 wt% NaCl solution aiming at identifying their corrosion mechanisms and discharge behaviors. The results suggested that indium exerts an improvement on both the corrosion rate and the discharge activity of Mg-Al-Zn alloy via the effects of grain refining, β-Mg₁₇Al₁₂ precipitation, dissolving-reprecipitation, and self-peeling. The Mg-6%Al-3%Zn-1.5%In alloy with the highest corrosion rate at free corrosion potential did not perform desirable discharge activity indicating that the barrier effect caused by the β-Mg₁₇Al₁₂ phase would have been enhanced under the conditions of anodic polarization. The Mg-6%Al-3%Zn-1.0%In alloy with a relative low corrosion rate and a high discharge activity is a promising anode material for both cathodic protection and chemical power source applications.

Graphitic carbon nitride (g-C₃N₄) is a promising material in the area of photoelectrochemical (PEC) cathodic protection. However, the fast secondary recombination of photogenerated charge carriers and the amphoteric property of g-C₃N₄ restrict its further application. In this work, the secondary reduced graphene oxide modified g-C₃N₄ (R-rGO-C₃N₄) was prepared by a thermal polycondensation method and subsequently secondary reduction process. The presence of reduced graphene oxide (rGO) and the increased reduction degree of rGO were proved by the X-ray photoelectron spectroscopy and UV/Vis diffuse reflectance spectroscopy. The rGO modification enhanced the electrical conductivity of g-C₃N₄, promoting the transfer and separation of the photogenerated charge carriers. It adjusted the band structure of g-C₃N₄ toward more negative direction, making it show stronger “n-type” semiconductor property. The properties were further improved after the secondary reduction of the rGO. These help to increase the PEC properties of g-C₃N₄, which makes a step toward the practical application of g-C₃N₄.