Improved photoelectrochemical cathodic protection properties of a flower-like SrTiO3 photoanode decorated With g-C3N4

A "green" and simple approach was used to prepare a composite of strontium titanate and graphite-like carbon nitride (an STO/g-CN composite) that protected 304 stainless steel (304 SS) via photoelectrochemical cathodic protection (PCP). The structural characterization and optical-absorption characterization of the composite showed that g-CN was successfully loaded onto STO. The optical absorption spectrum of the composite showed an obvious redshift, and the optical response range of the composite extended to 540 nm. In addition, the composite showed enhanced PCP performance. Coupling 304 SS with the STO/g-CN composite containing 30 wt% of g-CN shifted the potential of the 304 SS from −180 mV to −480 mV. Moreover, the STO/g-CN composite containing 30 wt% of g-CN generated 3.8 times more photocurrent density than STO did. After 4 intermittent-light cycles, the STO/g-CN composite retained its PCP performance. The flower-like structure on the STO surface had many voids that provided a large surface area and many reaction sites and improved the ability of the composite to refract and utilize visible light. In addition, STO and g-CN formed a heterojunction whose charge-transfer mechanism inhibited photogenerated electrons and holes from recombining and improved the PCP performance of the STO/g-CN composite.