CoP-loaded BiVO4 for highly active and robust photocathodic protection of 304 stainless steel

Despite the narrow band gap and the suitable band edge position, the BiVO 4 photoanode exhibits low metal anticorrosion performance due to inefficient charge separation and transfer. In this work, we introduce a CoP electrocatalyst with metal character on the BiVO 4 surface by cyclic voltammetry to address this challenge, which greatly enhances the electron injection efficiency into the protected metal. The modified BiVO 4 photoanode exhibits high solar water oxidation activity, resulting in a 123 mV cathodic shift on the self-corrosion potential of 304 stainless steel (304SS), enabling excellent metal protection. Additionally, the coupled composite photoanode shows high photo stability under light illumination, with only 8% decay on the open circuit potential after 51 h of photo-illumination. Our mechanism study shows that the CoP overlayer can act as the hole collector and electrocatalyst for water oxidation, and thus the BiVO 4 valence band holes are effectively transferred to the CoP and subsequently to water. Such an improvement inhibits the charge recombination increasing the electron lifetime, and thus realizing the effective protection of 304SS. The present work offers a rather simple process that allows the effective deposition of CoP electrocatalyst on BiVO 4 surfaces, which effectively protects metals from corrosion.