Binder-integrated Bi/BiOI/TiO2 as an anti-chloride corrosion coating for enhanced photocathodic protection of 304 stainless steel in simulated seawater

Abstract

Preparing Bi/BiOI catalysts for efficient photocathodic protection of metals in the marine environment has been always a tricky problem because of Bi oxidation and I- ion release under Cl- ion corrosion. Herein, by integrating sodium carboxymethyl cellulose (CMC) into the composites, petal-like Bi/BiOI-modified TiO2 (TBB) p-n heterostructure coatings with a "truncated schema" were successfully fabricated. The as-prepared coatings (CTBB) provided stable photocathodic protection for 304 stainless steel (304SS) in simulated seawater. Compared with TiO2, CMC integrated Bi/BiOI/TiO2 p-n heterostructure coatings showed enhanced photocathodic protection performance with a large photocurrent response of 43 μA cm−2 and a stable potential drop of − 250 mV in simulated seawater without the participation of hole scavengers, which was attributed to the improvement of visible-light utilization and fast electron-hole pair migration at the p-n heterojunction interface. Furthermore, CMC effectively protected Bi nanoparticles against oxidation and BiOI from corrosion of Cl- ions in the electrolyte due to electron density redistribution in the vicinity of I- ions. The as-fabricated CTBB coatings showed great potential as photoanodes for photocathodic protection of 304SS in simulated seawater.