Robust ZnO nanowire photoanodes with oxygen vacancies for efficient photoelectrochemical cathodic protection

Highlights: • Robust ZnO nanowire photoanodes with oxygen vacancies were synthesized. • The ZnO photoanode shows a superior photocathodic protection performance. • Benign effect of oxygen vacancies on the ZnO photoanode is demonstrated. Oxygen vacancy engineering of metal oxides is an effective strategy to modulate electronic structures and regulate active sites for improving their photoelectrochemical performances. Herein, a robust ZnO nanowire photoanode with an appropriate amount of oxygen vacancies was synthesized through a seed-assistant hydrothermal approach. Under intermittent sunlight illumination, the as-prepared ZnO nanowire photoanode shifts the open circuit potential of the coupled 304 stainless steel to − 770 mV with a potential drop of 503 mV relative to steel's corrosion potential (−267 mV), suggesting a superior photocathodic protection performance. In a durability test, the photocathodic protection potential further drops and stabilizes at − 930 mV for hours under continuous illumination, which is attributed to the formation of ZnO/ZnS core/shell heterostructures as well as the in-situ creation of anionic vacancies. This work demonstrates an advantageous effect of oxygen vacancies on the metal oxide photoanodes during photocathodic protection process.