RGO/WO₃/SrTiO₃ Nanocomposite For Enhanced Photocathodic Protection Of Stainless Steel

Photocathodic protection(PCP)can be realized by using semiconductor materials,which are capable to generate electrons under the illumination and maintain the steel at negative potential.In recent years,PCP has received special interests due to its advantages of energy saving and environmental friendly.However,its application is severely restricted by the low quantum efficiency and poor anticorrosion performance in dark environment.In this work,we report the preparation of novel RGO/WO₃/Sr Ti O₃ nanocomposite and using of the as-prepared composite for fabricating a continuous,uniform and compact film coating on type 304 stainless steel(304SS).The phase compositions,microstructure and surface structures of RGO,WO₃and Sr Ti O₃ nanocomposite were studied by XRD,SEM and TEM.The photoelectrochemical properties of the film and photocathodic protection performance towards for 304SS were systematically examined by the open circuit potential(OCP),the current-time curve,Tafel,and electrochemical impedance spectroscopy(EIS).The results show that 9.0%mass content of graphene in RGO/Sr Ti O₃composite film reveals a maximum photoelectric current response,as well as exhibiting best anticorrosion effect for 304SS.Moreover,for the RGO/WO₃/Sr Ti O₃ composite films,the Sr:W element ratio of 2:1 gives the best photoelectric current response and electron storing ability.In addition,when the composite films are under illumination,it protects metal by using photocathode protection properties;when in dark environment,the composite films can also protect the metal by acting as a physical layer between the metal and corrosion environment.It is also found that the RGO/WO₃/Sr Ti O₃ composite film has the best photoelectrochemical properties when one layer of the composite film is used(i.e.about 39?m of thickness).Importantly,304SS with the RGO/WO₃/Sr Ti O₃ composite films can maintain cathodic protection for 2.2 h in the dark after 1.0 hour illumination.Finally,we provide a reasonable mechanism to understand the observed promising photocathodic protection for 304SS by the RGO/WO₃/Sr Ti O₃ composite films.Both the inhibited charge recombination by the RGO and the improved electrons storing ability by WO₃ contribute to the enhanced photocathodic protection performance.This work highlights the advantages of using RGO and metal oxides as functional components for developing simple and effective anticorrosion technologies.Nevertheless,the practical application of PCP is still limited by the cost,efficiency,and stability of the composite film.More efforts,such as optimization of the process,understanding the anticorrosion mechanism,as well as finding better semiconductor materials,are substantially required in this field.