The Fabrication Of WO₃ Nanoflake Arrays With Photoelectrochemical Performance And Its Application

Nowadays,we depended heavily on fossil fuel.But the application of fossil fuel can lead to environment pollution and the storage of fossil fuel is also decreasing.Therefore,it is necessary to find an alternative energy.Solar energy is very promising as it is distributed everywhere and contains big energy which could meet most of our need for energy.In recent research,the application of solar energy includes solar cell,photocatalysis and photoelectrocatalysis water splitting et al.However,the absorbed wavelength we could use in solar energy is still limited and only accounts for a small amount of the solar energy and the transfer efficiency is still need to be improved.In this contribution,based on photo-electro transfer of solar energy,we fabricated nonstoichiometric WO₃ nanoflake arrays for the enhancement of solar energy water splitting.And superhydrophobic WO₃@TiO₂ nanoflake arrays were also synthesized,using photo-induced current for electrochemical corrosion resistance.Stricter environmental regulations and rising global energy demand motivates to search for efficient and sustainable energy.Hydrogen production by solar-powered water splitting with photoelectrochemical devices is considered to be a promising method to simultaneously harvest and store solar energy at a large scale.TiO₂ was first discovered as photo anode in the solar-driven photoelectrochemical water splitting process but wide bandgap of TiO₂ limits its development.WO₃ exhibits enhanced photoelectrochemical water splitting ability due to its narrower band gap.However,WO₃ still only absorb part of the solar energy.Thereby in this work,we synthesized nonstoichiometric tungsten trioxide(WO_3-x)nanoflake arrays via a new extremely facile route which involves electrodeposition,dealloying of Fe-W amorphous alloy,thermal treatment in air and properly cathodic polarization.Taking advantage of the structure of nanoflake arrays and O vacancy in WO_3-x,the efficiency of hydrogen production by PEC water splitting was significantly improved.It was found that WO_3-x with the appropriate reduction current presents a high photo current density of 8.7 mA·cm^-2 in the presence of methanol as a hole scavenger,five folds larger than that of pristine WO₃nanoflake.Electrochemical impedance spectroscopy implied that the unique nanoflake architecture and surface defects offer improved light harvesting as well as efficient charge transportation.Corrosion resistance of steel is of vital importance because of its widely use in modern society and various methods have been applied to inhibit corrosion.Electrochemical corrosion is always originated from the inherent micro/macro electrochemical inhomogeneity of steel in combination with environment factors,interruption between metal and surrounding environment interaction is therefore an effective method for corrosion resistance.Superhydrophobic layer has aroused much interest in corrosion resistance and self-cleaning in recent years.But the instability of superhydrophobic layer limits its application.Therefore,it is necessary to endow steel with extra protection besides superhydrophobicity to give stainless steel reliable corrosion resistance.As the essence in electrochemical corrosion is electron loss in anodic metals,photo-induced cathodic protection on metallic material is another effective method to inhibit metal corrosion without further material and energy loss.WO₃@TiO₂ nanocomposite is promising for photo-induced cathodic protection.WO₃has narrow bandgap energy of 2.6 eV,which can be motivated under visible light illumination.And WO₃ exhibits electron storage ability that stores electrons under illumination and then transports those electrons to the stainless steel once light is off.Band structure of WO₃ matches well with that of TiO₂,facilitating charge transfer process.Furthermore,WO₃@TiO₂ nanostructures,with a much bigger specific surface area,strengthen these advantages.Finally,interface incompatibility between semiconductor and metallic substrate often construct great difficulties in practical application and continuous composition change from substrate to the film is of vital importance.Therefore,we tactfully constructed superhydrophobic surface on 316 SS using WO₃@TiO₂ nanoflake arrays to combine photo-induced cathodic protection with superhydrophobicity,endowing stainless steel with multiple protections.Contact angle of the hierarchical nanostructured layer reached 162.3°and significant photo-induced potential drop was detected,suggesting good corrosion resistance ability which was further testified by Tafel curves.EIS and XPS were used to analyze the mechanism of the durable corrosion protection of the film.