Preparation And Photoelectrochemical Performance For The Photoanode Of WO₃ Based Semiconductor Heterojunction

High-efficiency and low-cost photoanode preparation is important for the photocatalytic water splitting.The metal oxides have been widely concerned due to their non-toxic,good chemical stability and easy access.WO₃ is a promising material which has stable chemical properties under acidic conditions,appropriate hole diffusion length and inherently good electronic properties,and pocesses a suitable bandgap of 2.7 eV.Moreover,BiVO₄ as a kind of direct band gap semiconductor can absorb more visible light?Eg=2.4eV?.But both of them have the similar disadvantages,such as sluggish kinetics of oxygen evolution reaction,serious surface recombination and so on.In this paper,we have synthesized a series of WO₃ with vertical nanostructures films,and combined with BiVO₄.The coupling photoanodes have a greatly improvement in photoelectrochemical properties.The main contents are as follows:We synthesized a series of vertical nanoarrays WO₃ on FTO substrate by hydrothermal and investigated the effect of hydrochloric acid and concluded that the initial nucleation rate is the key to the WO₃ morphology control.The crystal structure and morphology were studied by of XRD,SEM and TEM,and the optical and electrical properties were investigated by UV-Vis spectrophotometer and electrochemical workstation.Among the nanostructure films,the nanoflake?W-0.5 ml?and nanorods?W-1.5 ml?had the best photoelectrochemical properties,and the photocurrent densities were 1 and 0.8 mA/cm2,respectively.In the methyl orange?MO?degradation experiment,the photoelectrocatalytic efficiency of WO₃ nanoflake was 55%higher than the nanorods.WO₃/BiVO₄ composite photoanode was constructed by metal organic decomposition method?MOD?.The precursor of BiVO₄ was configured with bismuth nitrate and acetylacetone vanadium,and then droping on the WO₃ nanorods substrate through thermal pretreatment by a hot plate.We found the composite structure performs higher photoelectrochemical properties than single material due to the band bending at the interface accelerating the separation of photogenerated carriers.The photocurrent of WO₃/BiVO₄ was 2.7 mA/cm2,which was 2.7 and 5.4 times higher than single WO₃ and BiVO₄ anodes.The coating amount and heat treatment of BiVO₄ composite layer were also investigated.In addition,Pt cocatalyst was deposited on composite photoanode by photochemical reduction method which could inhibit the surface recombination,and the starting potential had a cathode shift of 0.2 V.