Photoelectrochemical Performance Of WO₃ Nanoplate Array Film

As an n-type semiconductor,WO₃ with a band gap from 2.6 to 2.8 eV exhibits the better electron transport properties(12 cm_·²V_·^-1s^-1)and stable physical/chemical properties.The larger surface area and the effective carrier transportation in the ordered nanoplate array are usually considered the suitable application in electrochromism and photoelectrochemical water splitting.In this dissertation,the effect of WO₃ nanoplate array thin film photoanode on the photoelectrochemical performance,which is hydrothermally prepared in controlling particle morphology,surface defect and surface cocatalyst,is investigated.The results are as follows:（1）The WO₃ nanoplate array film was synthesized by hydrothermal method.The effect of the thickness,density and crystallization of the WO₃ nanoplate on the PEC performance are investigated by adjusting the reaction time,the precursor and capping agent and the crystallization by the annealing temperature.The SEM characterization was shown the enhanced film thickness and density with the increase in reaction time,the precursor and capping agent concentration.The high crystallinity is obtained under high annealing temperature from XRD pattern.The electrochemical measurement is performed in J-V,J-t,EIS and the photocurrent density for the optimized sample is reached 1.62 mA·cm^-2.The main mechanism is probably ascribed to the improved interfacial charge transfer.（2）The introduction of surface defects including W⁵⁺,W⁴⁺and oxygen vacancy is performanced by Ar plasma treatment.The photoelectrochemical performance is obviously enhanced and the influence mechanism is confirmed by XPS in surface density increase,the broaden absorption spectra and the attenuated PL intensity.Electrochemical test showed the relevant photocurrent density with the Ar plasma treatment time and the optimal value is at 1.32 mA·cm^-2.The electrochemical water splitting for H₂ and O₂preformed and a five times in evolution rate than that of the original WO₃ nanoplate array film is obtained.（3）The introduction of p-type cocatalyst through surface deposition is believed an effective strategy for the PEC activity,which is ascribed to the extraction of photogenerated hole,the suppression of the carrier recombination,the acceleration of the surface charge separation as well as the reduction in water splitting reaction potential.In this work,The three structure of photoanodes including WO₃/Au,WO₃/FeOOH and WO₃/FeOOH/Au is prepared and the their photoelectrochemical characterization are compared.The optical current densities for WO₃/Au and WO₃/FeOOH are 1.97 and 2.22 times than the original WO₃ photoanode,respectively.The cooperative effect due to FeOOH and Au has shown the 3.16times in photocurrent density than that of the original WO₃ photoanode.