Phase Regulation And Performance Of WO_3-? Epitaxial Thin Films

It is universally acknowledged that energy conservations and environment protection become more and more necessary in development.Therefore environmentally friendly technologies like eletrochromism and water splitting also become‘pop stars'in research areas.WO_3-?is an ABO₃ perovskite oxide with A-site atoms deletion and has extensive prospects in the field of electrochromism and water splitting.Oxygen change in WO_3-?can derive diverse phases and physical properties.The difference of those properties will result in significant performance changes,including electrochromism and water splitting.Therefore,we hope to use advanced phase regulation technology to control the phase change between oxygen-rich WO₃and anoxic WO_2.8,which could bring performance changes in eletrochromism and water splitting.In this paper,pulsed laser deposition technology was used to prepare different YSZ/ITO/WO_3-?films.By using the advantage of precise adjustment of oxygen pressure,we have prepared films with oxygen pressure of 13 Pa to 1.3 mPa.After that,the phase transition of the oxygen-rich WO₃ to the anoxic WO_2.8.8 was found by continuously reducing the oxygen pressure.We also discovered that the transmittance could be modulated to a range of next to 90%in the ultraviolet and visible absorption spectra.Actually,the transmittance can be continuously shifted from about 100%to about 10%in the phase transition from WO₃ to WO_2.8.The extremely strong photocatalytic activity in the semiconductor oxide was found in the photoelectrochemical performance test of the oxygen-rich WO₃.Besides,we have found that the oxygen-rich WO₃ deposited at 13 Pa is capable of producing photocurrents greater than 200?A.Nevertheless,the photocurrent of WO_3-?is reduced by about 2 orders of magnitude when the oxygen pressure is below 3 Pa.This means that oxygen pressure has a great influence on the photocatalytic activity.In electrocatalysis,unlike conventional catalysts,oxygen in the catalyst participates in the oxygen evolution reaction.So we achieved a phase transition of oxygen-rich WO₃ to anoxic WO_2.8 by using WO₃ as a catalyst in water splitting.In addition,it takes only about 40 minutes for the anoxic WO_2.8 to self-recover to oxygen-rich WO₃ in the air.And meanwhile,-1.6 V is determined to be the best voltage of phase transition by the regulation of voltage and 85 s is determined to be the time of phase transition by the regulation of time.We found that the transmittance could be modulated to a range of nearly 45%in the ultraviolet and visible absorption spectra.The transmittance can be continuously shifted from about 100%to about 55%in the phase transition from WO₃ to WO_2.8.Accordingly,we have realized the self-recovery electrochromism of WO_3-?films at low voltage.Finally,we discovered that the ratio of photocurrent to dark current decreases as the negative voltage rises gradually in photoelectrochemical test.At higher voltages than-1.7 V,the photocurrent and dark current will be equal.This evidences that the phase transition of WO_3-?film regulated by electrocatalysis reaction also leads to great changes in the photolysis performance.