Synthesis,modification And Photoelectrochemical Performances Of BiFeO₃ Thin Film Photoelectrodes

Photoelectrochemistry has been regarded as a promising approach for solving the problems of energy shortage and environmental pollution,because it can convert solar energy into chemical energy.As one of the ferroelectric materials,BiFeO₃（BFO）has attracted great attention for using as a new category of photoelectrode materials in recent years owing to its large spontaneous polarization.However,the photoelectrochemical performance of BFO is still remarkably low because of its poor charge transport and high recombination rate of photo-generate electrons and holes.In this paper,several attempts were made to modify the BFO thin film photoelectrode,and the photoelectrochemical properties of the modified BFO photoelectrodeswerethenexamined.Meanwhile,thecorrespongding photoelectrochemical reaction mechanism was also investigated.The main research contents are listed as follows.1.Synthesis and photoelectrochemical performance of BiFeO₃ thin filmphotoelectrodesBiFe O₃ thin film photoelectrodes were prepared by a single sol-gel spin coating method,and the influence of calcination temperature on the photoelectrochemical properties of BFO thin film photoelectrodes was then studied.It was found that the BFO photoelectrode sample calcined at 550 ^oC possessed much higher carrier concentration,better charge separation and lower recombination efficiency of photo-generation electrons and holes than those samples calcined at 500,600 and 650^oC,thus leading to the enhanced photoelectrochemical performance.2.Synthesis and photoelectrochemical performance of Au/Nd-BiFeO₃composite thin film photoelectrodesAu was loaded on the surface of Nd doped BiFeO₃（Nd-BFO）photoelectrode by photodeposition method.From the photoelectrochemical measurements,it was revealed that the Au/Nd-BFO composite photoelectrode showed much better photoelectrochemical properties than the Au/BFO or Nd-doped BFO photoelectrode.The enhanced photoelectrochemical performance of Au/Nd-BFO could be attributed to the synergistic effect of Au nanoparticles deposition and Nd doping,thus leading to the increased carrier concentration,charge separation enhancement and suppressed recombination of photo-generation electrons and holes.3.Photoelectrochemical performance of Co-Pi cocatalyst modified BiFe O₃ thinfilm photoelectrodesFor the first time,Co-Pi cocatalyst were successfully deposited on the surface of BFO thin film photoelectrode by photo-assisted electrodeposition method.The deposited Co-Pi cocatalyst on the surface of BFO thin film was flocculent morphology,as verified by SEM image.It was found that the photoelectrochemical activity of Co-Pi/BFO was largely improved compared to the unmodified BFO.Moreover,with increasing the deposition time within 2 h,the photoelectrochemical activity of Co-Pi/BFO was also increased.On the basis of the photoelectrochemical measurements（such as electrochemical impedance spectra（EIS）,photoluminescence（PL）spectra）,the deposition of Co-Pi cocatalyst could improve the carrier concentration and charge separation efficiency,as well as suppress the recombination rate of photo-generation electrons and holes of BFO thin film photoelectrode,thus leading to the enhanced photoelectrochemical performance.