Synthesis Of TiO₂ And BiVO₄ For Photoelectrochemical Water Splitting

With the development of human society,the consumption of fossil fuels is also increasing rapidly,resulting in a series of ecological environmental problems such as ocean acidification and climate warming,which threaten the survival of human beings.Therefore,the energy transition is imminent.Solar energy is widely recognized as the most suitable alternative energy in the future due to its convenience,renewable energy and environmental friendliness.Since TiO2 discovered as photocatalyst in 1972,photoelectrochemical(PEC)cell has been considered as a promising and potential system for hydrogen production.However,the current research shows that the solar energy conversion efficiency is still far from meeting the actual application requirements.Thus,exploring suitable strategies to prepare high-performance photocatalytic materials is still the main task.Common methods include bulk doping or morphology control,etc.,which are dedicated to enhancing the overall conductivity and reducing the recombination of materials.However,it is worth noting that rapid electron-hole recombination also exists at the interface between electrode and electrolyte,which also limits its photocatalytic performance,so strategies should be explored to solve this problem.In this paper,two potential photocatalytic materials TiO2 and BiVO4 were selected.Based on the successful preparation of electrode materials,aiming at the serious carrier complex at the interface between electrode and electrolyte.Through structural design,the photogenic carriers are separated in space on the interface,so as to obtain higher catalytic efficiency.It provides a feasible idea for realizing an efficient photocatalytic system.(1)TiO2 nanorods array structure with unique core-shell structure was prepared by hydrothermal method.After in-situ transformation,an ultrathin amorphous MoOxNy layer was formed on the surface.MoOxNy layer was composed of molybdenum oxide,nitride and oxynitride.The optimized MoOxNy/TiO2 sample generated a photocurrent of about 2.5 times of pure TiO2 did,which confirms the critical importance of the amorphous MoOxNy layer for improving the solar-to-current conversion efficiency.A special Zscheme heterostructure of MoOxNy/TiO2 was formed with N atom as the interface hub through band matching.The built-in electric field generated between the valence band of TiO2 and the conduction band of MoOxNy layer hindered the flow of electrons from MoOxNy layer to TiO2.(2)Dense and uniform BiVO4 films were synthesized on the FTO surface by electrodeposition,and a novel Co-layer/BiVO4 photoanode with amorphous layer of cobalt was synthesized by simple chemical wet method.The Co layer was composed of carbonaceous cobalt oxide.The photocurrent generated by the modified Co-layer/BiVO4 photoanode was about 4 times that of pure BiVO4,confirming the effectiveness of the Co layer in improving surface carrier recombination.The Co layer not only enhanced the charge transfer and conductivity,but also had the effect of hole extraction,which promoted the charge separation between the photoanode and the electrolyte interface.In summary,by regulating the interface structure of the semiconductor,the carrier transport property of the photoanode can be changed,which opens up a new idea for improving the solar energy conversion efficiency.