Preparation And Photocatalytic Hydrogen Evolution Of Two-dimensional Black Phosphorus/Titanium Oxide Heterostructures

Black phosphorus?BP?,a phosphorus analogue of graphene,is an emerging two-dimensional?2D?material,which can be exfoliated into several layers or even single atomic layer.Thanks to its thickness-dependent bandgap,BP can response to a wide range of irradiation,which makes it a promising candidate in photocatalysis and optoelectronic applications.In this thesis,2D black phosphorus has been studied as a photocatalytic material for water splitting hydrogen evolution.Photocatalysis technology convert radiation energy into photo-induced electrons and holes,where electrons are used to reduce water into hydrogen and holes are used to oxidize water into oxygen or degrade organic matters.Photocatalytic water splitting transforms sunlight into high-energy-density hydrogen energy,can solve the current energy crisis and environmental pollution problems caused by the overuse of fossil fuels.Herein,heterostructures based on layered BP and TiO₂ have been prepared,which exhibit341%photocatalytic hydrogen evolution as compared to the bare TiO₂ under the simulated sunlight irradiation and a quantum efficiency as high as 18.23%?25 mg?at 365 nm.The photocatalytic mechanism of BP/TiO₂ has been ascribed to the Z-scheme mechanism,where the reduction site is located at the BP side.In addition,the electrons of TiO₂ can be transferred to the BP during the reaction and improve the stability of otherwise vulnerable BP during the photocatalytic reaction.Another study in this thesis is the improvement of the exfoliation method of BP.Liquid pulsed laser ablation method is used successfully to exfoliate the bulk BP into 2D nanosheets structure and 0D quantum dots?BPQDs?.High-energy injection of femtosecond pulsed laser can cause a local high-temperature and high-pressure environment,where BP can be successfully exfoliated into nanostructures.By adjusting the power of the laser and environmental solvents,prepared BP nanosheets have a good lattice quality,and the quantum dots have a very high uniformity with a diameter about 6 nm.