Design Of A One-dimensional ZnO Nano-array Based Photoelectrochemical Water Splitting Electrode

With the ever-decreasing energy sources and increasingly environmental pollution problems,it is urgent to find an efficient way to solve this problem.Hydrogen is believed to be one of the renewable and clean alternatives to overcome the energy and environmental challenges.Solar water splitting into hydrogen and oxygen over semiconductors photoelectrochemical(PEC)cells is widely recognized as a promising H2 production approach owing to owing to the carbon-free emission and low-cost nature and semiconductors itself has special physical properties.When the light irradiates on the surface of the semiconductor,the intrinsic electron-hole pair will be excited and then transfer to the surface to react with water to generate hydrogen and oxygen.Among semiconductor photoelectrode materials,zinc oxide(ZnO)possesses high electron transfer efficiency,electron transfer efficiency,good environmental compatibility,low price,non-toxicity,and has been extensively explored as PEC photoelectrode material to examine its PEC performances.However,ZnO itself is a wide-bandgap semiconductor and can only responds to light in the ultraviolet region.We know that ultraviolet light only accounts for 5%of sunlight,which greatly limits the application of ZnO.In addition,ZnO-based photoelectrodes are generally susceptible to hole-induced anode corrosion and the surface photoluminescence(PL)recombination of electron-hole pairs,which makes the commercial use of ZnO obstructed.In view of the defects existing in ZnO and the current researches of photoelectrochemistry,we choose ZnO as a substrate and adopt a method of surface modification of other materials to carry out a series of work to improve the photoelectrochemical activity and stability of ZnO.The details are as follows:1.The n-type ZnO nanoarrays were fabricated on p-type silicon wafers(Si)by hydrothermal method and nanogold(Au)particles were deposited on the surface of nanoarrays by self-assembly reduction method,and the photoelectrochemical properties of the junction were studied.The results show that such a ternary structure not only broadens the absorption range of sunlight,but also promotes the separation and migration of photogenerated electron-holes under the synergistic effect of p-n heterojunction and plasmon of Au nanoparticles,finally photoelectrocatalytic performance is significantly improved.2.The ZnO nanoarrays were grown on FTO conductive glass by hydrothermal method and then multi-band absorbed carbon quantum dots(CDs)were prepared by oil bath method and then attached on the surface of nanorods by spin coating.We study its photoelectrochemical performance,and the results show that CDs exhibits a multi-band absorption behavior,which we find is caused by their surface states,indicating that CDs is a good light-sensitive material.After loading it onto ZnO,the composite structure shows very good photoelectric properties in the visible light region comparing the pure ZnO.