Study On The Method Of In-situ Storage Of Hydrogen Atoms In Photocatalytic Water Splitting

The use of renewable energy is drawing rising concerns nowadays,as the energy issue is becoming a more and more serious problem.Among all the clean energy,hydrogen energy has been identified as the promising one that owns a bright future.Achieving hydrogen energy through photocatalysis is an ideal method that neither consumes fossil fuel nor produces air pollution.However,the problem of hydrogen purification in photocatalytic products and the energy consumption of hydrogen broken apart during chemical hydrogen storage are all obstacles to hydrogen utilization.For this reason,we propose a new method,which is expected to store hydrogen atoms in hydrogen storage materials directly in the process of photocatalytic water splitting.In order to verify the feasibility of this method,we explored it experimentally.It is found that hydrogen storage materials can be used to store atomic hydrogen directly in photocatalysis.The main researches and achievements are listed as follows:?1?A noble metal platinum,as a co-catalyst,was attached to the surface of TiO₂?P25?by the method of photo-induced deposition.We studied this TiO₂?Pt?material by using TEM.It was found that Pt nanoparticles were uniformly distributed on the surface of TiO₂ particles with a content of about 4 wt%.This laid a foundation for effective photocatalytic water splitting by Pt-loaded TiO₂ particles.?2?The in-situ hydrogen storage experiment of palladium?Pd?foil in the TiO₂?Pt?photocatalytic water splitting system using methanol aqueous solution was designed and implemented.Based on the characterization by XRD,it was found that Pd foil has been hydrogenated to H_0.706Pd after several hours of hydrogen storage treatment in aqueous solution.The successful hydrogenation of Pd confirms the practicability of hydrogen separation and in-situ storage in hydrogen-storage materials during photocatalytic water splitting.?3?Vanadium dioxide?VO₂?nanowires and/or microwires were synthesized by physical vapor deposition.The metal-insulator transition behavior of these VO₂nanowires and/or microwires caused by heat was confirmed by observing the intrinsic phase transition behavior at 68?.The effect of carrier concentration on VO₂ phase transition was also proved by the study of its electric triggered metal-insulator transition in TEM.?4?The in-situ hydrogen storage experiment of VO₂ nanowires and/or microwires in the TiO₂?Pt?photocatalytic water splitting system was designed and implemented using methanol aqueous solution.It is found that the phase transition temperature of VO₂ decreases due to hydrogen doping by using optical microscope,TEM and Raman spectrum.The hydrogenated vanadium nanowires and/or microwires presented a quite large supercooling for the phase transition during the process of cooling.The hydrogen doping in VO₂ was further confirmed by the characterization of the electrical properties of VO₂ after hydrogenated treatment.In addition,it was found that even the hydrogen concentration in VO₂ is low and not enough to trigger the metal-insulator transition,the resistance of VO₂ will still be significantly decreased due to the more carriers introduced by hydrogen doping.?5?VO₂ is not able to absorb hydrogen molecules directly,while hydrogen atoms can be absorbed.That is,there exist hydrogen atoms in the photocatalytic water splitting system and these hydrogen atoms can spread in the solution to the surface of VO₂nanowires and/or microwires.?6?After hydrogen was stored in vanadium oxide,hydrogen release at room temperature?M₁ phase?is very slow,but after heating to R phase,hydrogen will be rapidly released.