Effect Of Polymers On Performance Of Ni Nanoparticles Prepared By Visible-photoreduction Of Ni²⁺ And Its Dye-sensitized Photocatalytic Hydrogen Production

In the face of the shortage and increasing demand of fossil fuels,solar water splitting to hydrogen production attracts extensively attention.Dye sensitization is an important way to use visible light for hydrogen production.In the dye sensitization of photocatalytic hydrogen production system,choice of the efficient hydrogen evolution cocatalysts is very important.Pt is the most widely used cocatalyst for hydrogen evolution.However,because Pt is earth-scarce and expensive,it cannot be applied in the industry for mass production.Searching for earth-abundant,cheap and efficient cocatalysts to replace of precious metals is an important direction in the field of dye-sensitized photocatalytic hydrogen production.Metal Ni is an earth-abundant and cheap cocatalyst for hydrogen evolution.In this thesis,Ni nanoparticles were fabricated by photoreduction of Ni2+using xanthydrol dye eosin-Y(EY)as a sensitizer.Ni cocatalyst is directly applied to dye-sensitized photocatalytic hydrogen production.In the reaction system,the addition of polyvinyl alcohol(PVA)or sodium carboxymethyl cellulose(CMC),on the one hand,can control the growth of Ni nanoparticles,and on the other hand,the polymers absorbed on the nano Ni surface can promote the transfer of photoinduced electrons from EY to Ni cocatalyst,leading to increase of the activity and stability of the dye-sensitized photocatalytic hydrogen production.In the first part,nano Ni was prepared by in situ photoreduction method.The addition of a given amount of PVA in reaction system can control synthesis of nano Ni.The catalyst was characterized by XRD,FTIR,TEM,UV-Vis etc.means.The results show that in the absence of PVA sphere-like Ni nanoparticles were obtained by photoreduction;whereas in the presence of PVA,due to its template guiding role,the prepared Ni nanoparticles can promote the transfer of photoinduced electrons from EY to Ni cocatalyst.leading to increase of the activity and stability of the dye sensitized photocatalytic hydrogen production.Under the optimum conditions,the maximal apparent quantum yield(AQY)at 420 nm is 33.4%.In the second part,nano Ni was prepared by the same in situ photoreduction method using optimum amount of CMC.The catalyst was characterized by TEM,XRD,FTIR techniques.The results show that in the presence of CMC,Ni nanoparticles size is smaller than that in the absence of CMC.The smaller nano Nican expose more active sites,which can improve the activity of the dye sensitized hydrogen production.At the same time,the presence of the thin layer CMC on the surface of Ni catalyst can accelerate photoinduced electrons from EY to nano Ni,improving the activity and stability of the dye sensitized photocatalytic hydrogen production over nano Ni catalyst.Under the optimum conditions,the maximal AQY at520 nm is 20.9%.