Study On Preparation And Application Of Single Atom Catalysts In Photocatalytic Water Splitting And Photooxidation Reactions

Photocatalyt ic chemistr y react ions use c lean and non-pollut ing solar energy obtained more and more extens ive research.However,convent io na l photocatalyt ic semiconductors generally have the proble ms of narrow absorptio n range of visib le light and low e ffic ie ncy o f char ge separatio n and trans fer.Single atom cata lysts have attracted researchers’attent ion because the advanta ge of ma ximizing the use of meta l ato ms to achieve a high select ivity and convers ion.Recent ly,single atoms have been proved to remarkably improve the char ge trans fer effic ie ncy o f semico nductors while photocatalytic progress,making single atom photocatalysis a hot research issue.In this paper,a new kind of s ingle ato m archor ed carbon quant um dots and core-shell carbon nitr ide photocatalysts were prepared by pyrolysis and ther ma l polymer izat ion,respective ly,us ing vita min B₁₂as a carbon source and a metal source.The main contents are as follows:（1）V ita min B₁₂ was pyrolysed at a low temperature,and hydrolyzed in an alkaline enviro nment.A fter pur ificat ion,single atom carbon quantum dot catalyst was successfully prepared.This photocatalyst has a n exce llent opt ical properties and effective photon-generated electron-hole separatio n.Single meta l atoms can promote the for mat ion and trans fer of photon-generated charges.Due to the syner gy between meta l atoms a nd carbon quant um dots,single ato m carbon qua ntum dots could have a good catalyt ic photooxidatio n activit y effie ncy.The use o f s ingle ato m carbon quantum dots for three different p ho tooxidat ion react ions could prove its strong photooxidat ion abilit y.When sodium iodate was used as the electron trapp ing agent,carbon quant um dots could produced 168μmol g^-1 oxygen in the first ho ur wit h good stability.In the photocatalyt ic benzyla mine oxidat ion,benzyla mine and var ious derivat ives can take chemica l trans for matio n w it h extre mely high select ivity a nd high conversio n rate.Here,we prove d the process of benzyla mine oxidat ion and the act ive species invo lved in t he reaction.D ur ing t he rhodamine B degradatio n process,rhodamine B was rap idly degraded in a short period of t ime,which could also prove the photooxidation ability of single atom carbon quantum dots.（2）Vitamin B12 was added dur ing the ther ma l polymer izat ion of core-shell carbon nitr ide us ing silica as a te mp late to prepare a single atom loaded hollow carbon nitr ide photocatalyst.C arbon doping can s ignificant ly improve t he vis ib le light harvest ing abilit y,change the energy band structure to meet the require ment for water splitt ing.Single atoms in catalysts could also improve the photogenerated electron-hole pair separatio n.In the process of photocatalyt ic water splitt ing,single ato m loaded hollow carbon nitr ide could exhib it e ight t imes higher cata lyt ic act ivit y than bulk carbon nitride.