Microscopic Mechanism In Plasmon Induced Photocatalytic Reaction

Plasmon-driven photocatalytic reaction is studied in this thesis.Plasmonic metal nanoparticle can effectively utilize the solar energy to enhance the energy conversion efficiency.Plasmon-induced chemical reaction contains underlining mechanism for many enrich phenomena,such as charge transfer,field enhancement and nonlinear effect.So far the experiments have demonstrated plasmon-enhanced reaction,while the complex understanding of this process is not clear.We are dedicated to investigate the dynamics and microscopic mechanism of plasmon-induced photochemistry from first principles.Based on time-dependent density functional theory,this thesis first study the electron-ion dynamics of hydrogen split at the end of silver chain.Under the ultrafast pulse,hot electrons generated by plasmon of silver chain transfer to the anti-bonding orbital of hydrogen molecule,leading to hydrogen split.Increasing the laser intensity and atomic length would improve the reaction efficiency.Then we study the dynamics of water splitting on gold nanoparticles upon exposure to femtosecond laser.A linear fit of reaction rates on the laser intensity indicates this is a one-photon process,consistent with the experimental results.More importantly,we firstly put forward that the reaction is mode-selectivity.In detail,odd plasmonic mode is more effective than even mode.This stems from the better energy overlap between hot electron by plasmon decay and anti-bonding state of water molecule in the odd plasmonic mode.Furthermore,we extend the model to more realistic system: water splitting in gold cluster enclosed with liquid water.We observed the ultrafast hydrogen-production with the impact of two hydrogen atoms from different water molecules.In addition,we find the localized field enhancement will influence the reaction efficiency immensely.At last,when the silver chain illuminated by laser pulse,we observed the nonlinear response of tunneling current,and identified this results from the hot electrons by plasmon decay.By analysis of charge transfer and excited-state electronic dynamics in metal plasmon coupled with molecules,we deeply understand the microscopic mechanism of plasmon-induced photochemical reaction.We find adjusting laser parameters,size of nanoparticle and energy match of the system could improve the efficiency.These findings provide new insight for the development of plasmon-enhanced photochemistry.