单原子Pt负载在锐钛矿(001)表面的电光学特性研究

Electronic and optical properties of the platinum single atom catalyst loaded on anatase(001)surface

基于第一性原理的多体格林函数理论方法,系统探究了锐钛矿TiO_(2)(001)表面负载Pt单原子催化剂的电子结构和光学性质,考虑Pt在完美表面和缺陷表面(O空位)两种基底上的负载.结果发现,Pt会在TiO_(2)禁带中间、价带和导带边缘引入新能级,但不同基底负载的Pt单原子催化剂存在不同的带隙特性.Pt的负载会引起体系光学吸收红移,增大光学吸收范围,延伸光吸收至可见光甚至是红外区域,提升可见光活化的可能性,同时改善体系的激子束缚能,有利于空穴与电子有效分离,这可能是Pt负载后光催化性能提升的原因之一.然而,若在可见光或低能量紫外光激发后,分离的电子与空穴没有及时参与反应,体系衰变回最低激发态,此时极大的激子束缚能可能会加速电子与空穴重组,不利于表面催化反应的进行.负载在O空位的催化剂最低激发态的激子束缚能比完美表面小,重组速率慢.计算结果能够为理解单原子催化剂结构-性能关系提供一些见解.

Based on the first-principles many-body Green’s function theory(MBGFT),the electronic structure and optical properties of the Pt single atom loaded on the anatase TiO 2(001)surface with and without O vacancy defect were investigated systematically.The calculated results reveal that the Pt impurity levels appear in the band gap or near the edge of valence band maximum and conduction band minimum.The different band structures are found in two systems.And the loaded single atom Pt can increase its light absorption in visible light and infrared region.Meanwhile,the exciton binding energy of the system is lower,which is in favor of the separation of electron-hole pair.The catalytic activities are enhanced.Based on the results,the significantly improved photocatalytic performance is attributed to the lower exciton binding energy and extended optical absorption.However,if the electron or hole cannot participate in the catalytic reaction in time,the system may decay eventually the lowest excited states where the recombination of photogenerated electron-hole pairs is accelerated due to the larger exciton binding energy.The exciton binding energy for the lowest excited state of Pt anchored on the O vacancy defect is lower in comparison with the perfect surface,the recombination rate is slower.The results may provide some insights to reveal the structure-property relationship of single-atom catalysts.