Simultaneous Localization of Electrons/Holes by Surface Cationic Dangling-Bonds/Vacancies for Synergistically...

Simultaneous localization of photoelectrons and holes into different surface defects on a single-component photocatalyst is an ideal strategy for maximizing photocatalytic activity yet remains a huge challenge. We propose a novel concept of creating two distinct defects, cationic dangling bonds and vacancies, on the surface of frequently used CdSe and CdS quantum dots (QDs) for simultaneously confining the photoelectrons and holes to boost the photocatalytic activity. The coexisting cationic dangling bonds and vacancies left by a simple acid-etching of QDs localize photoelectrons and holes, respectively, and synchronously, which shortens the carrier lifetime but accelerates the exciton dissociation, carrier separation, and transfer, and thus promotes the photocatalytic reactions. For three typical photocatalytic reactions (benzyl alcohol oxidation, toluene oxidation, and allylic C(sp³)-H thiolation), the reaction rates catalyzed by CdSe or CdS with coexisting cationic dangling bonds and vacancies are elevated to 5.5-63 times, which are much higher than those by CdS or CdSe with only cationic dangling bonds (1.7-25 times). Density functional theory calculations confirm that individual defects lower the rate-determining step barrier, and the dual-defect exhibits the most favorable adsorption energy, effectively bridging the adsorption-activation trade-off. This study clarifies the rational design, creation, function, and application of two coexisting distinct defects on a single-component nanocrystal from both the atomic level and macro-perspective, offers new ways for designing ideal photocatalysts, and provides insightful understandings for the synergy of simultaneous localization of photocarriers in photocatalysis.