Near-infrared CdSexTe1-x@CdS “giant” quantum dots for efficient photoelectrochemical hydrogen generation

Abstract

Colloidal quantum dots (QDs) have attracted a lot of attention due to their unique optoelectronic properties. They have been widely used as building block materials for solar technologies such as solar cell, and photoelectrochemical (PEC) water splitting. Hydrogen generation by using QDs as photocatalysts has emerged a promising application in PEC devices. However, it is still very challenging to obtain high-efficiency PEC devices due to the limited absorption wavelength of QDs and the existence of surface traps which prohibit the efficient charge transfer. In this work, we synthesized ternary CdSexTe1-x/CdS (CdSeTe/CdS) “giant” QDs to extend the light absorption to near infrared, matched well with Sun's spectrum. The as-synthesized CdSeTe/CdS “giant” QDs exhibit quasi-type II band alignment as confirmed by its long lifetime and red-shifted emission peak compared with bare CdSeTe QDs. The wide absorption range of “giant” core/shell QDs and their long lifetime can improve the efficient absorption of Sun's spectrum and charge transfer. As a proof-of-concept, a PEC device using QDs sensitized TiO2 mesoporous thin film as a photoanode was used for hydrogen production. The corresponding photocurrent density was increased to 3.0 mA/cm2 with the introduction of CdS shell, which is 1.5 times higher than the PEC device using CdSeTe QDs. This study indicates that ternary or polynary alloyed core/shell QDs can be used as promising optoelectronic materials for applications of PEC devices.