High-Stability Ti3C2-QDs/ZnIn2S4/Ti(IV) Flower-like Heterojunction for Boosted Photocatalytic Hydrogen Evolution

Abstract

The practical application of photocatalytic H2-evolution is greatly limited by its sluggish charge separation, insufficient active sites, and stability of photocatalysts. Zero-dimensional (0D) Ti3C2 MXene quantum dots (MQDs) and amorphous Ti(IV) have been proven to be potential substitutes for noble co-catalyst to accelerate the separation of photogenerated electron-hole pairs and prevent the self-oxidation of photocatalysts, leading to better photocatalytic H2-evolution performance with long-term stability. In this study, amorphous Ti(IV) and MQDs co-catalysts were successfully deposited on ZnIn2S4 (ZIS) microspheres composed of ultra-thin nanosheets via a simple impregnation and self-assembly method (denoted as MQDs/ZIS/Ti(IV)). As expected, the optimal MQDs/ZIS/Ti(IV) sample exhibited a photocatalytic H2-evolution rate of 7.52 mmol·g−1·h−1 and excellent photostability without metallic Pt as the co-catalyst in the presence of Na2S/Na2SO3 as hole scavenger, about 16, 4.02 and 4.25 times higher than those of ZIS, ZIS/Ti(IV), and MQDs/ZIS, respectively. The significantly enhanced photocatalytic H2-evolution activity is attributed to the synergistic effect of the three-dimensional (3D) flower-like microsphere structure, the amorphous Ti(IV) hole co-catalyst, and a Schottky junction formed at the ZIS–MQDs interface, which offers more active sites, suppresses self-photocorrosion, and photo-generates the charge recombination of ZIS.

Emerging carbon-based quantum dots for sustainable photocatalysis

“…17g). 119 This study proves that MQDs can be used to catalyze HER; evolution is about three times as much as that of NGQDs and two times as much as BCNQDs, which opens up a new way to design semiconductors with surface-induced effects to obtain efficient photocatalysts, and provides more possibilities for the practical application of carbon-based QD photocatalysis technology.…”

“…The E f of MQDs is close to that of Pt and is more positive than the CB of ZIS, and the Schottky barrier effectively prevents electron reflux, which confirms that ZIS-MQDs are suitable for photocatalytic HER. 119 The H 2 O splitting energy of MQDs and MQD/Cu 2 O/Cu foam varies close to zero; the presence of MQDs increases the hydrogen binding energy and leads to excellent reaction kinetics. 99…”

“…117 In addition to the preparation process and structure, theoretical simulations can also predict the photocatalytic performance of carbon-based QDs, providing design guidance for high performance applications. 86,96,118,119 The adsorption effects of Al-GQDs and N-GQDs prove the strong adsorption capacity of the catalysts for small gas molecules and H 2 O, which means that GQDs play an important role in photocatalysis according to DFT theory (Fig. 13c-e).…”

Quantum Dots Compete at the Acme of MXene Family for the Optimal Catalysis

“…In addition, the Ti 3 C 2 MQDs/ZnIn 2 S 4 /Ti (IV) 3D hierarchical structure was constructed by impregnation and self-assembly methods (Fig. 11h) [78]. TEM and HRTEM images show that the Ti (IV) and MQDs are uniformly dispersed on the surface of 3D nanoflowers microspheres (Fig.…”

“…19g-h). Also, the Ti 3 C 2 -QDs/ ZnIn 2 S 4 /Ti(IV) heterojunction photocatalyst was prepared for improving hydrogen production performance [78].…”