RESUMEN
Mo2C MXene (Mo2CTx) is one of the most promising noble-metal-free cocatalysts for photocatalytic H2 production because of its excellent electron transport capacity and abundant Mo sites. However, Mo2CTx typically exhibits a strong MoâHads bond, resulting in that the produced H2 difficultly desorbs from the Mo surface for the limited activity. To effectively weaken the MoâHads bond, in this paper, a regulation strategy of electron donor Au releasing electrons to the d-orbitals of Mo sites in Mo2CTx is proposed. Herein, the Mo2CTx-Au/CdS photocatalysts are prepared through a two-step process, including the initial loading of Au nanoparticles on the Mo2CTx surface and the subsequent in situ growth of CdS onto the Mo2CTx-Au surface. Photocatalytic measurements indicate that the maximal H2-production rate of Mo2CTx-Au/CdS reaches up to 2799.44 µmol g-1 h-1, which is 30.99 and 3.60 times higher than that of CdS and Mo2CTx/CdS, respectively. Experimental and theoretical data corroborate that metallic Au can transfer free electrons to Mo2CTx to generate electron-enriched Moδ- sites, thus causing the increased antibonding-orbital occupancy state and the weakened MoâHads bond for the boosted H2-production efficiency. This research provides a promising approach for designing Mo2CTx-based cocatalysts by regulating the antibonding-orbital occupancy of Mo sites for improved photocatalytic performance.
RESUMEN
Turnip is a member of the Brassica rapa species and is characterized by a swollen taproot that develops from the hypocotyl and part of the root. Gibberellins (GAs) are plant growth regulators involved in promoting cell elongation and play important roles in many aspects of plant growth and development. Interestingly, exogenous application of GA3 was found to significantly inhibit taproot formation in turnip. Moreover, endogenous GA contents decreased during the early developmental stages of taproot formation, suggesting that GA plays a negative role in taproot formation. We examined the anatomical structure of the taproot and found that lignification of the xylem cell wall was enhanced after treatment with GA3. Yeast two-hybrid assays suggested the occurrence of protein interactions between DELLAs and NACs in turnip. We also found that the expression of NAC-targeted genes involved in lignification of the secondary cell wall was significantly upregulated upon GA3 treatment. Taken together, these results supported the hypothesis that GA induced DELLA proteins degradation to release NAC proteins and induced xylem lignification, therefore inhibiting taproot formation, providing new insight into the molecular mechanism underlying turnip taproot formation.