RESUMEN
Elemental Te is important for semiconductor applications including thermoelectric energy conversion. Introducing dopants such as As, Sb, and Bi has been proven critical for improving its thermoelectric performance. However, the remarkably low solubility of these elements in Te raises questions about the mechanism with which these dopants can improve the thermoelectric properties. Indeed, these dopants overwhelmingly form precipitates rather than dissolve in the Te lattice. To distinguish the role of doping and precipitation on the properties, we have developed a correlative method to locally determine the structure-property relationship for an individual matrix or precipitate. We reveal that the conspicuous enhancement of electrical conductivity and power factor of bulk Te stems from the dopant-induced metavalently bonded telluride precipitates. These precipitates form electrically beneficial interfaces with the Te matrix. A quantum-mechanical-derived map uncovers more candidates for advancing Te thermoelectrics. This unconventional doping scenario adds another recipe to the design options for thermoelectrics and opens interesting pathways for microstructure design.
RESUMEN
Polydopamine/defective ultrathin mesoporous graphitic carbon nitride (PDA/DCN) Z-scheme organic assembly is fabricated through high-temperature surface hydrogenation and ultrasonic freeze-dried strategies. PDA could be anchored on the surface of DCN with adequate N-vacancy defects firmly via π-π interactions, forming Z-scheme heterogenous structure for promoting charge separation. The visible and near-infrared light driven photocatalytic hydrogen evolution rate is up to 3420 µmol h-1 g-1, and the removal ratio of organic contaminant methylene blue is up to 98% within 70 min, which is several times higher than that of pristine graphitic carbon nitride and DCN. The important reason is the defects of DCN not only enhance the interaction with PDA, but also make the obvious polarized inbuilt electric field, and lead to Z-scheme structure for effective charge separation and rapid transfer, which is also confirmed by density functional theory (DFT) calculations. In addition, PDA extends the photoresponse to the near-infrared region and induces obvious photothermal effect to increase the reaction rate of the photocatalytic system. The efficient photothermal conversion of PDA/DCN should be another reason for the enhanced photocatalytic performance.
RESUMEN
Low charge separation efficiency of semiconductor materials is the main obstacle for high-performance photocatalyst. Herein, we report surface defects engineered uniform mesoporous TiO2 nanospheres (DMTNSs) through surfactant-mediated self-assembly solvothermal approach combined with hydrogenation strategy to promote charge separation. The surface defects induced charge imbalance result in the formation of built-in field, which can promote photogenerated charge separation efficiently and be confirmed by experimental and density functional theory (DFT) calculations. Under AM 1.5G irradiation, the photocatalytic hydrogen evolution of DMTNSs is ~3.34 mmol h-1 g-1, almost 3.5 times higher than that of pristine non-defective TiO2 nanospheres (0.97 mmol h-1 g-1), due to the engineered surface defects narrowing the bandgap (~3.01 eV) and inducing charge imbalance to boost spatial charge separation and extend visible-light response. The defect induced charge imbalance strategy opens a new valuable perspective for fabricating other high-efficient oxide photocatalysts.
RESUMEN
The low charge separation efficiency and sunlight utilisation of traditional titanium dioxide (TiO2) nanoparticle photocatalysts greatly limit their applications. Herein, one-dimensional (1D) mesoporous anatase TiO2 nanotubes with engineered surface defects are fabricated using a combination of simple solvothermal synthesis and high-temperature surface hydrogenation strategy. The obtained mesoporous anatase TiO2 nanotubes with mesopores in the nanotube walls and a specific surface area of 110 m2 g-1 decrease the bandgap from 3.18 to 2.98 eV, enhancing the photoresponse to the visible-light region of the solar spectrum. The defective mesoporous anatase TiO2 nanotubes exhibited an excellent photocatalytic hydrogen evolution rate of 9.8 mmol h-1 g-1, which is approximately 2.5 times higher than that of the pristine anatase TiO2 nanotubes. This can be ascribed to the engineered surface defects and 1D mesoporous nanotube structure favouring efficient spatial charge separation on the horizontal-vertical dimensions, enabling visible-light absorption and exposing abundant surface active sites. This study provides a facile and feasible strategy for the fabrication of high-performance 1D mesostructured semiconductor oxide photocatalysts for efficient solar energy conversion.
RESUMEN
Ferrate(VI) is an efficient multi-functional water treatment reagent that has several novel properties, such as strong oxidation, absorption, flocculation, disinfection and deodorization. The removal of cationic surfactants based on ferrate (K2FeO4) was performed in the case of cetylpyridinium bromide (CPB). The inï¬uence of operating variables on the mineralization efficiency was studied as a function of ferrate dosage, initial pH and reaction time. Total organic carbon (TOC), UV and infrared spectra were performed to gain a better understanding of the degradation process. Results show that the optimal treatment conditions are as follows, solution initial pH is over 5, oxidation time is 5 min and ferrate dosage is 1.5 times that of CPB. The removal efficiency of CPB above 99% and TOC removal percentage of 91.3% can be achieved in minutes. The reaction of CPB with K2FeO4 responds to a second-order kinetic law.