Zhihao Zhao

0D/2D Heterojunctions of Vanadate Quantum Dots/Graphitic Carbon Nitride Nanosheets for Enhanced Visible-Light-Driven Photocatalysis

0D/2D heterojunctions, especially quantum dots (QDs)/nanosheets (NSs) have attracted significant attention for use of photoexcited electrons/holes due to their high charge mobility. Herein, unprecedent heterojunctions of vanadate (AgVO3 , BiVO4 , InVO4 and CuV2 O6 ) QDs/graphitic carbon nitride (g-C3 N4 ) NSs exhibiting multiple unique advances beyond traditional 0D/2D composites have been developed. The photoactive contribution, up-conversion absorption, and nitrogen coordinating sites of g-C3 N4 NSs, highly dispersed vanadate nanocrystals, as well as the strong coupling and band alignment between them lead to superior visible-light-driven photoelectrochemical (PEC) and photocatalytic performance, competing with the best reported photocatalysts. This work is expected to provide a new concept to construct multifunctional 0D/2D nanocomposites for a large variety of opto-electronic applications, not limited in photocatalysis.

The evolution mechanism of defect dipoles and high strain in MnO2-doped KNN lead-free ceramics

Defect dipoles in acceptor-doped (K0.5Na0.5)NbO3-based ceramics have a significant influence on their electrical properties. The present study examined the influence of the sintering atmosphere on the electrical properties of MnO2-doped (K0.5Na0.5)NbO3. The poled and aged samples sintered in the Ar atmosphere depicted unusual behavior related to the formation of defect dipoles (Mn2+Nb‴−VO··)′, aligned in the poling direction having larger polarity. The S-E loop of the poled and aged MnO2-doped (K0.5Na0.5)NbO3 ceramics sintered in the Ar atmosphere revealed larger strains in the poling direction and restrained strains in the opposite direction. Furthermore, it is observed that the unipolar electro-strain could reach 0.28% (d33*u2009=u2009800u2009pm/V) at 3.5u2009kV/mm, a value nearly 5.6-fold higher than those obtained in the air atmosphere (0.05%). This method based on the sintering atmosphere and process control provides a promising way to obtain substantial electro-strain values suitable for applications in high-displa...

SiOC nanolayer wrapped 3D interconnected graphene sponge as a high-performance anode for lithium ion batteries

Silicon oxycarbides (SiOCs) are promising anode materials for high-energy LIBs because of their high theoretical capacity. However, due to their intrinsically poor electronic conductivity, the battery performance is often restricted. Herein, high performance anodes are demonstrated by designing a hierarchical 3D interconnected structure using graphene sponge as a scaffold. The graphene sponge was infiltrated with a polysiloxane precursor and further converted into porous frameworks consisting of multi-layered sandwich-like nanosheets (SiOC@graphene@SiOC) by subsequent pyrolysis. The deliberate structure not only improved the electrical conductivity, accelerated ion insertion, and shortened the ionic diffusion distance but also enabled full utilization of SiOC active sites in the anode. The 3D-GNS/SiOC anodes exhibited excellent electrochemical performance, including high initial discharge capacity (1280xa0mA h g−1 at 0.1 A g−1), high reversibility and stability (701 mA h g−1/371 μA h cm−2 after 100 cycles) and extreme rate performance (656 mA h g−1/348 μA h cm−2 at 0.5 A g−1). For full-cells, high initial charge capacity (680 mA h g−1 at 0.5 A g−1) and high stability (416 mA h g−1 at 0.5 A g−1 after 100 cycles) were obtained. Significantly, this simple and scalable method can be extended to fabricate high-rate and long-cycle SiOC or other anode materials for commercial LIBs.

Enhanced electromechanical strain response in (Fe 0.5 Nb 0.5 ) 4+ -modified Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 lead-free piezoelectric ceramics

By the traditional solid-state reaction method, Bi0.5(Na0.8K0.2)0.5Ti1−x(Fe0.5Nb0.5)xO3 (marked as BNKT-xFN; xxa0=xa00.00, 0.01, 0.02, 0.03 and 0.04) piezoelectric ceramics were fabricated, and the effects of FN substitution on the dielectric, ferroelectric, piezoelectric and electric field-induced strain performance were investigated. The relative dielectric permittivity and loss tangent reveal that the phase transition temperature between ferroelectric and ergodic relaxor phase is reduced from 90xa0°C to room temperature (RT), even below RT, with increasing FN content. Temperature dependence of polarization–electric field loops and strain-electric field curves exhibits that the ferroelectric order is disturbed gradually, and the ergodic relaxor phase forms with increasing FN content. A large unipolar strain of 0.42% and corresponding d33* (=xa0Smax/Emax) of 642xa0pm/V for the sample with xxa0=xa00.04 are obtained under 6.5xa0kV/mm due to the phase transition from ergodic relaxor to ferroelectric. These results indicate that the (Fe0.5Nb0.5)4+ complex ion-modified BNKT-based ceramics would have great potentials for lead-free electromechanical actuator applications.