ABSTRACT
A deep understanding of the shaping technique is urgently required to precisely tailor the pore structure of a graphene aerogel (GA) in order to fit versatile application backgrounds. In the present study, the microstructure and properties of GA were regulated by freeze-casting using an ice crystal template frozen from -10 °C to -196 °C. The phase field simulation method was applied to probe the microstructural evolution of the graphene-H2O system during freezing. Both the experimental and simulation results suggested that the undercooling degree was fundamental to the nucleation and growth of ice crystals and dominated the derived morphology of GA. The pore size of GA was largely regulated from 240 to 6 µm via decreasing the freezing temperature from -10 °C to -196 °C but with a constant density of 8.3 mg cm-3. Rapid freeze casting endowed GA with a refined pore structure and therefore better thermal, electrical, and compressive properties, whereas the GA frozen slowly had superior absorption properties owing to the continuous and tube-like graphene lamellae. The GA frozen at -196 °C exhibited the highest Young's modulus of 327 kPa with similar densities to those reported in the literature. These findings demonstrate the diverse potential applications of GA with regulated pore morphologies and also contribute to cryogenic-induced phase separation methods.
ABSTRACT
Graphdiyne (GDY), a new member of 2D carbon material family, was introduced into a Si heterojunction (SiHJ)-based photoelectrochemical water splitting cell. With assistance of magnetron-sputtered NiOx, the plateau photocurrent density of SiHJ/GDY/NiO x-10 nm with optimized NiO x film thickness was twice higher than that of SiHJ/NiO x-10 nm, demonstrating the catalytic function of GDY itself as well as the synergistic effect between GDY and NiO x. The results verified that GDY is a promising photoelectrode material candidate to realize highly efficient PEC performance, and pave a novel pathway to further improve Si-based PEC system.
ABSTRACT
2D transition metal dichalcogenide (2D-TMD) materials and their van der Waals heterostructures (vdWHs) have inspired worldwide efforts in the fields of electronics and optoelectronics. However, photodetectors based on 2D/2D vdWHs suffer from performance limitations due to the weak optical absorption of their atomically thin nature. In this work, taking advantage of an excellent light absorption coefficient, low-temperature solution-processability, and long charge carrier diffusion length, all-inorganic halides perovskite CsPbI3- x Br x quantum dots are integrated with monolayer MoS2 for high-performance and low-cost photodetectors. A favorable energy band alignment facilitating interfacial photocarrier separation and efficient carrier injection into the MoS2 layer inside the 0D-2D mixed-dimensional vdWHs are confirmed by a series of optical characterizations. Owing to the synergistic effect of the photogating mechanism and the modulation of Schottky barriers, the corresponding phototransistor exhibits a high photoresponsivity of 7.7 × 104 A W-1, a specific detectivity of ≈5.6 × 1011 Jones, and an external quantum efficiency exceeding 107%. The demonstration of such 0D-2D mixed-dimensional heterostructures proposed here would open up a wide realm of opportunities for designing low-cost, flexible transparent, and high-performance optoelectronics.
