Enhanced photoelectrochemical performance of ZnO/NiFe-layered double hydroxide for water splitting: Experimental and photo-assisted density functional theory calculations.

Hydrogen production technologies have attracted considerable attention with the increasing demand for renewable energy. Among them, the combined action of water electrolysis and solar energy has emerged. In this study, a hydrangea ZnO/NiFe-layered double hydroxide (LDH) heterojunction was synthesized using the two-step hydrothermal method. The resulting ZnO/NiFe-LDH improved the range and intensity of light response, thus meeting the requirement of electrocatalysis and photocatalysis in theory. Moreover, ZnO/NiFe-LDH demonstrated excellent activity in the electrochemical performance test in the presence of light. When used as a water splitting catalyst in a full cell, the cell voltage was 1.632 V, and Faradic efficiency was 99.1%. Moreover, from the in situ Raman and theoretical calculation results, it is possible to conclude that the synthesized ZnO/NiFe-LDH has the property of absorbing light energy, and the introduction of light energy can optimize the bandgap structure of the material and enhance the adsorption capacity of the system, thus significantly reducing the energy required for water splitting reaction. In sum, this study introduced a composition strategy for LDH heterojunction materials and presented a theoretical and experimental investigation of the light influence on the material structure and electrochemical reaction. Furthermore, it is believed that an important future direction of hydrogen production is photo-assisted water splitting.

Paraffin-Enabled Compressive Folding of Two-Dimensional Materials with Controllable Broadening of the Electronic Band Gap.

The capability to manipulate the size of the electronic band gap is of importance to semiconductor technology. Among these, a wide direct band gap is particularly helpful in optoelectronic devices due to the efficient utilization of blue and ultraviolet light. Here, we reported a paraffin-enabled compressive folding (PCF) strategy to widen the band gap of two-dimensional (2D) materials. Due to the large thermal expansion coefficient of paraffin, folded 2D materials can be achieved via thermal engineering of the paraffin-assisted transfer process. It can controllably introduce 0.2-1.3% compressive strain onto folded structures depending on the temperature differences and transfer the folding product to both rigid and soft substrates. Exemplified by MoS2, its folded multilayers demonstrated blue-shifts at direct gap transition peaks, six times stronger photoluminescence intensity, almost double mobility, and 20 times higher photoresponsivity over unfolded MoS2. This PCF strategy can attain controllable widening band gap of 2D materials, which will open up novel applications in optoelectronics.

Bifunctional organocatalysts for the conversion of CO2, epoxides and aryl amines to 3-aryl-2-oxazolidinones.

A route to synthesize 3-aryl-2-oxazolidinones is developed, which is achieved through a three component reaction between CO2, aryl amines, and epoxides with a binary organocatalytic system composed of organocatalysts and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The method allows wide scopes of epoxide and aryl amine substrates with various functional groups under mild reaction conditions. The control experiments indicate that a cyclic carbonate is formed via cycloaddition of epoxides with CO2, which further reacts with the ß-amino alcohol originating from epoxides and aryl amines, resulting in the formation of 3-aryl-2-oxazolidinones finally.

Direct growth of semiconducting single-walled carbon nanotube array.

By introducing the UV beam into our homemade chemical vapor deposition system, we had obtained a well aligned SWNT array on an ST-cut quartz substrate. After transfer onto a SiO(2)/Si substrate, the SWNT array was detected by Raman spectroscopy and electrical measurement, which showed that over 95% of the SWNTs were semiconducting ones. It is proposed that the selection process took place at the very beginning of the SWNT formation rather than destroying the metallic SWNTs after growth. This approach has solved one of the most important problems in SWNT application.