Showing papers by "Zhong Chen published in 2021"

Advanced Materials with Special Wettability toward Intelligent Oily Wastewater Remediation.

Abstract: Clean water resources are essential to our human society. Oil leakage has caused water contamination, which leads to serious shortage of clean water, environmental deterioration, and even increasing number of deaths. It is of great urgency to solve the oil-polluted water problems worldwide. Efficient oil/water separation, especially emulsified oil/water mixture separation, is widely used to mitigate water pollution issues. Recently, advanced materials with special wettability have been employed for oily wastewater remediation. Moreover, by endowing them with various intelligent functions, smart materials can effectively separate complex oil/water mixtures including extremely stable emulsions. In this review, oil/water separation mechanisms and various fabrication methods of special wettability separation materials are summarized. We highlight the special wettable materials with intelligent functions, including photocatalytic, self-healing, and switchable oil/water separation materials, which can achieve self-cleaning, self-healing, and efficient oily wastewater treatment. In each section, the acting mechanisms, fabricating technologies, representative studies, and separation efficiency are briefly introduced. Lastly, the challenges and outlook for oil/water separation based on the special wettability materials are discussed.

A fundamental viewpoint on the hydrogen spillover phenomenon of electrocatalytic hydrogen evolution.

Abstract: Hydrogen spillover phenomenon of metal-supported electrocatalysts can significantly impact their activity in hydrogen evolution reaction (HER). However, design of active electrocatalysts faces grand challenges due to the insufficient understandings on how to overcome this thermodynamically and kinetically adverse process. Here we theoretically profile that the interfacial charge accumulation induces by the large work function difference between metal and support (∆Φ) and sequentially strong interfacial proton adsorption construct a high energy barrier for hydrogen transfer. Theoretical simulations and control experiments rationalize that small ∆Φ induces interfacial charge dilution and relocation, thereby weakening interfacial proton adsorption and enabling efficient hydrogen spillover for HER. Experimentally, a series of Pt alloys-CoP catalysts with tailorable ∆Φ show a strong ∆Φ-dependent HER activity, in which PtIr/CoP with the smallest ∆Φ = 0.02 eV delivers the best HER performance. These findings have conclusively identified ∆Φ as the criterion in guiding the design of hydrogen spillover-based binary HER electrocatalysts. Despite the significance of hydrogen spillover on metal-supported electrocatalysts for hydrogen evolution, fundamental understandings on such a process are insufficient. Here the authors show that small work function difference between metal and support facilitates hydrogen spillover and enhances activity.

Recent advances in fabricating durable superhydrophobic surfaces: a review in the aspects of structures and materials

Abstract: Extensive attention has been concentrated toward the development of superhydrophobic coatings with unique structures and properties due to their extended applications in our daily life. However, the poor durability and short service life have greatly restricted the practical applications of superhydrophobic materials. The surface rough structure and material chemistry are important factors affecting the durability of superhydrophobic coatings. Only through fully understanding the roles played by the structure and material can we combine their advantages to prepare extremely durable coatings. In this review, we discuss ways to prolong the life-time of superhydrophobic surfaces (SHSs) in two aspects, namely the surface structures and materials. The strategy of rational design of hierarchical structures with or without special shapes, and addition of supportive structural shelters can effectively enhance the resistance to damage. The use of functional materials, such as self-healing materials, fully functionalized monolithic materials, elastic materials, and strong adhesive materials is another intelligent strategy to maintain superhydrophobicity against severe mechano-chemical attacks. This review provides a systematic account of the strategies together with deep fundamental insights for the development of durable superhydrophobic surfaces towards practical applications.

Underwater, Multifunctional Superhydrophobic Sensor for Human Motion Detection

Abstract: Superhydrophobic conductive materials have received a great amount of interest due to their wide applications in oil-water separation, electrically driven smart surface, electromagnetic shielding, and body motion detection. Herein, a highly conductive superhydrophobic cotton cloth is prepared by a facile method. A layer of polydopamine/reduced graphene oxide (PDA/rGO) was first coated on the cotton fabric, and then copper nanoparticles were in situ grown on the prepared surface. After further modification with stearic acid (STA), the wettability of the cotton surface changed from superhydrophilic to superhydrophobic (water contact angle (WCA) = 153°). The electrical conductivity of the PDA/rGO/Cu/STA cotton is as high as 6769 S·m-1, while the stearic acid effectively protects Cu NPs from oxidation. As a result, the superhydrophobic PDA/rGO/Cu/STA cotton has shown excellent electrical stability and can be used in detecting human motions in both ambient and underwater conditions. The sensor can recognize human motion from air into water and other underwater activities (e.g., underwater bending, stretching, and ultrasound). This multifunctional cotton device can be used as an ideal sensor for underwater intelligent devices and provides a basis for further research.

Tailoring Electronic Structure and Size of Ultrastable Metalated Metal–Organic Frameworks with Enhanced Electroconductivity for High-Performance Supercapacitors

Abstract: Utilization of metal-organic frameworks (MOFs) as electrodes for energy storage/conversion is challenging because of the low chemical stability and poor electrical conductivity of MOFs in electrolytes. A nanoscale MOF, Co0.24 Ni0.76 -bpa-200, possessing ultrahigh stability with uncommon semiconductor behavior (σ=4.2×10-3 S m-1 ) was fabricated. The MOF comprises a robust hydrophobic paddlewheel and an optimized Co/Ni ratio, with consequent control over MOF size and the degree of conjugation of the coligand. A DFT study revealed that appropriate Ni2+ doping reduces the activation energy of the system, thus providing a higher carrier concentration, and the strongly delocalized N-donor ligand notably increases the metal-ligand orbital overlap to achieve efficient charge migration, leading to continuous through-bond (-CoNi-N-CoNi-)∞ conduction paths. These structural features endow the MOF with a good cycling stability of 86.5 % (10 000 cycles) and a high specific capacitance of 1927.14 F g-1 among pristine MOF-based electrodes.

Perspectives on UVC LED: Its Progress and Application

Abstract: High-quality epitaxial layers are directly related to internal quantum efficiency. The methods used to design such epitaxial layers are reviewed in this article. The ultraviolet C (UVC) light-emitting diode (LED) epitaxial layer structure exhibits electron leakage; therefore, many research groups have proposed the design of blocking layers and carrier transportation to generate high electron–hole recombination rates. This also aids in increasing the internal quantum efficiency. The cap layer, p-GaN, exhibits high absorption in deep UV radiation; thus, a small thickness is usually chosen. Flip chip design is more popular for such devices in the UV band, and the main factors for consideration are light extraction and heat transportation. However, the choice of encapsulation materials is important, because unsuitable encapsulation materials will be degraded by ultraviolet light irradiation. A suitable package design can account for light extraction and heat transportation. Finally, an atomic layer deposition Al2O3 film has been proposed as a mesa passivation layer. It can provide a low reverse current leakage. Moreover, it can help increase the quantum efficiency, enhance the moisture resistance, and improve reliability. UVC LED applications can be used in sterilization, water purification, air purification, and medical and military fields.

Robust Superhydrophobic rGO/PPy/PDMS Coatings on a Polyurethane Sponge for Underwater Pressure and Temperature Sensing.

Abstract: Flexible wearable pressure sensors have attracted great interest from researchers in recent years because of their important applications in human-machine interaction, human behavior detection, medical diagnosis, and other fields. At present, integrating multiple functions such as pressure and temperature sensing and self-cleaning into a single material remains a challenging task. Here, by in situ reduction of graphene oxide (GO) grown on a sponge surface and deposition of polypyrrole (PPy) nanoparticles, we have built a highly sensitive, stable, and multifunctional rGO/PPy/poly(dimethylsiloxane) (PDMS) polyurethane (PU) sponge (GPPS) sensor for the detection of pressure, water level, and temperature. This multifunctional sensor shows excellent pressure-sensing performance, ultrasensitive loading sensing of a leaf (98 mg), and outstanding reproducibility over 5000 cycles. Due to the stability of the superhydrophobic surface water contact angle (WCA) = 153.3°, our sensor can work in an underwater environment, which can sense water levels from 1 cm (∼98 Pa) to 40 cm and also a variety of underwater behaviors (knock, ultrasonication, blow, etc.) with high stability. In addition, the sensor can be integrated into a circuit for the water level and pressure detection. The sensor can also be used as a smart underwater-temperature sensor; it shows a linear temperature coefficient of resistance (TCR) of 0.48% °C-1 in a temperature range of 35-80 °C. This multifunctional sensor shows potential application prospects in wearable electronic devices for sensing.

Bioinspired structural and functional designs towards interfacial solar steam generation for clean water production

Abstract: Fresh water shortage is rapidly emerging as a global crisis, threatening the future development of human society. Extracting fresh water from seawater, wastewater and even atmospheric water efficiently has become a critical challenge to the research community. In recent years, solar-driven evaporation has aroused enormous research interest owing to its low-cost and sustainable potential. As a new bioinspired approach for clean water production, interfacial solar steam generation makes direct use of solar energy to generate water steam through latent heat. Fresh water can then be collected by condensing the water steam on a colder substrate. To date, quite a number of photothermal materials and rational structure designs for efficient solar evaporators have been reported. In this review, the design principles and evaporation systems for interfacial solar evaporation are summarized. Multifunctional designs of evaporators, salt-rejection, and antifouling capability are also discussed, which is of great significance to long-term and efficient solar water collection. In the last section, some prospects for the development of solar evaporators are proposed.

CsPbBr 3 perovskite quantum-dot paper exhibiting a highest 3 dB bandwidth and realizing a flexible white-light system for visible-light communication

Abstract: We propose a flexible white-light system for high-speed visible-light communication (VLC) applications, which consists of a semipolar blue InGaN/GaN single-quantum-well micro-light-emitting diode (LED) on a flexible substrate pumping green CsPbBr3 perovskite quantum-dot (PQD) paper in nanostructure form and red CdSe QD paper. The highest bandwidth for CsPbBr3 PQD paper, 229 MHz, is achieved with a blue micro-LED pumping source and a high data transmission rate of 400 Mbps; this is very promising for VLC application. An 817 MHz maximum bandwidth and a 1.5 Gbps transmission speed are attained by the proposed semipolar blue micro-LEDs. The proposed flexible white light system and the high-bandwidth PQD paper could pave the way for VLC wearable devices.

Highly stable full-color display device with VLC application potential using semipolar μLEDs and all-inorganic encapsulated perovskite nanocrystal

Abstract: A promising approach for the development of effective full-color displays is to combine blue microLEDs (μLEDs) with color conversion layers. Perovskite nanocrystals (PNCs) are notable for their tolerance to defects and provide excellent photoluminescence quantum yields and high color purity compared to metal chalcogenide quantum dots. The stability of PNCs in ambient conditions and under exposure to blue light can be improved using a SiO2 coating. This study proposes a device that could be used for both display and visible light communication (VLC) applications. The semipolar blue μLED array fabricated in this study shows a negligible wavelength shift, indicating a significant reduction in the quantum confined Stark effect. Owing to its shorter carrier lifetime, the semipolar μLED array exhibits an impressive peak 3 dB bandwidth of 655 MHz and a data transmission rate of 1.2 Gb/s corresponding to an injection current of 200 mA. The PNC–μLED device assembled from a semipolar μLED array with PNCs demonstrates high color stability and wide color-gamut features, achieving 127.23% and 95.00% of the National Television Standards Committee standard and Rec. 2020 on the CIE 1931 color diagram, respectively. These results suggest that the proposed PNC–μLED device is suitable for both display-related and VLC applications.

Cobalt tungsten phosphide with tunable W-doping as highly efficient electrocatalysts for hydrogen evolution reaction

Abstract: It has been of interest in seeking electrocatalysts that could exercise equally high-efficient and durable hydrogen evolution upon nonselective electrolytes in both acidic and alkaline environments. Herein, we report a facile strategy to fabricate cobalt tungsten phosphides (CoxW2−xP2/C) hollow polyhedrons with tunable composition based on metal-organic frameworks (MOFs) template method. By the deliberate control of W doping, the synthesized catalyst with the composition of Co0.9W1.1P2/C is found to be able to achieve a current density of 10 mA·cm−2 at overpotentials of 35 and 54 mV in acidic and alkaline media, respectively. This combined electrochemical property stands atop the state-of-the-art electrocatalyst counterparts. To unveil the peculiar behavior of the structure, density functional theory (DFT) calculation was implemented and reveals that the surface W-doping facilitates the optimization of hydrogen absorption free energy (ΔGH*) as well as the thermodynamic and kinetics barriers for water dissociation, which is coupled with the hollow structure of Co-W phosphides, leading to the prominent HER catalytic performance.

All-inorganic encapsulation for remarkably stable cesium lead halide perovskite nanocrystals: toward full-color display applications

Abstract: Lead–halide perovskite nanocrystals (PeNCs), especially those composed of iodine, suffer from degradation problems. Water vapor, oxygen, light, and heat can damage PeNCs and consequently quench their photoluminescence (PL). Thus, robust encapsulation against all these stresses is urgently required. In this study, inorganic encapsulation of mesoporous SiO2, in conjunction with a high-temperature sintering synthesis process under an inert atmosphere, is introduced. This synthesis process is compatible with various halide contents, yielding PeNCs sealed in SiO2 particles that emit PL emission covering the entire visible range from 420 to 700 nm. The PeNCs–SiO2 sample showed remarkable stability after undergoing aging tests under various exaggerated stresses as well as mitigated thermal quenching during thermal cycling. The color gamut constituted by three PeNCs–SiO2 samples approached 135.36% NTSC and 101.07% Rec. 2020, with remarkable chromatic stability. The PeNCs–SiO2 can be blended into a photoresist and remains luminous during the development procedure, which is compatible with the photolithography process; this facilitates the mass production of color conversion layers. All these advantageous features show that the material proposed herein has great potential for application in full-color displays such as micro and mini light-emitting diode displays.

Solar-Assisted Isotropically Thermoconductive Sponge for Highly Viscous Crude Oil Spill Remediation

Abstract: Efficiently cleaning up high-viscosity crude oil spills is still a serious global problem. In this paper, a composite filler PPy-PDA/BN (PPB) with high photothermal effect and high thermal conductivity was first prepared. Then the polyurethane sponge is decorated with polydimethylsiloxane and PPB to obtain a solar-assisted isotropically thermoconductive adsorbent (PPB@PU), which exhibits remarkable stability and durable mechanical properties. Meanwhile, the PPB@PU sponge has good thermal conductivity, and its surface temperature rises to 91 °C in just 1 min under irradiation (1 sun). Therefore, the PPB@PU sponge can quickly heat and adsorb the crude oil contacted by the surface, significantly speed up the crude oil recovery process, and the adsorption capacity is as high as about 45 g/g. Finally, the oil adsorption method of the three-dimensional adsorbent is demonstrated, which provides a new idea for the subsequent development of advanced oil spill adsorbent.

A General Strategy towards Superhydrophobic Self-Cleaning and Anti-Corrosion Metallic Surfaces: An Example with Aluminum Alloy

Abstract: Corrosion and contamination of metallic structures can cause loss of their functionality as well as aesthetic values. In this study, we describe a general strategy to prepare superhydrophobic self-cleaning and anti-corrosion surfaces for metallic structures. As a specific example, a superhydrophobic coating (SHC) on aluminum alloy was prepared by a simple etching combined with the decoration of a low-surface-energy material. The optimal SHC has a water contact angle (CA) at ~157.4° and a sliding angle (SA) of ~8.3° due to the synergy of binary hierarchical structures and chemical modification. The SHC showed low adhesion to dry contaminants and a series of liquids, displaying a good self-cleaning effect. The SHC maintained superhydrophobicity after exposure to air and humid condition at 60 °C for 7 days. In addition, the electrochemical measurements reveal that the anti-corrosion performance was enhanced by reducing the corrosion current density (Jcorr) by 1 order of magnitude and increasing the corrosion potential (Ecorr) by 0.527 V as compared to the bare Al alloy substrate after immersion for 168 h.