Research into the evaporation of solutions is not only aimed at a better understanding the physics of evaporation, but increasingly at capitalizing on the extremely simple method it offers to ...assemble diverse nonvolatile solutes into complex ordered structures on the submicron and longer length scales. This Review highlights recent advances in evaporative assembly of confined solutions, focusing especially on recently developed approaches that provide structures with unprecedented regularity composed of polymers, nanoparticles, and biomaterials, by controlled evaporation‐driven, flow‐aided self‐assembly. A broad range of variables that can control the deposition are explored and the future directions of this rich field are presented.
Drying out: The evaporation of solutions of nonvolatile solutes is one way to generate complex ordered structures. An array of facile and robust preparative strategies based on controlled evaporative self‐assembly (CESA) of confined solutions have been exploited to rationally assemble various soft and hard materials into spatially ordered structures (see picture) with engineered properties and functionality over large surface areas.
The past several decades have witnessed significant advances in the synthesis and applications of PIEZOelectric semiconductors, an important class of materials, including piezoelectric, pyroelectric, ...and ferroelectric semiconductors. The intriguing combination of physical and chemical phenomena in PIEZOelectric semiconductors has triggered much interest in PIEZOcatalysis, that is, catalysis enabled by PIEZOpotential (i.e., piezopotential, pyropotential, and ferropotential)‐induced built‐in electric fields, which is the focus of this Minireview. First, the PIEZOelectric materials are briefly introduced. Second, recent developments in PIEZOcatalysis are highlighted, including the introduction of representative PIEZOelectric semiconductors, their possible catalytic mechanisms, novel techniques to produce their PIEZOelectric effects during the catalytic process, and several examples of PIEZOcatalysis. Finally, the challenges in the field and exciting opportunities to further improve the PIEZOcatalytic efficiency are discussed.
Piezo de résistance: This Minireview summarizes recent advances in PIEZOelectric‐semiconductor‐enabled PIEZOcatalysis resulting from PIEZOpotential (i.e., piezopotential, pyropotential, and ferropotential)‐induced built‐in electric fields. The challenges in this field and various opportunities for further improvement in the PIEZOcatalytic efficiency are also discussed.
A climax in the development of cost-effective and high-efficiency transition metal-based electrocatalysts has been witnessed recently for sustainable energy and related conversion technologies. In ...this regard, structure-activity relationships based on several descriptors have already been proposed to rationally design electrocatalysts. However, the dynamic reconstruction of the surface structures and compositions of catalysts during electrocatalytic water oxidation, especially during the anodic oxygen evolution reaction (OER), complicate the streamlined prediction of the catalytic activity. With the achievements in
operando
and
in situ
techniques, it has been found that electrocatalysts undergo surface reconstruction to form the actual active species
in situ
accompanied with an increase in their oxidation state during OER in alkaline solution. Accordingly, a thorough understanding of the surface reconstruction process plays a critical role in establishing unambiguous structure-composition-property relationships in pursuit of high-efficiency electrocatalysts. However, several issues still need to be explored before high electrocatalytic activities can be realized, as follows: (1) the identification of initiators and pathways for surface reconstruction, (2) establishing the relationships between structure, composition, and electrocatalytic activity, and (3) the rational manipulation of
in situ
catalyst surface reconstruction. In this review, the recent progress in the surface reconstruction of transition metal-based OER catalysts including oxides, non-oxides, hydroxides and alloys is summarized, emphasizing the fundamental understanding of reconstruction behavior from the original precatalysts to the actual catalysts based on operando analysis and theoretical calculations. The state-of-the-art strategies to tailor the surface reconstruction such as substituting/doping with metals, introducing anions, incorporating oxygen vacancies, tuning morphologies and exploiting plasmonic/thermal/photothermal effects are then introduced. Notably, comprehensive
operando
/
in situ
characterization together with computational calculations are responsible for unveiling the improvement mechanism for OER. By delivering the progress, strategies, insights, techniques, and perspectives, this review will provide a comprehensive understanding of the surface reconstruction in transition metal-based OER catalysts and future guidelines for their rational development.
The recent progress in activating surface reconstruction by integrating advanced characterizations with theoretical calculations for high-efficiency oxygen evolution reaction is reviewed.
Thermoelectric materials have garnered considerable attention due to their unique ability to directly convert heat to electricity and
vice versa
. Polymers carry many intrinsic advantages such as low ...thermal conductivity, solution processability, and roll-to-roll production for fabricating high-performance, light-weight, and flexible thermoelectric modules. In this review, we highlight recent advances in the preparation, modification and optimization of polymer thermoelectric materials, focusing especially on the current state-of-the-art strategies to minimize the thermal conductivity and maximize the power factor, and finally provide an outlook on the future development of this field.
Recent advances in the preparation, modification and optimization of polymer thermoelectric materials are reviewed.
Semiconductor photocatalysis is a promising physicochemical process for the photodegradation of organic contaminants and bacterial detoxification. Among various oxide semiconductor photocatalysts, ...TiO
2
has garnered considerable attention because of its outstanding properties including strong oxidizing activity, chemical and mechanical stability, corrosion resistance, and nontoxicity. This Review briefly introduces the key mechanisms of photocatalysis, highlights the recent developments pertaining to pure TiO
2
nanotube arrays and TiO
2
nanotube arrays modified by non-metals, metals and semiconductors, and their applications in the photocatalytic degradation of organic dyes. The improved photocatalytic efficiencies of modified TiO
2
nanotube arrays are compared with unmodified counterparts. Current challenges and prospective areas of interest in this rich field are also presented.
This Review highlights the recent developments pertaining to pure and modified TiO
2
nanotube arrays for photocatalysis.
Hydrogels are three‐dimensional (3D) crosslinked hydrophilic polymer networks that have garnered tremendous interests in many fields, including water treatment, energy storage, and regenerative ...medicine. However, conventional synthetic polymer hydrogels have poor biocompatibility. In this context, polysaccharides, a class of renewable natural materials with biocompatible and biodegradable properties, have been utilized as building blocks to yield polysaccharide‐based hydrogels through physical and/or chemical crosslinking of polysaccharides via a variety of monomers or ions. These polysaccharide‐derived hydrogels exhibit peculiar physicochemical properties and excellent mechanical properties due to their unique structures and abundant functional groups. This review focuses on recent advances in synthesis and applications of polysaccharide‐based hydrogels by capitalizing on a set of biocompatible and biodegradable polysaccharides (i.e., cellulose, alginate, chitosan, and cyclodextrins CDs). First, we introduce the design and synthesis principles for crafting polysaccharide‐based hydrogels. Second, polysaccharide‐based hydrogels that are interconnected via various crosslinking strategies (e.g., physical crosslinking, chemical crosslinking, and double networking) are summarized. In particular, the introduction of noncovalent and/or dynamic covalent interactions imparts polysaccharide‐based hydrogels with a myriad of intriguing performances (e.g., stimuli–response and self‐recovery). Third, the diverse applications of polysaccharide‐based hydrogels in self‐healing, sensory, supercapacitor, battery, drug delivery, wound healing, tissues engineering, and bioimaging fields are discussed. Finally, the perspectives of polysaccharide‐based hydrogels that promote their future design to enable new functions and applications are outlined.
The review presents the recent progresses in the design and synthesis of a series of polysaccharide‐based (i.e., cellulose, alginate, chitosan, and CDs) hydrogels as well as their potential applications in self‐healing hydrogels, sensors, energy storage and conversion as well as biomedical fields over the past decade.
Concerns over air quality reduction resulting from burning fossil fuels have driven the development of clean and renewable energy sources. Supercapacitors, batteries and solar cells serve as ...eco-friendly energy storage and conversion systems vitally important for the sustainable development of human society. However, many diverse elements influence the performance of energy storage and conversion systems. The overall efficiency of systems depends on the specific structure and properties of incorporated functional materials. Carbon materials, such as graphene, are especially promising for materials development in the energy storage and conversion fields. Graphene, a two-dimensional (2D) carbon material only a single atom thick, has massless Dirac fermions (electron transport is governed by Dirac's equation), displays outstanding electrical conductivity, superior thermal conductivity and excellent mechanical properties. 2D free-standing graphene films and powders have paved the way for promising energy applications. Recently, much effort has been spent trying to improve the number of active sites in electrode materials within 3D network/aerogel structures derived from graphene. This is because graphene aerogels are promising materials for energy systems due to their porous hierarchical structure which affords rapid electron/ion transport, superior chemical and physical stability, and good cycle performance. This review aims to summarize the synthetic methods, mechanistic aspects, and energy storage and conversion applications of novel 3D network graphene, graphene derivatives and graphene-based materials. Areas of application include supercapacitors, Li-batteries, H
2
and thermal energy storage, fuel cells and solar cells.
Concerns over air quality reduction and energy crisis resulting from rapid consumption of limited fossil fuels have driven the development of clean and renewable energy sources.
TiO2 nanotube arrays (TNTAs) sensitized by palladium quantum dots (Pd QDs) exhibit highly efficient photoelectrocatalytic hydrogen generation. Vertically oriented TNTAs were prepared by a three-step ...electrochemical anodization. Subsequently, Pd QDs with uniform size and narrow size distribution were formed on TiO2 nanotubes by a modified hydrothermal reaction (i.e., yielding nanocomposites of Pd QDs deposited on TNTAs, Pd@TNTAs). By exploiting Pd@TNTA nanocomposites as both photoanode and cathode, a substantially increased photon-to-current conversion efficiency of nearly 100% at λ = 330 nm and a greatly promoted photocatalytic hydrogen production rate of 592 μmol·h–1·cm–2 under 320 mW·cm–2 irradiation were achieved. The synergy between nanotubular structures of TiO2 and uniformly dispersed Pd QDs on TiO2 facilitated the charge transfer of photoinduced electrons from TiO2 nanotubes to Pd QDs and the high activity of Pd QDs catalytic center, thereby leading to high-efficiency photoelectrocatalytic hydrogen generation.
In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable ...electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.
This review describes an in-depth overview and knowledge on the variety of synthetic strategies for forming metal sulfides and their potential use to achieve effective hydrogen generation and beyond.
Dye-sensitized solar cells (DSSCs) based on hierarchically structured TiO2 nanotubes prepared by a facile combination of two-step electrochemical anodization with a hydrothermal process exhibited ...remarkable performance. Vertically oriented, smooth TiO2 nanotube arrays fabricated by a two-step anodic oxidation were subjected to hydrothermal treatment, thereby creating advantageous roughness on the TiO2 nanotube surface (i.e., forming hierarchically structured nanotube arraysnanoscopic tubes composed of a large number of nanoparticles on the surface) that led to an increased dye loading. Subsequently, these nanotubes were exploited to produce DSSCs in a backside illumination mode, yielding a significantly high power conversion efficiency, of 7.12%, which was further increased to 7.75% upon exposure to O2 plasma.
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