Few‐layer carbon nitride photocatalysts for solar fuels and chemicals:Current status and prospects

Converting sunlight directly to fuels and chemicals is a great latent capacity for storing renewable energy.Due to the advantages of large surface area,short diffusion paths for electrons,and more exposed active sites,few‐layer carbon nitride(FLCN)materials present great potential for production of solar fuels and chemicals and set off a new wave of research in the last few years.Herein,the recent progress in synthesis and regulation of FLCN‐based photocatalysts,and their applications in the conversion of sunlight into fuels and chemicals,is summarized.More importantly,the regulation strategies from chemical modification to microstructure control toward the production of solar fuels and chemicals has been deeply analyzed,aiming to inspire critical thinking about the effective approaches for photocatalyst modification rather than developing new materials.At the end,the key scientific challenges and some future trend of FLCN‐based materials as advanced photocatalysts are also discussed.

First-principles study on the diffusion behavior of Cs and I in Cr coating

Cs and I can migrate through fuel-cladding interfaces and accelerate the cladding corrosion process induced by the fuel-cladding chemical interaction.Cr coating has emerged as an important candidate for mitigating this chemical interaction.In this study,first-principles calculations were employed to investigate the diffusion behavior of Cs and I in the Cr bulk and grain boundaries to reveal the microscopic interaction mitigation mechanisms at the fuel-cladding interface.The interaction between these two fission products and the Cr coating were studied systematically,and the Cs and I temperature-dependent diffusion coefficients in Cr were obtained using Bocquet’s oversized solute-atom model and Le Claire’s nine-frequency model,respectively.The results showed that the Cs and I migration barriers were significantly lower than that of Cr,and the Cs and I diffusion coefficients were more than three orders of magnitude larger than the Cr self-diffusion coefficient within the temperature range of Generation-IV fast reactors(below 1000 K),demonstrating the strong penetration ability of Cs and I.Furthermore,Cs and I are more likely to diffuse along the grain boundary because of the generally low migration barriers,indicating that the grain boundary serves as a fast diffusion channel for Cs and I.

Products and production routes for the catalytic conversion of seed oil into fuel and chemicals: a comprehensive review

With the depletion of fossil resources, there is a need to find alternative resources of fuels and chemicals. The use of renewable feedstock such as those from seed oil processing is one of the best available resources that have come to the fore-front recently. This paper critically analyzes and highlights major factors in the biodiesel industry, such as seeds oil composition, production methods, properties of biodiesel, problems and potential solutions of using vegetable seed oil, the composition, quality and effective utilization of crude glycerol, the catalytic conversion of glycerol into possible fuels and chemicals.

Microstructure Analysis for Chemical Interaction between Cesium and SUS316 Steel in Fast Breeder Reactor Application

The objective of this study is to presume cesium corrosion process and its dominant factors in SUS316 steel, a fuel cladding material for fast breeder reactor application, based on both experimental results of cesium corrosion out-pile test and thermodynamic consideration. The cesium corrosion test was performed in simulated environment of high burn-up fuel pin. And main corrosion products in the specimen after the corrosion test were specified by TEM （transition electron microscopy） and SEM （scanning electron microscopy） in order to formulate a hypothesis of the cesium corrosion process. At the end of this study, it was found that the dominant factors of the corrosion process are the amount of cesium on the surface of the specimen, chromium content in the alloy, the supply rate of oxygen and temperature.

Segregation behavior and embrittling effect of lanthanide La, Ce, Pr,and Nd at Σ3(111) tilt symmetric grain boundary in α-Fe

The migration of lanthanide fission products to cladding materials is recognized as one of the key causes of fuel–cladding chemical interaction(FCCI) in metallic fuels during operation. We have performed first-principles density functional theory calculations to investigate the segregation behavior of lanthanide fission products(La, Ce, Pr, and Nd) and their effects on the intergranular embrittlement at Σ3(111) tilt symmetric grain boundary(GB) in α-Fe. It is found that La and Ce atoms tend to reside at the first layer near the GB with segregation energies of-2.55 eV and-1.60 eV, respectively,while Pr and Nd atoms prefer to the core mirror plane of the GB with respective segregation energies of-1.41 eV and-1.50 eV. Our calculations also show that La, Ce, Pr, and Nd atoms all act as strong embrittlers with positive strengthening energies of 2.05 eV, 1.52 eV, 1.50 eV, and 1.64 eV, respectively, when located at their most stable sites. The embrittlement capability of four lanthanide elements can be determined by the atomic size and their magnetism characters. The present calculations are helpful for understanding the behavior of fission products La, Ce, Pr, and Nd in α-Fe.

Transient self-assembly driven by chemical fuels

Self-assembly has been extensively studied in chemistry,physics,biology,and materials engineering and has become an important“bottom-up”approach in creating intriguing structures for different applications.Using dissipative self-assembly to construct fuel-dependent,energy-consuming,and dynamic nonequilibrium systems is important for developing intelligent life-like materials.Furthermore,dissipative self-assembly has become a research hotspot in materials chemistry,biomedical science,environmental chemistry,and physical chemistry.An in-depth understanding of the process and mechanism provides useful insights to the researchers for devel-oping materials using dissipative self-assembly and also helps guide future innovation in material fabrication.This critical review comprehensively analyzes various chemical fuel input and energy consumption mechanisms,supported by numerous illustrative examples.Versatile transient assemblies,including gels,vesicles,micelles,and nanoparticle aggregates,have been systematically studied in our and other laboratories.The relationship between the molecular structure of precursors and temporal assemblies in dissipative self-assemblies is discussed from the perspective of physical chemistry.Using dissipative self-assembly methods to construct functional assemblies provides important implications for constructing high-energy,nonequilibrium,and intelligent functional materials.

Dynamic Macro-and Microgels Driven by Adenosine Triphosphate-Fueled Competitive Host-Guest Interaction

Supramolecular host–guest systems are generally at thermodynamic equilibrium states or in kinetically trapped states.Herein,we demonstrate the concept of a chemical fuel-driven competitive host–guest assembly featuring autonomous dynamics.The enabling key principle is to design a chemical fuel that possesses a high binding affinity to defeat the guest transiently,undergoes conversion to a waste product,and exhibit weak binding affinity in order to recover the original host–guest pair.By following this principle,adenosine triphosphate(ATP;chemical fuel and competitive guest),biguanidine-functionalizedβ-cyclodextrin(βCD;host),and an adamantine species(ADA;guest)have been engineered to construct dynamic adaptive macrogels or chemo-mechanochromic microgels with programmed time domains.Our reported methodology provides temporal control over the host–guest process,representing a conceptually new tool for the design of living supramolecular materials.

Out-of-equilibrium supramolecular self-assembling systems driven by chemical fuel

A rich variety of smart materials developed via supramolecular assembly strategies have been introduced in the past decades.However,most materials reside in the thermodynamic equilibrium state,opposed to those nonequilibrium structures with sophisticated functions that are observed in living systems.To develop advanced synthetic systems,chemists have begun to focus on how to use strategies similar to those used in biological systems for fabricating artificial out-of-equilibrium systems.Heretofore,a rich variety of artificial out-of-equilibrium systems have been developed.In this review,we have summarized the recent progress of artificial out-of-equilibrium systems and categorized them in terms of the chemical fuel used,including adenosine triphosphate(ATP),acid/base,carbodiimide reagents,and many others.For these self-assembling systems,their design strategies,potential applications,as well as advantageous features have been discussed.At the end of this review,the remaining challenges and an outlook of the chemical-fuel-driven out-of-equilibrium systems were also discussed.It is believed that this review has provided some insights and could be useful for those who are interested in the out-of-equilibrium supramolecular assembling systems and their subsequent constructing strategies for various transient materials.

A novel coated-particle design and fluidized-bed chemical vapor deposition preparation method for fuel-element identification in a nuclear reactor

Particle coating is an important method that can be used to expand particle-technology applications. Coated-particle design and preparation for nuclear fuel-element trajectory tracing were focused on in this paper. Particles that contain elemental cobalt were selected because of the characteristic gamma ray spectra of 60Co. A novel particle-structure design was proposed by coating particles that contain elemental cobalt with a high-density silicon-carbide （SiC） layer. During the coating process with the high-density SiC layer, cobalt metal was formed and diffused towards the coating, so an inner SiC–CoxSi layer was designed and obtained by fluidized-bed chemical vapor deposition coupled with in-situ chemical reaction. The coating layers were studied by X-ray diffractometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy techniques. The chemical composition was also determined by inductively coupled plasma optical emission spectrometry. The novel particle design can reduce the formation of metallic cobalt and prevent cobalt diffusion in the coating process, which can maintain safety in a nuclear reactor for an extended period. The experimental results also validated that coated particles maintain their structural integrity at extremely high temperatures （～1950 °C）, which meets the requirements of next-generation nuclear reactors.

Recent Progress of Fuel-Driven Temporary Materials

Fuel-driven dissipative self-assembly,which is a well-established concept in recent years,refers to out-of-equilibrium molecular self-assembly initiated and supported by the addition of active molecules (chemical fuel).It widely exists in nature since many temporary,active micro- or nanostructures in living bodies are generated by the dissipative self-assembly of biomolecules.Therefore,the study on dissipative self-assembly provides a good opportunity to have an insight into the microscopic mechanism of living organisms.In the meantime,dissipative assembly is thought to be a potential pathway to achieve dynamic,temporary supramolecular materials.Recently,a number of temporary materials have been developed with the aid of strategies for realizing dissipative self-assembly.Some of their properties,including solubility,stiffness,turbidity,color,or self-healing ability,change upon the addition of chemical fuel but spontaneously restore with chemical fuel consumption.The dynamic of these materials brings them various unprecedented functions.In this review,the principles of fabricating a fuel-driven temporary material are first reviewed.Subsequently,recent examples of fuel-driven temporary materials are emphatically summarized,including gels,self-erased inks,nanoreactors,self-healing materials,nanochannels,and droplets.Finally,the challenges of developing fuel-driven temporary materials and some perspectives on the function and application of such kind of materials are discussed.

Out-of-Equilibrium Assembly Based on Host-Guest Interactions

The field of supramolecular chemistry is rapidly progressing,transitioning from the creation of thermodynamically stable systems found in local or global minima on the free energy landscape to the development of out-of-equilibrium systems that rely on chemical reactions to establish and maintain their structures.Over the past decade,numerous artificial out-of-equilibrium systems have been devised in various domains of supramolecular chemistry,many of which have been extensively reviewed.However,one area that has received limited attention thus far is the use of out-of-equilibrium processes to regulate host-guest interactions.This minireview aims to address this gap by exploring the construction of out-ofequilibrium systems based on host-guest complexation,which likely employs similar strategies to those employed in analogous noncovalent interactions.The review begins with a summary of these shared strategies.Subsequently,it discusses representative publications that exemplify these strategies and classifies thembased onwhich component is being modulated-host,guest,or competitive molecules.Through this examination,our objective is to shed light on the design of out-of-equilibrium systems relying on host-guest interactions and provide valuable insights into the preparation strategies for various transient materials.

Solar-driven photothermal catalytic CO_(2) conversion:a review

It is highly desirable to seek green and sustainable technologies,such as employing photo thermal effects to drive energy catalysis processes to address the high energy demand and associated environmental impacts induced by the current methods.The photothermocatalysis process is an emerging research area with great potential in efficiently converting solar energy through various catalytic reactions.However,achieving simultaneously high conversion efficiency,cyclability,and durability is still a daunting challenge.Thus,tremendous work is still needed to enhance solar photo thermal catalytic conversion and promote its large-scale applications.This review developed the principles of coupling solar photon and thermal fields underlying the photothermal effect,exploration of efficient nanocatalysts,development of optofluidic reactor model,and photo thermal synergistic-driven CO_(2) reduction mechanisms.The ultimate goal was to provide an effective approach that can effectively convert solar energy into photocarriers/hot-electrons and heat,and importantly,can couple them to regulate catalysis reaction pathways toward the production of value-added fuel and chemical energy.

Programming Supramolecular Hydrogels by Constructing a Multibranch Selection Structure

Developing chemical systems capable of executing multipath nonequilibrium processes provides valuable insights into the study of multistage dissipative structures in living systems.Here,we report a nonequilibrium multipath evolution in a three-state supramolecular system,which is clarified by associating it with a multibranch selection structure.This system is constructed by synergistically combining an assembly-induced sol-gel transition with the color change of an acid-base indicator.Depending on the initial condition and chemical fuel composition,this system can execute five distinct nonequilibrium processes.In addition,the set of structured programming can be replayed by repeatedly introducing the chemical fuel.It is further utilized to explore the applications of information encryption and establish its universality.These findings offer novel avenues for future transient material design and may make significant contributions to systems chemistry.

Recent advances in carbon-based materials for electrochemical CO_(2) reduction reaction

The increase of atmospheric CO_(2)concentration has caused many environmental issues.Electrochemi-cal CO_(2)reduction reaction(CO_(2)RR)has been considered as a promising strategy to mitigate these chal-lenges.The electrocatalysts with a low overpotential,high Faradaic efficiency,and excellent selectivity are of great significance for the CO_(2)RR.Carbon-based materials including metal-free carbon catalysts and metal-based carbon catalysts have shown great potential in the CO_(2)RR,owing to the tailorable porous structures,abundant natural resources,resistance to acids and bases,high-temperature stability,and en-vironmental friendliness.In this review,various carbon materials including graphene,carbon nanotubes,quantum dots,porous carbon,and MOF-derived catalysts,etc.,for the CO_(2)RR have been summarized.Particularly,recent progress in terms of the mechanism and pathway of CO_(2)conversion has been com-prehensively reviewed.Finally,the opportunities and challenges of carbon-based electrocatalysts for the CO_(2)RR are proposed.

Porous fixed-bed photoreactor for boosting C-C coupling in photocatalytic CO_(2)reduction

Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass transfer.Here,a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C-C coupling in photocatalytic CO_(2)reduction.The photocatalytic results show that∼90%selectivity towards C^(2+)products is obtained by a Cu/Cd_(0.5)Zn_(0.5)S photocatalyst,with a yield of 6.54μmol/h(an irradiation area of 0.785 cm^(2)),while only 0.94μmol/h(an irradiation area of 19.625 cm^(2))is achieved with a commonly used suspension photocatalytic reactor.We find that under the same CO_(2)feed rate,the local CO_(2)concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension photoreactor.The larger local CO_(2)coverage derived from a higher CO_(2)supply and aggregation enhances the C-C coupling,thereby generating more C^(2+).Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO_(2)supply,for which the optimal gas inlet rate is 5-10 sccm.

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

It remains a great challenge to balance the kinetic stability and intrinsic healing ability of polymer materials.Here,we present an efficient strategy of using a synthetic reaction cycle to regulate the intrinsic healing ability of thermodynamically stable and kinetically inert multifunctional organohydrogels.By combining a double decomposition reaction with spontaneous energy dissipation,we can construct the simplest synthetic reaction cycle that can induce a transient out-of-equilibrium state for achieving the healing of organohydrogels with kinetically locked acylhydrazone bonds.In addition to balancing kinetic stability and healing ability,the synthetic reaction cycle also enables the polymer materials to have high tolerance to organic solvents,high ionic strength,high and low temperatures,and other harsh conditions.Therefore,the kinetically stable and healable organohydrogels remain mechanically flexible and electrically conductive even down to−40°C and are readily recyclable.The integration of chemical networks into healable polymers may provide novel,versatile materials for building next-generation electronic devices.