Bi-directional charge transfer channels in highly crystalline carbon nitride enabling superior photocatalytic hydrogen evolution.

Introducing a donor-acceptor (D-A) unit is an effective approach to facilitate charge transfer in polymeric carbon nitride (PCN) and enhance photocatalytic performance. However, the introduction of hetero-molecules can lead to a decrease in crystallinity, limiting interlayer charge transfer and inhibiting further improvement. In this study, we constructed a novel D-A type carbon nitride with significantly higher crystallinity and a bi-directional charge transfer channel, which was achieved through 2,5-thiophenedicarboxylic acid (2,5-TDCA)-assisted self-assembly followed by KCl-templated calcination. The thiophene and cyano groups introduced serve as the electron donor and acceptor, respectively, enhancing in-plane electron delocalization. Additionally, introduced potassium ions are intercalated among the adjacent layers of carbon nitride, creating an interlayer charge transfer channel. Moreover, the highly ordered structure and improved crystallinity further facilitate charge transfer. As a result, the as-prepared photocatalyst exhibits superior photocatalytic hydrogen evolution (PHE) activity of 7.449 mmol h-1 g-1, which is 6.03 times higher than that of pure carbon nitride. The strategy of developing crystalline D-A-structured carbon nitride with controlled in-plane and interlayer charge transfer opens new avenues for the design of carbon nitride with enhanced properties for PHE.

Recent advances in biopolymers-based carbon materials for supercapacitors.

Supercapacitors as potential candidates for novel green energy storage devices demonstrate a promising future in promoting sustainable energy supply, but their development is impeded by limited energy density, which can be addressed by developing high-capacitance electrode materials with efforts. Carbon materials derived from biopolymers have received much attention for their abundant reserves and environmentally sustainable nature, rendering them ideal for supercapacitor electrodes. However, the limited capacitance has hindered their widespread application, resulting in the proposal of various strategies to enhance the capacity properties of carbon electrodes. This paper critically reviewed the recent research progress of biopolymers-based carbon electrodes. The advances in biopolymers-based carbon electrodes for supercapacitors are presented, followed by the strategies to improve the capacitance of carbon electrodes which include pore engineering, doping engineering and composite engineering. Furthermore, this review is summarized and the challenges of biopolymer-derived carbon electrodes are discussed. The purpose of this review is to promote the widespread application of biopolymers in the domain of supercapacitors.

Enhancing Photocatalytic Degradation via the Synergetic Effect of Vacancies and Built-In Potential in a BiOCl/BiVO4 p-n Heterojunction.

Photoinduced charge separation and surface reactions are essential for ensuring high quantum efficiency of the photochemical and photophysical processes. BiVO4-based heterojunctions are promising materials for high-performance photocatalysts; however, their photocatalytic performance is significantly lower than the theoretical limit due to the sluggish water oxidation dynamics and rapid recombination of charge carriers on the catalyst surface. To address these issues, oxygen vacancies (OVs) are introduced to a rationally designed BiVO4-based heterojunction using built-in potential and gradient OVs to promote the separation of carriers and increase the photocatalytic activity. The heterojunctions with OVs exhibit a 2-fold increase in the photocatalytic activity for phenol degradation compared with that of pristine BiVO4. Additionally, density functional theory is applied to elucidate the synergistic mechanism of light absorption and charge separation in BiOCl/BiVO4 p-n heterojunction photocatalysts containing vacancies. The obtained results demonstrate a synergistic effect of vacancies and the built-in potential, providing a pathway for defect engineering in photocatalytic processes.

Research Progress of Polymer Biomaterials as Scaffolds for Corneal Endothelium Tissue Engineering.

Nowadays, treating corneal diseases arising from injury to the corneal endothelium necessitates donor tissue, but these corneas are extremely scarce. As a result, researchers are dedicating significant efforts to exploring alternative approaches that do not rely on donor tissues. Among these, creating a tissue-engineered scaffold on which corneal endothelial cells can be transplanted holds particular fascination. Numerous functional materials, encompassing natural, semi-synthetic, and synthetic polymers, have already been studied in this regard. In this review, we present a comprehensive overview of recent advancements in using polymer biomaterials as scaffolds for corneal endothelium tissue engineering. Initially, we analyze and present the key properties necessary for an effective corneal endothelial implant utilizing polymer biomaterials. Subsequently, we focus on various emerging biomaterials as scaffolds for corneal endothelium tissue engineering. We discuss their modifications (including natural and synthetic composites) and analyze the effect of micro- and nano-topological morphology on corneal endothelial scaffolds. Lastly, we highlight the challenges and prospects of these materials in corneal endothelium tissue engineering.

Nanoarchitectonics on Z-scheme and Mott-Schottky heterostructure for photocatalytic water oxidation via dual-cascade charge-transfer pathways.

The bottleneck for water splitting to generate hydrogen fuel is the sluggish oxidation of water. Even though the monoclinic-BiVO4 (m-BiVO4)-based heterostructure has been widely applied for water oxidation, carrier recombination on dual surfaces of the m-BiVO4 component have not been fully resolved by a single heterojunction. Inspired by natural photosynthesis, we established an m-BiVO4/carbon nitride (C3N4) Z-scheme heterostructure based on the m-BiVO4/reduced graphene oxide (rGO) Mott-Schottky heterostructure, constructing the face-contact C3N4/m-BiVO4/rGO (CNBG) ternary composite to remove excessive surface recombination during water oxidation. The rGO can accumulate photogenerated electrons from m-BiVO4 through a high conductivity region over the heterointerface, with the electrons then prone to diffuse along a highly conductive carbon network. In an internal electric field at the heterointerface of m-BiVO4/C3N4, the low-energy electrons and holes are rapidly consumed under irradiation. Therefore, spatial separation of electron-hole pairs occurs, and strong redox potentials are maintained by the Z-scheme electron transfer. These advantages endow the CNBG ternary composite with over 193% growth in O2 yield, and a remarkable rise in ·OH and ·O2- radicals, compared to the m-BiVO4/rGO binary composite. This work shows a novel perspective for rationally integrating Z-scheme and Mott-Schottky heterostructures in the water oxidation reaction.

Uniformizing the lithium deposition by gradient lithiophilicity and conductivity for stable lithium-metal batteries.

The practical application of lithium metal batteries is hindered by the poor reversibility and large volume change caused by the uncontrollable dendritic growth and the highly reactive surface. In this work, favorable Li deposition is achieved by generating gradient lithiophilicity and conductivity in an Ag-decorated graphene/holey graphene film (G-HGA). Dendrite-free Li metal is deposited on the G-HGA matrix, which greatly reduces the surface area and suppresses the side reaction between the electrolyte and the dendritic Li. The average Li-metal plating-stripping coulombic efficiency (CE) on the G-HGA matrix maintains ∼98.7% over 350 cycles, compared to a worse average CE (∼97.3%) with the bare Cu matrix, only for less than 100 cycles. A full cell constructed by using LiFePO4 and prelithiated G-HGA exhibits excellent rate capability and a high capacity retention of 99.6% for 175 cycles at a low negative to positive capacity ratio of 1.13. This advanced design can inspire further development of high-energy and long-lived Li-metal batteries.

Nanoarchitectonics of RGO-Wrapped CNF/GO Aerogels with Controlled Pore Structures by PVA-Assisted Freeze-Casting Approach for Efficient Sound and Microwave Absorption.

Acoustic absorption materials play an important role in eliminating the negative effects of noise. Herein, a polyvinyl alcohol (PVA)-assisted freeze-casting was developed for controllably fabricating reduced graphene oxide wrapped carbon nanofiber (RGO@CNF)/graphene oxide composite aerogel. During the freeze-casting, PVA was used as an icing inhibitor to control the size of ice crystals. While the concentration of PVA increased from 0 to 15 mg ⋅ ml-1 , the average pore size of the aerogel was reduced from 154 to 45 µm. Due to the modulation of the pore size and composition, the propagation path and friction loss for sound were optimized, especially at low frequency. For instance, the normalized sound absorption coefficient of RGO@CNF/GO-10 achieves 0.79 (250-6300 Hz). The sample also exhibits a desirable microwave absorbing property whose maximum reflection loss is -47.3 dB (9.44 GHz, d=3.0 mm). Prospectively, this synthetic strategy can be extended to develop other forms of elastic aerogel with a controlled pore size.

Graphene-Based Nanomaterials for Solar-Driven Overall Water Splitting.

Water splitting through photocatalysis and photoelectrochemical methods is a promising strategy for solar energy utilization. Graphene is widely used in solar-driven overall water splitting because of its versatile properties. This review summarizes the preparation of graphene-based photocatalysts and photoelectrodes and the functions of graphene, and highlights the challenges and prospects of the future applications of graphene in solar-driven water splitting.

Synergetic Nanoarchitectonics of Defects and Cocatalysts in Oxygen-Vacancy-Rich BiVO4/reduced graphene oxide Mott-Schottky Heterostructures for Photocatalytic Water Oxidation.

Water oxidation process is a pivotal step of photosynthesis and stimulates the progress of high-performance catalysts for renewable fuel production. Despite the performance benefit of cocatalysts, defect engineering holds promise to settle inherent limitations of semiconductors aiming at sluggish water oxidation. Here, we modify the in situ growth pathway of monoclinic BiVO4 (m-BiVO4) on reduced graphene oxide (rGO), constructing abundant surface oxygen vacancies (OV)-incorporated m-BiVO4/rGO heterostructure toward water oxidation reaction under visible light. Owing to the OV in the m-BiVO4 component, a vacancy-related defect level allows more electrons to be photoexcited by low-energy photons to cause the electron transition, boosting photoabsorption as well as photoexcitation. Besides, the OV can reinforce surface adsorption and reduce the dissociation energy of water molecules. Particularly because of the synergy of OV and cocatalyst rGO, the OV functions as electron-trapped sites to facilitate the carrier separation; the rGO not only receives electrons from m-BiVO4 promoted by internal electric field over Mott-Schottky heterostructures but also spurs further electron diffusion along a highly conductive carbon network. These merits enable the OV-incorporated m-BiVO4/rGO heterostructure with an over 209% growth in O2 yield relative to the counterpart. The increased performance is also validated by the significant rise of •OH radicals and •O2- radicals. The current work paves a novel avenue for the integration of defect engineering and cocatalyst coupling in artificial photosynthesis.

One-step sonochemical fabrication of biomass-derived porous hard carbons; towards tuned-surface anodes of sodium-ion batteries.

A facile one-step sonochemical activation method is utilized to fabricate biomass-derived 3D porous hard carbon (PHC-1) with tuned-surface and is compared with the conventional two-step activation method. As raw biomass offers good KOH impregnation, ultrasonication power diffuses both K+ and OH- ions deep into its interior, creating various nanopores and attaching copious functional groups. In contrast, conventional activation lacks these features under the same carbonization/activation parameters. The high porosity (1599 m2/g), rich functional groups (O = 8.10%, N = 0.95%), and well-connected nanoporous network resulting from sonochemical activation, remarkably increased specific capacity, surface wettability, and electrode stability, consequently improved electrochemical performance. Benefiting from its suitable microstructure, PHC-1 possesses superior specific capacity (330 mAh/g at 20 mA/g), good capacity retention (89.5%), and excellent structural stability over 500 sodiation/desodiation cycles at high current density (1000 mA/g). Apart from modus operandi comparison, the two activation methods also provide mechanistic insights as the low-voltage plateau region and graphitic layers decrease simultaneously. This work suggests a scalable and economical approach for synthesizing large-scale activated porous carbons that are used in various applications, be it energy storage, water purification, or gas storage, to name a few.

State of the Art of Non-Invasive Electrode Materials for Brain-Computer Interface.

The brain-computer interface (BCI) has emerged in recent years and has attracted great attention. As an indispensable part of the BCI signal acquisition system, brain electrodes have a great influence on the quality of the signal, which determines the final effect. Due to the special usage scenario of brain electrodes, some specific properties are required for them. In this study, we review the development of three major types of EEG electrodes from the perspective of material selection and structural design, including dry electrodes, wet electrodes, and semi-dry electrodes. Additionally, we provide a reference for the current chaotic performance evaluation of EEG electrodes in some aspects such as electrochemical performance, stability, and so on. Moreover, the challenges and future expectations for EEG electrodes are analyzed.

Construction of a Bioinspired Hierarchical BiVO4/BiOCl Heterojunction and Its Enhanced Photocatalytic Activity for Phenol Degradation.

Development of a p-n heterojunction to achieve efficient degradation of organic pollutants is a promising approach in the field of photocatalysis. Herein, BiVO4 with bioinspired hierarchical structures was prepared with the sol-gel method and combined with BiOCl nanoplates to construct a 3D/2D configuration via an in situ deposition route. The hierarchical BiVO4 served as an excellent substrate to achieve the uniform loading of BiOCl nanoplates. The obtained 3D/2D BiVO4/BiOCl hybrids exhibited significantly enhanced photocatalytic efficiency for degrading phenol under visible light irradiation, with a first-order reaction rate constant that was 9.9 and 1.9 times higher than those of hierarchical BiVO4 and the BiVO4/BiOCl hybrids without hierarchical structures, respectively. Moreover, the hierarchical BiVO4/BiOCl also displayed good photochemical stability for the degradation of phenol after three recycles. The p-n heterojunction and hierarchical structure worked together to form a spatial conductive network framework, which possessed improved visible light absorption, high specific surface area, as well as effective separation and transfer of photogenerated charge carriers.

Cellulose nanocrystals reinforced highly stretchable thermal-sensitive hydrogel with ultra-high drug loading.

Hydrogels often have poor mechanical properties which limit their application in load-bearing tissues such as muscle and cartilage. In this work, a near-infrared light-triggered stretchable thermal-sensitive hydrogel with ultra-high drug loading was developed by a combination of natural polymeric nanocrystals, a network of synthetic thermo-responsive polymer, and magnetic Fe3O4 nanoparticles. The hydrogels comprise cellulose nanocrystals (CNCs) decorated with Fe3O4 nanoparticles (Fe3O4/CNCs) dispersed homogeneously in poly(N-isopropylacrylamide) (PNIPAm) networks. The composite hydrogels exhibit an extensibility of 2200%. Drug loading of vancomycin (VCM) reached a high value of 10.18 g g-1 due to the dispersion of Fe3O4/CNCs and the interactions between the CNCs and the PNIPAm network. Importantly, the hydrogels demonstrated a thermo-response triggered by NIR, with the temperature increasing from 26 to 41 °C within 60 s. The hydrogels have high biocompatibility evidenced by cell proliferation tests, illustrating that these hydrogels are promising as dressings for wound closure, and wound healing.

Dynamic single-site polysulfide immobilization in long-range disorder Cu-MOFs.

The structural transformation of MOFs in a polysulfide electrode process is poorly understood. We report the electrochemical amorphization of Cu3(BTC)2 MOFs in polysulfide electrolyte. We unveil the dynamic single-site polysulfide immobilization at the interconvertible Cu2+/Cu+ cation centres upon polysulfide adsorption and desorption, along with the reversible distortion of the Cu-O square planar unit.

In situ modification of BiVO4 nanosheets on graphene for boosting photocatalytic water oxidation.

Owing to the sluggish water oxidation process, unearthing an ideal model for disclosing the impact of an architectural approach on the water oxidation activity of photocatalysts becomes a vital issue. Here, we propose an innovative in situ modification strategy for constructing ultrapure BiVO4 nanosheets on graphene (u-BVG) toward the accelerated photocatalytic water oxidation reaction. Considering the Mott-Schottky heterojunctions at the contact interface in u-BVG, the feasible electron transfer from excited BiVO4 to graphene facilitates the holes to migrate onto the BiVO4 surface for the water oxidation reaction. Compared with the conventional synthesis strategies, our strategy avoids the introduction of Cl impurities. This modification allows for not only a ca. 0.1 eV deeper valence band edge position to generate holes with a stronger oxidation potential but the extraction of the impurity level to suppress the carrier recombination. And density functional theory calculations are in accordance with the above results. Impressively, these merits endow the u-BVG with ca. 16.8 times growth in the amount of ˙OH radicals derived from OH-/H2O oxidation, an over 260% enhancement in O2 yield and a 1.6-fold increase in the apparent quantum efficiency relative to the impure counterpart. This work paves the way for the reconstruction of graphene-based binary systems with high performance in solar-to-chemical energy conversion.

Ultrasensitive Magnetic Tuning of Optical Properties of Films of Cholesteric Cellulose Nanocrystals.

Chiral photonic crystals derived from the self-assembly of cellulose nanocrystals (CNCs) have found important applications in optical devices due to the capacity to adjust the chiral nematic phase under external stimulus, in particular an applied magnetic field. To date, strong magnetic fields have been required to induce an optical response in CNC films. In this work, the self-assembly of films of CNCs can be tuned by applying an ultrasmall magnetic field. The CNCs, decorated with Fe3O4 nanoparticles (Fe3O4/CNCs), were dispersed in suspensions of neat CNCs so as to alter the magnetic response of the CNCs. A subsequent process of dispersion not only prevents the clumping of the magnetic nanoparticles but also enhances the sensitivity to an applied magnetic field. A small magnetic field of 7 mT can tune the self-assembly and the microstructure of the CNCs. The pitch of the chiral structure decreased with an increase in applied magnetic field, from 302 to 206 nm, for fields from 7 to 15 mT. This phenomenon is opposite that observed for neat CNCs, in which the pitch is observed to increase with an increase in the external magnetic strength. The optical response under application of an ultrasmall magnetic field could help with theoretical research and enable more applications, such as sensors or nanotemplating agents.

Assembly of 1T'-MoS2 based fibers for flexible energy storage.

As a new type of 2D material, 1T'-MoS2 has become one of the fastest growing topics, owing to its extraordinary electrical conductivity and electrochemical activity. Nevertheless, these marvelous properties have not yet been realized in their macroscopic structures such as films and fibers, due to the lack of an assembly method. Herein, we report the synthesis of well-soluble 1T'-MoS2 sheets, which can form a nematic liquid crystalline structure in their aqueous suspensions. The liquid crystalline suspensions were then assembled into macroscopic 1T'-MoS2 fibers via a simple and cost-effective dry-spinning process. A similar process can be used for the preparation of 1T'-MoS2/graphene oxide (1T'-MoS2/GO) fibers from 1T'-MoS2/GO 2D/2D composite liquid crystals. The fabricated 1T'-MoS2/GO fibers exhibited an excellent electrical conductivity of 1.5 × 104 S m-1 as well as a high tensile strength of 145 MPa. When used as an electrode, the fibers showed an extremely high capacitance of 1379.8 F cm-3 (∼645 F g-1) at a scan rate of 10 mV s-1 by using K3[Fe(CN)6]/K4[Fe(CN)6] as the electrolyte. Our findings will open up an avenue for liquid crystal physics of low dimensional non-carbon materials beyond graphene, and stimulate a wide range of application explorations, especially on energy storage.

Recent advancements in g-C3N4-based photocatalysts for photocatalytic CO2 reduction: a mini review.

Carbon dioxide (CO2) is a very important micro-molecular resource. Using CO2 captured from the atmosphere for high-output synthesis of chemicals as raw materials has great significance and potential for various industrial applications. Since the industrial revolution in the 18th century, manmade CO2 emission has increased by 45%, which negatively impacts the planetary climate by the so-called greenhouse effect. Therefore, high-efficiency photocatalysis and photocatalysts for CO2 conversion have become the most important challenges and milestones throughout the world. In consideration of this, various catalysts have been explored. Among these, graphitic carbon nitride (g-C3N4) as a semiconductor is emerging as a highly promising photocatalyst for removing CO2 from the atmosphere. Moreover, due to its excellent chemical stability and unique band structure, g-C3N4 has exhibited significant application potential for photocatalysis. This review summarizes the advancements that have been made in the synthesis and photocatalytic applications of g-C3N4-based catalysts for CO2 reduction in recent years and explains the future challenges and prospects in this vital area of research.

Assembly of MnO/CNC/rGO fibers from colloidal liquid crystal for flexible supercapacitors via a continuous one-process method.

Flexible supercapacitors based on fiber shaped electrodes exhibit great potential for practical applications in smart fabrics owing to their light weight, good flexibility, and excellent weaveability. Herein, manganosite/carbonized cellulose nanocrystal/reduced graphene oxide (MnO/CNC/rGO) ternary composite fibers were fabricated from liquid crystal spinning dopes through a continuous one-process method. The assembly of CNC and manganese oxide nanoparticles in GO aqueous dispersion not only prevents GO nanosheets from restacking, but also ensures a uniform intercalation of nanoparticles. After a chemical and thermal reduction, the carbonized CNC contributes for additional electrical double layer capacitance while the MnO for faradaic pseudocapacitance. A fiber supercapacitor was assembled by arranging two MnO/CNC/rGO ternary composite fibers coated with PVA/H3PO4 gel electrolyte in parallel and it exhibited an energy density of 0.14 mWh cm-3 at 4 mW cm-3 and the maximum power density of 40 mW cm-3. The fiber supercapacitor also demonstrated a good cycling stability (retains 82% of its initial capacitance after 6000 cycles) and bending robustness. This assembly approach is facile and scalable. More importantly the homogeneous dispersion of the nanoparticles in the ternary composite fibers shows promise for the future spreading of wearable electronic products.

Superior removal of Hg (II) ions from wastewater using hierarchically porous, functionalized carbon.

The removal of heavy metal ions from industrial wastewater by adsorption has been central to the environment for decades, where common adsorbent materials are often limited by poor efficiency, complex fabrication and long processing time. Porous carbon derived from biospecies holds promise to address the limitations. In this study we converted bagasse into a carbon composite having hierarchically porous structure; the composite's dispersion phases - iron oxide and manganese oxide - were synthesized by a simple one-step liquid-phase reaction method. Featuring large specific surface area of 350.8 m2 g-1, the composite demonstrated exceptional Hg (II) removal efficiency of 96.8%, adsorption rate of up to 96.8% within 150 min and adsorption capacity of 9.8 mg g-1. In comparison with other removal materials, our work is outstanding in terms of both removal efficiency and synthesis simplicity. The high efficiency is attributed to the synergy between physical adsorption referring to hierarchically porous structure and chemical adsorption relating to functional complexation processes. It provides a new avenue for the development of high-performance adsorbent materials for heavy metal removal from aqueous media.