Recent advances in the functionalization, substitutional doping and applications of graphene/graphene composite nanomaterials

Recently, graphene and graphene-based nanomaterials have emerged as advanced carbon functional materials with specialized unique electronic, optical, mechanical, and chemical properties. These properties have made graphene an exceptional material for a wide range of promising applications in biological and non-biological fields. The present review illustrates the structural modifications of pristine graphene resulting in a wide variety of derivatives. The significance of substitutional doping with alkali-metals, alkaline earth metals, and III-VII group elements apart from the transition metals of the periodic table is discussed. The paper reviews various chemical and physical preparation routes of graphene, its derivatives and graphene-based nanocomposites at room and elevated temperatures in various solvents. The difficulty in dispersing it in water and organic solvents make it essential to functionalize graphene and its derivatives. Recent trends and advances are discussed at length. Controlled reduction reactions in the presence of various dopants leading to nanocomposites along with suitable surfactants essential to enhance its potential applications in the semiconductor industry and biological fields are discussed in detail.

Graphene materials in pollution trace detection and environmental improvement

Water scarcity is a pressing issue experienced in numerous countries and is expected to become increasingly critical in the future. Anthropogenic activities such as mining, agriculture, industries, and domestic waste discharge toxic contaminants into natural water bodies, causing pollution. Addressing these environmental crises requires tackling the challenge of removing pollutants from water. Graphene oxide (GO), a form of graphene functionalized with oxygen-containing chemical groups, has recently garnered renewed interest due to its exceptional properties. These properties include a large surface area, mechanical stability, and adjustable electrical and optical characteristics. Additionally, surface functional groups like hydroxyl, epoxy, and carboxyl groups make GO an outstanding candidate for interacting with other materials or molecules. Because of its expanded structural diversity and enhanced overall properties, GO and its composites hold significant promise for a wide range of applications in energy storage, conversion, and environmental protection. These applications encompass hydrogen storage materials, photocatalysts for water splitting, the removal of air pollutants, and water purification. Serving as electrode materials for various lithium batteries and supercapacitors. Graphene-based materials, including graphene, graphene oxide, reduced graphene oxide, graphene polymer nanocomposites, and graphene nanoparticle metal hybrids, have emerged as valuable tools in energy and environmental remediation technologies. This review article provides an overview of the significant impact of graphene-based materials in various areas. Regarding energy-related topics, this article explores the applications of graphene-based materials in supercapacitors, lithium-ion batteries, and catalysts for fuel cells. Additionally, the article investigates recent advancements in detecting and treating persistent organic pollutants (POPs) and heavy metals using nanomaterials. The article also discusses recent developments in creating innovative nanomaterials, nanostructures, and treatment methods for addressing POPs and heavy metals in water. It aims to present the field's current state and will be a valuable resource for individuals interested in nanomaterials and related materials.

Cu/Co/CoS2 embedded in S,N doped carbon as highly-efficient oxygen reduction and evolution electrocatalyst for rechargeable zinc-air batteries

In order to improve the retarded oxygen reduction and evolution reaction (ORR/OER) in rechargeable metal-air cells in electrochemical energy conversion systems, constructing multiphase nanostructured catalysts is an alternative strategy, where...

Identifying active sites of boron, nitrogen co-doped carbon materials for the oxygen reduction reaction to hydrogen peroxide

The electrochemical synthesis of hydrogen peroxide (H₂O₂) from two-electron oxygen reduction reaction (2e^- ORR) is a promising alternative for producing chemicals on demand, but its widespread application is still hampered by the low efficiency. Here, we successfully prepared a boron and nitrogen co-doped porous carbon (B/NC) aerogel with a tunable B, N co-doped configuration by the gelation of PVA-graphene, borax and PANI, followed by pyrolysis. Due to a hierarchical porous structure and optimized B, N co-doping, B/NC aerogel showed an excellent electrocatalytic performance for H₂O₂ production in alkaline solution with a high H₂O₂ selectivity (94.16%) at positive applied potential (0.6 V vs. RHE), superior than most of the other reported electrocatalysts. Density functional theory (DFT) calculations reveal that the hexagonal boron nitride (hBN) coupled with neighboring pyridinic-N species act as the active sites to lower free energy barrier for formation of HOO* intermediate, thus facilitating H₂O₂ production. Practically, B 2p electron plays an important role for the adsorption of HOO* intermediates. B and Nco-doping into carbon materials provides an effective and facile method to reasonably construct carbon-based catalysts for electroreduction of O₂ to H₂O₂.

Polymer-Derived Lightweight SiBCN Ceramic Nanofibers with High Microwave Absorption Performance

Lightweight SiBCN ceramic nanofibers were prepared by a combination of electrostatic spinning and high-temperature annealing techniques, showing tunable electromagnetic wave absorption. By controlling the annealing temperature, the nanoscale architectures and atomic bonding structures of as-prepared nanofibers could be well regulated. The resulting SiBCN nanofibers ∼300 nm in diameter, which were composed of an amorphous matrix, β-SiC, and free carbon nanocrystals, were defect-free after annealing at 1600 °C. SiBCN nanofibers annealed at 1600 °C exhibited good microwave absorption, obtaining a minimum reflection coefficient of -56.9 dB at 10.56 GHz, a sample thickness of 2.6 mm with a maximum effective absorption bandwidth of 3.45 GHz, and a maximum dielectric constant of 0.44. Owing to the optimized A + B + C microstructure, SiBCN ceramic nanofibers with satisfying microwave absorption properties endowed the nanofibers with the potential to be used as lightweight, ultrastrong radar wave absorbers applied in military and the commercial market.

Enhanced electrostatic potential with high energy and power density of a symmetric and asymmetric solid-state supercapacitor of boron and nitrogen co-doped reduced graphene nanosheets for energy storage devices

Schematic representation of boron and nitrogen co-doped graphene nanosheets.

Single-Atom Catalysts across the Periodic Table

Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

Direct Assembly of 3D-BCN Microspheres as a Microsupercapacitor Electrode for Wearable Energy Storage

Scalable and cost-effective fabrication of three-dimensional (3D) boron carbon nitride (BCN) microspheres was first demonstrated by hydrothermal and annealing methods. In particular, the specific surface area of 3D-BCN-4 reached 1390.12 m² g^-1 and had a high hierarchical pore structure. An all-printed solid-state flexible microsupercapacitor (MSC) based on 3D-BCN-4 microspheres as an electrode material was fabricated for the first time by a screen printing method, which also provided efficacious properties. The single MSC areal capacitance reached 41.6 mF cm^-2. Furthermore, the remarkable mechanical flexibility was also achieved for the device with evidence that no obvious capacitance loss occurred even upon bending to 180°, and the device had a 93.3% capacitance retention after 1000 cycles. In addition, the maximum energy density reached 0.00832 mW h cm^-2, and the highest power density was 2 mW cm^-2. These results show the synthesis of 3D-BCN by a facile and effective method with excellent electrochemical performance, which should provide a promising direction to wearable energy storage devices.

Boron-Doped Reduced Graphene Oxide with Tunable Bandgap and Enhanced Surface Plasmon Resonance

Graphene and its hybrids are being employed as potential materials in light-sensing devices due to their high optical and electronic properties. However, the absence of a bandgap in graphene limits the realization of devices with high performance. In this work, a boron-doped reduced graphene oxide (B-rGO) is proposed to overcome the above problems. Boron doping enhances the conductivity of graphene oxide and creates several defect sites during the reduction process, which can play a vital role in achieving high-sensing performance of light-sensing devices. Initially, the B-rGO is synthesized using a modified microwave-assisted hydrothermal method and later analyzed using standard FESEM, FTIR, XPS, Raman, and XRD techniques. The content of boron in doped rGO was found to be 6.51 at.%. The B-rGO showed a tunable optical bandgap from 2.91 to 3.05 eV in the visible spectrum with an electrical conductivity of 0.816 S/cm. The optical constants obtained from UV-Vis absorption spectra suggested an enhanced surface plasmon resonance (SPR) response for B-rGO in the theoretical study, which was further verified by experimental investigations. The B-rGO with tunable bandgap and enhanced SPR could open up the solution for future high-performance optoelectronic and sensing applications.

The Tribological Properties of Reduced Graphene Oxide Doped by N and B Species with Different Configurations

Reduced graphene oxide (rGO) was doped by nitrogen (N) and/or boron (B), leading to four different configurations: N-rGO (N-doped rGO), B-rGO (B-doped rGO), N-B-rGO (N and B codoped rGO with formation of B-N bond), and N,B-rGO (N and B isolate-doped rGO without formation of B-N bond). The preparations of different configurations were controlled by the chemical vapor deposition procedure, and their structures were further confirmed by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD). The tribological performance of these was tested via a ball-on-flat tribometer under 5 N load. N,B-rGO displayed better friction-reducing and antiwear performance than N-rGO and B-rGO, while N-B-rGO presented poorer tribological properties. The morphology and components of the wear track after friction were further explored, revealing that N,B-rGO can be adsorbed on the rubbing surface to form a graphene-based protective layer, while N-B-rGO cannot. In addition, first-principles calculations based on density functional theory further confirmed a stronger interfacial energy of N,B-rGO on steel surface than that of N-B-rGO on the steel surface, which was in accordance with the experimental results.

NiSe2-anchored N, S-doped graphene/Ni foam as a free-standing bifunctional electrocatalyst for efficient water splitting

It is still challenging to develop non-precious free-standing bifunctional electrocatalysts with high efficiency for hydrogen and oxygen evolution reactions. Herein, for the first time, we present a novel hybrid electrocatalyst synthesized via a facile hydrothermal reaction, which is constructed from ultrafine NiSe2 nanoparticles/nanosheets homogeneously anchored on 3D graphene/nickel foam (NiSe2/3DSNG/NF). This hybrid delivers superior catalytic performances for hydrogen/oxygen evolution reactions and overall water splitting: it shows an ultra-small Tafel slope of 28.56 mV dec-1 for hydrogen evolution in acid, and a small Tafel slope of 42.77 mV dec-1 for the oxygen evolution reaction; particularly, in a two-electrode setup for water splitting, it requires an ultra-small potential of 1.59 V to obtain 10 mA cm-2 with nearly 100% faradaic efficiencies for H2 and O2. This study presents a new approach of catalyst design and fabrication to achieve highly efficient and low-cost water electrolysis.

Compositional and morphological engineering of in-situ-grown Ag nanoparticles on Cu substrate for enhancing oxygen reduction reaction activity: A novel electrochemical redox tuning approach

Silver nanoparticles (NPs) developed on a copper substrate, Ag NPs/Cu, are synthesized by a novel and facile galvanic replacement method performed in Ethaline deep eutectic solvent (DES). It reveals that the Ag NPs could be well dispersed on the Cu support via an in-situ electrochemical oxidation-reduction (ECO-ECR) activation process, which deliver significantly enhanced activity and stability for the oxygen reduction reaction (ORR) in alkaline media. The in-situ redox tuning triggers a reversible phase transformation of the formed initially Ag NPs, Ag ↔ Ag₂O, with surface reconstruction and gives rise to a strong metal-support interaction with tailored atomic/electronic structures, resulting in enhanced ORR activity. Impressively, the introduction of Ni^II ions can regulate the galvanic replacement kinetics by mediating the diffusion of Ag^I ions and subsequent growth of Ag on the Cu surface in Ethaline, leading to the formation of uniformly distributed Ag NPs. Coupled with redox activation, the optimal Ag-Ni₁ NPs/Cu_ECO-ECR exhibits ORR activity similar to that of the commercial state-of-the-art Pt/C catalyst, and better long-term durability (95% activity retention after 30,000 s), cyclic stability performance, and anti-poisoning capacity for methanol (96% after 3300 s), suggesting it a promising ORR electrocatalyst for practical application.

Nitrogen moieties -dominated Co-N-doped nanoparticle-modified cathodes in heterogeneous-electro-Fenton-like system for catalytic decontamination of EDTA-Ni(II)

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. In this study, with the same doping level of Co and N, MoO₂ and ZIF-67 were used as precursors to prepare MoO₂@Co/N and FeC@Co/N electrocatalysts for the modified graphite felt cathodes in heterogeneous-electro-Fenton-like reaction (HEFL) system. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that both of the catalysts are dominated with pyridinic N (2.42% and 2.82%) upon co-doping Co/N, and FeC@Co/N exhibited an obviously higher additional sp-hybridized nitrogen (sp-N) peak. The co-doping of Co/N induced the lattice modifications to produce more lattice defects, where pyridinic N and sp-N, related with the active sites (C-N, Co-Nx), were formed at near-ring defects along sheet edges through the nitrogen replacement of CC groups. FeC@Co/N demonstrated superior oxygen reduction reaction catalytic activity in terms of Cyclic Voltammetry and Rotating Ring-disk Electrode, and exhibited the remarkably higher current density (30 mA) and lower onset potential (-0.208 V) in Linear Sweep Voltammetry analysis. In the FeC@Co/N/CF modified HEFL system, despite the generated H₂O₂ concentrations (62.5 mg L^-1) is not very high, the reducing reaction of ≡Fe(III)/Co(III)-OH could get the electron directly from the cathode, which would greatly reduce the consumption of H₂O_2, high utilization efficiency of H₂O₂ (η: 87.63%) could greatly improve the EDTA-Ni removal (97.5%) and TOC (92.6%). This work demonstrates the feasibility of utilizing FeC@Co/N/CF as a cathode for breaking metal-complex in HEFL process.

Scalable synthesis of gyroid-inspired freestanding three-dimensional graphene architectures

Three-dimensional porous architectures of graphene are desirable for energy storage, catalysis, and sensing applications. Yet it has proven challenging to devise scalable methods capable of producing co-continuous architectures and well-defined, uniform pore and ligament sizes at length scales relevant to applications. This is further complicated by processing temperatures necessary for high quality graphene. Here, bicontinuous interfacially jammed emulsion gels (bijels) are formed and processed into sacrificial porous Ni scaffolds for chemical vapor deposition to produce freestanding three-dimensional turbostratic graphene (bi-3DG) monoliths with high specific surface area. Scanning electron microscopy (SEM) images show that the bi-3DG monoliths inherit the unique microstructural characteristics of their bijel parents. Processing of the Ni templates strongly influences the resultant bi-3DG structures, enabling the formation of stacked graphene flakes or fewer-layer continuous films. Despite the multilayer nature, Raman spectra exhibit no discernable defect peak and large relative intensity for the Raman 2D mode, which is a characteristic of turbostratic graphene. Moiré patterns, observed in scanning tunneling microscopy images, further confirm the presence of turbostratic graphene. Nanoindentation of macroscopic pillars reveals a Young's modulus of 30 MPa, one of the highest recorded for sp² carbon in a porous structure. Overall, this work highlights the utility of a scalable self-assembly method towards porous high quality graphene constructs with tunable, uniform, and co-continuous microstructure.

Interface and defect engineering of hybrid nanostructures toward an efficient HER catalyst

The hydrogen evolution reaction (HER) plays a key role in hydrogen production for clean energy harvesting. Designing novel efficient and robust electrocatalysts with sufficient active sites and excellent conductivity is one of the key parameters for hydrogen production using water splitting devices. Recently, low-dimensional carbon materials have gained attention as metal-free catalysts for hydrogen production. Such nanostructures need to be engineered to improve their catalytic activity. Here, we designed and synthesized a B and N doped carbon nanostructure (CNS)-hBN heterostructure as an improved HER catalyst. The hBN layers on CNS could provide exposed defects and edges that act as active sites for proton adsorption and reduction. The composition, structure and chemical properties of the B and N doped CNS-hBN heterostructure were tuned to obtain excellent HER activity. Detailed morphological, structural and electrochemical characterization demonstrated that the synergistic effect rising from the interaction between B and N doped CNS and hBN structures contributes to enhance the electrocatalytic performances. To get more insight into the role of defects and doping, we performed density functional theory (DFT) calculations on the CNS-hBN heterostructure.

Three-dimensional Composite Catalysts for Al-O2 Batteries Composed of CoMn2O4 Nanoneedles Supported on Nitrogen-Doped Carbon Nanotubes/Graphene

Great efforts have been focused on studying high-efficiency and stable catalysts toward oxygen reduction reaction (ORR) in metal-air batteries. In view of synergistic effects and improved properties, carbon nanotubes and three-dimensional graphene (CNTs-3D graphene) hybrid catalysts developed via a well-controlled route are urgently required. Herein, a CoMn₂O₄ (CMO) nanoneedle-supported nitrogen-doped carbon nanotubes/3D graphene (NCNTs/3D graphene) composite was prepared by in situ chemical vapor deposition (CVD) along with hydrothermal methods over a Ni foam substrate. The cyclic voltammetry and linear sweep voltammograms results indicate that the CMO/NCNTs/3D graphene hybrid possesses remarkable electrocatalytic performance toward ORR in alkaline conditions compared with NCNTs/3D graphene, CMO/3D graphene, and 3D graphene catalysts, even outperforming the commercial 20 wt % Pt/C catalyst. Moreover, the Al-air coin cell employing CMO/NCNTs/3D graphene as cathode catalysts obtains an open circuit voltage of 1.55 V and a specific capacity of 312.8 mA h g^-1, which are superior to the Al-air coin cell with NCNTs/3D graphene as catalysts. This work supplies new insights to advanced electrocatalysts introducing NCNTs/3D graphene as a catalyst support to develop scalable transition-metal oxide/NCNTs/3D graphene hybrids with excellent catalytic activity toward ORR in Al-air systems.

Flexible Graphene/Carbon Nanotube Electrochemical Double-Layer Capacitors with Ultrahigh Areal Performance

The fabrication of electrochemical double-layer capacitors (EDLCs) with high areal capacitance relies on the use of elevated mass loadings of highly porous active materials. Herein, we demonstrate a high-throughput manufacturing of graphene/carbon nanotubes hybrid EDLCs. The wet-jet milling (WJM) method is exploited to exfoliate the graphite into single-few-layer graphene flakes (WJM-G) in industrial volumes (production rate ca. 0.5 kg/day). Commercial single-/double-walled carbon nanotubes (SDWCNTs) are mixed with graphene flakes in order to act as spacers between the flakes during their film formation. The WJM-G/SDWCNTs films are obtained by one-step vacuum filtration of the material dispersions, resulting in self-standing, metal- and binder-free flexible EDLC electrodes with high active material mass loadings up to around 30 mg cm^-2 . The corresponding symmetric WJM-G/SDWCNTs EDLCs exhibit electrode energy densities of 539 μWh cm^-2 at 1.3 mW cm^-2 and operating power densities up to 532 mW cm^-2 (outperforming most of the reported EDLC technologies). The EDCLs show excellent cycling stability and outstanding flexibility even in highly folded states (up to 180°).

Chemical and Bio Sensing Using Graphene-Enhanced Raman Spectroscopy

Graphene is a two-dimensional (2D) material consisting of a single sheet of sp² hybridized carbon atoms laced in a hexagonal lattice, with potentially wide usage as a Raman enhancement substrate, also termed graphene-enhanced Raman scattering (GERS), making it ideal for sensing applications. GERS improves upon traditional surface-enhanced Raman scattering (SERS), combining its single-molecule sensitivity and spectral fingerprinting of molecules, and graphene's simple processing and superior uniformity. This enables fast and highly sensitive detection of a wide variety of analytes. Accordingly, GERS has been investigated for a wide variety of sensing applications, including chemical- and bio-sensing. As a derivative of GERS, the use of two-dimensional materials other than graphene for Raman enhancement has emerged, which possess remarkably interesting properties and potential wider applications in combination with GERS. In this review, we first introduce various types of 2D materials, including graphene, MoS₂, doped graphene, their properties, and synthesis. Then, we describe the principles of GERS and comprehensively explain how the GERS enhancement factors are influenced by molecular and 2D material properties. In the last section, we discuss the application of GERS in chemical- and bio-sensing, and the prospects of such a novel sensing method.

Borocarbonitrides as Metal-Free Catalysts for the Hydrogen Evolution Reaction

Hydrogen generation by water splitting is clearly a predominant and essential strategy to tackle the problems related to renewable energy. In this context, the discovery of proper catalysts for electrochemical and photochemical water splitting assumes great importance. There is also a serious intent to eliminate platinum and other noble metal catalysts. To replace Pt by a non-metallic catalyst with desirable characteristics is a challenge. Borocarbonitrides, (B_x C_y N_z ) which constitutes a new class of 2D material, offer great promise as non-metallic catalysts because of the easy tunability of bandgap, surface area, and other electronic properties with variation in composition. Recently, B_x C_y N_z composites with excellent electrochemical and photochemical hydrogen generation activities have been found, especially noteworthy being the observation that B_x C_y N_z with a carbon-rich composition or its nanocomposites with MoS₂ come close to Pt in electrocatalytic properties, showing equally good photochemical activity.

3D Heteroatom-Doped Carbon Nanomaterials as Multifunctional Metal-Free Catalysts for Integrated Energy Devices

Sustainable and cost-effective energy generation has become crucial for fulfilling present energy requirements. For this purpose, the development of cheap, scalable, efficient, and reliable catalysts is essential. Carbon-based heteroatom-doped, 3D, and mesoporous electrodes are very promising as catalysts for electrochemical energy conversion and storage. Various carbon allotropes doped with a variety of heteroatoms can be utilized for cost-effective mass production of electrode materials. 3D porous carbon electrodes provide multiple advantages, such as large surface area, maximized exposure to active sites, 3D conductive pathways for efficient electron transport, and porous channels to facilitate electrolyte diffusion. However, it is challenging to synthesize and functionalize isotropic 3D carbon structures. Here, various synthesis processes of 3D porous carbon materials are summarized to understand how their physical and chemical properties together with heteroatom doping dictate the electrochemical catalytic performance. Prospects of attractive 3D carbon structural materials for energy conversion and efficient integrated energy systems are also discussed.

Chemical Approaches to Carbon-Based Metal-Free Catalysts

Highly active and durable catalysts play a key role in clean energy technologies. However, the high cost, low reserves, and poor stability of noble-metal-based catalysts have hindered the large-scale development of renewable energy. Owing to their low cost, earth abundance, high activity, and excellent stability, carbon-based metal-free catalysts (CMFCs) are promising alternatives to precious-metal-based catalysts. Although many synthetic methods based on solution, surface/interface, solid state, and noncovalent chemistries have been developed for producing numerous CMFCs with diverse structures and functionalities, there is still a lack of effective approaches to precisely control the structures of active sites. Therefore, novel chemical approaches are needed for the development of highly active and durable CMFCs that are capable of replacing precious-metal catalysts for large-scale applications. Herein, a comprehensive and critical review on chemical approaches to CMFCs is given by summarizing important advancements, current challenges, and future perspectives in this emerging field. Through such a critical review, our understanding of CMFCs and the associated synthetic processes will be significantly increased.

A Hybrid Material Combined Copper Oxide with Graphene for an Oxygen Reduction Reaction in an Alkaline Medium

In this work, an electrode material based on CuO nanoparticles (NPs)/graphene (G) is developed for ORR in alkaline medium. According to the characterization of scanning electron microscope and transmission electron microscope, CuO NPs are uniformly distributed on the wrinkled G sheets. The X-ray diffraction test reveals that the phase of CuO is monoclinic. The CuO/G hybrid electrode exhibits a positive onset potential (0.8 V), high cathodic current density (3.79 × 10^-5 mA/cm²) and high electron transfer number (four-electron from O₂ to H₂O) for ORR in alkaline media. Compared with commercial Pt/C electrocatalyst, the CuO/G electrode also shows superior fuel durability. The high electrocatalytic activity and durability are attribute to the strong coupling between CuO NPs and G nanosheets.

Ornamental morphology of ionic liquid functionalized ternary doped N, P, F and N, B, F-reduced graphene oxide and their prevention activities of bacterial biofilm-associated with orthopedic implantation

The multifunctional biological active material design for bone tissue engineering is essential to induce osteoblast cell proliferation and attachment. Adhesion of bacteria on biomaterials to produce biofilms can be major contributors to the pathogenesis of implant material associated infections. This research work focuses on NPF& NBF elemental doping and functionalization of reduced graphene oxide using an imidazolium-based ionic liquid such as BMIM PF₆ and BMIM BF₄ by hydrothermal method. The resulting tri doped reduced graphene oxide (NPF-rGO and NBF-rGO) composite was further used as a scaffold for bone tissue engineering and anti-biofilm activities. The observation of the effect of NPF-rGO and NBF-rGO on the morphology, adhesion and cell proliferation of HOS cell was investigated. Moreover, the tri doped composite tested its antibiofilm properties against B. subtilis, E. coli, K. pneumoniae, and P. aeruginosa pathogenic bacteria. In-vitro studies clearly show the effectiveness of N, P, B, and F doping promoting the rGO mineralization, biocompatibility, and destruction of bacterial biofilm formation. The result of this study suggests that NPF-rGO and NBF-rGO hybrid material will be a promising scaffold for bone reaeration and implantation with a minimal bacterial infection.

Microporous N,P-Codoped Graphitic Nanosheets as an Efficient Electrocatalyst for Oxygen Reduction in Whole pH Range for Energy Conversion and Biosensing Dissolved Oxygen

Microporous N,P-codoped graphitic nanosheets (N,P-CMP-1000) were synthesized by thermal annealing (1000 °C) of as-synthesized conjugated microporous polymers (CMPs) in the presence of phytic acid, which can be used as an effective metal-free electrocatalyst for the oxygen reduction reaction (ORR) for energy conversion. In the whole pH range (i.e. alkaline, acidic, and neutral solutions), the obtained N,P-CMP-1000 exhibits superior electrocatalytic activity for ORR with a low overpotential, high current density, and good stability. Furthermore, N,P-CMP-1000 can also be applied for electrochemically sensing dissolved oxygen (DO), with a high sensitivity (1.89 μA mg^-1  L) and broad detection range (2.56 to 16.65 mg L^-1 ) due to its good electrocatalytic performance towards ORR in neutral solution. In vitro cytotoxicity tests (CCK-8 and Live/Dead Cell Double Staining Assay) of N,P-CMP-1000 extracts demonstrated its good biocompatibility to Human Corneal Epithelial Cells (HCEC), which shows its great potential as an eye-wearable biosensor for sensing DO in tears.

Three-Dimensional Heteroatom-Doped Nanocarbon for Metal-Free Oxygen Reduction Electrocatalysis: A Review

The oxygen reduction reaction (ORR) at the cathode is a fundamental process and functions a pivotal role in fuel cells and metal–air batteries. However, the electrochemical performance of these technologies has been still challenged by the high cost, scarcity, and insufficient durability of the traditional Pt-based ORR electrocatalysts. Heteroatom-doped nanocarbon electrocatalysts with competitive activity, enhanced durability, and acceptable cost, have recently attracted increasing interest and hold great promise as substitute for precious-metal catalysts (e.g., Pt and Pt-based materials). More importantly, three-dimensional (3D) porous architecture appears to be necessary for achieving high catalytic ORR activity by providing high specific surface areas with more exposed active sites and large pore volumes for efficient mass transport of reactants to the electrocatalysts. In this review, recent progress on the design, fabrication, and performance of 3D heteroatom-doped nanocarbon catalysts is summarized, aiming to elucidate the effects of heteroatom doping and 3D structure on the ORR performance of nanocarbon catalysts, thus promoting the design of highly active nanocarbon-based ORR electrocatalysts.

Band gap-Tunable Porous Borocarbonitride Nanosheets for High Energy-Density Supercapacitors

Band gap-tunable porous borocarbonitride (BCN) nanosheets were successfully fabricated with cheap and readily available precursors by annealing and exfoliating. The band gap of the as-prepared BCN materials ranges from 5.5 to 1.0 eV; these samples exhibit beneficial structural features suitable for the application in supercapacitors. Especially, the BCN material with a band gap of 1.0 eV exhibits a great specific surface area (600.9 m² g^-1), massive active sites, and excellent conductivity (10.8 S m^-1). In addition, this example displays great specific capacitance (464.5 F g^-1), excellent cycle stability (98.5% performance retention after 10 000 cycles), and ultrahigh energy density (50.4 W h kg^-1, in 1 M Et₄NBF₄ electrolyte). This excellent electrochemical performance and facile effective synthesis of band gap-tunable BCN materials will provide a promising strategy for configuring nanostructured multiple compound electrodes for other energy storage and conversion devices.