Graphene supported Co-g-C3N4 as a novel metal-macrocyclic electrocatalyst for the oxygen reduction reaction in fuel cells

Single-atom Pt supported on holey ultrathin g-C3N4 nanosheets as efficient catalyst for Li-O2 batteries

As for electrocatalysis, single-atom metal catalysts have been proved to lower the cost and utilize precious metals more efficiently. Herein, single-atom Pt catalyst supported on holey ultrathin g-C₃N₄ nanosheets (Pt-CNHS) was synthesized via a facile liquid-phase reaction of g-C₃N₄ and H₂PtCl₆. The single-atom Pt can achieve high dispersibility and stability, which can promote the utilization efficiency as well as enhance the electrochemical activity. When employed as Li-O₂ batteries' cathode catalyst, Pt-CNHS exhibits excellent electrocatalytic activity. Li-O₂ batteries utilizing Pt-CNHS show much higher discharge specific capacities than those with pure CNHS. Li-O₂ batteries with Pt-CNHS cathode can be cycled stably for 100 times under the discharge capacity of 600 mAh g^-1. Based on experimental results and density functional theory calculations, the superior electrocatalytic activity of Pt-CNHS can be ascribed to the large surface area, the enhanced electrical conductivity and the efficient interfacial mass transfer through Pt atoms and porous structure of CNHS.

Stable cuprous active sites in Cu+-graphitic carbon nitride: Structure analysis and performance in Fenton-like reactions

Cu⁺-based catalysts have great potential in Fenton reactions under neutral pH conditions. However, cuprous (Cu⁺) materials are instable in the aqueous environment. Herein, using the cheap precursors, a Cu⁺-graphitic carbon nitride complex with an efficient Fenton-like activity as well as relative stability was prepared. 99.2% removal of Rhodamine B with an initial concentration of 50 mg/L could be attained in 1 h. Several experimental techniques are employed to study the structure of this catalyst. Results show that after the addition of Cu, the graphitic carbon nitride (g-C₃N₄) network is partially destroyed and the reduced Cu is therefore firmly embedded in the fragmentary g-C₃N₄ sheet. The X-ray adsorption fine spectra illustrates the chemical state and the local structure of the bonded Cu. Due to the strong orbital hybridization, Cu⁺ could be stabilized through the coordination with pyridinic N. A two-coordinate structure with a bond length of 1.90 Å is confirmed and this structure is not changed even after the Fenton-like reaction. Singlet oxygen (¹O₂) and hydroxyl radicals (HO•) are produced by the rapid interaction of bonded Cu⁺ with H₂O₂ and the resulting Cu²⁺ can be easily reduced to its cuprous state due to its structure stability, leading to its high activity in the Fenton-like reaction.

Palladium Nanoparticles/Graphitic Carbon Nitride Nanosheets-Carbon Nanotubes as a Catalytic Amplification Platform for the Selective Determination of 17α-ethinylestradiol in Feedstuffs

A new kind of nanocomposite, graphitic carbon nitride (g-C₃N₄)-carbon nanotubes (CNTs), has been synthesized via solid grinding, and followed by thermal polymerization process of melamine and CNTs. Pd nanoparticles were loaded on the as-prepared nanocomposite by the self-assembly method. The Pd/g-C₃N₄-CNTs nanocomposite exhibited excellent electrocatalytic activity toward the oxidation of 17α-ethinylestradiol (EE2), and compared with other detection methods of EE2, such as HPLC, this detection platform does not need the samples for further purification processing. And this detection platform was compared with HPLC, there is no significant difference between two methods, and the accuracy and precision of the determination of EE2 in feedstuff sample by differential pulse voltammetry (DPV) to a satisfactory level. Thus, the Pd/g-C₃N₄-CNTs nanocomposite can be used as a signal amplification platform for the detection of EE2 in feedstuffs samples. Under the optimum condition, the current response increased linearly with EE2 concentration from 2.0 × 10⁻⁶ ~ 1.5 × 10⁻⁴ M with a detection limit of 5.0 × 10⁻⁷ M (S/N = 3) by DPV. The Pd/g-C₃N₄-CNTs showed good reproducibility and excellent anti-interference ability that the relative standard deviation was 3.3% (n = 5). This strategy may find widespread and promising applications in other sensing systems involving EE2.

Photocatalytic mineralization of hard-degradable morphine by visible light-driven Ag@g-C3N4 nanostructures

The entrance of some hard-degradable pharmaceutical contaminants can cause irreparable damage to humans and other organisms; therefore, removing these pollutants from water is one of the most important activities in water purification field. In this work, the mineralization of morphine was performed using photocatalytic degradation method. Graphitic carbon nitride (g-C₃N₄) nanosheets, due to their promising tunable characteristics, were chosen as visible-light-driven nanostructured heterogeneous photocatalyst. To enhance the photocatalytic activity, g-C₃N₄ was doped with Ag noble metal due to its surface plasmon resonance effect and acting as an electron sink. The photodegradation of morphine was evaluated under different pH values, the dosage of the photocatalyst, initial concentration of morphine, and Ag% loading under sunlight as green energy. The maximum efficiency was obtained in the very low concentration of Ag@g-C₃N₄ photocatalyst with the superior low value of 0.17 g L^-1. Near complete mineralization of morphine was achieved by Ag@g-C₃N₄ with metal content percentage equal to 5 in 180 min and pH = 2. Also, using various active species scavengers, superoxide anion radical was identified as the main responsible species in the photocatalysis reaction of morphine degradation.

Salt-Assisted Synthesis of 3D Porous g-C3N4 as a Bifunctional Photo- and Electrocatalyst

Graphitic carbon nitride (g-C₃N₄), characterized with a suitable bandgap, has aroused great interest as a robust and efficient catalyst for solar energy utilization. Herein, we introduce a new strategy to fabricate a three-dimensional (3D) porous g-C₃N₄ by a facile NaCl-assisted ball-milling strategy. The porous structure-induced advantages, such as a higher specific surface area, more efficient charge separation, and faster electron-transfer efficiency, enable the 3D porous g-C₃N₄ to achieve impressive properties as a bifunctional catalyst for both photocatalytic hydrogen evolution and electrocatalytic oxygen evolution reaction (OER). As a result, the 3D porous g-C₃N₄ exhibits a hydrogen evolution rate of 598 μmol h^-1 g^-1 with an apparent quantum yield of 3.31% at 420 nm for photocatalytic H₂ generation, which is much higher than that of the bulk g-C₃N₄. Simultaneously, the porous g-C₃N₄ also presents an attractive OER performance with a low onset potential of 1.47 V (vs reversible hydrogen electrode) in an alkaline electrolyte after rational cobalt-doping. Accordingly, the NaCl-assisted ball-milling strategy paves the way to the rational design of a controllable porous structure.

Development of Fe-doped g-C3N4/graphite mediated peroxymonosulfate activation for degradation of aromatic pollutants via nonradical pathway

A new composite catalyst, i.e., Fe doped g-C₃N₄/graphite (Fe-CN/G), was successfully constructed to activate peroxymonosulfate (PMS) for efficient phenolic compounds (i.e., p-chlorophenol, 4-CP) degradation in the pH range of 3-10. The optimized Fe-CN/G, i.e., Fe_3.75-CN/G_5.0, was fabricated at the dosage of 3.75 mmol FeCl₃·6H₂O, 5.0 g dicyandiamide, and 5.0 mmol glucose. Fe complexed in the nitrogen pots of Fe_3.75-CN/G_5.0 was demonstrated to be the primary active site for PMS activation, and the introduction of graphite favored the exposure of more accessible active sites in Fe_3.75-CN/G_5.0, suggesting a synergistic effect between the Fe and graphite of Fe_3.75-CN/G_5.0 on 4-CP degradation. Multiple experiments confirmed that sulfate radical (SO₄^-), hydroxyl radical (HO), singlet oxygen (¹O₂) and superoxide radical (O₂^-) exerted negligible contribution on 4-CP degradation. The in-situ Fe K-edge X-ray absorption near-edge structure (XANEX) analysis revealed a redox cycle of Fe in PMS/Fe_3.75-CN/G_5.0, suggesting the formation of high-valent iron-oxo species (Fe^IVO) was responsible for 4-CP degradation. In addition, PMS/Fe_3.75-CN/G_5.0 exhibited acceptable degradation of 4-CP in the presence of coexisting anions and natural organic matters (NOM). We believe this study provides new insights into the design and development of Fe-based heterogeneous catalysts for PMS-based wastewater treatment.

Three-dimensional mesoporous sandwich-like g-C3N4-interconnected CuCo2O4 nanowires arrays as ultrastable anode for fast lithium storage

Inspite of their impressive high theoretical capacity as Lithium-ion batteries (LIBs) anodes, spinel transition-metal oxides (TMOs) suffer serious volume expansion, aggregation and the pulverization of crystal structures during lithiation/delithiation, and this process severely restrict their industrial application. Multi-dimensional morphological engineering of spinel TMO nanostructures is an effective way to solve this issue. In this work, using facile hydrothermal synthetic methods, spinel CuCo₂O₄ nanowires arrays are synthesized and supported on g-C₃N₄ nanosheets, thus forming a unique sandwich-like interconnected three-dimensional mesoporous structure containing high amount of void spaces. Addition of g-C₃N₄ nanosheets to CuCo₂O₄ nanowire arrays may shorten the Li⁺ diffusion distance and electron transfer pathway, and may also provide more active sites for Li⁺ diffusion into electrolyte and buffer for the volume expansion and aggregation of CuCo₂O₄. As a LIB anode material, CuCo₂O₄@g-C₃N₄ shows initial lithiation capacity of 840.6 mAh g^-1, and capacity retention of 641.2 mAh g^-1 after 60 cycles at the current density of 0.1 A g^-1 and 499.2 mAh g^-1 after 40 cycles at high current of 1 A g^-1, which is significantly better than value of pure CuCo₂O₄ nanowires. This work affords a new way to tackle the problem of volume expansion of high capacity spinel TMO anode materials using g-C₃N₄ nanosheets as buffering agent.

Oxygen Reduction Reaction Activity of Microwave Mediated Solvothermal Synthesized CeO2/g-C3N4 Nanocomposite

Electrocatalytic active species like transition metal oxides have been widely combined with carbon-based nanomaterials for enhanced Oxygen Reduction Reaction (ORR) studies because of the synergistic effect arising between different components. The aim of the present study is to synthesize CeO₂/g-C₃N₄ system and compare the ORR activity with bare CeO₂. Ceria (CeO₂) embedded on g-C₃N₄ nanocomposite was synthesized by a single-step microwave-mediated solvothermal method. This cerium oxide-based nanocomposite displays enhanced ORR activity and electrochemical stability as compared to bare ceria.

Synthesis and Electrochemical Study of Mesoporous Nickel-Cobalt Oxides for Efficient Oxygen Reduction

Development of a cost-effective and efficient electrocatalyst for the sluggish oxygen reduction reaction (ORR) is a crucial challenge for clean energy technologies. In this study, we have synthesized various Ni and Co oxide (NCO) nanomaterials via a facile coprecipitation, followed by the calcination method. The morphology of the formed NCO nanomaterials was controlled by varying the percentage of the Ni and Co precursors, leading to the formation of a template-free mesoporous spinel phase structure of Ni _xCo_{3- x}O₄. It was found that the number of the octahedral site cations and the defect sites with lower oxygen in the spinel oxides can be tunable by taking appropriate ratios of the Ni and Co precursors. The optimized NCO nanomaterial exhibits superior electrocatalytic activity compared to the mono-metal oxides of NiO and Co₃O₄ with over 3 times higher current density and ∼0.250 V lower onset potential toward ORR in a 0.1 M KOH solution. Scanning electrochemical microscopy was utilized in mapping the activity of the catalyst and monitoring the ORR products, further confirming that a four-electron transfer pathway was facilitated by the NCO nanomaterial. Moreover, the developed mesoporous NCO nanomaterial exhibits a high methanol tolerance capability and long-term stability when compared to the commercial state-of-the-art Pt/C electrocatalyst. The improvement of the catalytic activity and stability of this advanced NCO nanomaterial toward ORR may be attributed to the facile accessible mesoporous structure, and the abundance of octahedral site cations and defective oxygen sites.

Identifying the Activation of Bimetallic Sites in NiCo2 S4 @g-C3 N4 -CNT Hybrid Electrocatalysts for Synergistic Oxygen Reduction and Evolution

Hybrid materials composed of transition-metal compounds and nitrogen-doped carbonaceous supports are promising electrocatalysts for various electrochemical energy conversion devices, whose activity enhancements can be attributed to the synergistic effect between metallic sites and N dopants. While the functionality of single-metal catalysts is relatively well-understood, the mechanism and synergy of bimetallic systems are less explored. Herein, the design and fabrication of an integrated flexible electrode based on NiCo₂ S₄ /graphitic carbon nitride/carbon nanotube (NiCo₂ S₄ @g-C₃ N₄ -CNT) are reported. Comparative studies evidence the electronic transfer from bimetallic Ni/Co active sites to abundant pyridinic-N in underlying g-C₃ N₄ and the synergistic effect with coupled conductive CNTs for promoting reversible oxygen electrocatalysis. Theoretical calculations demonstrate the unique coactivation of bimetallic Ni/Co atoms by pyridinic-N species (a Ni, Co-N₂ moiety), which simultaneously downshifts their d-band center positions and benefits the adsorption/desorption features of oxygen intermediates, accelerating the reaction kinetics. The optimized NiCo₂ S₄ @g-C₃ N₄ -CNT hybrid manifests outstanding bifunctional performance for catalyzing oxygen reduction/evolution reactions, highly efficient for realistic zinc-air batteries featuring low overpotential, high efficiency, and long durability, superior to those of physical mixed counterparts and state-of-the-art noble metal catalysts. The identified bimetallic coactivation mechanism will shed light on the rational design and interfacial engineering of hybrid nanomaterials for diverse applications.

Controlled Microwave-Assisted Synthesis of the 2D-BiOCl/2D-g-C3N4 Heterostructure for the Degradation of Amine-Based Pharmaceuticals under Solar Light Illumination

Designing efficient 2D-bismuth oxychloride (BiOCl)/2D-g-C₃N₄ heterojunction photocatalysts by the microwave-assisted method was studied in this work using different amounts of BiOCl plates coupled with g-C₃N₄ nanosheets. The effects of coupling the 2D structure of g-C₃N₄ with the 2D structure of BiOCl were systematically examined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, X-ray diffraction, photoluminescence (PL), lifetime decay measurement, surface charges of the samples at various pH conditions, and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The prepared photocatalysts were used for the degradation of amine-based pharmaceuticals, and nizatidine was used as a model pollutant to evaluate the photocatalytic activity. The UV-vis DRS and other optical properties indicated the major effect of coupling of BiOCl with g-C₃N₄ into a 2D/2D structure. The results showed a narrowing in the band gap energy of the composite form, whereas the PL and lifetime analysis showed greater inhibition of the electron-hole recombination process and slightly longer charge carrier lifetime. Accordingly, the BiOCl/g-C₃N₄ composite samples exhibited an enhancement in the photocatalytic performance, specifically for the 10% BiOCl/g-C₃N₄ sample. Moreover, the zeta potential of this sample at different pH values was evaluated to determine the isoelectric point of the synthesized composite material. Consequently, the pH was adjusted to match the isoelectric point of the complex materials, which further enhanced the activity. Further degradation of pharmaceuticals was studied under solar light irradiation, and 96% degradation was achieved within 30 min.

Decorating g-C3N4 Nanosheets with Ti3C2 MXene Nanoparticles for Efficient Oxygen Reduction Reaction

One of the major challenges associated with fuel cells is exploring highly efficient and low-cost electrocatalysts for the oxygen reduction reaction (ORR). Herein, the feasibility of using Ti₃C₂ MXene nanoparticles (NPs) to enhance the electrocatalytic activity of g-C₃N₄ for ORR was investigated. By varying the content of Ti₃C₂ NPs, a series of g-C₃N₄/Ti₃C₂ heterostructures were obtained, displaying enhanced electrocatalytic activity, including a positive shift in both onset and peak potentials toward ORR, compared to the original g-C₃N₄ in basic solution. We attribute the improvement to the favorable electrical conductivity of well-dispersed Ti₃C₂ MXene nanoparticles and also enhanced O₂ adsorption due to the electronic coupling effect between g-C₃N₄ and Ti₃C₂ in the heterostructures. This work demonstrates the potential of earth-abundant MXene family materials to construct low-cost and high-performance electrocatalysts.

Selective liquid phase oxidation of ethyl benzene to acetophenone by palladium nanoparticles immobilized on a g-C3N4–rGO composite as a recyclable catalyst

A hybrid structure g-C₃N₄–rGO with honeycomb units was prepared for immobilizing Pd nanoparticles by a simple wet impregnation method.

Fabrication of 2D heterojunction photocatalyst Co-g-C3N4/MoS2 with enhanced solar-light-driven photocatalytic activity

Co-Doping and formation of a 2D heterojunction with MoS₂ can significantly boost the photocatalytic activity of g-C₃N₄.

First-principles study of the effect of compressive strain on oxygen adsorption in Pd/Ni/Cu-alloy-core@Pd/Ir-alloy-shell catalysts

Through synergism between the ligand effect, the d-band center shift, and the surface alloying effect, the Pd₃CuNi@PdIr catalyst exhibits the poorest dioxygen adsorption and, consequently, the best catalytic ORR performance.

Au-TiO2-Loaded Cubic g-C3N4 Nanohybrids for Photocatalytic and Volatile Organic Amine Sensing Applications

A green and efficient approach for efficient nanohybrid photocatalysts in extending the light response to the visible spectrum is a hot research topic in sustainable energy technologies. In this work, novel Au-TiO₂@m-CN nanocomposite was synthesized using hard template of cubic ordered mesoporous KIT-6 via the nanocasting process. The as-prepared Au-TiO₂@m-CN nanohybrids exhibit enhanced photocatalytic activities with improved stability and reusability using methyl orange dye. The enhanced photocatalytic performance is a result of the conjugated effect of catalytic active Au and TiO₂ nanoparticles supported on highly efficient visible light sensitizer, graphitic carbon nitride (m-CN or g-C₃N₄), and ordered mesoporous morphology. Besides, the sensing performance of Au-TiO₂@m-CN nanohybrids was also tested for the detection of amine gases, wherein a significant response was reported for triethylamine at low operating temperatures. This study reveals a simple and scalable methodology to design and develop next generation of layered mesoporous materials for multifunctional applications.

AA- and ABA-stacked carbon nitride (C3N4): novel photocatalytic water splitting solar-to-hydrogen energy conversion

We report the development of the C3N4 structure by integrating two different structures: (i) two identical layers as AA-stacked C3N4 and (ii) intercalating one different layer between two identical layers as ABA-stacked C3N4. This in turn endows C3N4 with significantly promoted charge migration, up-shifted conduction-band (CB) level, enhanced CB potential from -0.89 eV (AA-stacked C3N4) to -1.03 eV (ABA-stacked C3N4), broadened band gap as well as enhanced surface area, all of which favor the enhancement of the photocatalytic performance. The optical absorption level exhibited significant enhancement in the visible light region when shifting from AA-stacked C3N4 to ABA-stacked C3N4, where the absorption edge moves from λ = 508.1 → λ = 454.1 nm. This corresponds to the direct optical band gap of 2.44 eV → 2.73 eV, which is well matched with the solar spectrum and the sufficient negative CB potential for H+/H2 reduction. Based on these results, we can conclude that AA-stacked and ABA-stacked C3N4 satisfies all the requirements to be efficient photocatalysts. This study will significantly improve the search efficiency and considerably aid the experimentalists in the exploration of novel photocatalysts.

Graphitic Carbon Nitride Doped with the s-Block Metals: Adsorbent for the Removal of Methyl Blue and Copper(II) Ions

The synthesis of graphitic carbon nitride (g-C₃N₄) doped with s-block metals is described. The materials were synthesized via thermal polycondensation of cyanamide and the appropriate metal chloride. The inclusion of the metal precursor strongly influenced the surface chemistry features as well as the textural, morphological, and structural properties of the g-C₃N₄. The doping of g-C₃N₄with s-block metals markedly enhanced its adsorption performance, which was studied during the removal of two model solutes (methyl blue and copper ions) from aqueous solutions. The maximum adsorption capacity for the organic dye was increased by 680 times after the doping process. The uptake of copper(II) increased ca. 30 times for the doped g-C₃N₄. The improvement of the adsorption performance is discussed in terms of the surface chemistry and textural features.

An Electrochemical Sensor of Poly(EDOT-pyridine-EDOT)/Graphitic Carbon Nitride Composite for Simultaneous Detection of Cd2+ and Pb2

In this study, poly(2,5-bis(3,4-ethylenedioxythienyl)pyridine)/graphitic carbon nitride composites (poly(BPE)/g-C₃N₄) were prepared by an in situ chemical polymerization method. Composites were characterized by using Fourier transform infrared spectroscopy (FT-IR), ultraviolet⁻visible absorption spectra (UV⁻vis), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, electrochemical sensors were applied for the electrochemical determination of Cd²⁺ and Pb²⁺ using the differential pulse voltammetry (DPV) method. The results indicated that 10 wt % poly(BPE)/g-C₃N₄ composite-modified electrode exhibited linear detection ranging from 0.12 to 7.2 μM and 0.08 to 7.2 μM for Cd²⁺ and Pb²⁺, with detection limits (S/N = 3) of 0.018 μM and 0.00324 μM. Interference analysis suggested that the 10 wt % poly(BPE)/g-C₃N₄-modified electrode can be applied for the detection of the Cd²⁺ and Pb²⁺ in real samples.

In Situ Formation of AgCo Stabilized on Graphitic Carbon Nitride and Concomitant Hydrolysis of Ammonia Borane to Hydrogen

The development of highly-efficient heterogeneous supported catalysts for catalytic hydrolysis of ammonia borane to yield hydrogen is of significant importance considering the versatile usages of hydrogen. Herein, we reported the in situ synthesis of AgCo bimetallic nanoparticles supported on g-C₃N₄ and concomitant hydrolysis of ammonia borane for hydrogen evolution at room temperature. The as-synthesized Ag0.1Co0.9/g-C₃N₄ catalysts displayed the highest turnover frequency (TOF) value of 249.02 mol H₂·(molAg·min)−1 for hydrogen evolution from the hydrolysis of ammonia borane, which was higher than many other reported values. Furthermore, the Ag0.1Co0.9/g-C₃N₄ catalyst could be recycled during five consecutive runs. The study proves that Ag0.1Co0.9/g-C₃N₄ is a potential catalytic material toward the hydrolysis of ammonia borane for hydrogen production.

Insight into the Crucial Factors for Photochemical Deposition of Cobalt Cocatalysts on g-C3N4 Photocatalysts

Photochemical preparation of inexpensive hydrogen evolution cocatalysts is of great significance and is challenging. Currently, the crucial factors in the photochemical preparation of nonnoble metals are still unknown. In this work, taking Co/g-C₃N₄ composite photocatalysts as a case, complexing agents and sacrificial agents were found to be the crucial factors for the photochemical deposition process. Cobalt was supported on the electron outlet points of g-C₃N₄ for 1 h, and the ratio of Co in the Co/g-C₃N₄ composite photocatalyst can be regulated by changing the irradiation time of the preparation process. The optimized hydrogen evolution rate of Co/g-C₃N₄ was about 11.48 μmol h^-1, which was 75 times more than pure g-C₃N₄. The photocatalytic H₂ evolution rate was stable after 48 h. The mechanism for the high activity of Co/g-C₃N₄ composites was explored by surface photovoltage spectra and photoluminescence spectra. Co effectively promoted the separation of the photogenerated electrons and holes of g-C₃N₄ and improved the H₂ production rate.

Oxygen Vacancy Engineering in Europia Clusters/Graphite-Like Carbon Nitride Nanostructures Induced Signal Amplification for Highly Efficient Electrochemiluminesce Aptasensing

Oxygen vacancy is an intrinsic defect in metal oxide semiconductors and has a crucial influence on their physicochemical and electronic properties. To boost the electrochemiluminescence (ECL) efficiency of the graphite-like carbon nitride (g-C₃N₄), the wet-chemical-calcination method was developed to introduce an oxygen vacancy in Eu-doped g-C₃N₄ nanostructures for the first time. The morphology and structure characterization suggest that the Eu element was present in the matrix of the europia (Eu₂O₃) clusters. Because of the effect of oxygen vacancy promoting catalytic activity, the doping of Eu caused a great positive shift of onset potential and large signal amplification in cathodic ECL signals compared with pure g-C₃N₄. Furthermore, a novel and ultrasensitive ECL aptasensor was realized with 17β-estradiol (E2) as a prototype target by adsorption of E2 aptamer onto the Eu₂O₃-doped g-C₃N₄ (Eu₂O₃- g-C₃N₄) surface via van der Waals force. Given the specific recognition between aptamer and E2, the ECL signal decreased with the increasing concentration of E2, because the formation of E2-aptamer complex impeded the diffusion of luminophor molecules and the electrons approaching the surface of the electrode. Under the optimal cases, the as-prepared ECL aptasensor showed superior performances and also manifested outstanding selectivity toward E2. The present conceptual strategy offers a novel methodology to boost the sensitivity of the ECL sensor and promote the activity of ECL reagents.

Cobalt nanoparticles incorporated into hollow doped porous carbon capsules as a highly efficient oxygen reduction electrocatalyst

MOF nanocrystals are employed for the design and synthesis of cobalt nanoparticles embedded into hollow doped porous carbon electrocatalyst.

Molecular engineering of polymeric carbon nitride: advancing applications from photocatalysis to biosensing and more

Different designs and constructions of molecular structures of carbon nitride for emerging applications, such as biosensing, are discussed.

Constructing Sheet-On-Sheet Structured Graphitic Carbon Nitride/Reduced Graphene Oxide/Layered MnO₂ Ternary Nanocomposite with Outstanding Catalytic Properties on Thermal Decomposition of Ammonium Perchlorate

We unprecedentedly report that layered MnO₂ nanosheets were in situ formed onto the surface of covalently bonded graphitic carbon nitride/reduced graphene oxide nanocomposite (g-C₃N₄/rGO), forming sheet-on-sheet structured two dimension (2D) graphitic carbon nitride/reduced graphene oxide/layered MnO₂ ternary nanocomposite (g-C₃N₄/rGO/MnO₂) with outstanding catalytic properties on thermal decomposition of ammonium perchlorate (AP). The covalently bonded g-C₃N₄/rGO was firstly prepared by the calcination of graphene oxide-guanidine hydrochloride precursor (GO-GndCl), following by its dispersion into the KMnO₄ aqueous solution to construct the g-C₃N₄/rGO/MnO₂ ternary nanocomposite. FT-IR, XRD, Raman as well as the XPS results clearly demonstrated the chemical interaction between g-C₃N₄, rGO and MnO₂. TEM and element mapping indicated that layered g-C₃N₄/rGO was covered with thin MnO₂ nanosheets. Furthermore, the obtained g-C₃N₄/rGO/MnO₂ nanocomposite exhibited promising catalytic capacity on thermal decomposition of AP. Upon addition of 2 wt % g-C₃N₄/rGO/MnO₂ ternary nanocomposite as catalyst, the thermal decomposition temperature of AP was largely decreased up by 142.5 °C, which was higher than that of pure g-C₃N₄, g-C₃N₄/rGO and MnO₂, respectively, demonstrating the synergistic catalysis of the as-prepared nanocomposite.

Uncondensed Graphitic Carbon Nitride on Reduced Graphene Oxide for Oxygen Sensing via a Photoredox Mechanism

Melon, a polymeric, uncondensed graphitic carbon nitride with a two-dimensional structure, has been coupled with reduced graphene oxide (rGO) to create an oxygen chemiresistor sensor that is active under UV photoactivation. Oxygen gas is an important sensor target in a variety of areas including industrial safety, combustion process monitoring, as well as environmental and biomedical fields. Because of the intimate electrical interface formed between melon and rGO, charge transfer of photoexcited electrons occurs between the two materials when under UV (λ = 365 nm) irradiation. A photoredox mechanism wherein oxygen is reduced on the rGO surface provides the basis for sensing oxygen gas in the concentration range 300-100 000 ppm. The sensor response was found to be logarithmically proportional to oxygen gas concentration. DFT calculations of a melon-oxidized graphene composite found that slight protonation of melon leads to charge accumulation on the rGO layer and a corresponding charge depletion on the melon layer. This work provides an example of a metal-free system for solid-gas interface sensing via a photoredox mechanism.

Promotion of the excited electron transfer over Ni- and Co -sulfide co-doped g-C3N4 photocatalyst (g-C3N4/NixCo1-xS2) for hydrogen Production under visible light irradiation

A Ni- and Co- sulfide co-doped g-C₃N₄ photocatalyst (g-C₃N₄/Ni_xCo_1-xS₂) was prepared by hydrothermal method and this photocatalyst, namely, g-C₃N₄/Ni_xCo_1-xS₂ shown excellent photocatalytic properties due to the special structure of Ni-Co-S with boundary different exposure to active site of transition metal-metal (Ni-Co) active planes. With the introduction of Co atoms, the H₂ production amount reached the maximum about 400.81 μmol under continuous visible light irradiation for 4 hours based on the efficiently charge separation and greatly improved electron transfer resulted from the presence of sufficient active exposure at the boundary. The serial studies shown that the existence of Ni-Co-S structure over g-C₃N₄ active surface is the key factor of activity affections by means of several characterizations such as SEM, XRD, XPS diffuse reflectance etc. and the results of which were in good agreement with each other. A possible reaction mechanism over eosin Y-sensitized g-C₃N₄/Ni_xCo_1-xS₂ photocatalyst under visible light irradiation was proposed.

Metal-Free Photocatalyst with Visible-Light-Driven Post-Illumination Catalytic Memory

A novel metal-free photocatalyst with post-illumination catalytic memory was fabricated by the graphitic carbon nitride (g-C₃N₄), carbon nanotubes (CNTs), and graphene (Gr), in which g-C₃N₄ acts as an efficient photocatalyst and the CNTs and Gr act as supercapacitors. The removal of phenol was achieved in the dark by post-illumination catalytic memory because the photocatalyst could store a portion of its photoactivity via photogenerated electrons in the CNTs and Gr under visible-light illumination and then release the electrons again in the dark. Therefore, this metal-free photocatalyst is capable of operation in the dark for a broad range of applications.