Two-dimensional Graphitic Carbon Nitride Research Articles

Intercalated PtCo Electrocatalyst of Vanadium Metal Oxide Increases Charge Density to Facilitate Hydrogen Evolution.

Efforts to develop high-performance electrocatalysts for the hydrogen evolution reaction (HER) are of utmost importance in ensuring sustainable hydrogen production. The controllable fabrication of inexpensive, durable, and high-efficient HER catalysts still remains a great challenge. Herein, we introduce a universal strategy aiming to achieve rapid synthesis of highly active hydrogen evolution catalysts using a controllable hydrogen insertion method and solvothermal process. Hydrogen vanadium bronze HxV2O5 was obtained through controlling the ethanol reaction rate in the oxidization process of hydrogen peroxide. Subsequently, the intermetallic PtCoVO supported on two-dimensional graphitic carbon nitride (g-C3N4) nanosheets was prepared by a solvothermal method at the oil/water interface. In terms of HER performance, PtCoVO/g-C3N4 demonstrates superior characteristics compared to PtCo/g-C3N4 and PtCoV/g-C3N4. This superiority can be attributed to the notable influence of oxygen vacancies in HxV2O5 on the electrical properties of the catalyst. By adjusting the relative proportions of metal atoms in the PtCoVO/g-C3N4 nanomaterials, the PtCoVO/g-C3N4 nanocomposites show significant HER overpotential of η10 = 92 mV, a Tafel slope of 65.21 mV dec-1, and outstanding stability (a continuous test lasting 48 h). The nanoarchitecture of a g-C3N4-supported PtCoVO nanoalloy catalyst exhibits exceptional resistance to nanoparticle migration and corrosion, owing to the strong interaction between the metal nanoparticles and the g-C3N4 support. Pt, Co, and V simultaneous doping has been shown by Density Functional Theory (DFT) calculations to enhance the density of states (DOS) at the Fermi level. This augmentation leads to a higher charge density and a reduction in the adsorption energy of intermediates.

Theoretical design of bifunctional single-atom catalyst over g-C2N2 for oxygen evolution and reduction reactions

The two-dimensional graphitic carbon nitride (g-CxNy) is a promising support for electrochemistry catalysts owing to its stability and controllable chemical composition. Here, by density functional theory (DFT) a serial of transition metal single-atom catalysts (SAC) supported on the g-C2N2 with vacancy (denoted as TM1/C2N2, TM=Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir and Pt) were studied for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The non-noble Ni and Co single atom exhibited relatively strong binding energies over the defective g-C2N2 support. The d-band center of TM performed a good descriptor for adsorption free energies of intermediates. For OER, the overpotential of non-noble Co1/C2N2 was as low as 0.30 V, comparable to Rh1/C2N2. For ORR, both Co1/C2N2 and Rh1/C2N2 displayed excellent performance with overpotentials of around 0.50 V. The volcano plot revealed that the proper binding strength of O* and OH* on Co1/C2N2 rendered it an excellent bifunctional catalyst for both OER and ORR. Considering the superior performance of Co SAC over g-C2N2 than not only g-C3N4 but also defective graphene, we postulate that there could exist an optimized C/N ratio of carbon-rich g-CxNy support for improving the non-noble Co SAC activity on oxygen electrode.

When 2D g-C3N4 meets 0D CNQDs and 1D CNTs: A strategy for photocatalytic hydrogen production over a ternary non-metallic catalyst

Utilizing solar energy to facilitate photocatalytic hydrogen production holds great promise in addressing the energy crisis. One material that shows tremendous potential in this field is two-dimensional graphitic carbon nitride (2D g-C3N4). However, the fast recombination rate of photogenerated carriers and the limited specific surface area impede its photocatalytic activity. This research endeavors to address these limitations by developing a ternary composite photocatalyst, CNQDs/g-C3N4/CNTs, by employing the microwave hydrothermal method. g-C3N4 was co-modified with zero-dimensional g-C3N4 quantum dots (0D CNQDs) and one-dimensional carbon nanotubes (1D CNTs). Incorporating CNQDs and the g-C3N4 interface facilitates the separation of photogenerated carriers, while the tubular channel of CNTs provides favorable conditions for transferring photogenerated electrons. Additionally, the introduction of CNQDs and CNTs significantly increases the specific surface area of the sample, thereby enhancing the number of reaction active sites available for the photocatalytic production of hydrogen. The hydrogen generation rate of the CNQDs/g-C3N4/CNTs is 1109.388 μmol⋅g−1⋅h−1, surpassing that of the single g-C3N4 specimen by 3.62 times. The application of density functional theory (DFT) calculations reinforces the enhanced performance of the composite through the synergistic effect of CNQDs and CNTs. This effect optimizes the adsorption behavior of the active intermediate (H*) and reduces the Gibbs free energy ΔG(H*) associated with the photocatalytic hydrogen evolution reaction.

Photocatalytic activity of dual defect modified graphitic carbon nitride is robust to tautomerism: machine learning assisted ab initio quantum dynamics.

Two-dimensional graphitic carbon nitride (GCN) is a popular metal-free polymer for sustainable energy applications due to its unique structure and semiconductor properties. Dopants and defects are used to tune GCN, and dual defect modified GCN exhibits superior properties and enhanced photocatalytic efficiency in comparison to pristine or single defect GCN. We employ a multistep approach combining time-dependent density functional theory and nonadiabatic molecular dynamics (NAMD) with machine learning (ML) to investigate coupled structural and electronic dynamics in GCN over a nanosecond timescale, comparable to and exceeding the lifetimes of photo-generated charge carriers and photocatalytic events. Although frequent hydrogen hopping transitions occur among four tautomeric structures, the electron-hole separation and recombination processes are only weakly sensitive to the tautomerism. The charge separated state survives for about 10 ps, sufficiently long to enable photocatalysis. The employed ML-NAMD methodology provides insights into rare events that can influence excited state dynamics in the condensed phase and nanoscale materials and extends NAMD simulations from pico- to nanoseconds. The ab initio quantum dynamics simulation provides a detailed atomistic mechanism of photoinduced evolution of charge carriers in GCN and rationalizes how GCN remains photo-catalytically active despite its multiple isomeric and tautomeric forms.

Pyrolysis-assisted synthesis of two-dimensional graphitic carbon nitride nanosheets embedded with transition metal oxide (Ni or Fe) for high-performance asymmetric supercapacitors

This study employed a one-step pyrolysis-assisted technique to successfully synthesized with two different transition metal oxides (M = Ni, Fe) embedded on graphitic carbon nitride nanosheets (g-C3N4-NS). The resulting nanocomposites exhibit exceptional electrochemical performance in supercapacitor applications due to various parameters such as morphology, specific surface area and crystallinity. Notably, the NiO/g-C3N4-NS and Fe2O3/g-C3N4-NS electrodes simplify the Faradaic reactions and achieve the maximum capacitance of 816 F g−1 and 703 F g−1 at 0.5 A g−1, respectively. Additionally, these electrodes demonstrate superior cycling stability, retaining approximately 96 % of their capacity retention after 5000 cycles. Furthermore, the NiO/g-C3N4-NS//AC and Fe2O3/g-C3N4-NS//AC devices exhibit promising supercapacitor device performance, yielding respectable specific capacity of 53 F g−1 (NiO/g-C3N4-NS//AC) and 43.5 F g−1 (Fe2O3/g-C3N4-NS//AC) at 0.5 A g−1, underscoring the commendable rate capability of the asymmetric electrodes and the energy densities of 19 Wh kg−1 and 16 Wh kg−1 at a power density of 400 W kg−1, respectively. These findings underscore the potential of metal oxide/g-C3N4-NS composites as an electrode material for power storing applications, as demonstrated by these asymmetric supercapacitor devices.

Nanopore rigidity as an atomic descriptor of ion-transfer kinetics in sieving membranes: Insights from two-dimensional g-C3N4

Kinetics of ions play a crucial role in the performance of materials for a wide range of applications, including solid electrolytes, fuel cells, and sieving membranes. However, establishing a quantitative correlation between microscopic characteristics of a material and kinetics of conducting species inside remains a major challenge. Combining first-principles and metadynamics methods, we investigate sieving behavior of two-dimensional graphitic carbon nitride (g-C3N4) for various species (H+, Na+, K+, and Cl−). We reveal that mechanism of proton conduction changes with a pore size of carbon-nitrogen ring in g-C3N4: varying from a pure H+ transportation when crossing narrow pores into a dual pathways (via both H+ and hydronium ions H3O+) when transmitting across wide pores. We introduce a novel local descriptor, nanopore rigidity (C), to quantify the rigidity of a material and relate the dynamics of sieving species to mechanics of the pore. The kinetic barrier of an arbitrary intercalating ion (ΔGion) can then be obtained via ΔGion=Cδρ2+B with B being a residual barrier of the pore and δρ being the local strain of the pore induced by the conducting ion. The descriptor as a microscopic metric can be extended to other porous materials, allowing a screening for electrochemical energy transition materials.

Recent advances in two-dimensional graphitic carbon nitride based photodetectors

Graphitic carbon nitride (g-C3N4) is a kind of low cost and environment-friendly 2D polymer semiconductor that exhibits a tunable band gap, high thermal stability, intriguing optoelectronic properties and broad device applications. However, there is hardly any review of g-C3N4′s recent development in photodetection devices. Herein, we summarized the recent advances in the 2D g-C3N4 based photodetector. Firstly, the structure and optoelectronic properties of 2D g-C3N4 were introduced. Secondly, recent progress in 2D g-C3N4 based photodetectors with different device types, such as 2D g-C3N4 based photoconductor, hybrid nanostructure photodetector, photodiode, perovskite photodetector and piezo-phototronic photodetector were summarized. Finally, some major challenges and opportunities towards the practical optoelectronic device applications of 2D g-C3N4, which need be further investigated, had been discussed. As a pioneer, this review systematically presented the development of 2D g-C3N4 based photodetector in the past years and highlighted their great potential in field of broadband, low-cost, fast-response and high-performance photodetectors. We hope that this review could guide the following development and research of g-C3N4 based photodetectors.

Effective detection of acetone by ZnFe2O4 microspheres decorated with g-C3N4 nanosheets

A single SMO limits the adsorption of gas, resulting in poor performance of the gas sensor. Herein, two-dimensional (2D) graphitic carbon nitride (g-C3N4) were modified on ZnFe2O4 microspheres as efficient gas sensing materials via hydrothermal route. The modification of g-C3N4 can alter the energy band structure of ZnFe2O4, resulting in an increase in the bandgap, thus, effectively optimizing the carrier concentration in ZnFe2O4 and elevating the baseline resistance of ZnFe2O4/g-C3N4 microspheres. The sensor based on ZnFe2O4/g-C3N4-20 microspheres (mass ratio of ZnFe2O4: g-C3N4 =10:2) had a higher response value (53.3) which was 3.4 times higher than that of ZnFe2O4, better selectivity and rapid response/recovery speeds towards 100 ppm acetone, as well as a low detection limit of 255 ppb. The enhanced performance of ZnFe2O4/g-C3N4 microsphere could be ascribed to the catalysis of C3N4, regulating the energy structure, and heterojunction formation between ZnFe2O4 and g-C3N4. Thus, this work demonstrated their promising applications in various fields.

Improving the charge kinetics through in-situ growth of NiSe nanoparticles on g-C3N4 nanosheets for efficient hybrid supercapacitors

Nickel selenide (NiSe) has been a promising positive electrode for hybrid supercapacitors due to its multiple oxidation states, tunability, and high specific capacity. However, sluggish ion transfers and particle agglomeration hamper its electrochemical performance. In the present study, we have grown NiSe nanoparticles on two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets to realize three-dimensional (3D) architecture. The 2D support, high nitrogen content, and features of g-C3N4 enhanced the specific capacity of the NiSe/g-C3N4 nanocomposite material. The resulting nanocomposite shows a specific capacity of 320 mA h g−1 at a current density of 1 A g−1, which is considerably higher than pristine NiSe. Later, the hybrid supercapacitor (HSC) device was fabricated using NiSe/g-C3N4 composite as positive and activated carbon (AC) as negative electrodes. The cell delivered an energy density of 52.5 Wh kg−1 at a power density of 1488 W kg−1 with excellent cyclic stability of 84.9% over 8000 cycles. The electrochemical performance enhancement corresponds to a 3D structure, high electrochemical active sites, and improved charge transportation at the electrode/electrolyte interface. Thus, the present work offers an easy approach and architectural design for high-performance HSC.

Defects-enriched two-dimensional ultrathin g-C3N4/In2O3 nanoparticles for effective NO2 detection at room temperature

Rational integration of ultrathin two-dimensional(2D) graphitic carbon nitride(g-C3N4) nanosheets and indium oxide(In2O3) nanoparticles was implemented by hydrothermal and calcination. The optimized composites demonstrated an outstanding NO2 response of 1470 (5 ppm) and short response/recovery time (67/46 s). Moreover, the prepared composites displayed excellent reproducibility, low detection limit (18 ppb), and satisfactory selectivity to NO2 at room temperature (RT). The gas sensing mechanism was also proposed and verified by the density functional theory calculation. The outstanding gas sensing properties might be due to the combination of heterojunction, enhanced specific surface, and enriched defects. This study gives a reference for designing sensing materials by forming heterojunctions between metal oxides and g-C3N4 for superior gas sensitivity and exploring the manufacture of advanced gas sensors.

High-performance robust graphitic carbon nitride nanosheets embedded membranes for desalination through direct contact membrane distillation

Two-dimensional (2D) graphitic carbon nitride (g-C3N4)-based membranes have recently received widespread attention due to their fantastic separation performance. In the present investigation, for the first time, we assessed the desalination performance of membranes incorporated with g-C3N4 nanosheets through the membrane distillation (MD) process. For this purpose, different concentrations (0–0.06 wt.%) of synthesized nanosheets were embedded within the hydrophobic PVDF matrix by simple phase inversion method. Upon loading 0.03 wt.% g-C3N4, the water contact angle and LEP augmented from 80.5° and 6 bar for the pure PVDF membrane to 95.2° and 8 bar, respectively. Adding the g-C3N4 nanosheets also improved both the tensile strength and the elongation at break by 21.32% and 36.46% than the pristine membrane, respectively. The mixed matrix membranes favorably improved MD performance; so that, 0.03 wt.% g-C3N4 embedded membrane exhibited a flux of 27.63 kg/m2h with an enhancement of 70% relative to its pure counterpart. Continuous testing for up to 24 h filtration of a 3.5 wt.% NaCl solution still showed a stable flux and almost complete salt rejection for the mentioned mixed matrix membrane. The anti-fouling properties of the membranes were also improved by incorporation of the g-C3N4 nanosheets. The 0.03 wt.% gCN embedded membrane recovered about 90% of the original permeation flux after 20 h desalination operations using real seawater as a feed solution. This work holds promise for developing next-generation MD membranes with superior desalination performance in terms of water vapor permeability and salt rejection.

1D-2D intercalated network CMC@g-C3N4/IL membrane with high permeability and selectivity for the CO2 capture

The structural advantages of the membrane material itself are critical to the membrane separation performance. Two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets can achieve minimal mass-transfer barrier and high gas sieving performance due to their ultra-thin thickness, inherent surface porosity and abundance of amine groups. However, the 2D g-C3N4 nanosheets are prone to stacking during the self-assembly process, which reduces the membrane permeability. Based on this line, herein, we proposed a concept of construction of 1D-2D intercalated network supported ionic liquid membrane composed by one-dimensional (1D) carboxymethylcellulose (CMC) and g-C3N4 nanosheets to overcome the low permeability of 2D graphitic carbon nitride membrane in separating CO2/N2 and CO2/CH4. The as-prepared 1D-2D intercalated network supported ionic liquid gas separation membrane exhibits superior CO2 permeance of 953.96 GPU, CO2/N2 selectivity of 55.46 in separation of CO2/N2, and CO2 permeance of 854.00 GPU, CO2/CH4 selectivity of 50.62 in separation of CO2/CH4. In addition, the resulting CMC@g-C3N4/IL membrane has excellent durability. After 120 h of testing, it still has outstanding separation performance. In short, this concept in this study provides an effective modulation of molecular sieving of g-C3N4 membrane for high-efficiency CO2 capture by combination of the advantages of the 1D (CMC) and 2D (g-C3N4) materials.

Two-Dimensional Graphitic Carbon Nitride for Improving the Performance of Organic Solar Cells.

Organic solar cells (OSCs) have attracted lots of attention owing to their low cost, lightweight, and flexibility properties. Nowadays, the performance of OSCs is continuously improving with the development of active layer materials. However, the traditional hole transport layer (HTL) material Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) presents insufficient conductivity and rapid degradation, which decreases the efficiency and stability of OSCs. To conquer the challenge, the two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanomaterials incorporated into the PEDOT:PSS as hybrid HTL are reported. The addition of g-C3N4 into PEDOT:PSS enables the thickness of the HTL to decrease for enhancing the transmittance of the film and increase the conductivity of PEDOT:PSS. Thus, the device exhibts improved charge transport and suppressed carrier recombination, leading to the increase in short-circuit current density and power conversion efficiency of the devices. This work demonstrates that the incorporation of 2D g-C3N4 into PEDOT:PSS for D18:Y6 and PM6:L8-BO-based OSCs can significantly improve the device efficiency to 17.48% and 18.47% with the enhancement of 7.04% and 8.46%, respectively.

Sustainable and photoresponse triboelectric nanogenerators based on 2D-gC3N4 and agricultural wastes

Two bio-friendly and photoactive triboelectric nanogenerators (TENG) are introduced, employing sustainable and biocompatible materials as functional components. The TENGs utilize corn husk and coconut coir fibers as the positive layers and incorporate two-dimensional graphitic carbon nitride (g-C3N4) nanosheets as negative layers. Upon simple biomechanical forces, the optimized devices fabricated from corn husk and coconut fibers produce a maximum output voltage of 630 V and 581 V, respectively. Under short-circuit conditions, the measured current was approximately 0.79 mA for corn husk-TENG and 11.47 mA for coconut fibers-TENG. Also, the maximum output power of 131 mW and 1980 mW were achieved over a 2 × 2 cm2 area of corn husk-TENG and coconut fibers-TENG. The TENGs were also tested under blue commercial lights and UV light, and an increase of approximately 1.5 times was observed in the output voltages of both TENGs under UV light. These g-C3N4-based TENGs perform superior under UV illumination and can be used as nanogenerators and active photosensors. This paper proposes two eco-environmentally friendly and robust electronic devices for energy harvesting and photo-sensing applications based on two agricultural wastes, corn husk, and coconut coir fibers.

2D-Graphitic Carbon Nitride Nanosheet/Metal Nanocomposites for Electrochemical Sensors of Hydroquinone in Real Sample Analysis

In the present work, we have investigated a low-cost fabrication method in preparing two-dimensional (2D) graphitic carbon nitride (g-C3N4) with nanosheet/metal nanocomposites by a rapid calcination process. The synthesized metal/g-C3N4 nanosheet was analyzed further by using UV–visible, Fourier transform-infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDAX) with elemental analysis mapping. Through field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), the metal/g-C3N4 nanosheet was observed to have a porous nanostructure. X-ray diffraction patterns of the 2D-GCN nanostructure were confirmed to be of fine crystalline size. X-ray photoelectron spectroscopy provided qualitative and quantitative data about the structure of C3N4. An electrochemical performance was carried out by using cyclic and differential pulsed voltammetry techniques. The metal/g-C3N4 nanosheet/nanocomposite was fabricated on the glassy carbon electrode (GCE) for electrochemical determination of hydroquinone (HQ). The electrocatalytic mechanism of HQ was scrutinized, which proved fast electron and ion transfer phenomena. The as-prepared Ag/g-C3N4/GCE exposed greater performance with a low limit of detection (LOD) of 5.8 μM in a wide linear range from 0.99 to 999.96 μM, which shows better repeatability, reproducibility, stability and an outstanding selectivity. The Ag/g-C3N4/GCE-fabricated electrode exhibited good sensitivity at 0.067 μA Mm–1 cm–2. The proposed sensor additionally verified its practical feasibility in real-time monitoring on river and tap water samples with a satisfactory recovery.

Tailoring of Three-Atom Metal Cluster Catalysts for Ammonia Synthesis

Electrocatalytic nitrogen reduction reaction (NRR) can realize the green production of ammonia while developing electrocatalysts with high selectivity and ability is still an ongoing challenge. Two-dimensional (2D) graphitic carbon nitride (CN) frameworks can provide abundant hollow sites for stably anchoring several transition metal (TM) atoms to facilitate single-cluster catalysis, promising to overcome the problems of low activity and poor selectivity in the process of ammonia synthesis. Herein, extensive density functional theory (DFT) calculations were performed to investigate the feasibility of six bimetallic triatomic clusters FexMoy (x = 1, 2; x + y = 3) supported on C6N6, C2N, and N-doped porous graphene (NG) as NRR electrocatalysts. Through a systematic screening strategy, we found that the Fe2Mo–NG possesses the highest activity with a limiting potential of –0.36 V through the enzymatic mechanism and could be the promising catalyst for NH3 synthesis. The Fe2Mo moiety in Fe2Mo–NG moderately regulates the electron transfer between reaction intermediates and NG, which is ascribed to enhanced performance. This work accelerates the rational design of catalysts in the field of NRR and contributes to broadening the understanding of cluster catalysis.

Fabrication of iron tin oxide/tin oxide intertwined graphitic carbon nitride hybrid composite electrocatalyst for electrochemical detection of 5-aminosalicylic acid in human urine and pharmaceutical tablet samples

Background5-Aminosalicylic acid (5-ASA) is known as a cornerstone in the treatment of inflammatory bowel diseases, to prevent the synthesis of cytokines and inflammatory mediators. However, an overdose of this drug is a rare and unique condition in patients and can lead to kidney failure. Therefore, a rapidly sensitive method is needed for the monitoring of 5-ASA. Methodswe synthesized novel iron tin oxide/tin oxide (FeSnO3/SnO2, FSO/SO) nanostructures via a facile precipitation method. Further, the FSO/SO intertwined two-dimensional (2D) graphitic carbon nitride (g-C3N4) hybrid composite electrocatalyst was developed by the wet-chemical process. The proposed materials were characterized by XRD, Raman, XPS, FESEM, TEM and TGA. Further, the glassy carbon electrode (GCE) modified with FSO/SO/g-C3N4 was revealed to sensitive detection of 5-ASA in PBS (pH-7) by CV, LSV and DPV methods. Significant findingsThe surface modification of FSO/SO/g-C3N4/GCE can enhance the synergistic action of different dimensional active catalysts. The limit of detection (LOD=3σ/S) proposed sensor was found to be 0.00625 µM and 0.0075 µM via LSV and DPV methods, also the calculated sensitivity has 3.428 µA µM−1 cm−2 and 2.857 µA µM−1 cm−2 respectively. The developed sensor demonstrated outstanding feasibility test results for detecting 5-ASA in samples of human urine and mesalamine tablet using the DPV method.

Correlations of Precursor and Carbon Coating with Electrochemical Property of 2D Graphitic Carbon Nitride (g-C3N4) Nanosheets as High-Reversibility Cathode of Nonaqueous Al-Ion Batteries

Al-ion batteries (AIBs) represent promising multivalent-ion battery alternatives to Li-ion batteries (LIBs). Exploration of cathode materials is the key to improving the electrochemical performance of AIBs. Here we demonstrate a promising AIB cathode candidate based on two-dimensional graphitic carbon nitride (g-C3N4) nanosheets with reversible de/embedding of [AlCl4]− anions in its special layered porous structure during the cyclic charge/discharge process. To address the sluggish ion/charge transportation kinetics that is inherently present in AIBs due to the intrinsically low conductivity of g-C3N4, we optimize different synthetic precursors of g-C3N4 including dicyandiamide, urea, and melamine and, further, develop a facile method for uniformly coating a N-doped carbon (N–C) coating layer on the optimal g-C3N4 derived from dicyandiamide. The resultant AIBs consisting of the g-C3N4@N–C cathode and Al metal anode in the AlCl3/[EMIm]Cl electrolyte exhibit an initial capacity of ∼54.9 mAh·g–1 at 0.2 C with a high Coulomb efficiency ∼99.9%, and they possess long-term cycling over 200 cycles. The underlying charge/discharge process of AIBs, revealed by the ex situ X-ray diffraction and scanning electron microscopy analyses, involves the extraction/insertion of Al species (mainly Al3+, AlCl4–, and Al2Cl7–) into the g-C3N4 crystal lattices with the formation of intermediate Al8C3N4 and (ClCN)3.

Ultrathin C3N4 nanosheets-based oxidase-like 2D fluorescence nanozyme for dual-mode detection of organophosphorus pesticides

Engineering efficient dual-mode portable sensor with built-in cross reference correction is of great significance for onsite reliable and precise detection of organophosphorus pesticides (OPs) and evading the false-positive outputs, especially in emergency case. Currently, most nanozyme-based sensors for OPs monitoring primarily replied on the peroxidase-like activity, which involved unstable and toxic H2O2. In this scenario, a hybrid oxidase-like 2D fluorescence nanozyme (PtPdNPs@g-C3N4) was yielded by in situ growing PtPdNPs in the ultrathin two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheet. When acetylcholinesterase (AChE) hydrolyzed acetylthiocholine (ATCh) to thiocholine (TCh), it ablated O2−• from the dissolved O2 catalyzed by PtPdNPs@g-C3N4’s oxidase-like activity, hampering the oxidation of o-phenylenediamine (OPD) into 2,3-diaminophenothiazine (DAP). Consequently, with the increasing concentration of OPs which inhibited the blocking effect by inactivating AChE, the produced DAP caused an apparent color change and a dual-color ratiometric fluorescence change in the response system. Through integrating into a smartphone, a H2O2-free 2D nanozyme-based onsite colorimetric and fluorescence dual-mode visual imaging sensor for OPs was proposed with acceptable results in real samples, which holds vast promise for further development of commercial point-of-care testing platform in early warning and controlling of OPs pollution for safeguarding environmental health and food safety.

A High-Throughput Screening toward Efficient Nitrogen Fixation: Transition Metal Single-Atom Catalysts Anchored on an Emerging π-π Conjugated Graphitic Carbon Nitride (g-C10N3) Substrate with Dirac Dispersion.

TM-Nx is becoming a comforting catalytic center for sustainable and green ammonia synthesis under ambient conditions, resulting in increasing interest in single-atom catalysts (SACs) for the electrochemical nitrogen reduction reaction (NRR). However, given the poor activity and unsatisfactory selectivity of existing catalysts, it remains a long-standing challenge to design efficient catalysts for nitrogen fixation. Currently, the two-dimensional (2D) graphitic carbon-nitride substrate provides abundant and evenly distributed holes for stably supporting transition-metal atoms, which presents a fascinating prospect for overcoming this challenge and promoting single-atom NRR. An emerging holey graphitic carbon-nitride skeleton with a C10N3 stoichiometric ratio (g-C10N3) from a supercell of graphene is constructed, which provides outstanding electric conductivity for achieving high-efficiency NRR due to the Dirac band dispersion. Herein, a high-throughput first-principles calculation is carried out to evaluate the feasibility of π-d conjugated SACs resulting from a single TM atom anchored on g-C10N3 (TM = Sc-Au) for NRR. We find that W metal embedded in g-C10N3 (W@g-C10N3) can compromise the ability to adsorb the key target reaction species (N2H and NH2), hence acquiring an optimal NRR behavior among 27 TM-candidates. Our calculations demonstrate that W@g-C10N3 shows a well-suppressed HER ability and, impressively, a low energy cost of -0.46 V. Additionally, all-around descriptors are proposed to uncover the fundamental mechanism of NRR activity, among which a 3D volcano plot (limiting potential, screening strategy, and electron origin) uncovers the NRR activity trend, achieving a quick and high-efficiency prescreening for numerous candidates. Overall, the strategy of the structure- and activity-based TM-Nx-containing unit design will offer useful insight for further theoretical and experimental attempts.