g-C3N4 Monolayer Research Articles

Construction of novel β-XY (X = Ge, Sn, Y = S)/g-C3N4 heterostructures: efficient visible light-driven water splitting catalysts

The logical design of inexpensive, non-polluting, and extremely effective photocatalysts is a crucial step toward achieving clean energy. The currently low solar-to-hydrogen (STH) conversion efficiency (ηSTH) makes hydrogen production technologies less than optimal. Herein, novel β-XY (X = Ge, Sn, Y = S)/g-C3N4 heterostructures have been constructed. Among them, the β-SnS/g-C3N4 exhibits low carrier recombination, and its geometry, optoelectronic properties, as well as the thermodynamic feasibility of its reaction, have been thoroughly examined through DFT calculations. The results demonstrate that the β-SnS/g-C3N4 heterostructure is a type-II heterostructure, exhibiting an indirect band gap of 2.57 eV. Photocatalysis is more efficient because of the built-in electric field that extends from the g-C3N4 monolayer to the β-SnS monolayer, effectively separating electrons and holes. The continuously decreasing free energy validates the thermodynamic spontaneity of water splitting. Additionally, the heterostructure demonstrates robust absorption in both the visible and UV ranges. Notably, the ηSTH of 15.54 % underscores the commercial viability of this material. These findings thus suggest that β-SnS/g-C3N4 heterostructure is a good candidate material for water splitting via photocatalysis.

Polyacid-Modulated Carrier Dynamic Behavior at the Interface of 0D/2D Heterojunctions.

Heterojunctions formed by polyoxometalates and 2D materials draw attention owing to their remarkable photoelectric and catalytic properties. However, the intrinsic mechanisms of polyoxometalates regulating the heterojunction photoelectric properties are unclear. Herein, we constructed two types of heterojunctions by integrating polyoxometalates (Keggin-type H3PW12O40 and Lindqvist-type H2W6O19) on g-C3N4 monolayers, exploring photoexcited carrier dynamics in these heterojunctions by ab initio calculations combined with nonadiabatic molecular dynamics (NAMD) simulations. Our results show that electrons and holes in H3PW12O40 on g-C3N4 monolayers relax within 583 and 760 fs, respectively. The electron-hole recombination occurs at 342 fs, faster than carrier separation, aligning with the behavior of Z-type heterojunctions. Contrarily, the H2W6O19/g-C3N4 heterojunction exhibits the typical characteristics of type II heterojunctions, with a long photogenerated carrier lifetime reaching 652 fs. These findings show tunable band alignment in polyoxometalate-supported systems by modulating polyoxometalate type, influencing hot electron dynamics, and guiding 0D/2D heterojunction design.

Hydrogen production mechanism and catalytic productivity of Ni-X@g-C3N4 (X = precious and non-precious promoter metals) catalysts from KBH4 hydrolysis under stress loading and atmospheric pressure: Experimental analysis and molecular dynamics approach

In this study, the pressure effect of Ni-based catalysts added a second promoter metal to increase of catalyst performance supported a graphite carbon nitride (g-C3N4) monolayer on hydrogen release mechanisms from potassium boron hydride (KBH4) hydrolysis was investigated using molecular dynamics (MD) method based on tight-binding density functional theory (DFT). The use of the various promoters, such as transition metals (X = Cu, Ta and W) and noble metals (X = Pd, Pt and Rh) with applying a high external pressure was investigated to understand the role on catalytic performance of the Ni-based catalysts under stress loading. The g-C3N4 monolayer doped with Ni-X nano-catalysts was used for efficient H2 release from KBH4 hydrolysis. The computational results show that the number of H2 shows more increment with MD time for NiW and NiRh catalysts than other NiTa and NiCu (transition metals) and NiPd and NiPt (noble metals) under 0 GPa pressure. On the other hand, a notable increase in H2 amount is seen only NiCu and NiRh catalysts under 50 GPa. Also, the mechanism of the H2 production reaction from KBH4 hydrolysis of g-C3N4 doped NiCo catalysts was clarified. High-performance cost metal catalysts such as NiCo was investigated as both experimentally and modeling under atmospheric pressure to enhance its commercial application value. Some experimental applications and analyzes were also performed to measure the accuracy of the modeling for the relevant molecular groups in the system.

DFT and experimental study on photocatalytic degradation of tetracycline by Sulfur-doped monolayer g-C3N4 as a peroxymonosulfate activator

Doping enhances the activation of peroxymonosulfates (PMS) by metal-free carbon materials, addressing their inherent limitations in performance. In this study, experimental and theoretical calculations are combined to carry out the study of efficient activation of PMS for tetracycline degradation based on sulfur-doped g-C3N4 (SCN) as a promising photocatalyst. Calculation of the energy band structure, electronic and optical properties by density-functional theory methods suggests that doping results in a smaller band gap, smaller bond populations, and work function, leading to a redistribution of charges and dipoles at the g-C3N4 interface with a better ability to separate photogenerated h+/e− pairs. Meanwhile, the characterization and catalyst activity measurements indicate that doping improves the photocatalytic activity, which is in agreement with the theoretical calculations. In particular, the SCN synthesized at 1:1 ratio exhibited the best catalytic activity, and the degradation efficiency of TC within 2 h could reach 89.4 %. This study provides a highly effective metal-free carbon activator for the degradation of antibiotics from wastewater by PMS.

Revitalizing CO2 photoreduction: Fine-tuning electronic synergy in ultrathin g-C3N4 with amorphous (CoFeNiMnCu)S2 high-entropy sulfide nanoparticles for enhanced sustainability

Sustainability is a key issue in developing stable and efficient catalysts for solar-catalyzed CO2 conversion. The concept of structural stabilization by quenching the Gibbs free energy, which is achieved by increasing the configurational entropy level of the system, introduced high-entropy materials. However, because alloying immiscible multimetallic atoms into a unit system is still an arduous process, the potential of high-entropy materials has not yet been fully exploited. Surprisingly, although metal sulfide photocatalysts have an enviable reputation for CO2 photoreduction (CO2-PR) owing to their optical/electronic merits and more negative redox potential than other materials, the capability of high-entropy metal sulfides has been completely disregarded. Herein, an adaptable, self-templating metal alkoxide appropriately addresses the immiscibility of metallic constituents by the well-blended metal ions with polyalcohol in the metal glycerate. Consequently, (CoFeNiMnCu)S2 high-entropy metal sulfide nanoparticles (HEMS-Nps) were grown in situ on crossed ultrathin g-C3N4 (UCN) monolayers during the sulfidation of the metal glycerate. The as-synthesized HEMS-Np has a crystalline–amorphous structure, which is conducive to the acceleration of charge transfer to/from reaction sites, and a convincing orientation for CO2 adsorption. These features are combined with synergistic electronic multimetallic interactions, facilitating a heterogeneous valence electron distribution and atomic disorder. The CO2-PR power of the (CoFeNiMnCu)S2@UCN nanostructure was noticeable in realizing added-value products in both the liquid–solid (1063 µmol/g h of syngas and 250 µmol/g h of methane) and gas–solid phases (1883 µmol/cm2 h of syngas and 321 µmol/cm2 h of methane). To prove its utility, long-term and corresponding time-equivalent cycling experiments were conducted, demonstrating a highly stable system that endured for a long time. Overall, this approach simultaneously exploits the advantages of sulfide-based materials and high-entropy materials in stable structures to generate sustainable CO2-PR materials.

Computational design of single-atom catalysts embedded on reduced graphitic carbon nitride monolayers

The design of efficient single-atom catalysts (SACs) with optimal activity and selectivity for sustainable energy and environmental applications remains a challenge. In this work, comprehensive first-principles calculations are performed to validate the feasibility of single TM atoms (3d, 4d, and 5d series) embedded in two different conformations of graphitic carbon nitride (g-C3N4) monolayers. Additionally, we investigate the effect of nitrogen vacancies in the g-C3N4 monolayers on the absorption of SACs considering three potential absorption scenarios that correspond to different experimental conditions. Our results point to the most stable configurations with the lowest formation energies and indicate that the absorption of single TM atoms on-vacancy and on-center sites are more favorable than via-substitution. In addition to the thermodynamic stability, electrochemical stability is also investigated through the calculation of the dissolution potential of the SACs. Within the scenarios considered in this study, we find that Pt, Pd, Rh, Au, Ru, Ir, Cu, Co, Fe, and Ni will produce the most robust SACs on both (edge and bridge) N vacancy site of reduced g-C3N4. Our findings provide guidance for the design and development of g-C3N4 sheets decorated with single TM atoms for technological applications such as pollutant degradation, CO2 reduction, N2 fixation, selective oxidation, water splitting, and metal ion-based batteries.

Enhanced photocatalytic properties of s-triazine-based-g-C3N4/BlueP and g-C3N4/G/BlueP vdW heterostructures: A DFT study

Constructing a Z-scheme heterostructure from selected semiconductors has been proved to be an effective route for attaining the strong redox capability and broad light absorption range simultaneously. In this work, we investigated the electronic, optical and photocatalytic properties of g-C3N4/BlueP and g-C3N4/G/BlueP van der waals heterostructures (vdWHs) by density functional theory (DFT) calculations. The staggered band alignment and the interfacial built-in electric field originated from the charge transfer from g-C3N4 to BlueP depict the Z-scheme photocatalytic mechanism of the g-C3N4/BlueP vdWH. Meanwhile, the vdWH shows an enhanced absorbance at the ultraviolet and visible light range compared to the individual g-C3N4 and BlueP monolayers. Furthermore, the intercalation of Graphene monolayer between g-C3N4 and BlueP is proved to modulate the interfacial built-in electric field, while retaining the staggered band alignment simultaneously. The significant enhancement of the visible light region absorption efficiency promoted by the gap-state of intercalated Graphene manifests the co-catalytic effect of Graphene and the applicable prospect of the constructed ternary heterostructure in photocatalysis area.

Two-Dimensional SiH/g-C3N4 van der Waals Type-II Heterojunction Photocatalyst: A New Effective and Promising Photocatalytic Material

The two-dimensional layered heterostructure have been demonstrated as an effective method for achieving efficient photocatalytic hydrogen production. In this work, we propose, for the first time, the creation of van der Waals heterostructures from monolayers of SiH and g-C3N4 using first-principle calculations. We also systematically investigated additional properties for the first time, such as the electronic structure and optical behavior of van der Waals heterostructures composed of SiH and g-C3N4 monolayers. The results of this study show that the SiH/g-C3N4 heterostructure is categorized as a type-II heterostructure, which has a bandgap of 2.268 eV. Furthermore, the SiH/g-C3N4 heterostructure interface was observed to efficiently separate and transfer photogenerated charges, resulting in an enhanced photocatalytic redox performance. Moreover, the calculation of HOMO (Highest occupied molecular orbital) and LUMO (Least unoccupied molecular orbital) and charge density difference can further confirm that the SiH/g-C3N4 heterojunction is a type-II heterojunction, which has excellent photocatalytic hydrogen production and water decomposition performance. In addition, the SiH/g-C3N4 heterostructure exhibited excellent HER (Hydrogen evolution reaction) efficiency. This is essential for the process of photocatalytic water splitting. In SiH/g-C3N4 heterojunctions, the redox potential required for water splitting is spanned by the band edge potential. Calculating the absorption spectra, it was discovered that the SiH/g-C3N4 heterostructure possesses outstanding optical properties within the visible-light range, implying its high efficiency in photocatalytic hydrogen production. This research provides a broader research direction for the investigation of novel efficient photocatalysts and offers effective theoretical guidance for future efficient photocatalysts.

Theoretical Insights on the Charge State and Bifunctional OER/ORR Electrocatalyst Activity in 4d-Transition-Metal-Doped g-C3N4 Monolayers.

Exploring efficient and stable electrocatalysts for the bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is vital to developing renewable energy technologies. However, due to the substantial and intricate design space associated with these bifunctional OER/ORR electrocatalysts, their development presents a formidable challenge, resulting in their cost-prohibitive nature in both experimental and computational studies. Herein, using the defect physics method, we systematically investigate the formation energies and bifunctional overpotential (ηBi) of 4d-transition-metal (4d-TM, 4d-TM = Zr, Nb, Mo, Ru, Rh, Pd, and Ag)-doped monolayer supercell g-C3N4 (4d-TM@C54N72) based on the density functional theory (DFT) calculations. Under N-rich and C-rich conditions, we find that the formation energies of RhN@C54N71 (Rh occupation N) and PdN@C54N71 (Pd occupation N) are smaller than that of other 4d-TMN@C54N71 (4d-TM occupation N site); for the 4d-TMint@C54N72 (4d-TM interstitial site occupation), the lowest-formation energy defects are Pdint@C54N72. These results indicate that they have better stabilities. Interestingly, for these formation energy lower systems, Pd0int@C54N72 (ηBi = 1.00 V) and Rh1+N@C54N71 (ηBi = 0.73 V) have ultralow overpotential and can be great candidates for bifunctional OER/ORR electrocatalysts. We find the reason is that adjusting the charge states of 4d-TM@C54N72 can tune the interaction strength between the oxygenated intermediates and the 4d-TM@C54N72, which plays a crucial role in the activity of reactions. Additionally, the data obtained through machine learning (ML) application suggest that the electronegativity (Nm) and bond length of 4d-TM and coordination atoms (dTM-OOH) are primary descriptors characterizing the OER and ORR activities, respectively. The charged defect tuning of the bifunctional OER/ORR activity for 4d-TM@C54N72 would enable electrocatalytic performance optimization and the development of potential electrocatalysts for renewable energy applications.

Electron, hole and radical competition mechanism of layered porous g-C3N4 for hydrogen generation and organic pollutant degradation

Halogen doping is an effective approach to regulate the electronic structure and improve photocatalytic properties of g-C3N4. Here, a salt-assisted approach was employed to prepare layered porous halogen-doped g-C3N4. The effects of halogen electronegativity and pore morphology were discussed. Highly electronegative F-doped g-C3N4 with smaller pore size and higher surface area displayed the enhanced absorption property on reactants. The H2 production rate decreased and the RhB degradation significantly increased with increasing the electronegativity of layered porous g-C3N4, which was significantly different from the conventional halogen-doped g-C3N4 prepared with halogenated acid and monolayer g-C3N4. The decreased H2 evolution can be ascribed to the strong adsorption property, and the strong interactions between halide ions and H+ were difficult to be disassociated. Additionally, the RhB degradation performance of halogen-doped g-C3N4 significantly increased with increasing the electronegativity. The most active species that dominated the RhB degradation of F-doped g-C3N4 are leaved holes (h+), which are totally different from that of the pristine g-C3N4 and Cl/Br-doped g-C3N4 (superoxide radicals,·O2–). This work helps us to well understand the role and importance of electronegativity and pore morphology on the H2 generation and RhB degradation properties of layered porous g-C3N4.

Electronic transitions and vibrational properties of bulk and monolayer g-C3N4, and a g-C3N4/MoS2 heterostructure from a DFT study.

Successful recognition of a dynamically stable carbonitride structure revealed that unlike other planar layered structures in the case of g-C3N4 the stable configurations are distorted [J. Wang et al., Chem. Mater., 2017, 29(7), 2694-2707, DOI: https://doi.org/10.1021/acs.chemmater.6b02969.]. This generates interest in a detailed study of the possibilities of controlling the structure and its properties both in its pristine and heterostructure forms. Here, we present the results of the investigation of dynamically stable bulk and monolayer g-C3N4, and a g-C3N4/MoS2 heterostructure. The bulk g-C3N4 was found to be an indirect band gap semiconductor exhibiting an indirect-to-direct band gap transition upon dimensionality reduction. In the case of the heterostructure, the analysis of partial density of states shows a charge transfer from nitrogen ions in g-C3N4 to the MoS2 layer. The Raman spectra of bulk g-C3N4 are discussed in detail, and the changes occurring in the spectra upon the transition to the monolayer form and in the g-C3N4/MoS2 heterostructure are demonstrated. It was found that the characteristic features of such an atomic transition can be seen in the region below 300 cm-1 and between 700 and 800 cm-1.

Mechanistic study of the competition between carbon dioxide reduction and hydrogen evolution reaction and selectivity tuning via loading single-atom catalysts on graphitic carbon nitride.

In the context of catalytic CO2 reduction (CO2RR), the interference of the inherent hydrogen evolution reaction (HER) and the possible selectivity towards CO have posed a significant challenge to the generation of formic acid. To address this hurdle, in this work, we have investigated the impact of different single-atom metal catalysts on tuning selectivity by employing density functional theory (DFT) calculations to scrutinize the reaction pathways. Single-atom catalysts supported on carbon-based systems have proven to be pivotal in altering both the activity and selectivity of the CO2RR. In this study, a series of single-atom-metal-loaded g-C3N4 monolayers (MCN, M = Ni, Cu, Zn, Ga, Cd, In, Sn, Pb, Ag, Au, Bi, Pd and Pt) were systematically examined. Through detailed DFT calculations, we explored their influence on reaction selectivity between the *COOH and *OCHO intermediates. Notably, NiCN favors the reaction via the *OCHO route, with a significantly lower rate-determining potential of 0.36 eV, which is approximately 73.5% lower than that of the CN system (1.36 eV). Most importantly, the Ni single-atom catalyst with lower coordination significantly enhances CO2 adsorption, promoting CO2RR over HER. Overall, this study, guided by DFT calculations, provides a theoretical prediction of how the selection of single-atom metal catalysts can effectively modulate the reaction pathway, thereby offering a potential solution for achieving high product selectivity in CO2RR.

Unlocking the potential of V2O5 decorated on crossed g-C3N4 monolayers derived from synergistic bio-transformation of ZnMn2O4 for antibiotic photodegradation

The optimized ZnMn2O4 nanoparticles were fabricated through an AV-assisted sol–gel method and employed to form crossed g-C3N4 monolayers as an innovative solution for the delamination of stacked layers.

Theoretical insights into single-atom catalysts for improved charging and discharging kinetics of Na-S and Na-Se batteries.

Dissolution of poly-sulfide/selenides (p-S/Ses) intermediates into electrolytes, commonly known as the shuttle effect, has posed a significant challenge in the development of more efficient and reliable Na-S/Se batteries. Single-atom catalysts (SACs) play a crucial role in mitigating the shuttling of Na-pS/Ses and in promoting Na2S/Se redox processes at the cathode. In this work, single transition metal atoms Co, Fe, Ir, Ni, Pd, Pt, and Rh supported in nitrogen-deficient graphitic carbon nitride (rg-C3N4) are investigated to explore the charging and discharging kinetics of Na-S and Na-Se batteries using Density Functional Theory calculations. We find that SAs adsorbed on reduced g-C3N4 monolayers are substantially more effective in trapping higher-order Na2Xn than pristine g-C3N4 surfaces. Moreover, our ab initio molecular dynamics calculations indicate that the structure of X8 (X = S, Se) remains almost intact when adsorbed on Fe, Co, Ir, Ni, Pt, and Rh SACs, suggesting that there is no significant S or Se poisoning in these cases. Additionally, SACs reduce the free energies of the rate-determining step during discharge and present a lower decomposition barrier of Na2X during charging of Na-X electrode. The underlying mechanisms behind this fast kinetics are thoroughly examined using charge transfer, bonding strength, and d-band center analysis. Our work demonstrates an effective strategy for designing single-atom catalysts and offers solutions to the performance constraints caused by the shuttle effect in sodium-sulfur and sodium-selenium batteries.

Defect-Regulated Two-Dimensional Superlattice of Holey g-C3N4-TiO2 Nanohybrids: Contrasting Influence of Vacancy Content on Hybridization Impact and Photocatalyst Performance.

Defect engineering provides an effective way to explore efficient nanostructured catalysts. Herein, we synthesize defect-regulated two-dimensional superlattices comprising interstratified holey g-C3N4 and TiO2 monolayers with tailorable interfacial coupling. Using this interfacial-coupling-controlled hybrid system, a strong interdependence among vacancy content, performance, and interfacial coupling was elucidated, offering key insights for the design of high-performance catalysts. The defect-optimized g-C3N4-TiO2 superlattice exhibited higher photocatalytic activity toward visible-light-induced N2 fixation (∼1.06 mmol g-1 h-1) than defect-unoptimized and disorderly assembled g-C3N4-TiO2 homologues. The high photocatalytic performance of g-C3N4-TiO2 was attributed to the hybridization-induced defect creation, facilitated hydrogenation of adsorbed nitrogen, and improvement in N2 adsorption and charge transport. A comparison of the defect-dependent photocatalytic activity of g-C3N4, g-C3N4 nanosheets, and g-C3N4-TiO2 revealed the presence of optimal defect content for improving photocatalytic performance and the continuous increase of hybridization impact with the defect content. Sophisticated mutual influence among defect, electronic coupling, and photocatalytic ability underscores the importance of defect fine control in exploring high-performance hybrid photocatalysts. Along with the DFT calculation, the excellent photocatalyst performance of defect-optimized g-C3N4-TiO2 can be ascribed to the promotion of the uphill *N hydrogenation step as well as to enhancement of N2 adsorption, charge transfer kinetics, and mass transports.

Graphitic carbon nitride supported trimeric metal clusters as electrocatalysts for N2 reduction reaction

As a cleaner and more energy-efficient alternative, the electrochemical reduction of N2 to NH3 under mild conditions has emerged as a promising avenue for environmental protection. However, developing catalysts with both high activity and selectivity has been a challenging task. The advent of atomically dispersed catalysts is revolutionizing the field of catalysis. Drawing inspiration from the successful fabrication of Ru trimer on graphitic carbon nitride (g-C3N4) nanosheets, herein, we adopted a series of trimeric metal clusters anchored on g-C3N4 monolayer (TM3@g-C3N4, TM = 3d, 4d and 5d transition metal atom), as well as utilized the criteria range to describe the stability, activity, energy cost and selectivity of supported trimers for N2 reduction reaction based on ab initio calculations combined with multi-level screening strategies. Finally, 5 candidate TM3@g-C3N4 (TM = Rh, Ru, V, Mo, and Re) exhibits decent catalytic activity with limiting potential ranging of –0.50 – –0.02 V. These spatially confined triatomic metal centers demonstrated proficiency in activating N2 molecules while exhibiting tunable surficial reactivity through modulation of the metal elements and interfacial electron coupling between trimers and underlying substrates. More importantly, a structure–activity relationship was established, which provides crucial insights for precise design of highly efficient atomically-precise catalysts at an atomic level for hydrogen fuel storage.

The performance improvement method of g-C3N4 based catalyst for hydrogen production from ammonia borane: A DFT investigation

In the study, based on the purpose of efficient catalytic AB for hydrogen production, the photochemical properties influence of metal(Ru, Ni) and nonmetal(B,P) elements doping on the g-C3N4 are studied systematacially. The design method of high performance bifunctional catalyst of photocatalysis and metal catalysis are provided. The results have proved that both non-metals B, P and metal Ru, Ni have an efficient regulatory effect on the band structure of g-C3N4, which make the band gap of the clean monolayer g-C3N4(001) decrease from 1.175 eV to 0.261eV(B-g-C3N4(001)) and 0.671eV(P-g-C3N4(001)), 0.164 eV(Ni-g-C3N4(001)) and 0.260 eV(Ru-g-C3N4(001)), respectively. B element have the better modification effect compared with the P element. The reduction of band gap is attributed to the electronic orbit modification effect of impurity element B, P, Ni, Ru in g-C3N4. Ru metal doped g-C3N4 is reduces the barrier of OH bond breakage of CH3OH(reduced from 4.551 eV to 1.530 eV), which is beneficial to the hydrogen-producing reaction of AB alcoholysis. The construction and design of a new bifunctional catalyst(photocatalysis and metal catalysis) RuNiB@g-C3N4 is an efficient route in catalyze AB for hydrogen production. The process of molecule NH3BH3, CH3OH and H2O adsorbed on the B-g-C3N4 are exothermic process, the adsorption energy are -1.562 eV, -1.392 eV and -1.443 eV, respectively. AB is preferentially adsorbed on the B-g-C3N4 catalyst, increasing the adsorption energy of CH3OH and H2O on B-g-C3N4-based catalysts is beneficial to the hydrogen production from AB. The study provides a theoretical method for the research on the technology of the coupling of metal catalysis/photocatalysis ammonia borane to produce hydrogen.

Tunable electronic and optical properties of GeC/g-C3N4 vdWH by electric field and biaxial strain

van der Waals heterostructures (vdWHs) show great potential for optoelectronic devices and photocatalysis. This work investigates the stability, electronic structure and optical properties of GeC/g-C3N4 using first-principles and considers the role of external electric fields and biaxial strain in the heterostructure. The results show a reduced band gap of GeC/g-C3N4 vdWH with strong optical absorption in the visible light range compared to monolayer GeC and g-C3N4. The heterostructure is a type-II semiconductor that is extremely suitable for the development of optoelectronic devices and photocatalytic materials. The external electric field can flexibly tune the band gap and band alignment of GeC/g-C3N4 vdWH, enabling it to transition between type-I, type-II and type-III. Biaxial strain effectively tunes the band structure of GeC/g-C3N4 vdWH, reducing the band gap and further increasing optical absorption capacity. These results suggest that external electric fields and biaxial strain are effective ways to tune GeC/g-C3N4 vdWH, providing a theoretical basis for relevant experimental preparation.

Photocatalytic splitting of water on g-C3N4-based single-atom Pt catalysts with stable “sandwich” structure: a combined first principles and semi-empirical investigation

Solar-to-hydrogen energy conversion is a promising strategy to solve environmental pollution and energy crisis by utilizing photocatalytic water splitting. In this work, a “sandwich” structure of g-C3N4-based single-atom platinum (Pt) catalyst for photocatalytic water splitting is proposed and investigated using a combined first principles and semi-empirical study method. The calculation results indicate that, without any co-catalyst, the photogenerated holes in the valence band of BL-g-C3N4 cannot oxidize H2O to O2, and its oxygen evolution reaction (OER) performance is not better than that of the pristine monolayer g-C3N4. Significantly, the photogenerated holes in the valence band of the “sandwich”-structured photocatalyst g-C3N4–Pt1–g-C3N4 can oxidize H2O to O2 without any co-catalyst. That is, the OER performance of g-C3N4–Pt1–g-C3N4 is better than that of the pristine g-C3N4 and the pristine bilayer-g-C3N4 (BL-g-C3N4). However, it can be found that the introduction of single Pt atom confinement in the BL-g-C3N4 cannot effectively reduce hydrogen evolution reaction (HER) energy barrier or improve the hydrogen evolution kinetics of BL-g-C3N4. In other words, the introduction of the confined single Pt atom in the BL-g-C3N4 not only fails to improve HER performance of BL-g-C3N4, but deteriorates HER catalytic performance of BL-g-C3N4. These findings provide some theoretical insights for engineers to prepare photocatalysts with higher activity and stability.

Furfural adsorption on the g-C3N4 monolayer: A DFT analysis

Graphitic carbon nitride (g-C3N4) has attracted much attention in recent years as a material for catalytic processes due to its promising structural and physicochemical properties. However, the role played by the g-C3N4 during the catalytic activity is often briefly discussed. Consequently, the mechanism behind these substrate-adsorbate processes involving g-C3N4 still needs to be better understood. This study analyzed furfural (FAL) adsorption on h-g-C3N4 monolayers based on DFT, including Van der Waals (vdW) interactions. To elucidate the role of the h-g-C3N4 in catalytic systems, the adsorption of a FAL molecule was evaluated at high and low coverages. At high coverage, due to proximity effects, FAL molecules interact with neighboring FAL molecules forming a monolayer that lays over the h-g-C3N4 nanosheet. At low coverage, weak interactions govern the FAL-h-g-C3N4 interaction. In both cases, vdW interactions are the main forces that bring stability to the composites. No chemical interactions are observed. The obtained results led us to conclude that in reactions including FAL and h-g-C3N4 nanosheets, the latter will serve as a support structure that favors the adsorbate mobility to reach the reactive centers.