Defect-induced graphene ferroelectric-antiferroelectric transition switch modulation method for hydrogen evolution reaction and application

Abstract

This invention discloses a method for on / off modulation of the hydrogen evolution reaction (HER) by defect-induced ferroelectric-antiferroelectric transition in graphene and its application. The method constructs a bilayer system of defective graphene (D-graphene) containing g-C₃N₄-like vacancy pores and g-C₃N₄ layers, with the layers coupled by van der Waals forces. A reversible ferroelectric-antiferroelectric phase transition is achieved through interlayer slip, and the HER is precisely modulated using changes in polarization intensity and direction. The defective graphene bilayer can form an ON-OFF ferroelectric switch, with the Gibbs free energy ΔG for ferroelectric hydrogen adsorption. H * Approaching the optimal value, the catalysis is in the on state; however, excessive hydrogen adsorption in the antiferroelectric state leads to catalysis shutdown. The g-C₃N₄ bilayer can achieve three-level regulation (ON-OFF-ON) through ferroelectric-paraelectric-ferroelectric polarization switching, with the ferroelectric polarization state significantly enhancing HER activity. This invention is free of precious metals, has a low interlayer sliding barrier, and exhibits catalytic performance comparable to platinum-based catalysts. It provides a new strategy for the design of highly efficient intelligent electrocatalysts and novel catalytic switching devices, and has significant application value in the field of clean energy.

Description

Technical Field

[0001] This invention relates to the fields of materials science, computational physics, and electrocatalysis, specifically to a method for controlling the hydrogen evolution reaction by utilizing defect-induced graphene and g-C3N4 bilayer materials to achieve ferroelectric-antferroelectric transition through interlayer sliding. Background Technology

[0002] Ferroelectric materials, with their stable and switchable spontaneous polarization properties, have wide applications in non-volatile memory devices (such as ferroelectric random access memory, ferroelectric tunnel junctions, and ferroelectric field-effect transistors), high-dielectric-constant dielectric materials, electromechanical integrated actuators, and pyroelectric sensors. However, with technological advancements, the demands for miniaturization and integration of multifunctional devices are increasing. Traditional perovskite-structured ferroelectrics are constrained by finite size effects, depolarization fields, and charge shielding effects, making it difficult to meet these requirements. Two-dimensional materials, due to their reduced dimensionality, are more prone to spatial symmetry breaking, which is conducive to the emergence of ferroelectricity. They also possess characteristics such as weak interlayer van der Waals interactions and no dangling bonds on the surface, making them easy to stack and integrate with other materials, giving them a natural advantage in device miniaturization and integration. Although two-dimensional ferroelectric materials such as CuInP2S6 and In2Se3 have been prepared, the candidate system types are limited, and the ferroelectricity of most materials is dominated by ion displacement. Sliding ferroelectric materials still need further development and expansion.

[0003] The hydrogen evolution reaction (HER) is the core reaction in water electrolysis for hydrogen production. However, in practical applications, it generally faces problems such as slow kinetic rates, high reaction energy barriers, and large energy losses, which greatly limit the large-scale development of this energy conversion technology. Traditional HER catalytic systems typically use two-dimensional van der Waals monolayer materials as supports. Their catalytic activity and reaction pathways are highly dependent on the inherent electronic structure of the material, with limited tunability. Constructing two-dimensional van der Waals bilayer materials can introduce significant interlayer coupling effects, effectively controlling the electronic state distribution and adsorption behavior, providing a new approach to improve HER catalytic performance and achieve controllable catalysis. The emergence of two-dimensional slip ferroelectrics allows bilayer materials to switch between different stacking configurations through interlayer slip, thereby changing the polarization state and surface adsorption intensity, potentially enabling in-situ, reversible, and efficient control of the HER catalytic process.

[0004] Theoretical studies have shown that nonferroelectric two-dimensional graphene-like g-C3N4 bilayers can acquire slip-induced ferroelectricity under specific stacking configurations, while pure graphene bilayers maintain inversion symmetry under any slip vector and cannot produce slip ferroelectric effects. Inspired by the vacancy defect structure within g-C3N4 monolayers, this invention, through first-principles calculations, has discovered that defective graphene (D-graphene) bilayers constructed by introducing vacancy defects into graphene can stably exhibit reversible slip-induced ferroelectric and antiferroelectric transition behaviors. Based on this, a ferroelectric switch and multi-level control system capable of precisely regulating the HER catalytic process were designed. The related technical solutions and mechanism findings have significant scientific value and application prospects for revealing new mechanisms of slip ferroelectric regulation of HER catalytic reactions, expanding the application boundaries of two-dimensional ferroelectric materials, and promoting the development of new technologies in the interdisciplinary field of condensed matter theoretical physics and catalytic chemistry. Summary of the Invention

[0005] This invention discloses a method for controlling the switching of the hydrogen evolution reaction based on defect-induced interlayer sliding of graphene and g-C3N4 bilayers. Through defect structure design, interlayer stacking control, ferroelectric-antiferroelectric phase transition switching, and optimization of hydrogen adsorption performance, precise and controllable ON-OFF and ON-OFF-ON catalysis of the hydrogen evolution reaction is achieved. The specific implementation steps are as follows:

[0006] Step 1: Construct a bilayer structure model of defective graphene (D-graphene) and g-C3N4;

[0007] Step 2: Perform architecture optimization and stability calculations based on density functional theory (DFT);

[0008] Step 3: Achieve polarization state switching and phase transition path calculation through interlayer slip;

[0009] Step 4: Calculate the hydrogen adsorption energy and Gibbs free energy ΔG H* To evaluate the HER catalytic performance;

[0010] Step 5: Establish polarization-catalysis structure-activity relationship and determine the optimal regulation mode of HER.

[0011] In step 1 above, using a graphene monolayer as a substrate, carbon atom vacancies are introduced into the graphene lattice, mimicking the in-plane natural vacancy defects of g-C3N4, to form a defective graphene (D-graphene) monolayer with a regular porous structure. D-graphene bilayers and g-C3N4 bilayer van der Waals structures are then constructed, with weak van der Waals coupling between the layers. A 30 Å vacuum layer is used to eliminate interlayer interference and ensure the system remains a quasi-two-dimensional structure. The D-graphene bilayer can form four typical stacking configurations: PE-AA, AFE-AA1, FE-AB, and FE-BA, while the g-C3N4 bilayer can form three stacking configurations: FE-AB, FE-BA, and PE-AA.

[0012] In step 2 above, the main steps for architecture optimization and stability calculation based on density functional theory (DFT) are further divided into:

[0013] Step 2.1: First-principles calculations were performed using VASP and DS-PAW software. The PBE functional was selected to handle electron exchange correlation, and the projected enhanced wave (PAW) method was used to describe electron-ion interactions. The plane wave cutoff energy was set to 520 eV.

[0014] Step 2.2: Set the energy convergence accuracy to 10⁻ 7 eV, the atomic force convergence criterion is set to 0.001 eV / Å, and DFT-D3 correction is added to accurately calculate the interlayer van der Waals interactions;

[0015] Step 2.3: Brillouin zone integration was performed using a Γ-centered 13×13×1 grid. The dynamic and thermodynamic stability of D-graphene monolayer, bilayer and various stacked configurations was verified by phonon dispersive spectroscopy and 3 ps first-principles molecular dynamics (AIMD) simulations at 300 K.

[0016] In the interlayer slip calculation of the aforementioned step 3 to achieve polarization state switching and phase transition path calculation, one layer of the double-layer material is fixed, and the other layer is slipped along the in-plane [11-0] direction to obtain different stacking configurations.

[0017] The CI-NEB method was used to calculate the ferroelectric-antiferroelectric and ferroelectric-paraelectric phase transition paths and glide barriers. In a D-graphene bilayer, a reversible transition between the antiferroelectric AFE-AA1 and the ferroelectric FE-AB / FE-BA was achieved with a glide barrier as low as 25–45 meV.

[0018] In the g-C3N4 bilayer, a continuous polarization switching from FE-AB to PE-AA to FE-BA is achieved, forming a ferroelectric-paraelectric-ferroelectric three-phase transition. Out-of-plane polarization intensity is calculated using dipole moment correction, determining that the ferroelectric polarization of D-graphene is approximately 0.36 pC / m, and the ferroelectric polarization of g-C3N4 is approximately 0.22 pC / m.

[0019] In step 4 above, material defect sites are selected as active centers for hydrogen adsorption, and the hydrogen adsorption energy (Eads) and the hydrogen adsorption Gibbs free energy (ΔG) are calculated under different stacking configurations. H* ), with |ΔG H* |≈0 eV is the optimal HER activity criterion. The results indicate that the FE-AB state ΔG of D-graphene... H* =0.032 eV, ΔG of FE-AB state of g-C3N4 H* =−0.030 eV, FE-BA state ΔG H* =0.059 eV, both close to the ideal value. However, the adsorption of D-graphene in the AFE-AA1 state is too strong, and the adsorption of g-C3N4 in the PE-AA state is too weak, neither of which possesses efficient HER activity. Combined with density of states (PDOS) analysis, the intrinsic mechanism by which polarization changes the surface electronic state and thus regulates the hydrogen adsorption intensity is revealed.

[0020] In step 5 above, by comparing the changes in electronic structure, adsorption energy, and catalytic activity under different polarization states, a complete regulatory mechanism of interlayer sliding → polarization switching → hydrogen adsorption intensity change → HER activity switching was established. In the Dgraphene system, the FE state is the HERON state, and the AFE state is the OFF state, realizing reversible dual-state switching. In the g-C3N4 system, the FE state is the ON state, and the PE state is the OFF state, enabling ON-OFF-ON three-level regulation. Finally, the optimal operating conditions of low barrier slip, high stability, and no noble metals were determined, forming an engineeringable intelligent HER regulation scheme. Attached Figure Description

[0021] Figure 1 shows the structures of graphene, g-C3N4, and defective graphene (D-graphene), with pink and purple spheres representing C and N atoms, respectively.

[0022] Figure 2 shows the crystal structures of bilayer D-graphene in PE-AA stack (a) and AFE-AA1 stack (b).

[0023] Figure 3 is a schematic diagram of the transition between the BA and AB polar states of a two-dimensional bilayer D-graphene, used for ON-OFF switching in the HER process;

[0024] Figure 4 shows three different stacking configurations of bilayer g-C3N4 in FE-AB, FE-BA and PE-AA stacks, and the corresponding ON-OFF switching diagrams of the HER process;

[0025] Figure 5 illustrates the mechanism of the ON-OFF switching of the hydrogen evolution reaction (HER) between two-dimensional defective graphene and g-C3N4 bilayer through interlayer sliding, as well as the extremely low sliding energy barrier between the polarization states of the two materials. (a) is a schematic diagram of the effect of the sliding ferroelectricity of the two-dimensional bilayer D-graphene on the ON-OFF switching of the HER process, with orange arrows indicating the polarization direction; (b) shows the negligible sliding energy barrier between the D-graphene bilayer and g-C3N4 bilayer on the transition path between the two polarization states AB and BA.

[0026] Figure 6 shows a systematic comparison of the total energy, hydrogen adsorption energy, hydrogen adsorption Gibbs free energy, and hydrogen evolution reaction volcano curves of g-C3N4 and defective graphene under different stacking configurations, intuitively revealing the correlation between polarization state and HER catalytic performance. (a) Total energy of g-C3N4 and D-graphene under different stacking configurations; (b) Corresponding hydrogen adsorption energy (E0). ads (c) Gibbs free energy change of HER (ΔG) H* (d) HER volcano curve;

[0027] Figure 7 shows the projected density of states (PDOS) of the ferroelectric stacked configurations of g-C3N4 and defective graphene before and after hydrogen atom adsorption, elucidating the regulatory mechanism of electronic structure changes on hydrogen adsorption and hydrogen evolution reaction activity. (a) Projected density of states (PDOS) of AB@g-C3N4, (b) AB@D-graphene, (c) AB-H@g-C3N4 and (d) AB-H@gD-graphene. Detailed Implementation

[0028] Example 1

[0029] A two-layer model of D-graphene and g-C3N4 was constructed using Materials Studio software. When constructing the D-graphene model, defects similar to the natural in-plane defects of g-C3N4 were precisely introduced, and the location and number of defects were adjusted to simulate real-world conditions. The geometry of the constructed two-layer model was optimized to minimize its energy, ensuring its stability and rationality. Different stacking configurations such as AA, AB, and BA were generated through interlayer slip operations, and the symmetry breaking of the model was carefully checked to ensure that the model met the research requirements.

[0030] Example 2

[0031] A density functional theory-based computational approach was employed, using the Vienna ab initio Simulation Package (VASP) software. The plane wave cutoff energy was set to 520 eV, and a 13×13×1 k-point grid was used. Electron exchange-correlation interactions were described using a PBE functional under the generalized gradient approximation (GGA), and van der Waals interactions were handled with Grimme DFT-D3 empirical correction to ensure computational accuracy. During the calculations, the energy convergence criterion for structural optimization was set to 10⁻⁻⁴. 7 eV, with the force convergence criterion set at 0.001 eV / Å.

[0032] Example 3

[0033] Using the Bader charge analysis tool built into VASP, we calculated in detail the charge transfer of each atom in the D-graphene and g-C3N4 bilayer systems under different stacking configurations. By analyzing charge transfer, we gained a deeper understanding of the microscopic mechanisms of interlayer interactions and polarization changes. Band structure calculations were performed to study the band gap changes of the materials under different stacking configurations, and the relationship between the band gap and HER catalytic performance was analyzed, exploring the influence of electronic structure on catalytic activity. The calculation results under different stacking configurations were compared to verify the effectiveness and stability of the ferroelectric-antiferroelectric transition in regulating HER catalytic performance. Furthermore, the results were compared with existing experimental data and theoretical studies to further validate the reliability of our methods and results.

Claims

1. A method for regulating the hydrogen evolution reaction using defect-induced graphene and g-C3N4 bilayer materials, characterized in that... Includes the following steps: (1) Construct a defect-induced graphene (D-graphene) and g-C3N4 bilayer model, wherein the D-graphene has a defect structure similar to the in-plane natural defect type pores of g-C3N4, and the layers are coupled by weak van der Waals forces. (2) Based on density functional theory (DFT), the constructed bilayer model was optimized in structure, calculated in electronic structure, analyzed in phonon spectrum and simulated in molecular dynamics to verify the thermodynamic and kinetic stability of the material; (3) By changing the stacking configuration of the bilayer material through interlayer in-plane slip, the reversible ferroelectric-antiferroelectric transformation of D-graphene bilayer and the polarization switching of g-C3N4 bilayer ferroelectric-paraelectric-ferroelectric are realized, with the slip barrier as low as 25–45 meV. (4) Calculate the adsorption energy and Gibbs free energy change (ΔG) of the bilayer material for hydrogen atoms under different stacking configurations. H* Key parameters such as density of states, based on |ΔG H* The optimal criterion for evaluating the catalytic performance of the hydrogen evolution reaction is approximately 0 eV. (5) Analyze the structure-activity relationship between polarization intensity, dipole arrangement and HER catalytic performance during the ferroelectric-antiferroelectric transition, and determine the optimal stacking configuration and operating conditions that can achieve efficient switching control.

2. The method according to claim 1, characterized in that... The DFT calculations employed the Peder-Burke-Enzehoff (PBE) exchange-correlated functional and projected enhanced wave (PAW) method to describe the interaction between electrons and ions, with a plane-wave cutoff energy of 520 eV and an energy convergence criterion of 10⁻⁻⁴. 7 eV, with a force convergence criterion of 0.001 eV / Å, and combined with DFT-D3 correction to accurately consider interlayer van der Waals interactions, Brillouin zone integration is performed using a Γ-centered grid.

3. The method according to claim 1, characterized in that, The magnitude and direction of out-of-plane ferroelectric polarization were determined by calculating the dipole moments of bilayer materials under different stacking configurations. The out-of-plane polarization of the D-graphene bilayer ferroelectric state reached 0.36 pC / m, while that of the g-C3N4 bilayer ferroelectric state was about 0.22 pC / m. Based on this, the regulatory mechanism of polarization changes on the adsorption, migration and desorption behavior of hydrogen atoms during HER catalysis was analyzed.

4. The method according to claim 1, characterized in that, The D-graphene bilayer can reversibly transition between the antiferroelectric AA1 configuration and the ferroelectric AB, BA configuration, with an extremely low and negligible sliding energy barrier during the transition; the hydrogen adsorption Gibbs free energy ΔG in the ferroelectric state... H* When the HER catalysis is close to 0 eV, it is in the "ON" state. In the antiferroelectric state, hydrogen adsorption is too strong, and the catalysis switches to the "OFF" state, thereby realizing the reversible ON-OFF switching control of the HER catalysis process.

5. The method according to claim 1, characterized in that, Ferroelectric g-C3N4 bilayers significantly enhance the HER catalytic performance under AB and BA ferroelectric polarization states, while their catalytic activity decreases significantly under the AA paraelectric state. By switching the polarization from AB to AA to BA through interlayer slip, precise three-level ON-OFF-ON control of HER can be achieved.

6. The method according to claim 1, characterized in that, The D-graphene and g-C3N4 bilayer materials do not contain any precious metals or transition metals, which can avoid the problems of metal aggregation at catalytic sites, high cost and catalyst deactivation. Their activity is comparable to that of commercial platinum-based catalysts.

7. The method according to claim 1, characterized in that, The preferential adsorption sites for hydrogen atoms on bilayer materials are defect sites. The defect structure significantly alters the surface electronic state distribution and is the core structural basis for achieving polarization-dependent HER catalytic regulation.

8. The application of defective graphene bilayer and g-C3N4 bilayer materials designed based on the method of any one of claims 1-7 in hydrogen production by water electrolysis, intelligent electrocatalytic switches, ferroelectric-controlled electrocatalysts and novel electrocatalytic devices.

Images