Method for improving gallium oxide hydrogen sensing based on first principle

Abstract

The invention discloses a method for improving gallium oxide hydrogen sensing based on a first principle, which comprises the following steps: S1, constructing a supercell model of an experimental crystal face, S2, constructing a crystal structure model before H2 adsorption activation, S3, carrying out adsorption activation test, S4, comparing the difference between the electronic structure and the physical parameter of the crystal structure model before and after H2 adsorption activation, and S5, determining the hydrogen sensing of gallium oxide according to the difference between the electronic structure and the physical parameter of the crystal structure model before and after H2 adsorption activation. And the H2 sensing response difference is judged, so that the hydrogen sensing effect of gallium oxide is improved. According to the method for improving gallium oxide hydrogen sensing based on the first principle, the first principle is adopted for calculation, the specific mechanism of adsorption and activation of a beta-Ga2O3 material to H2 can be disclosed from the atomic and electronic scale, and the chemical active crystal face of beta-Ga2O3 is defined; the problem that the crystal face activity mechanism is not clear when the gallium oxide material is applied to medium-high temperature H2 sensing at present is solved, and theoretical guidance is effectively provided for medium-high temperature H2 sensing.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas adsorption and activation, and in particular, relates to a method for improving gallium oxide hydrogen gas sensing based on first principles. Background Art

[0002] H2 is a clean energy that is expected to solve the problems of CO2 emissions and greenhouse effect. In order to avoid the risk of explosion due to H2 leakage in harsh environments such as industrial process control and combustion monitoring, H2 sensors with high temperature resistance, high sensitivity and high selectivity are needed. Among the existing H2 sensors such as semiconductor, thermal conductivity, optical and electrochemical sensors, metal oxide gas sensors based on SnO2 are widely used in industry and daily life due to their stability and low cost. However, when the operating temperature is >350°C, they will face the problem of sensor failure.

[0003] Ga2O3 is an ideal sensing material for H2 detection because of its high operating temperature of ~1,000°C and its extremely high sensitivity to H2. First, the unique activity of Ga2O3 towards H makes it a suitable co-catalyst in catalytic reactions involving the formation and breaking of hydrogen-containing bonds. For example, Ga2O3 can enhance the dehydrogenation of propane by an order of magnitude over In2O3 / Al2O3 mixtures. Second, the conductivity of hydrogen-induced nanostructured Ga2O3 can be enhanced by 9 orders of magnitude due to the presence of interstitial and substitutional hydrogen. Pt / Ga2O3 Schottky diodes are used in device integration because of their high temperature stability and excellent selectivity. For example, when detecting gases such as H2, N2, CO, CO2, O2, CH4, NO2, and NH3, Pt / Ga2O3 Schottky diodes only show a current change response to H2 because Pt can promote the dissociation of H2 and the surface coverage of H species. As the hydrogen concentration at the Pt / Ga2O3 interface increases, hydrogen diffusion increases, and the Schottky barrier at the Pt / Ga2O3 interface decreases, resulting in a response current to H2.

[0004] At present, Pt / Ga2O3 Schottky diodes mainly use (100) crystal planes and (−201) and (010) crystal planes. β -Ga2O3 substrate, which is cut from a Ga2O3 single crystal grown by guided mode method. Gas sensing experiments using two different devices show that the sensitivity of Pt / Ga2O3 Schottky diode to H2 depends on the crystal plane, decreasing in the order of (−201)>(100)>(010), and the H2 sensing sensitivity is simply proportional to the density of O dangling bonds on the crystal surface. However, the influence of different atomic structures of Ga2O3 on the H2 sensing mechanism and the source of H atom activity in Ga2O3 are still unclear. For example, Ga on Pt-modified Ga2O3 catalyst δ+–H species are also crucial in the catalytic reaction process, but this factor is often overlooked because O is more electronegative than Ga and it is believed that the adsorption of H atoms occurs only on O sites. H2 usually forms Ga–H on the surface of Ga2O3. − , 2020 cm in infrared spectrum −1 Appearing ν Ga–H The peaks reveal this. Therefore, understanding the adsorption and response mechanism of H2 on different Ga2O3 surfaces is crucial to improving the performance of Ga2O3-based H2 sensing materials. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the hydrogen sensing of gallium oxide based on the first principles, using gallium oxide as the activation material of high-temperature H2, analyzing the activation effect of the low-index end facets in gallium oxide, and then selecting the low-index end facets in gallium oxide with corresponding high-proportion activity as the raw material for hydrogen sensing.

[0006] The technical solution of the present invention to solve the above technical problems is: A method for improving gallium oxide hydrogen sensing based on first principles comprises the following steps: S1 builds a supercell model of the experimental crystal surface and selects β -Build supercell models for the low-index end faces of Ga2O3 that are more sensitive to H2 and optimize their structures; S2 constructs the crystal structure model before H2 adsorption activation, uses vasp for modeling, and uses GGA to describe the exchange correlation effect. β -Based on the low-index end face supercell model of Ga2O3, the Ga sites and O sites corresponding to the crystal surface were selected to further construct the crystal structure model before H2 adsorption activation; S3 adsorption activation test, the physical adsorption and chemical adsorption configuration tests were performed on the Ga site and O site on the crystal surface of the established crystal structure model, and the energy difference converged to 10 –5 eV, the residual stress converges to 0.05eV / Å, and the electronic structure and physical parameters of the crystal structure model after H2 adsorption activation are analyzed; S4 Compare the differences in electronic structure and physical parameters of the crystal structure model before and after H2 adsorption activation, and determine the differences in H2 sensing response, and then select the crystal face with better H2 sensing response effect to design the corresponding low-index end face of Ga2O3, thereby improving the hydrogen sensing effect of gallium oxide.

[0007] Specifically, in the steps S3 and S4, the electronic structure and physical parameters include electronic state density and adsorption energy.

[0008] Specifically, in step S4, the difference in the electron affinity of the crystal structure model before H2 activation and the changes in the chemical bonds, electronic structure and adsorption energy of the crystal structure model after H2 activation are analyzed to determine the difference in the H2 sensing response.

[0009] Specifically, the calculation formula of the adsorption energy is configured as: E ads (H) = E (Ga2O3-H2)− E (Ga2O3)−1 / 2 E (H2) E ads (H2) = E (Ga2O3-H2)− E (Ga2O3)− E (H2) in, E ads (H) and E ads (H2) are the adsorption energies of H atoms and H2 molecules, E (Ga2O3-H2) is the total energy of the adsorption system, E (Ga2O3) is the total energy of Ga2O3 substrate on the experimental crystal plane, E (H2) is the total energy of an isolated H2 molecule.

[0010] Specifically, the adsorption energy of the H atom is −2.0~−0.8 eV, and the adsorption energy of the H2 molecule is −2.5~−1.5 eV.

[0011] Preferably, the β The medium and low index facets in -Ga2O3 that are more sensitive to H2 include the (−201), (100) and (010) crystal planes.

[0012] Specifically, the hydrogen sensing performance of the (−201) crystal plane, the (100) crystal plane, and the (010) crystal plane decreases in sequence.

[0013] Preferably, the (−201) crystal plane includes the (−201)A crystal plane, the (−201)B crystal plane and the (−201)C crystal plane, and the hydrogen sensing performance thereof is (−201)A crystal plane<(−201)B crystal plane<(−201)C crystal plane.

[0014] The present invention has the following beneficial effects: (1) The present invention uses first-principles calculations to reveal the β -The specific mechanism of H2 adsorption and activation of Ga2O3 materials has been clarifiedβ -Ga atoms and O atoms in the chemically active crystal face of Ga2O3 can contribute to electron transfer, solving the problem of unclear crystal face activity mechanism in the current application of gallium oxide materials in medium and high temperature H2 sensing, and revealing the medium and low index end faces (exposed crystal faces) of Ga2O3 crystals that effectively sense H2, effectively providing theoretical guidance for medium and high temperature H2 sensing; (2) Gallium oxide was used as the gas-sensitive material. Through the optimization of different crystal plane structure models, physical and chemical adsorption tests of H2 were carried out on the O and Ga sites on different crystal planes. The mechanism of H2 adsorption and activation on the gallium oxide surface was clarified, and the optimal active crystal surface for gallium oxide hydrogen sensing was determined and designed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the adsorption configuration of chemically adsorbed H atoms on the (−201)A crystal plane (a), the (100)A crystal plane (b) and the (010) crystal plane (c) in Example 1 of the present invention.

[0016] Figure 2 Schematic diagram of the adsorption configuration of chemically adsorbed H atoms on the (−201)B crystal plane (a), the (100)B crystal plane (b) and the (010) crystal plane (c) in Example 2 of the present invention.

[0017] Figure 3 The adsorption site distribution (a) and corresponding adsorption energy (b) of H atoms chemically adsorbed on the (−201)C crystal plane in Example 3 of the present invention.

[0018] Figure 4 This is a migration potential energy diagram of active H atoms on the (−201)A crystal plane, the (−201)B crystal plane, and the (−201)C crystal plane combining with each other to form H2 in Example 3 of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the embodiments. Example

[0020] A method for improving hydrogen gas sensing of gallium oxide based on first principles according to embodiment 1 of the present invention comprises the following steps: S1 builds a supercell model of the experimental crystal surface and selects β A supercell model was constructed for the medium- and low-index end planes (−201), (100) and (010) of -Ga2O3 that are more sensitive to H2, and its structure was optimized.

[0021] S2 constructs the crystal structure model before H2 adsorption activation, uses vasp for modeling, and uses GGA to describe the exchange correlation effect. β -Ga2O3 medium and low index end face supercell model, selectβ -O(III) on the (−201)A crystal plane of Ga2O3 3c, u Site, O(II) on (100)A crystal plane 2c, u Site, O(I) of (010) crystal plane 2c, u The sites were used as adsorption sites to further construct the crystal structure model before H2 adsorption activation.

[0022] S3 adsorption activation test, respectively, the H atom on the established crystal structure model of the surface of the Ga site and O site for physical adsorption and chemical adsorption configuration test, the energy difference converges to 10 –5 eV, the residual stress converges to 0.05eV / Å, and the electronic structure and physical parameters of the crystal structure model after H adsorption activation are analyzed, including the electronic state density and adsorption energy. The calculation formula of the adsorption energy is configured as: E ads (H) = E (Ga2O3-H2)− E (Ga2O3)−1 / 2 E (H2) E ads (H2) = E (Ga2O3-H2)− E (Ga2O3)− E (H2) in, E ads (H) and E ads (H2) are the adsorption energies of H atoms and H2 molecules, E (Ga2O3-H2) is the total energy of the adsorption system, E (Ga2O3) is the total energy of Ga2O3 substrate on the experimental crystal plane, E (H2) is the total energy of isolated H2 molecules. The adsorption energies calculated in this embodiment are shown in the following table. In addition, the H activation mechanism diagrams constructed in this embodiment are shown in Figure 1 shown. S4 Compare the differences in electronic structure and physical parameters of the crystal structure model before and after H adsorption activation. By analyzing the difference in electron affinity of the crystal structure model before H2 activation and the changes in chemical bonds, electronic structure and adsorption energy of the crystal structure model after H2 activation, the difference in H2 sensing response can be determined, and then the crystal face with better H2 sensing response effect can be selected to design the corresponding low-index end face of Ga2O3, thereby improving the hydrogen sensing effect of gallium oxide. Figure 1The H activation mechanism diagram constructed for this embodiment shows that the lower the adsorption energy, the lower the energy of the system after adsorption and the more stable it is. Therefore, from the perspective that the (−201)A crystal plane has the lowest H atom adsorption energy of −1.91 eV, it can be seen that the (−201)A crystal plane has a more obvious adsorption effect on H than the (100)A crystal plane and the (010) crystal plane. At the same time, the total electronic state density of the (−201)A crystal plane is 2.52, while that of (100)A and (010) is 2.23 and 0.25, respectively, indicating that the (−201)A crystal plane system has more carrier transport. Therefore, it can be concluded that the (−201)A crystal plane has a more obvious gas sensing effect on H2 than the (100)A crystal plane and the (010) crystal plane. Example

[0023] A method for improving hydrogen gas sensing of gallium oxide based on first principles according to embodiment 2 of the present invention comprises the following steps: S1 builds a supercell model of the experimental crystal surface and selects β A supercell model was constructed for the medium- and low-index end planes (−201), (100) and (010) of -Ga2O3 that are more sensitive to H2, and its structure was optimized.

[0024] S2 constructs the crystal structure model before H2 adsorption activation, uses vasp for modeling, and uses GGA to describe the exchange correlation effect. β -Ga2O3 medium and low index end face supercell model, select β -Ga(II) on the (−201)B plane of Ga2O3 3c, 1u Site, O(III) on (100)B crystal plane 3c, u Site, O(II) on (010) crystal plane 2c, u The sites were used as H adsorption sites to further construct the crystal structure model before H2 adsorption activation.

[0025] S3 adsorption activation test, the physical adsorption and chemical adsorption configuration tests were performed on the Ga site and O site on the crystal surface of the established crystal structure model, and the energy difference converged to 10 –5 eV, the residual stress converges to 0.05eV / Å, and the electronic structure and physical parameters of the crystal structure model after H2 adsorption activation are analyzed, including the electronic state density and adsorption energy. The calculation formula of the adsorption energy is configured as: E ads (H) = E (Ga2O3-H2)− E (Ga2O3)−1 / 2 E (H2) Eads (H2) = E (Ga2O3-H2)− E (Ga2O3)− E (H2) in, E ads (H) and E ads (H2) are the adsorption energies of H atoms and H2 molecules, E (Ga2O3-H2) is the total energy of the adsorption system, E (Ga2O3) is the total energy of Ga2O3 substrate on the experimental crystal plane, E (H2) is the total energy of isolated H2 molecules. The adsorption energies calculated in this embodiment are shown in the following table. In addition, the H activation mechanism diagrams constructed in this embodiment are shown in Figure 2 shown. S4 Compare the differences in electronic structure and physical parameters of the crystal structure model before and after H2 adsorption activation. By analyzing the difference in electron affinity of the crystal structure model before H2 activation and the changes in chemical bonds, electronic structure and adsorption energy of the crystal structure model after H2 activation, the difference in H2 sensing response is determined, and then the crystal face with better H2 sensing response effect is selected to design the corresponding low-index end face of Ga2O3, thereby improving the hydrogen sensing effect of gallium oxide. Figure 2 The H activation mechanism diagram constructed for this embodiment shows that the lower the adsorption energy, the lower the energy of the system after adsorption and the more stable it is. Therefore, from the perspective that the (−201)B crystal plane has the lowest H atom adsorption energy of −0.92 eV, it can be shown that the (−201)B crystal plane has a more obvious adsorption effect on H than the (100)B crystal plane and the (010) crystal plane. At the same time, the total electronic state density of the (−201)B crystal plane is 3.22, while that of (100)A and (010) is 0.82 and 0.51, respectively, indicating that the (−201)B crystal plane system has more carrier transport. Therefore, in summary, it can be shown that the (−201)B crystal plane has a more obvious gas sensing effect on H2 than the (100)B crystal plane and the (010) crystal plane. Example

[0026] A method for improving hydrogen gas sensing of gallium oxide based on first principles according to embodiment 3 of the present invention comprises the following steps: S1 builds a supercell model of the experimental crystal surface and selects β A supercell model was constructed for the medium- and low-index end facets (−201) of -Ga2O3 that are more sensitive to H2, and its structure was optimized.

[0027] S2 constructs the crystal structure model before H2 adsorption activation, uses vasp for modeling, and uses GGA to describe the exchange correlation effect.β -Ga2O3 medium and low index end face supercell model, select β -O(III) on the (−201)A crystal plane of Ga2O3 3c, u Site, Ga(II) on (−201)B surface 3c, 1u Site, O(III) on (−201)C crystal plane 3c, 2u Site, Ga(II) on (−201)C crystal plane 4c, u The sites were used as adsorption sites to further construct the crystal structure model before H2 adsorption activation.

[0028] S3 adsorption activation test, the physical adsorption and chemical adsorption configuration tests were performed on the Ga site and O site on the crystal surface of the established crystal structure model, and the energy difference converged to 10 –5 eV, the residual stress converges to 0.05eV / Å, and the electronic structure and physical parameters of the crystal structure model after H2 adsorption activation are analyzed, including the electronic state density and adsorption energy. The calculation formula of the adsorption energy is configured as: E ads (H) = E (Ga2O3-H2)− E (Ga2O3)−1 / 2 E (H2) E ads (H2) = E (Ga2O3-H2)− E (Ga2O3)− E (H2) in, E ads (H) and E ads (H2) are the adsorption energies of H atoms and H2 molecules, E (Ga2O3-H2) is the total energy of the adsorption system, E (Ga2O3) is the total energy of Ga2O3 substrate on the experimental crystal plane, E (H2) is the total energy of isolated H2 molecules. The adsorption energies calculated in this embodiment are shown in the following table. In addition, the H activation mechanism diagrams constructed in this embodiment are shown in Figure 3 shown. S4 Compare the differences in electronic structure and physical parameters of the crystal structure model before and after H2 adsorption activation. By analyzing the difference in electron affinity of the crystal structure model before H2 activation and the chemical bonds, electronic structure and adsorption energy of the crystal structure model after H2 activation, and judging the change in gas-sensitive response current by the change in conductivity, the difference in H2 sensing response is judged, and then the crystal face with better H2 sensing response effect is selected to design the corresponding low-index end face of Ga2O3, thereby improving the hydrogen sensing effect of gallium oxide. Figure 3 is the H activation mechanism diagram of the (−201)C crystal plane structure in this embodiment, and when analyzing the migration potential energy of active H atoms combining with each other to form H2, Figure 4 As shown in the figure, a H2 dissociation barrier of 2.56 eV is shown on the (−201)C crystal plane, while no H2 dissociation barrier is found on the (−201)A crystal plane and the (−201)B crystal plane. This shows that the (−201)C crystal plane has a more obvious gas sensing effect on H2 than the (−201)A crystal plane and the (−201)B crystal plane, and also has a better corresponding recovery time. The integral of the electronic state density of H atoms on the (−201)B crystal plane in the (−0.5, 0.5) eV range is 0.0052, while the corresponding integral of the (−201)A crystal plane is 0, indicating that the (−201)B crystal plane has a better H2 response effect than the (−201)A crystal plane.

[0029] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for improving gallium oxide hydrogen sensing based on first principles, characterized in that: The steps include: S1 builds a supercell model of the experimental crystal surface and selects β -Build supercell models for the low-index end faces of Ga2O3 that are more sensitive to H2 and optimize their structures; S2 constructs the crystal structure model before H2 adsorption activation, uses vasp for modeling, and uses GGA to describe the exchange correlation effect. β -Based on the low-index end face supercell model of Ga2O3, the Ga sites and O sites corresponding to the crystal surface were selected to further construct the crystal structure model before H2 adsorption activation; S3 adsorption activation test, the physical adsorption and chemical adsorption configuration tests were performed on the Ga site and O site on the crystal surface of the established crystal structure model, and the energy difference converged to 10 –5 eV, the residual stress converges to 0.05 eV / Å, and the electronic structure and physical parameters of the crystal structure model after H2 adsorption activation are analyzed; S4 Compare the differences in electronic structure and physical parameters of the crystal structure model before and after H2 adsorption activation, and determine the differences in H2 sensing response, and then select the crystal face with better H2 sensing response effect to design the corresponding low-index end face of Ga2O3, thereby improving the hydrogen sensing effect of gallium oxide.

2. The method for improving gallium oxide hydrogen sensing based on first principles according to claim 1, characterized in that: In the steps S3 and S4, the electronic structure and physical parameters include electronic state density and adsorption energy.

3. The method for improving gallium oxide hydrogen sensing based on first principles according to claim 2, characterized in that: In the step S4, the difference in the electron affinity of the crystal structure model before H2 activation and the changes in the chemical bonds, electronic structure and adsorption energy of the crystal structure model after H2 activation are analyzed to determine the difference in the H2 sensing response.

4. The method for improving gallium oxide hydrogen sensing based on first principles according to claim 2, characterized in that: The calculation formula of the adsorption energy is configured as follows: <h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> ads <h2 style=";text-align:left;direction:ltr"> (H) =<h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> (Ga2O3-H2)−<h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> (Ga2O3)−1 / 2<h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> (H2) <h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> ads <h2 style=";text-align:left;direction:ltr"> (H2) =<h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> (Ga2O3-H2)−<h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> (Ga2O3)−<h2 style=";text-align:left;direction:ltr"> E <h2 style=";text-align:left;direction:ltr"> (H2) in, E ads (H) and E ads (H2) are the adsorption energies of H atoms and H2 molecules, E (Ga2O3-H2) is the total energy of the adsorption system, E (Ga2O3) is the total energy of Ga2O3 substrate on the experimental crystal plane, E (H2) is the total energy of an isolated H2 molecule.

5. The method for improving gallium oxide hydrogen sensing based on first principles according to claim 4, characterized in that: The adsorption energy of the H atom is −2.0~−0.8 eV, and the adsorption energy of the H2 molecule is −2.5~−1.5 eV.

6. The method for improving gallium oxide hydrogen sensing based on first principles according to any one of claims 1 to 5, characterized in that: Said β The medium and low index facets in -Ga2O3 that are more sensitive to H2 include the (−201), (100) and (010) crystal planes.

7. The method for improving gallium oxide hydrogen sensing based on first principles according to claim 6, characterized in that: The hydrogen sensing performance of the (−201) crystal plane, (100) crystal plane and (010) crystal plane decreases in sequence.

8. The method for improving gallium oxide hydrogen sensing based on first principles according to claim 7, characterized in that: The (−201) crystal plane includes the (−201)A crystal plane, the (−201)B crystal plane and the (−201)C crystal plane, and the hydrogen sensing performance thereof is (−201)A crystal plane<(−201)B crystal plane<(−201)C crystal plane.

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