Method for improving graphite phase carbon nitride exciton separation

Abstract

The invention discloses a method for improving graphite phase carbon nitride exciton separation. The method specifically comprises the following steps: preparing graphite phase carbon nitride g-C3N4 through a thermal polymerization method of urea; 4-bromotriphenylamine is added, and a 4-bromotriphenylamine / g-C3N4 mixed catalyst is prepared; a 4-bromotriphenylamine / g-C3N4 mixed catalyst is filled between the two pieces of ITO to package the device; and the photovoltaic response range is improved by natural illumination and application of a direct-current electrostatic field. A liquid phase mixing method is adopted, and the preparation method is simple, mild in reaction, low in energy consumption, free of special requirements on equipment and suitable for large-scale production; meanwhile, the g-C3N4 composite material prepared by the method can be directly used as a photocatalysis and photovoltaic device, the synthesis steps are few, the operation is simple, and the prepared material has excellent performance.

Description

Technical Field

[0001] The invention belongs to optoelectronic material technology, and in particular relates to a method for improving graphite phase carbon nitride exciton separation. Background Art

[0002] Bulk graphitic carbon nitride (g-C3N4) exhibits high exciton binding energy due to the strong Coulomb interaction between Frenkel excitons, which leads to slow exciton dissociation and severe charge recombination. Secondly, due to the small specific surface area of ​​bulk g-C3N4, even if the excitons dissociate into free charges, the charge transport will be hindered. In addition, the insufficient reactive sites on the surface of g-C3N4 may also lead to slow reaction kinetics. To address these challenges, various strategies have been adopted to improve the photocatalytic performance of bulk g-C3N4.

[0003] g-C3N4 exhibits a high exciton binding energy of up to 328meV, which is much larger than the room temperature energy of 26meV. Therefore, the photogenerated carriers of g-C3N4 are easy to form excitons at room temperature but difficult to separate, which seriously restricts the optoelectronic application of g-C3N4. Therefore, how to promote the exciton separation of g-C3N4 is the key to improving its optoelectronic performance.

[0004] Common methods to improve the photoelectric response range of g-C3N4 include:

[0005] Doping: Changing the electronic structure of a material by incorporating non-metals (such as different forms of sulfur, phosphorus, and nitrogen) or metallic elements (such as tungsten and molybdenum) to extend its light response range.

[0006] Heterostructure construction: Combining with other optoelectronic materials (such as TiO2, ZnO, Graphene, etc.) to form a heterojunction can improve the light absorption range of g-C3N4.

[0007] Spectral tuning: The spectral response range of g-C3N4 can be optimized by adjusting the synthesis conditions (such as reaction temperature and precursors).

[0008] Modification: Use surface modification technology to introduce functional groups or defects to improve its light absorption properties.

[0009] Quantum dot modification: quantum dots are embedded in g-C3N4 to increase its responsiveness to light of different wavelengths.

[0010] Most of these methods rely on adding a second substance that responds to visible light. There are fewer methods that improve the photoelectric response range of g-C3N4 by promoting exciton separation. Summary of the invention

[0011] In view of the above problems, the present invention provides a method for improving the exciton separation of graphite phase carbon nitride.

[0012] A method for improving exciton separation in graphite phase carbon nitride of the present invention comprises the following specific steps:

[0013] Step 1: Preparation of graphite carbon nitride g-C3N4 by thermal polymerization of urea.

[0014] 10 g of urea was put into an alumina crucible with a lid, and then placed in a muffle furnace and calcined at 550 °C for 3 hours at a heating rate of 5 °C / min. After the temperature dropped to room temperature, a light yellow powder sample was collected, which was the final g-C3N4 catalyst.

[0015] Step 2: Prepare 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0016] Take 0.1-30 parts by weight of 4-bromotriphenylamine and 99.9-70 parts by weight of g-C3N4 catalyst, mix them, add them to 100 parts by weight of anhydrous ethanol, stir them at room temperature for 3 hours at a speed of 300 rpm, then filter and dry them at 80°C for 1 hour to obtain a 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0017] Step 3: Device packaging.

[0018] Fill 4-bromotriphenylamine / g-C3N4 mixed catalyst between two ITOs, with the conductive surfaces facing each other, to form an ITO / 4-bromotriphenylamine / g-C3N4 / ITO sandwich structure with an area of ​​1-10cm 2 , thickness 0.5-2 microns, sealed with epoxy resin all around, upper and lower ITO connecting wires.

[0019] Step 4: Improve performance.

[0020] Under natural light, a DC electrostatic field of 0.1-0.5V is applied between ITO / 4-bromotriphenylamine / g-C3N4 / ITO through the ITO wire to increase the photovoltaic response range from 300-400nm to 300-550nm.

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] The present invention adopts liquid phase mixing method, and its preparation method is simple, reaction is mild, energy consumption is low, there is no special requirement for equipment, and it is suitable for large-scale production. At the same time, the g-C3N4 composite material prepared by this method can be directly used as photocatalysis and photovoltaic devices, with few synthesis steps, simple operation, and excellent performance of the obtained material. Experiments have shown that, thanks to the strong coupling between 4-bromotriphenylamine and g-C3N4, π electron delocalization is extended, and the positive synergistic effect of the two significantly improves the exciton separation efficiency of g-C3N4, greatly expanding the photovoltaic response range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the surface photovoltaic response diagram of pure 4-bromotriphenylamine.

[0024] Figure 2 This is the surface photovoltaic response diagram of g-C3N4 prepared in Example 1 of the present invention.

[0025] Figure 3 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 1 of the present invention under 0 bias.

[0026] Figure 4 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 1 of the present invention under a bias voltage of 0.1V.

[0027] Figure 5 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 2 of the present invention under a bias voltage of 0.3V.

[0028] Figure 6 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 3 of the present invention under a bias voltage of 0.5V. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Embodiment 1:

[0031] A method for improving exciton separation in graphite phase carbon nitride, comprising the following steps:

[0032] Step 1: Preparation of graphite carbon nitride g-C3N4 by thermal polymerization of urea.

[0033] 10 g of urea was put into an alumina crucible with a lid, and then placed in a muffle furnace and calcined at 550 °C for 3 hours at a heating rate of 5 °C / min. After the temperature dropped to room temperature, a light yellow powder sample was collected, which was the final g-C3N4 catalyst.

[0034] Step 2: Prepare 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0035] Take 3 parts of 4-bromotriphenylamine and 97 parts of g-C3N4 catalyst, mix them, add them to 100 parts of anhydrous ethanol, stir at room temperature for 3 hours at a speed of 300 rpm, then filter and dry at 80°C for 1 hour to obtain a 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0036] Step 3: Device packaging.

[0037] A 4-bromotriphenylamine / g-C3N4 mixed catalyst was filled between two ITO blocks, with the conductive surfaces facing each other, to form an ITO / 4-bromotriphenylamine / g-C3N4 / ITO sandwich structure with an area of ​​1cm 2 , thickness 0.5 micron, sealed with epoxy resin all around, upper and lower ITO connecting wires.

[0038] Step 4: Improve performance.

[0039] Under natural light, a 0.1V DC electrostatic field is applied between ITO / 4-bromotriphenylamine / g-C3N4 / ITO through the ITO wire to increase the photovoltaic response range from 300-400nm to 300-550nm.

[0040] Figure 1 This is the surface photovoltaic response diagram of pure 4-bromotriphenylamine. It can be seen that there is no photovoltage signal.

[0041] Figure 2 The surface photovoltaic response diagram of g-C3N4 prepared in Example 1 shows that the photovoltaic response range does not change at 0.5V, which is an intrinsic process, and is located between 300-400nm.

[0042] Figure 3 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 1 under 0 bias. There is no change in the photovoltaic response range under 0 bias, which is also an intrinsic process, and is located between 300-400nm.

[0043] Figure 4 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 1 under a bias of 0.1V. The photovoltaic response range changes significantly under a bias of 0.1V, and an obvious band edge exciton peak appears at 450nm. The entire photovoltaic response range is between 300-550nm, which greatly improves the photovoltaic response range and intensity.

[0044] Embodiment 2:

[0045] A method for improving exciton separation in graphite phase carbon nitride, comprising the following steps:

[0046] Step 1: Preparation of graphite carbon nitride g-C3N4 by thermal polymerization of urea.

[0047] 10 g of urea was put into an alumina crucible with a lid, and then placed in a muffle furnace and calcined at 550 °C for 3 hours at a heating rate of 5 °C / min. After the temperature dropped to room temperature, a light yellow powder sample was collected, which was the final g-C3N4 catalyst.

[0048] Step 2: Prepare 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0049] Take 10 parts by mass of 4-bromotriphenylamine and 90 parts by mass of g-C3N4 catalyst, mix them, add them to 100 parts by mass of anhydrous ethanol, stir them at room temperature for 3 hours at a speed of 300 rpm, then filter and dry them at 80°C for 1 hour to obtain a 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0050] Step 3: Device packaging.

[0051] A 4-bromotriphenylamine / g-C3N4 mixed catalyst was filled between two ITO blocks, with the conductive surfaces facing each other, to form an ITO / 4-bromotriphenylamine / g-C3N4 / ITO sandwich structure with an area of ​​5 cm 2 , 1 micron thick, sealed with epoxy resin all around, with upper and lower ITO connecting wires.

[0052] Step 4: Improve performance.

[0053] Under natural light, a DC electrostatic field of 0.1-0.5V is applied between ITO / 4-bromotriphenylamine / g-C3N4 / ITO through the ITO wire to increase the photovoltaic response range from 300-400nm to 300-550nm.

[0054] Figure 5 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 2 under a bias of 0.3V. The photovoltaic response range changes significantly under a bias of 0.3V, and an obvious band edge exciton peak appears at 450nm. The entire photovoltaic response range is between 300-550nm, which greatly improves the photovoltaic response range and intensity.

[0055] Embodiment three:

[0056] A method for improving exciton separation in graphite phase carbon nitride, comprising the following steps:

[0057] Step 1: Preparation of graphite carbon nitride g-C3N4 by thermal polymerization of urea.

[0058] 10 g of urea was put into an alumina crucible with a lid, and then placed in a muffle furnace and calcined at 550 °C for 3 hours at a heating rate of 5 °C / min. After the temperature dropped to room temperature, a light yellow powder sample was collected, which was the final g-C3N4 catalyst.

[0059] Step 2: Prepare 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0060] Take 30 parts by mass of 4-bromotriphenylamine and 70 parts by mass of g-C3N4 catalyst, mix them, add them to 100 parts by mass of anhydrous ethanol, stir them at room temperature for 3 hours at a speed of 300 rpm, then filter and dry them at 80°C for 1 hour to obtain a 4-bromotriphenylamine / g-C3N4 mixed catalyst.

[0061] Step 3: Device packaging.

[0062] A 4-bromotriphenylamine / g-C3N4 mixed catalyst was filled between two ITO blocks, with the conductive surfaces facing each other, to form an ITO / 4-bromotriphenylamine / g-C3N4 / ITO sandwich structure with an area of ​​10 cm 2 , thickness 2 microns, sealed with epoxy resin all around, upper and lower ITO connecting wires.

[0063] Step 4: Improve performance.

[0064] Under natural light, a DC electrostatic field of 0.1-0.5V is applied between ITO / 4-bromotriphenylamine / g-C3N4 / ITO through the ITO wire to increase the photovoltaic response range from 300-400nm to 300-550nm.

[0065] Figure 6 This is the surface photovoltaic response diagram of 4-bromotriphenylamine / g-C3N4 prepared in Example 3 under a bias of 0.5V. The photovoltaic response range changes significantly under a bias of 0.5V, and an obvious band edge exciton peak appears at 450nm. The entire photovoltaic response range is between 300-550nm, which greatly improves the photovoltaic response range and intensity.

Claims

1. A method for improving exciton separation in graphite phase carbon nitride, characterized in that: The specific steps are: Step 1: preparing graphite carbon nitride g-C3N4 by thermal polymerization of urea; 10 g of urea was placed in an alumina crucible with a lid, and then placed in a muffle furnace and calcined at 550°C for 3 hours at a heating rate of 5°C / min. After the temperature dropped to room temperature, a light yellow powder sample was collected, which was the final g-C3N4 catalyst. Step 2: preparing a 4-bromotriphenylamine / g-C3N4 mixed catalyst; 0.1-30 parts by weight of 4-bromotriphenylamine and 99.9-70 parts by weight of g-C3N4 catalyst are mixed, added to 100 parts by weight of anhydrous ethanol, stirred at room temperature for 3 hours at a speed of 300 rpm, then filtered, and dried at 80° C. for 1 hour to obtain a 4-bromotriphenylamine / g-C3N4 mixed catalyst; Step 3: Device packaging; Fill 4-bromotriphenylamine / g-C3N4 mixed catalyst between two ITOs, with the conductive surfaces facing each other, to form an ITO / 4-bromotriphenylamine / g-C3N4 / ITO sandwich structure with an area of ​​1-10cm 2 , thickness 0.5-2 microns, sealed with epoxy resin around, upper and lower ITO connected wires; Step 4: Improve performance; Under natural light, a DC electrostatic field of 0.1-0.5V is applied between ITO / 4-bromotriphenylamine / g-C3N4 / ITO through the ITO wire to increase the photovoltaic response range from 300-400nm to 300-550nm.

Images