Photocatalytic reduction in dislocations

Abstract

The present invention relates to a method of photocatalytic reduction in dislocations and a setup comprising a photocatalyst with dislocations.

Description

[0001] The present invention relates to a method of photocatalytic reduction at dislocations and a setup comprising a photocatalyst with dislocations. The term "at dislocations" as used here includes both photocatalytic reactions precisely at the position where the dislocation is located and photocatalytic reactions in the vicinity of the dislocation. For example, in some embodiments, the dislocation acts as a "highway" for electron conductivity to the photocatalyst surface. background

[0002] Over the past few decades, energy consumption, particularly from fossil fuels, has increased significantly with the rapid development of modern industries and explosive population growth. Statistics reveal that in 2017, over 65% of total energy consumption was attributable to fossil fuels. Oil companies estimate that the remaining fossil resources will be depleted within a few decades if no changes are implemented. Finding suitable solutions for the efficient conversion of energy from renewable sources is therefore of great social and economic importance.

[0003] Extensive consumption of fossil fuels inevitably results in CO2 emissions into the environment, which has already caused global warming of 1.2°C, as CO2 is currently the dominant greenhouse gas. In accordance with the goal of the Paris Agreement, which aims to limit warming to below 1.5°C, the consumption of fossil resources should be restricted to a low level. Otherwise, the resulting negative impacts of global warming would be far-reaching. Therefore, we must become more dependent on renewable energy sources than on fossil fuels.

[0004] Solutions for energy conversion in a sustainable and environmentally friendly way are urgently needed. Energy conversion through the production of synthetic fuels can support this effort. For example, catalytic energy conversion using water, O2, or CO2 as reactants, driven by sunlight, has been proposed as photocatalysis. These reactants and sunlight are abundant in nature, making these energy conversion reactions a clean and sustainable approach, thus providing a promising solution to both the energy crisis and global warming.

[0005] In 1972, researchers discovered the phenomenon of water splitting using TiO2 as a catalyst under ultraviolet (UV) light illumination, suggesting a possible catalytic energy conversion driven by light. Inspired by this finding, extensive efforts were undertaken with semiconductor catalysts to expand their energy conversion applications under light illumination. Light illumination, particularly sunlight, can be used to drive energy conversion reactions in combination with catalysts that have an optimal band gap for light absorption.

[0006] Besides the classical photocatalytic process of water splitting, energy conversion associated with photocatalytic reduction has attracted the most attention. For example, research focuses heavily on the greenhouse gas CO2, which can be reduced to various carbon-containing fuel forms, such as CO, CH4, CH3OH, CH3CH2OH, and others. Therefore, photocatalytic CO2 reduction is referred to as "artificial photosynthesis." This offers the vision of a carbon-neutral energy cycle based on the photocatalytic conversion of CO2. It encompasses the link between renewable energy consumption, CO2 emissions, and CO2 recycling. However, no photocatalyst has yet been found that is efficient enough for CO2 reduction with high selectivity for the resulting products.

[0007] Due to the intrinsically stable nature of the C=O bond and the highest oxidation state of C in CO₂, photocatalytic CO₂ reduction generally faces the challenges of low energy conversion efficiency, diverse but uncontrollable reaction pathways and products, and competing H₂ production from water in the reactant solution. Furthermore, the recombination of photogenerated holes and electrons is unavoidable, especially in the bulk of the catalyst, which prevents electron transfer to the reactive surface sites for CO₂ reduction. All these factors limit the product yield of CO₂ reduction to a low level, e.g., for TiO₂ rutile particles, with a CH₄ product yield of 0.225 µmol / g per hour and CO yield of 0.188 µmol / g per hour. Here, the weight of the catalyst is used to normalize the molar amount of product.

[0008] To improve the photocatalytic CO2 conversion efficiency, various approaches have been developed, including impurity doping, metal deposition, heterojunction structuring, and cocatalyst loading. However, none have yet proven effective. Even in cases where photochemical reduction of CO2 was successful, only gaseous components could be obtained (e.g., CH4, CO). However, liquid products that can be easily separated are of significant industrial interest.

[0009] Another industrially desirable photocatalytic conversion is the production of H₂O₂ from a light-induced two-electron reduction process of O₂. Besides being a strong industrial oxidizing agent, H₂O₂ is crucial in the field of fuel cells, contributing to an annual consumption of approximately 2.2 million tons. Using naturally abundant O₂ as a reactant and driving the reaction with light to produce H₂O₂ should make the conversion sustainable and environmentally friendly compared to the currently used anthraquinone oxidation (AO) process. However, no industrially relevant strategy has yet been developed for this purpose. Regarding the production of H₂O₂, there is a process for its synthesis that is already a century old and still predominates in industry.It involves costly Pd-containing catalysts, low H₂O₂ selectivity, and the explosion risk of the H₂ / O₂ mixture in this byproduct. Therefore, a sustainable solution is needed for this important chemical. Summary of the invention

[0010] Photocatalysts with a suitable band gap value can absorb light within the corresponding wavelength range. Electrons and holes are activated and generated when the absorbed photon energy is large enough to overcome the band gap. Thus, a photocurrent can be measured in a closed circuit when a small bias voltage is applied under illumination. When the illumination is switched off, there are no photogenerated charges. Consequently, no photocurrent is induced. The related scheme of the mechanism is described in Fig. Figure 1 shows these photogenerated holes and electrons, which are used in the following photocatalytic reactions and form the basis of photocatalysis.

[0011] Typically, the wavelength range for the measurement related to photocatalysis is 320 nm to 780 nm, which includes ultraviolet A (UVA) (320 to 400 nm) and visible light (400 to 780 nm), but not ultraviolet B (UVB) (280 to 320 nm), ultraviolet C (UVC) (100 to 280 nm), and infrared light (> 780 nm). UVB and UVC are extensively absorbed by the atmosphere, and little reaches the Earth's surface. Therefore, sunlight reaching Earth contains very little UVB and UVC. Infrared light is generally not considered for photocatalysis.

[0012] By using a variety of experimental methods to introduce dislocation networks into several ceramic photocatalysts, the inventors demonstrated an increase in catalytic efficiency for multiple chemical reduction reactions using generated electronic charge carriers.

[0013] Dislocations can be introduced into catalytic materials by various methods, including uniaxial bulk deformation and surface treatments such as localized ball impression, polishing, milling, or rolling, performed at both room temperature and elevated temperatures. These processes can also be performed in cycles to further increase the dislocation density. Additionally, suitable sintering conditions (e.g., flash sintering, spark plasma sintering) have been claimed as feasible in the synthesis of polycrystalline ceramics, but have not been confirmed for several materials.

[0014] The industrially highly desired photochemical CO2 reduction from an aqueous solution was effectively achieved by introducing dislocations into the catalysts in combination with and without sacrificial agents.

[0015] The products of photochemical CO2 reduction exhibited high selectivity towards liquid organic products, resulting in a significant economic advantage and industrial suitability compared to gases.

[0016] The photochemical synthesis of H₂O₂ has been successfully scaled up to pave the way for efficient, industrial-scale production with and without sacrificial agents. Sacrificial agents include dyes, alcohols, oxalate, nitrate, nitrite, sulfite, metal cations, etc., which can be used to trap electrons or holes for redox reactions. H₂O₂ production reactions include both the oxygen reduction reaction (ORR) and the water oxidation reaction (WOR). The photocatalysts used for H₂O₂ production via the ORR pathway preferably have a conduction band (CB) greater than 0.68 V, and those used for the WOR pathway preferably have a valence band (VB) greater than 1.76 V. Details of the invention

[0017] The invention relates to a method of photocatalytic reduction in dislocations and an electrochemical setup comprising a photocatalyst with dislocations.

[0018] In particular, the invention relates to a method of photocatalytic reduction of a reactant, wherein the method comprises the following steps: a) Providing a setup comprising a photocatalyst immersed in an aqueous solution comprising the reactant, and b) Illuminating the photocatalyst with light, so that in particular the photocatalyst / reactant interface in the vicinity of or at dislocations acts as a reactive site for photocatalytic reactions, and c) If necessary, separation of liquid (especially organic) products.

[0019] The process is characterized by the photocatalyst comprising or consisting of a semiconductor photocatalyst with dislocations, wherein the surface dislocation density on at least a part of a surface of the photocatalyst is at least 1.0*10 11 m -2The surface dislocation density may optionally be at least 20%, at least 40%, at least 60%, or at least 80% of the total surface area of ​​the photocatalyst. In this context, the surface dislocation density refers to the number of dislocations within an area of ​​the photocatalyst surface, i.e., dislocations whose dislocation line terminates at the surface of the photocatalyst. The photocatalyst of the invention preferably absorbs light in the visible to ultraviolet range. In particular, the photocatalyst of the invention absorbs light in the wavelength range from 320 nm to 780 nm, including ultraviolet A (UVA) (320 to 400 nm) and visible light (400 to 780 nm).

[0020] A dislocation is a line defect. When this line penetrates the surface, it is effective at that surface.

[0021] The terms "liquid" and "gaseous" as used herein refer to the state of matter of the respective products at standard temperature and pressure (NTP, 20 °C, 101.325 kPa), unless otherwise specified. The products of the process of the present invention can include liquid products, gaseous products, and / or mixtures of liquid and gaseous products. The gaseous products can include, for example, H₂, CO, or mixtures thereof. The liquid products can be polar organic products. The liquid products are preferably soluble in water. In particular, water can be a solvent. The liquid products are, in particular, liquid organic products. The liquid products can include, for example, ketones, aldehydes, alcohols, and / or mixtures of two or more of these, such as CH₂O, CH₃OH, CH₃CHO, CH₃CH₂OH, and / or mixtures of two or more of these.The process may optionally include a step of separating the liquid products, for example by distillation, especially under different pressures if azeotropic mixtures with water are formed.

[0022] In some embodiments, the photocatalyst has a band gap in the range of 1.0 eV to 5.5 eV, 1.5 eV to 5.0 eV, 2.0 eV to 4.5 eV, or 2.5 eV to 4.0 eV, for example, 3.0 to 3.5 eV. The band gap may optionally be at least 1.0 eV, at least 1.5 eV, at least 2.0 eV, at least 2.5 eV, or at least 3.0 eV. The band gap may optionally be at most 5.5 eV, at most 5.0 eV, at most 4.5 eV, at most 4.0 eV, or at most 3.5 eV. In some embodiments, the band gap can be approximately 3.1 eV (especially in the case of TiO2) or approximately 3.2 eV (especially in the case of SrTiO3).

[0023] In some embodiments, the setup is an electrochemical setup and the photocatalyst is a photocatalyst working electrode.

[0024] In some embodiments, the method includes the steps of detecting and quantifying the products of the photocatalytic reactions.

[0025] The light preferably consists of electromagnetic radiation with a wavelength of 320 nm to 780 nm. For example, the light source for illuminating the photocatalyst working electrode can be an Xe arc lamp. Xe arc lamps are particularly suitable because they produce bright white light to simulate sunlight.

[0026] The aqueous solution contains in particular more than 50 vol% H2O, for example at least 60 vol%, at least 70 vol%, at least 80 vol%, at least 90 vol%, at least 95 vol%, at least 98 vol% or at least 99 vol% H2O.

[0027] In some embodiments, the aqueous solution is deionized water. In other embodiments, the aqueous solution comprises one or more inorganic salts, in particular in a total amount of at least 10 mM, at least 20 mM, at least 50 mM, at least 100 mM, at least 200 mM, or at least 500 mM. The total amount of inorganic salts is preferably at most 8.0 M, for example at most 7.0 M, at most 6.0 M, at most 5.0 M, at most 4.0 M, or at most 3.0 M. The total amount of inorganic salts can, for example, be in the range of 10 mM to 8.0 M, 20 mM to 7.0 M, 50 mM to 6.0 M, 100 mM to 5.0 M, 200 mM to 4.0 M, or 500 mM to 3.0 M.

[0028] The pH value of the aqueous solution lies, in particular, in a range of 5.5 to 8.5, for example, from 6.0 to 8.0 or from 6.5 to 7.5. The pH value of the aqueous solution can, for example, be at least 5.5, at least 6.0, or at least 6.5. The pH value of the aqueous solution can, for example, be at most 8.5, at most 8.0, or at most 7.5.

[0029] The aqueous solution may optionally comprise one or more sacrificial agents. Sacrificial agents may be used to trap electrons or holes for redox reactions. In some embodiments, the aqueous solution comprises one sacrificial agent. In other embodiments, the aqueous solution does not comprise a sacrificial agent. In some embodiments, the sacrificial agents are selected from the group consisting of dyes, alcohols, oxalate, nitrate, nitrite, sulfite, metal cations, and combinations of two or more thereof. In some embodiments, the sacrificial agents are selected from the group consisting of aliphatic amines, aromatic amines, ascorbic acid, and combinations of two or more thereof. Triethanolamine is a particularly preferred sacrificial agent.

[0030] The volume ratio of the sacrificial agent to the total volume of the aqueous solution can, for example, be in a range of 1:20 to 1:5, 1:15 to 1:7, or 1:12 to 1:8, and in particular approximately 1:10. In some embodiments, the volume ratio of the sacrificial agent to the total volume of the aqueous solution is at least 1:20, at least 1:15, or at least 1:12. In some embodiments, the volume ratio of the sacrificial agent to the total volume of the aqueous solution is at most 1:5, at most 1:7, or at most 1:8.

[0031] The reactant can be, in particular, CO2 / HCO3 - / CO3 2- or comprise or consist of O2. The reactant can also comprise or consist of H2O. In particular, H2O could be included in reactions, acting as an intermediate for photogenerated electron transfer.

[0032] In some embodiments, the reactant comprises CO2 / HCO3- / CO3 2- or consists of it. In aqueous solution, CO2 is in equilibrium with HCO3. - and CO3 2- Therefore, the present disclosure concerns “CO2 / HCO3”. - / CO3 2- “as the reactant. An aqueous solution containing CO2 / HCO3 - / CO3 2- The aqueous solution can be provided in various ways. In particular, it can be a carbonate or bicarbonate solution (especially NaHCO3) with or without bubbles of CO2 gas inside, or it can be deionized water with bubbles of CO2 gas inside.

[0033] For example, in some embodiments, a hydrogen carbonate solution (especially NaHCO3) can be percolated with CO2 gas, particularly until CO2 saturation is reached. The gas pressure of the percolating CO2 gas is preferably equal to or higher than atmospheric pressure (101 kPa) in order to completely drive off the dissolved oxygen.

[0034] In some embodiments, a hydrogen carbonate solution (especially NaHCO3) can be used without the bubbling CO2 gas inside.

[0035] In some embodiments, deionized water can be perfused with CO2 gas, particularly until CO2 saturation is reached. As described above, the gas pressure of the perforating CO2 gas is preferably equal to or higher than atmospheric pressure (101 kPa) in order to completely drive off the dissolved oxygen.

[0036] The bubbling CO2 gas is not necessarily pure CO2, but may also contain other components. However, the proportion of CO2 in the bubbling CO2 gas is preferably higher than the proportion of CO2 in air. More preferably, CO2 is the main component of the bubbling CO2 gas. The proportion of CO2 in the bubbling CO2 gas is preferably at least 50 vol%, more preferably at least 75 vol%, more preferably at least 90 vol%, more preferably at least 95 vol%, more preferably at least 98 vol%, more preferably at least 99 vol%, more preferably at least 99.9 vol%, more preferably at least 99.999 vol%, more preferably at least 99.999 vol%.

[0037] The reduction of CO2 / HCO3 - / CO3 2-The products obtained include, in particular, CO, CH4, CH2O, CH3OH, CH3CHO, CH3CH2OH, or combinations of two or more thereof. Ketones, aldehydes, alcohols, and mixtures of two or more of these, such as CH2O, CH3OH, CH3CHO, CH3CH2OH, or combinations thereof, are particularly preferred. A particular advantage of the present invention is to provide a photochemical CO2 reduction process with high selectivity for liquid organic products, which offer significant economic advantages and industrial suitability compared to gases. The distinction between liquid and gaseous products relates to their state of matter at standard temperature and pressure. In particular, the molar ratio of liquid products to gaseous products obtained by the process of the invention is at least 1:1.For example, the molar fraction of liquid products in relation to the total product fraction can be at least 50 mol%, such as at least 60 mol%, at least 70 mol%, at least 80 mol%, at least 90 mol%, at least 95 mol%, at least 98 mol% or at least 99 mol%.

[0038] In some embodiments, the reactant consists of O₂. In such embodiments, the aqueous solution can be, in particular, deionized water, preferably percolated with air or O₂, especially to saturation. The percolating O₂ gas is not necessarily pure O₂, but can also comprise other components. However, the proportion of O₂ in the percolating O₂ gas is preferably higher than the proportion of O₂ in air. More preferably, O₂ is the main component of the percolating O₂ gas. The proportion of O₂ in the percolating O₂ gas is preferably at least 50 vol%, more preferably at least 75 vol%, more preferably at least 90 vol%, more preferably at least 95 vol%, more preferably at least 98 vol%, more preferably at least 99 vol%, more preferably at least 99.9 vol%, more preferably at least 99.999 vol%, more preferably at least 99.999 vol%.

[0039] The products obtained by the reduction of O2 include, in particular, H2O2. Preferably, H2O2 is the main product of the O2 reduction. For example, the molar fraction of H2O2 in relation to the total products can be at least 50 mol%, 60 mol%, 70 mol%, 80 mol%, 90 mol%, 95 mol%, 98 mol%, or 99 mol%.

[0040] According to the present invention, the process is carried out using a setup comprising a photocatalyst immersed in the aqueous solution comprising the reactant.

[0041] In some embodiments, the setup is electrochemical, and the photocatalyst is a working electrode. The electrochemical setup may further include a counter electrode (in particular a platinum electrode) and / or a reference electrode (in particular an Ag / AgCl electrode). The electrochemical setup may also include an electrochemical workstation.

[0042] The present invention relates to the pure photocatalytic reaction. An electrochemical setup (application of an additional voltage) is optionally used in some embodiments. In particular, a workstation can be used to demonstrate the presence of an induced photocurrent.

[0043] The core of the present invention is the photocatalyst. According to the invention, the photocatalyst comprises a semiconductor photocatalyst comprising dislocations or consists thereof, wherein the surface dislocation density is at least 1.0 × 10 11 m-2 amounts.

[0044] The photocatalyst of the invention is a semiconductor, in particular a polycrystalline ceramic or a single-crystal ceramic, for example as a bulk ceramic or film. In some embodiments, the photocatalyst comprises or consists of transition metal oxides. Preferably, the photocatalyst comprises or consists of BaTiO3, SrTiO3, or TiO2.

[0045] In some embodiments, the photocatalyst has a conduction band of less than 0.68 V and / or a valence band of more than 1.76 V.

[0046] The photocatalyst contains dislocations. The surface dislocation density is at least 1.0 × 10⁻⁶. 11 m -2 , for example at least 2.0*10 11 m -2 , at least 5.0*10 11 m -2 , at least 1.0*10 12 m -2 , at least 2.0*10 12 m -2 , at least 5.0*10 12 m -2 or at least 1.0*1013 m- 2 In some embodiments, the surface dislocation density is at most 1.0*10 17 m -2 , at most 5.0*10 16 m -2 , at most 2.0*10 16 m -2 , at most 1.0*10 16 m -2 , at most 5.0*10 15 m -2 , at most 2.0*10 15 m -2 or at most 1.0*10 15 m- 2 The surface dislocation density can, for example, be in the range of 1.0*10 11 m -2 up to 1.0*10 17 m -2 , as from 2.0*10 11 m -2 up to 5.0*10 16 m -2 , of 5.0*10 11 m -2 up to 2.0*10 16 m -2 , of 1.0*10 12 m -2 up to 1.0*10 16 m 2 , of 2.0*10 12 m -2 up to 5.0*10 15 m -2 , of 5.0*10 12 m -2 up to 2.0*10 15 m -2 or of 1.0*10 13 m-2 up to 1.0*10 15 m -2 lay.

[0047] The quantification of surface dislocation density is particularly possible using transmission electron microscopy (TEM) or scanning transmission electron microscopy (STEM). Those skilled in the art are familiar with these methods. In particular, a thin sample, with a thickness of less than approximately 100 nm, such as about 20 nm, is prepared, preferably by grinding and ion-thinning down to electron transmittance. Diffraction contrast then allows imaging and quantification of the dislocations and determination of the surface density of the dislocations. A representative STEM image is shown in Fig. 18 shown.

[0048] This technique relies on imaging of small surface areas, but clearly shows whether an increased density of dislocations has been imprinted or not (imprinted dislocation structures, in particular, result in an increased density by at least a factor of 100 compared to untreated samples). Furthermore, small surface areas can be particularly representative of, and allow for the determination of, the surface dislocation density of a portion representing at least 20%, at least 40%, at least 60%, or at least 80% of the total surface area of ​​the photocatalyst.

[0049] The process of the present invention is characterized by a particularly high product yield and conversion efficiency. The CO2 conversion efficiency can be evaluated by the carbon ratio of the products to the reactants: CO2 conversion efficiency = n(carbon) products(carbon) reactants

[0050] The amount of moles n(carbon) Reaktanden in the reactants CO2 / HCO3 - The amount of carbon contained can be calculated using the ideal gas law. The molar amount n(carbon) Produkte The amount of carbon contained in the products can be quantified by chromatographic analysis. Therefore, the CO2 conversion efficiency can be calculated using the formula above.

[0051] The CO2 conversion efficiency of the process of the present invention can, for example, be at least 40%, at least 50%, at least 60%, or at least 70%. In some embodiments, the CO2 conversion efficiency can be at most 90%, at most 85%, at most 80%, or at most 75%. The conversion efficiency can, for example, be in a range of 40% to 90%, 50% to 85%, 60% to 80%, or 70% to 75%.

[0052] The method of the invention is carried out in particular at a temperature in a range of >0°C to <100°C, for example from 1°C to 90°C, from 2°C to 80°C, from 3°C to 70°C, from 4°C to 60°C, from 5°C to 55°C, from 6°C to 50°C, from 7°C to 45°C, from 8°C to 40°C, from 9°C to 35°C or from 10°C to 30°C as well as from 11°C to 25°C, from 12°C to 20°C or from 13°C to 17°C. The temperature can be, for example, at least >0°C, at least 1°C, at least 2°C, at least 3°C, at least 4°C, at least 5°C, at least 6°C, at least 7°C, at least 8°C, at least 9°C, at least 10°C, at least 11°C, at least 12°C, or at least 13°C. The temperature can be, for example, at most <100°C, such as at most 90°C, at most 80°C, at most 70°C, at most 60°C, at most 55°C, at most 50°C, at most 45°C, at most 40°C, at most 35°C, at most 30°C, at most 25°C, at most 20°C, or at most 17°C.The method of the invention is carried out particularly at standard pressure (1 atm).

[0053] The present invention also relates to a setup comprising a photocatalyst comprising or consisting of a semiconductor photocatalyst comprising dislocations, wherein the surface dislocation density is at least 1.0*10 11 m -2 amounts.

[0054] In some embodiments, the setup is an electrochemical setup, and the photocatalyst is a photocatalyst working electrode. The electrochemical setup may further comprise a counter electrode (in particular a platinum electrode) and / or a reference electrode (in particular an Ag / AgCl electrode). The electrochemical setup may also include an electrochemical workstation.

[0055] According to the invention, the photocatalyst comprises or consists of a semiconductor photocatalyst comprising dislocations, wherein the surface dislocation density is at least 1.0*10 11 m -2 amounts.

[0056] The photocatalyst of the invention is a semiconductor, in particular a polycrystalline ceramic or a monocrystalline ceramic. In some embodiments, the photocatalyst comprises or consists of transition metal oxides. Preferably, the photocatalyst comprises or consists of BaTiO3, SrTiO3, or TiO2. In some embodiments, the photocatalyst comprises or consists of (Ba,Sr)TiO3.

[0057] In some embodiments, the photocatalyst comprises or consists of a titanate ceramic, in particular a ceramic with the molecular formula RTiO3, where R is an alkaline earth metal or a combination of two or more alkaline earth metals.

[0058] In some embodiments, the photocatalyst has a conduction band of less than 0.68 V and / or a valence band of more than 1.76 V. The band gap can be in the range of 1.0 eV to 5.5 eV, 1.5 eV to 5.0 eV, 2.0 eV to 4.5 eV, or 2.5 eV to 4.0 eV, for example, 3.0 to 3.5 eV. The band gap can optionally be at least 1.0 eV, at least 1.5 eV, at least 2.0 eV, at least 2.5 eV, or at least 3.0 eV. The band gap can optionally be at most 5.5 eV, at most 5.0 eV, at most 4.5 eV, at most 4.0 eV, or at most 3.5 eV. In some embodiments, the photocatalyst has a band gap range from 1.59 eV to 3.88 eV.

[0059] The photocatalyst contains dislocations. The surface dislocation density is at least 1.0 × 10⁻⁶. 11 m -2 , for example at least 2.0*10 11 m -2 , at least 5.0*10 11 m -2, at least 1.0*10 12 m -2 , at least 2.0*10 12 m -2 , at least 5.0*10 12 m -2 or at least 1.0*10 13 m- 2 In some embodiments, the surface dislocation density is at most 1.0*10 17 m -2 , at most 5.0*10 16 m -2 , at most 2.0*10 16 m -2 , at most 1.0*10 16 m -2 , at most 5.0*10 15 m -2 , at most 2.0*10 15 m -2 or at most 1.0*10 15 m- 2 The surface dislocation density can, for example, be in the range of 1.0*10 11 m -2 up to 1.0*10 17 m 2 , as from 2.0*10 11 m -2 up to 5.0*10 16 m -2 , of 5.0*10 11 m -2 up to 2.0*10 16 m -2 , of 1.0*10 12 m -2 up to 1.0*10 16 m 2 , of 2.0*10 12m -2 up to 5.0*10 15 m -2 , of 5.0*10 12 m -2 up to 2.0*10 15 m -2 or of 1.0*10 13 m -2 up to 1.0*10 15 m -2 lay.

[0060] The setup preferably includes a light source adapted for illuminating the photocatalyst. This light source can, for example, be an Xe arc lamp. Xe arc lamps are particularly suitable because they produce bright white light to simulate sunlight.

[0061] The present invention also relates to the use of a setup of the present invention in a process of photocatalytic reduction of a reactant, in particular in a process of the present invention.

[0062] The present invention also relates to the use of a semiconductor photocatalyst comprising dislocations with a surface dislocation density of at least 1.0*10 11 m -2 as a photocatalyst or in a photocatalyst, preferably in a process of photocatalytic reduction of a reactant, in particular in a process of the present invention.

[0063] The present invention also relates to a method for producing a semiconductor photocatalyst comprising dislocations with a surface dislocation density of at least 1.0*10 11 m -2 , wherein the procedure comprises one or more of the following steps: • Uniaxial or biaxial macroscopic deformation of a semiconductor photocatalyst, particularly in a temperature range from room temperature to 1600°C, for example from 100°C to 1500°C, from 200°C to 1400°C, from 300°C to 1300°C, from 400°C to 1200°C, from 500°C to 1100°C, from 600°C to 1000°C, from 700°C to 900°C or from 750°C to 850°C, • Surface treatment of a semiconductor photocatalyst, wherein the surface treatment comprises indentation, polishing, grinding, rolling, scratching, or combinations of two or more thereof. The foregoing may be performed in one cycle or multiple cycles.

[0064] In some embodiments, uniaxial or biaxial macroscopic deformation of the semiconductor photocatalyst is carried out in a temperature range from room temperature (especially about 20°C) to 1000°C.

[0065] The term room temperature as used in the present disclosure refers in particular to a temperature of 20°C.

[0066] Uniaxial or biaxial macroscopic deformation of the semiconductor photocatalyst can be carried out, for example, at a temperature of at least room temperature (in particular at least approximately 20°C), at least 100°C, at least 200°C, at least 300°C, at least 400°C, at least 500°C, at least 600°C, at least 700°C, or at least 750°C. Uniaxial or biaxial macroscopic deformation of the semiconductor photocatalyst can be carried out, for example, at a temperature of at most 1600°C, at most 1500°C, at most 1400°C, at most 1300°C, at most 1200°C, at most 1100°C, at most 1000°C, at most 900°C, or at most 850°C.

[0067] In some embodiments, the uniaxial or biaxial deformation includes at least 0.5% and / or at most 30% plastic deformation. Uniaxial or biaxial deformation can, for example, include 0.5% to 30%, 1.0% to 15%, or 2.0% to 10% plastic deformation. Uniaxial or biaxial deformation can, for example, include at least 0.5%, at least 1.0%, or at least 2.0% plastic deformation. Uniaxial or biaxial deformation can, for example, include at most 30%, at most 15%, or at most 10% plastic deformation.

[0068] In some embodiments, the uniaxial or biaxial deformation is uniaxial or biaxial macroscopic deformation.

[0069] In some embodiments, the uniaxial or biaxial deformation is carried out under load control or under displacement control.

[0070] In some embodiments, the surface treatment includes indentation.

[0071] The load on the indenter is typically in the range of 1.0 N to 100 N, for example, 2.0 N to 50 N or 5.0 N to 25 N. The load on the indenter may optionally be at least 1.0 N, at least 2.0 N, or at least 5.0 N. The load on the indenter may optionally be at most 100 N, at most 50 N, or at most 25 N.

[0072] In some embodiments, the contact length between the indenter and the semiconductor photocatalyst is in the range of 100 µm to 1.0 mm, for example, from 200 µm to 500 µm. The contact length between the indenter and the semiconductor photocatalyst can optionally be at least 100 µm or at least 200 µm. The contact length between the indenter and the semiconductor photocatalyst can optionally be at most 1.0 mm or at most 500 µm.

[0073] The material of the indenter is particularly harder than the material receiving the indentation. In some embodiments, the material of the indenter comprises hardened steel or hard metals or materials used for ball bearings, such as SiC, Si3N4, or ZrO2. In some embodiments, the material of the indenter comprises a material selected from the group consisting of steel (particularly hardened steel), SiC, Si3N4, ZrO2, and combinations of two or more thereof.

[0074] In some embodiments, the surface treatment comprises polishing, grinding, rolling, scraping, or combinations of two or more of these. In some embodiments, the lateral velocity of the polishing, grinding, rolling, or scraping tool on the surface of the semiconductor catalyst is in the range of 0.01 mm / s to 10.0 mm / s, for example, from 0.02 mm / s to 5.0 mm / s, from 0.05 mm / s to 2.0 mm / s, from 0.1 mm / s to 1.0 mm / s, or from 0.2 mm / s to 0.5 mm / s. The lateral velocity of the polishing, grinding, rolling, or scraping tool on the surface of the semiconductor catalyst may optionally be at least 0.01 mm / s, at least 0.02 mm / s, at least 0.05 mm / s, at least 0.1 mm / s, or at least 0.2 mm / s. The lateral speed of the polishing, grinding, rolling or scraping tool on the surface of the semiconductor catalyst may, if necessary, be at most 10.0 mm / s, at most 5.0 mm / s, at most 2.0 mm / s, at most 1.0 mm / s or at most 0.5 mm / s.

[0075] In some embodiments, impressioning, polishing, grinding, rolling, scraping, or combinations of two or more of these processes are performed in one cycle or multiple cycles totaling 100 cycles or fewer. The number of cycles can, for example, range from 1 to 100, 2 to 50, or 5 to 15. The number of cycles can be at least 1, for example, at least 2, or at least 5. Optionally, the number of cycles can be at most 100, at most 50, or at most 15. Description of the characters Fig. Figure 1 schematically shows photogenerated holes on the left side (h + ) and electrons (e - ) in a photocatalyst 11 when illuminated with light 12. The band gap between the valence band 13 and the conduction band 14 is called E g specified. The right side of Fig. Figure 1 schematically shows a photocatalyst with ordered dislocations at the top and a photocatalyst with disordered dislocations at the bottom. The solid T-like structures show an inset lattice half-plane ending with a step dislocation. The dashed lines indicate the traces of the respective dislocations. In general, dislocations can be step dislocations, screw dislocations, or mixtures of the above. For simplicity, we generally refer only to dislocations here. Fig. Figure 2 schematically shows a catalyst with a high dislocation density of ordered dislocations ( Fig. 2 (a)), a catalyst with a high dislocation density of disordered dislocations ( Fig. 2 (b)) and a catalyst with low dislocation density ( Fig. 2 (c)). The solid T-shaped structures show an inset lattice half-plane, which terminates with an edge dislocation. The dashed lines show the traces of the respective dislocations. Fig. Figure 3 shows a typical uniaxial stress / deformation scheme for the deformation of BaTiO3 at 1150°C to introduce the ordered dislocation structure from a defined slip system. The 0.2% yield stress (σ) 0,2 ) is marked with 43.5 MPa. Fig. Figure 4 shows an optical micro-image of regions of cyclic surface sphere impression of SrTiO3, resulting in disordered dislocations. Fig. Figure 5 schematically shows an electrochemical setup 51 comprising a photocatalyst working electrode 52 immersed in an aqueous solution 53. A typical three-electrode configuration is shown with a platinum plate as the counter electrode 54 and an Ag / AgCl electrode as the reference electrode 55. The electrochemical setup further includes an electrochemical workstation 56 for photocurrent measurement. The aqueous solution 53, including the photocatalyst working electrode 52, is illuminated with light 57. Fig. Figure 6 shows the photocurrent response of five on / off illumination cycles measured in uniaxially deformed BaTiO3 samples with a high / low dislocation density. Fig. Figure 7 shows the photocurrent response of six on / off illumination cycles measured in uniaxially deformed TiO2 samples with a high / low dislocation density. Fig. Figure 8 shows the photocurrent response of six on / off illumination cycles measured in surface-treated SrTiO3 samples with a high / low dislocation density. Fig. Figure 9 shows the results of photocatalytic conversion of CO2 reduction using BaTiO3 as the photocatalyst, a hydrogen carbonate solution (NaHCO3) with the percolating CO2 gas inside, and triethanolamine as the sacrificial agent. (a)-(b) show the results obtained with photocatalysts having a high dislocation density, and (c)-(d) show the results obtained with photocatalysts having a low dislocation density. Fig. Figure 10 shows the results of photocatalytic conversion of CO2 reduction with TiO2 as photocatalyst using hydrogen carbonate solution (NaHCO3) with the percolating CO2 gas inside and using triethanolamine as the sacrificial agent. Fig. Figure 11 shows the results of photocatalytic conversion of CO2 reduction with SrTiO3 as photocatalyst using hydrogen carbonate solution (NaHCO3) with the percolating CO2 gas inside and using triethanolamine as the sacrificial agent. Fig. Figure 12 shows the results of photocatalytic conversion of CO2 reduction with TiO2 as photocatalyst using deionized water with the percolating CO2 gas and without the use of any sacrificial agent. Fig. Figure 13 shows the results of photocatalytic H2O2 production using deionized water and bubbling air as reactants and BaTiO3 as catalyst under light illumination. Fig. Figure 14 shows the results of photocatalytic H2O2 production using deionized water and bubbling pure O2 as reactants and BaTiO3 as catalyst under light illumination. Fig. Figure 15 shows the results of photocatalytic H2O2 production by performing cycles with deionized water and bubbling pure O2 as reactants and BaTiO3 as catalyst under light illumination. Fig. Figure 16 shows the results of photocatalytic H2O2 production using deionized water and bubbling pure O2 as reactants and TiO2 as catalyst under light illumination. Fig. Figure 17 shows the results of photocatalytic H2O2 production by performing cycles with deionized water and bubbling pure O2 as reactants and TiO2 as catalyst under light illumination. Fig. Figure 18 is a scanning transmission electron microscope (STEM) image showing dislocations in (001) sectioned BaTiO3 (BTO) caused by high-temperature deformation. The image in Fig. Image 18 is a two-dimensional projection, so the dislocations shown in the image represent projections of the surface dislocation lines. Typical projected dislocation morphologies of either points or short segments are marked by arrowheads. The magnification was 20,000x. The scale bar shows 2 µm. The total image area is 36 x 10 -12 m 2 The number of dislocations shown in the image is 70. Consequently, the surface dislocation density is 70 divided by 36 * 10⁻⁶. -12 m 2 , which is approximately 2*10 12 m -2 corresponds. Examples 1. Introduction of transfers

[0076] Dislocations can be introduced into catalytic materials by various methods. a) Macroscopic bulk deformation

[0077] Uniaxial or biaxial deformation of bulk samples introduces dislocation arrays of defined slip systems. For this reason, several benchmark tests are performed with appropriate uniaxial deformation. Single crystals of BaTiO3 and TiO2 were uniaxially deformed at high temperatures to generate ordered dislocation structures. These oxides are abundant functional ceramics and therefore cost-effective materials.

[0078] Fig. Figure 3 describes a typical uniaxial stress / deformation scheme, where BaTiO3 was deformed at 1150°C to introduce the dislocation structure from a defined slip system. Using this method, the dislocation density increased by 2-3 orders of magnitude. b) Surface treatment

[0079] Surface techniques were applied to both single-crystal and polycrystalline SrTiO3, polishing at room temperature to induce disordered surface dislocations. These oxides are abundant functional ceramics and consequently inexpensive materials. Surface treatment produces very high density but tends to result in disordered dislocations, which are induced by laterally moving or laterally static contact loads. Therefore, we use surface grinding and polishing (moving contact) or indentation (static contact), e.g., Brinell surface ball indentation. Cyclic indentation, in particular, has been found to be very effective in introducing dislocations into all types of ceramics, including polycrystalline material. Successive surface indentation, scratching, or rolling are highly scalable methods for industrially introducing dislocations into surfaces in the micrometer range.2 Dislocation densities can be increased by up to 4 or 5 orders of magnitude to 10 13 / m 2 up to 10 15 / m 2 compared to the initial low dislocation density of 10 8 / m 2 up to 10 10 / m 2 be increased. 2. Making transfers visible

[0080] Multiple techniques can be used to investigate dislocations and their structure. Transmission electron microscopy has proven useful in visualizing the distinct structure of dislocations, particularly the core and mesoscopic structures. A STEM image showing dislocations in (001) sectioned BTO from high-temperature deformation is presented in Fig. 18 were shown. There were 70 displacements on an area of ​​36*10 -12m 2 present. Consequently, the surface dislocation density was approximately 2*10 12 m- 2 .

[0081] Surface etching is another technique for evaluating dislocation density. Depending on the orientation of the crystal (or grain in a polycrystalline material), surface etching with acidic or alkaline solutions results in an etch pit pattern. Chemicals are more likely to attack the surface around dislocations. Therefore, dislocations are preferentially etched, leaving behind etch pits that can even be seen under a light microscope. In the benchmark experiments, the following etching techniques were used: TiO2: Samples were immersed in 70% KOH buffer at 370°C for 4.5 min, followed by neutralization in 1 mol / l sulfuric acid for 1 min. SrTiO3: Etching with 15 drops of 50% HF aq . in 15 ml of 50% ENT 3 aq. for about a minute.

[0082] Another method for investigating dislocations is electron channel contrast imaging (ECCI). This is a scattering technique using the secondary beam of an electron microscope. Crystal defects such as dislocations or stacking faults can be visualized due to the different scattering behavior of electrons near the defects. An advantage of this method is that it is non-destructive and does not require hazardous etching techniques. Further information, taking dislocation density statistics into account, was obtained using electron backscatter diffraction (EBSD) techniques, which allow for the characterization of lattice misorientation by mapping the geometrically necessary dislocations (GNDs). 3. Catalyst materials

[0083] SrTiO3, TiO2, and BaTiO3 were used as benchmark examples. All samples exhibited a band gap of over 3 eV. The materials were deformed by uniaxial deformation or surface grinding.

[0084] The catalysts closed the semiconductor oxides and sulfides with a band gap E g The catalysts covered a range of 1.59 eV to 3.88 eV, capable of absorbing and utilizing light with wavelengths from 320 nm to 780 nm. The crystal structures of these catalysts included perovskite, quasi-perovskite, rutile, anatase, zinc blende, rock salt, fluorite, and spinel structures.

[0085] In Fig. Figure 2 shows a schematic representation of the investigated samples with the introduced dislocations. The measured samples had a size of 4 mm × 4 mm × 1 mm and a total exposed reactive surface area of ​​48 mm². 2 on. 4. Photoelectric current generation under light illumination

[0086] A typical three-electrode configuration was used, with a platinum plate as the counter electrode and an Ag / AgCl electrode as the reference electrode. Samples with and without additionally introduced dislocations were used as the working electrode and immersed in an electrolyte (0.5 to 5 M Na₂SO₄ electrolyte solution) at room temperature with a pH of 6.5 to 7.5. A 300 W Xe arc lamp (Beijing Perfect Light Technology Co., Ltd., China) was used to provide simulated sunlight with a wavelength range of 320 nm to 780 nm. The setup is shown schematically in Fig. 5 shown.

[0087] The photocurrent generated by switching the light on and off was measured using a commercial electrochemical workstation (CHI760E, Shanghai Chenhua Instrument Ltd., China) for several on / off illumination cycles.

[0088] The Fig. 6, Fig. 7 to Fig. Figure 8 shows the measured photocurrents (measurement setup is in Fig. Figure 5 shows the results of several on / off illumination cycles of catalytic samples with high / low dislocation density, introduced by uniaxial bulk deformation or surface indentation. The difference between high and low density is 2-3 orders of magnitude for the uniaxially deformed samples and 4-5 orders of magnitude for the surface-treated samples. Low dislocation density describes the reference samples. A high photocurrent indicates high photocatalytic activity, which consistently coincides with a high dislocation density. This means that the photocurrent, and consequently the photoelectrochemical conversion, is increased by at least a factor of 2 for all oxide semiconductors used. 5. Photocatalytic CO2 reduction

[0089] The photocatalyst samples were transferred to the reactant solution contained in a reaction vessel with a volume of 4 to 500 ml. Pure CO₂ gas (99.999%) was bubbled through the solution at a pressure of 101 kPa until CO₂ saturation was reached, in order to completely expel the dissolved oxygen. The solution was then placed in darkness for half an hour to allow adsorption / desorption equilibrium to be reached on the surface of the measured catalyst sample. Throughout the entire reaction, a 300 W Xe arc lamp (Beijing Perfect Light Technology Co., Ltd., China) was used to provide simulated sunlight with a wavelength range of 320 nm to 780 nm. All experiments were performed in a sealed vessel at approximately 15°C using a water cooling system.The reduction products were qualitatively analyzed by chromatography (GC9790, FuLi, China), equipped with both a thermal conductivity detector and a flame ionization detector.

[0090] The solution for photochemical CO2 reduction could contain either hydrogen carbonate or CO2 gas. In addition, sacrificial agents (e.g., aliphatic amines, aromatic amines, and ascorbic acid), which are widely used in photocatalytic reduction, were added as electron donors to capture the photogenerated holes.

[0091] Here we investigated the photocatalytic CO2 conversion using three reactant systems. The first is in the hydrogen carbonate solution (NaHCO3) with the bubbling CO2 gas inside and using triethanolamine as the sacrificial agent ( Fig. 9 and Fig. 10). The second is in the hydrogen carbonate solution (NaHCO3) without the bubbling CO2 gas inside and using triethanolamine as the sacrificial agent ( Fig. 11). The third is the deionized water with the bubbling CO2 gas and without the use of any sacrificial agent ( Fig. 12) before.

[0092] Using the evaluation methods given in the following section (“6. Quantitative evaluation of CO2 conversion efficiency”), the photocatalytic CO2 conversions were quantitatively determined by the product yield (mol / m³). 2 ) evaluated. The CO2 conversion was illustrated by the carbon ratio of products / reactants (%), which allows a quantification of the influence of the introduced dislocations on the conversion efficiency.

[0093] Of particular relevance is the quantification of the resulting reaction products. The present invention specifically focuses on a high yield of liquid carbon products and a low yield of gaseous products. These were quantified as described below, comparing the case with and without dislocation networks.

[0094] The Fig. 9 and Fig. Figure 10 shows the results of the photocatalytic CO2 conversion from catalytic samples with a high / low dislocation density, introduced either by uniaxial deformation or surface treatment (loop) indentation. A sample measuring 4 mm × 4 mm × 1 mm was used as the catalyst and placed in a 0.1 M, 50 mL NaHCO3 solution contained in a 100 mL reaction vessel. 5 mL of triethanolamine (99.9%, Aladdin Reagent Co., Ltd., Shanghai, China) was added to the reactant solution as the sacrificial agent. CO2 gas (99.999%) was bubbled through the solution at a pressure of 101 kPa until CO2 saturation was reached, in order to completely expel the dissolved oxygen. The solution was then placed in darkness for half an hour to achieve adsorption / desorption equilibrium on the surface of the measured catalyst sample. A 300 W Xe arc lamp (Beijing Perfect Light Technology Co.) was used throughout the entire process., Ltd., China) was used to supply simulated sunlight with a wavelength range of 320 nm to 780 nm. All experiments were conducted in sealed containers at ~15°C using a water cooling system. This allowed the difference in reaction conversion to be attributed to the effect of the light, and not to the influence of temperature. The reaction products were qualitatively analyzed by chromatography (GC9790, FuLi, China) at each time interval.

[0095] With a high dislocation density, the product yield of H2, CO and CH3CHO after reaction for 8 h is 5.9 mol / m³. 2 , 1.5 mol / m³ 2 or 89.7 mol / m³ 2 , as in Fig. Figures 9 (a) and (b) show the total CO2 conversion with a high dislocation density of ~72% after 8 h of reaction, with the liquid product acetaldehyde being the main product.

[0096] With a low dislocation density, the product yield of H2, CO and CH3CHO after a reaction lasting 8 h is 35.1 mol / m³. 2 , 6.2 mol / m³ 2 or 40.6 mol / m³ 2 , as in Fig. Figures 9(c) and (d) show that the total CO2 conversion with a high dislocation density is approximately 35% after 8 h of reaction, with lower production of the liquid product acetaldehyde and higher production of H2 and CO. This corresponds to approximately a twofold increase (from approximately 35% to 72%) in the CO2 conversion due to the introduced dislocations, as well as a sixfold reduction (from 35.1 mol / m³). 2 to 5.9 mol / m³ 2 The reduction of competing H2 production during CO2 reduction is achieved through dislocation introduction. Both the increase in CO2 reduction and the damping of competing H2 production are beneficial for CO2 reduction.

[0097] The product yield of CH3CHO after reaction for 4 h was 81.88 mol / m³. 2 with a high dislocation density and 26.25 mol / m³ 2 with a low dislocation density, as in Fig. Figure 10 shows that the overall CO2 conversion ratio was ~65% with a high dislocation density and ~21% with a low dislocation density. No gas product was detected, although the reactants remained the same as for BaTiO3, as shown in Figure 10. Fig. Figure 9 shows that this indicates different reaction pathways and product types for photocatalytic CO2 reduction with different ceramics. Fig. Figure 10 shows approximately a threefold increase in CO2 conversion (from ~21% to 65%) due to the introduced dislocations with TiO2 as a catalyst.

[0098] Fig. Figure 11 shows the results of photocatalytic CO2 conversion from surface-treated SrTiO3 samples with a high / low dislocation density. In this case, the reaction solution consisted only of NaHCO3 solution (0.1 M, 50 ml) in a 100 ml reaction vessel without the CO2 gas bubbling inside. 5 ml of triethanolamine (99.9%, Aladdin Reagent Co., Ltd., Shanghai, China) was added to the reactant solution as the sacrificial agent.

[0099] The product yield of CH3CHO after reaction for 8 h was 22.53 mol / m³. 2 with a high dislocation density and 2.87 mol / m³ 2 with a low dislocation density, as in Fig. Figure 11 shows that the total CO2 conversion with a high dislocation density was ~43%, and ~6% with a low dislocation density. No gas product was detected. This indicates an approximately sevenfold increase in CO2 conversion (from ~6% to 43%) due to the introduced dislocations.

[0100] This means that SrTiO3 exhibited the most significant increase, by a factor of 7, in CO2 conversion due to the introduced dislocations from the surface treatment with the highest dislocation density. This can be explained by the higher dislocation density achieved through surface grinding compared to uniaxial deformation. While uniaxial deformation increases the dislocation density by 2-3 orders of magnitude, surface grinding results in a 4-5 order of magnitude higher dislocation density.

[0101] Fig. Figure 12 quantifies the results of photocatalytic CO2 conversion from uniaxially deformed TiO2 samples with a high / low dislocation density. In this case, the reaction solution consisted only of deionized water (10 ml) in a 100 ml reaction vessel, with the CO2 gas bubbling through the interior until saturation. No sacrificial agent was used; therefore, a lower conversion efficiency is observed compared to the Fig. 9-11 with the use of the sacrificial means.

[0102] For the reference experiment, 6.75×10 -3 g of TiO2 rutile powder (detailed estimate is given in the following section (“7. Quantitative comparison with the powder catalyst”)) were weighed out to carry out the same catalytic reaction for comparison, in Fig. 12 labeled with TiO2 powder.

[0103] The product yield of CO after reaction for 7 h was 0.348 mol / m³. 2 with a high dislocation density, 0.024 mol / m³ 2 With a low dislocation density, CO production was observed, whereas with the chemical TiO2-rutile powder, no CO production was detected. The overall CO2 conversion efficiency is approximately 0.39% with a high dislocation density and approximately 0.027% with a low dislocation density. This indicates an approximately fifteen-fold increase in CO2 conversion (from approximately 0.027% to 0.39%) due to the introduced dislocations. 6. Quantitative evaluation of product yield and CO2 conversion efficiency

[0104] Product yield is widely used to evaluate the photocatalytic CO2 reduction efficiency, quantifying the molar amounts of products normalized by the weight of catalysts during the reaction. However, the reaction mainly takes place on the surface of the catalyst. Here, the exposed surface area is taken from the sample measurement to normalize the product yield for the measured catalytic reactions according to equation (1) below. The product amount was quantitatively analyzed by chromatography, and the exposed reactive surface area was determined to be 48 mm². 2 assumed. Product yield = amount of product exposed reactive surface area

[0105] Alternatively, the CO2 conversion efficiency can be assessed by the carbon ratio of the products to the reactants. The molar amount n of carbon contained in the CO2 / HCO3 reactants - The volume of CO2 gas can be calculated using the ideal gas law given below, where P, V, and T are the pressure, volume, and temperature respectively, and R is the ideal gas constant. The pressure used to bubble CO2 gas through the solution is 101 kPa, the temperature is 15°C (288 K), the solubility of CO2 gas in water at 288 K and 1 atm partial pressure is 101.9 ml CO2 per 100 ml water, and R is 8.31 J / mol / K. PV=nRT

[0106] The amount of carbon (n) contained in the products can be quantified by chromatographic analysis. Therefore, the CO2 conversion efficiency can be calculated. 7. Quantitative comparison with the powder catalyst

[0107] The heterocatalytic reaction occurs at the surface of the catalyst where reactants are adsorbed. For the powder catalyst reference sample, the specific surface area (SSA) can be determined by Brunauer-Emmett-Teller (BET) analysis, for example, 25.96 m². 2 The amount of BaTiO3 powder used (99.9%, Aladdin Reagent Co., Ltd., Shanghai, China) can be determined per gram. Consequently, it can be estimated that approximately 1.85 × 10⁻⁵ g of the powder is present. -6 g BaTiO3 powder has the same exposed reactive surface area as 48 mm 2 like the measured sample measuring 4 mm × 4 mm × 1 mm. In practical experiments, this weight of 1.85 × 10 -6 g cannot be handled with the laboratory balance. For the comparison experiment, 1.85 × 10 were first used. -3g (corresponding to 1000 times the estimated weight) of BaTiO3 powder was weighed out to carry out the same catalytic reaction, and then the yield was divided by 1000 for comparison. A similar comparison was also made for TiO2 catalyst samples with dislocations, using rutile titanium oxide (99.99%, Aladdin Reagent Co., Ltd., Shanghai, China) for comparison. The measured SSA of the titanium oxide-rutile powder was 7.11 M. 2 / g according to BET analysis, which means approximately 6.75×10 -6 g TiO2 powder has an exposed reactive surface area of ​​48 mm² 2 exhibits, so that 6.75×10 -3 g of TiO2 were weighed out to perform the reference experiment. 8. Photocatalytic H2O2 production

[0108] A 4 mm x 4 mm x 1 mm piece of each material type was used as the catalyst. It was placed in deionized water (20 ml) and air or pure O₂ was bubbled through until saturation with the gas. No sacrificial agent was used. An Xe arc lamp was used to supply artificial sunlight. The resulting H₂O₂ was quantitatively detected using the colorimetric DPD method based on the oxidation of N,N-diethyl-p-phenylenediamine (DPD) catalyzed by horseradish peroxidase (POD).

[0109] According to the Fig. 13, Fig. 14 and Fig. Based on the H2O2 yields, it could be concluded that the introduced dislocations resulted in approximately a twofold increase in photocatalytic H2O2 production. Cyclic experiments were performed with 5 cycles to demonstrate the stability of photocatalysts, as described in the Fig. 15 and Fig. 17 were provided. For the reference experiments, 1.85×10 -3 g BaTiO3 powder and 6.75×10 -3 TiO2 rutile powder was weighed out to carry out the same reaction as in the Fig. 14 and Fig. 16 shown. No production of H2O2 was obtained with the powder reference samples.

Claims

[1] A photocatalytic reduction process of a reactant, wherein the process comprises the following steps: a) Providing a setup comprising a photocatalyst immersed in an aqueous solution comprising the reactant, and b) Illuminating the photocatalyst with light, wherein the method characterized by is that the photocatalyst comprises or consists of a semiconductor photocatalyst comprising dislocations, wherein the surface dislocation density on at least a part of a surface of the photocatalyst is at least 1.0*10 11 m -2 amounts. [2] Method according to claim 1, wherein the reactant is CO2 / HCO3 - / CO3 2- or includes O2. [3] Method according to at least one of the preceding claims, wherein the light comprises electromagnetic radiation with a wavelength in the range of 320 nm to 780 nm. [4] Method according to at least one of the preceding claims, wherein the photocatalyst is a ceramic. [5] Method according to at least one of the preceding claims, wherein the photocatalyst is a polycrystalline ceramic. [6] Method according to at least one of the preceding claims, wherein the surface dislocation density is at least 1.0*10 12 m -2 amounts. [7] Method according to at least one of the preceding claims, wherein the reactant is O2 and wherein the products obtained by reduction of the reactant comprise H2O2. [8] Method according to at least one of claims 1 to 6, wherein the reactant is CO2 / HCO3 - / CO3 2- includes and wherein the products obtained by reduction of the reactant include CO, CH4, CH2O, CH3OH, CH3CHO, CH3CH2OH or combinations of two or more thereof. [9] Method according to at least one of the preceding claims, wherein the molar ratio of liquid products to gaseous products is at least 1:

1. [10] Method according to at least one of the preceding claims, wherein the conversion efficiency is at least 50%. [11] Method according to at least one of the preceding claims, wherein the light source for illuminating the photocatalyst working electrode is an Xe arc lamp. [12] Method according to at least one of the preceding claims, wherein the aqueous solution comprises at least one sacrificial agent. [13] Method according to at least one of the preceding claims, wherein the method comprises the step of bubbling the reactant through the aqueous solution. [14] Method according to at least one of the preceding claims, wherein the aqueous solution has a pH value of 6.0 to 8.

0. [15] Method according to at least one of the preceding claims, wherein the aqueous solution is deionized water. [16] Method according to at least one of claims 1 to 14, wherein the aqueous solution comprises one or more inorganic salts in an amount of at least 100 mM. [17] Method according to at least one of the preceding claims, wherein the method is carried out at a temperature in a range of 10°C to 30°C. [18] Method according to at least one of the preceding claims, wherein the photocatalyst has a conduction band that is more negative than 0.68 V and / or a valence band that is more positive than 1.76 V. [19] Method according to at least one of the preceding claims, wherein the photocatalyst consists of BaTiO3, SrTiO3 or TiO2. [20] Method according to at least one of the preceding claims, wherein the photocatalyst is illuminated with light, such that the photocatalyst / reactant interface acts as a reactive site for photocatalytic reactions in the vicinity of or at dislocations. [21] Method according to at least one of the preceding claims, wherein the method further comprises the step of separating the liquid organic products from the gaseous products. [22] Method according to at least one of the preceding claims, wherein the setup is an electrochemical setup and wherein the photocatalyst is a photocatalyst working electrode. [23] Method according to claim 22, wherein the electrochemical setup further comprises a counter electrode. [24] Method according to at least one of claims 22 to 23, wherein the electrochemical setup further comprises a reference electrode. [25] Method according to at least one of claims 22 to 24, wherein the electrochemical setup further comprises an electrochemical workstation. [26] Structure comprising a photocatalyst comprising or consisting of a semiconductor photocatalyst comprising dislocations, wherein the surface dislocation density is at least 1.0*10 11 m -2 amounts. [27] Structure according to claim 26, wherein the photocatalyst is a ceramic. [28] Structure according to at least one of claims 26 and 27, wherein the photocatalyst is a polycrystalline ceramic. [29] Structure according to at least one of claims 26 to 28, wherein the surface dislocation density is at least 1.0*10 12 m -2 amounts. [30] Assembly according to at least one of claims 26 to 29, wherein the assembly comprises a light source adapted for illuminating the photocatalyst. [31] Setup according to claim 30, wherein the light source is an Xe arc lamp. [32] A structure according to at least one of claims 26 to 31, wherein the photocatalyst has a conduction band that is more negative than 0.68 V and / or a valence band that is more positive than 1.76 V. [33] Structure according to at least one of claims 26 to 32, wherein the photocatalyst consists of BaTiO3, SrTiO3 or TiO2. [34] Setup according to at least one of claims 26 to 33, wherein the setup is an electrochemical setup and wherein the photocatalyst is a photocatalyst working electrode. [35] Setup according to claim 34, wherein the electrochemical setup further comprises a counter electrode. [36] Setup according to at least one of claims 34 to 35, wherein the electrochemical setup further comprises a reference electrode. [37] Setup according to at least one of claims 34 to 36, wherein the electrochemical setup further comprises an electrochemical workstation. [38] Use of a setup according to at least one of claims 26 to 37 in a photocatalytic reduction process of a reactant, in particular in a process according to at least one of claims 1 to 25. [39] Use of a semiconductor photocatalyst comprising dislocations with a surface dislocation density of at least 1.0*10 11 m -2 as a photocatalyst or in a photocatalyst. [40] Use according to claim 39, wherein the photocatalyst is used in a photocatalytic reduction process of a reactant, in particular in a process according to at least one of claims 1 to 25. [41] Method for producing a semiconductor photocatalyst comprising dislocations with a surface dislocation density of at least 1.0*10 11 m-2 , wherein the procedure comprises one or more of the following steps: • Uniaxial or biaxial deformation of a semiconductor photocatalyst, • Surface treatment of a semiconductor photocatalyst, wherein the surface treatment includes impressioning, polishing, grinding, rolling, scratching or combinations of two or more of these. [42] Method according to claim 41, wherein the uniaxial or biaxial deformation includes at least 0.5% and / or at most 30% plastic deformation. [43] Method according to at least one of claims 41 and 42, wherein the uniaxial or biaxial deformation is carried out at a temperature in a range from room temperature to 1000°C. [44] Method according to at least one of claims 41 to 43, wherein the uniaxial or biaxial deformation is uniaxial or biaxial macroscopic deformation. [45] Method according to at least one of claims 41 to 44, wherein the uniaxial or biaxial deformation is carried out under load control or under displacement control. [46] Method according to at least one of claims 41 to 45, wherein the surface treatment comprises indentation and wherein the load on the indentation body is in a range of 1.0 N to 100 N. [47] Method according to at least one of claims 41 to 46, wherein the surface treatment comprises indentation and wherein the contact zone between the indentation body and the semiconductor photocatalyst is in a range of 100 µm to 1.0 mm. [48] ​​Method according to at least one of claims 41 to 47, wherein the surface treatment comprises indentation and wherein the material of the indentation body comprises a material selected from the group consisting of hardened steel, SiC, Si3N4, ZrO2 and combinations of two or more thereof. [49] Method according to at least one of claims 41 to 48, wherein the surface treatment comprises polishing, grinding, rolling, scraping or combinations of two or more thereof and wherein the lateral velocity of the polishing, grinding, rolling or scraping tool on the surface of the semiconductor catalyst is in a range of 0.01 mm / s to 10 mm / s. [50] Method according to at least one of claims 41 to 49, wherein impressioning, polishing, grinding, rolling, scratching or combinations of two or more thereof are carried out in one cycle or multiple cycles with a total of 100 cycles or less.

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