Cadmium chalcogenide and / or zinc chalcogenide nanoparticles as catalytic materials for CO2 reduction

Abstract

The present invention relates to an electrode for the reduction of carbon dioxide CO2, for example, to carbon monoxide CO and / or syngas CO / H2, the electrode containing cadmium chalcogenide and / or zinc chalcogenide nanoparticles as a catalyst, an electrochemical process for the reduction of carbon dioxide CO2, for example, to carbon monoxide CO and / or syngas CO / H2 using an electrode containing cadmium chalcogenide and / or zinc chalcogenide nanoparticles, and the use of cadmium chalcogenide and / or zinc chalcogenide nanoparticles as catalysts in an electrode for the electrochemical reduction of a reduced species, such as carbon dioxide CO2, to carbon monoxide CO and / or syngas CO / H2.

Description

[Technical Field]

[0001] The present invention relates to an electrode for the reduction of carbon dioxide CO2 to, for example, carbon monoxide CO and / or synthesis gas CO / H2, which contains cadmium chalcogenide and / or zinc chalcogenide nanoparticles as catalysts; Electrochemical processes for the reduction of carbon dioxide CO2 to, for example, carbon monoxide CO and / or synthesis gas CO / H2, using electrodes containing cadmium chalcogenide and / or zinc chalcogenide nanoparticles; and the use of cadmium chalcogenide and / or zinc chalcogenide nanoparticles as catalysts in electrodes for the electrochemical reduction of reduced species, such as carbon dioxide CO2, to carbon monoxide CO and / or syngas CO / H2. Regarding. [Background technology]

[0002] In particular, reducing CO2 emissions from established and largely unavoidable industrial plants, such as waste incineration plants and cement plants, as well as from dependence on fossil fuels, requires comprehensive defossilization of industry and society through increased use of closed CO2 cycles. Conversion processes that aim to produce little or no CO2, while desirable, are time-consuming or even impossible to implement. Therefore, to ensure the time horizon of current climate goals, technologies that can be retrofitted into existing plants and directly extract CO2 from exhaust streams and upgrade the CO2 for subsequent processing are needed. This can achieve both societal benefits through resource conservation and CO2 reduction, and economic benefits through the production of energy-rich carbon derivatives (e.g., inexpensive syngas), increasing the sustainability of existing plants.

[0003] The conversion of CO2 to reactive forms is fundamentally possible through electrocatalytic conversion. This process is well established. However, the catalysts used in this process, such as nanoparticle silver, are extremely sensitive to foreign substances. For example, sulfur-containing compounds are absorbed on the surface of these catalysts, significantly impairing the efficiency of CO2 conversion. This adverse effect is called catalyst poisoning. Therefore, when using established methods, the conversion of CO2 from exhaust streams is only possible after prior purification. However, the purification process is complex and cost-intensive, and therefore not used industrially. Therefore, the conversion of CO2 in exhaust streams using established catalysts is not performed. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention enables the direct electrocatalytic conversion of CO from raw exhaust streams. Thus, CO is converted to CO or syngas for synthetic, fossil-free fuels and other carbon-based chemicals. The present invention describes cadmium chalcogenide and / or zinc chalcogenide nanoparticles as active materials for cathode catalysts in electrodes, particularly gas diffusion electrodes. These nanoparticles do not exhibit high chemical affinity for pollutants in exhaust streams and are therefore robust against catalyst poisoning. Surprisingly, high efficiency of electrocatalytic CO conversion has been demonstrated using the nanoparticles described in the present invention, even in the presence of typical catalyst poisons. [Means for solving the problem]

[0005] In a first aspect, the present invention relates to an electrode for the reduction of carbon dioxide CO2 to carbon monoxide CO and / or synthesis gas CO / H2, the electrode containing cadmium chalcogenide and / or zinc chalcogenide nanoparticles as catalyst.

[0006] In a second aspect, the present invention provides a method for reducing carbon dioxide CO2, comprising: providing an electrochemical cell comprising an electrode as described herein; applying a current to the electrodes; contacting a carbon dioxide-containing gas stream with cadmium chalcogenide and / or zinc chalcogenide nanoparticles within said electrode such that the carbon dioxide is preferably reduced to carbon monoxide CO and / or synthesis gas CO / H; The present invention relates to a method comprising:

[0007] In a third aspect, the present invention relates to the use of cadmium chalcogenide and / or zinc chalcogenide nanoparticles in the electrodes described herein as catalysts for the electrochemical reduction of carbon dioxide CO to reduced species such as carbon monoxide CO and / or syngas CO / H. [Brief explanation of the drawings]

[0008] [Figure 1] Figure 1 shows a comparison of the faradaic efficiencies of H and CO determined by chronopotentiometry at 50 mA cm (top) and 200 mA cm (bottom) after 1 h (left bar) and 2 h (right bar) using a gas diffusion electrode in a liquid electrolyte flow cell. Cadmium chalcogenide nanoparticles in the form of spherical CdSe particles, spherical particles with a CdSe core and a CdS shell, spherical CdS particles, coin-shaped particles with a CdSe core and a CdS shell, rod-shaped particles with a CdSe core and a CdS shell, and rod-shaped CdS particles were used as catalysts in the gas diffusion electrode and compared with silver-containing nanoparticles as a reference. [Figure 2] Figure 2 shows a comparison of the faradaic efficiencies of H and CO determined by chronopotentiometry at 50 mA cm (top) and 200 mA cm (bottom) using untreated and poisoned gas diffusion electrodes containing rod-shaped CdS nanoparticles in a liquid electrolyte flow cell after 1 h (left bar) and 2 h (right bar). NaS, H2S, SO2, and NO2 were used as catalyst poisons. [Figure 3]Figure 3 shows a comparison of the faradaic efficiencies of H and CO determined using a gas diffusion electrode in a zero-gap electrolytic cell with a solid polymer electrolyte using chronopotentiometry at 200 mA cm. The catalysts used in the gas diffusion electrode were cadmium chalcogenide nanoparticles in the form of spherical particles with a CdSe core and a CdS shell, spherical CdS particles, rod-shaped particles with a CdSe core and a CdS shell, and rod-shaped CdS particles. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention relates to an electrode for the reduction of carbon dioxide CO2 to carbon monoxide CO and / or synthesis gas CO / H2, which electrode contains cadmium chalcogenide and / or zinc chalcogenide nanoparticles as catalyst.

[0010] The electrode is typically a porous electrode, allowing for large-area contact between the catalytic material and the carbon dioxide (CO2) to be reduced. The carbon dioxide (CO2) is usually dissolved in a liquid electrolyte, such as a carbonate solution, and contacted with the electrode, preferably a porous electrode. Alternatively, the carbon dioxide (CO2) can be wetted with a non-ionically or weakly ionically conductive liquid, such as water, and contacted with the electrode, preferably a porous electrode. In this embodiment, the electrolyte is typically a solid electrolyte, such as an ionically conductive polymer (ionomer). The manufacture of porous electrodes is well known, for example, in the fields of lithium ion batteries, fuel cells, and electrolyzers.

[0011] The electrodes are preferably gas diffusion electrodes. A gas diffusion electrode is commonly known as an electrode in which three media—electrolyte, catalyst, and reactants—are in contact with each other and a solid, electronically conducting catalyst catalyzes the electrochemical reaction between the liquid and gas phases. A design using a solid polymer electrolyte instead of a liquid electrolyte is also contemplated. Preferably, the catalyst is mixed with a hydrophobic plastic, preferably polytetrafluoroethylene PTFE, and formed into an electrode. To optimize the conductivity of ionic species in the catalyst layer, a design using ion-conducting polymers (ionomers) is also considered. The mixture may be an aqueous dispersion containing water, an (ionically conductive) plastic, and a catalyst, or a dry mixture containing a plastic powder and a catalyst powder, both variants being well known. The mixture may contain additional materials such as binders, wettability enhancers, conductive materials, and support materials (carriers). Materials commonly known for these purposes are used. One example is carbon black, which can increase the electrical conductivity of the gas diffusion electrode and also function as an additional support material. The manufacture of gas diffusion electrodes is well known.

[0012] Gas diffusion electrodes can be used as cathodes in electrochemical cells for the reduction of carbon dioxide CO to carbon monoxide CO and / or syngas CO / H. Electrochemical cells generally also include an anode and one or more electrolytes. Any commonly used materials can be used as the anode and electrolyte, depending on the type of electrochemical cell. The electrochemical cell can be a liquid electrolyte cell, such as a liquid electrolyte flow cell, or a solid electrolyte cell, such as a solid electrolyte flow cell or a zero-gap electrolysis cell. A suitable example of a liquid electrolyte flow cell comprises, in addition to gas diffusion electrodes, a salt dissolved in a solvent such as water as the electrolyte, e.g., KHCO3 / K2SO4, a metal electrode as the anode, e.g., titanium coated with a metal or metal oxide, preferably IrO2 coated titanium or Pt coated titanium, and a suitable ion exchange membrane. A suitable example of a solid electrolyte flow cell or zero-gap electrolytic cell comprises, in addition to a gas diffusion electrode, an anion exchange membrane as the electrolyte, which is conditioned with an anodic substrate such as KOH and KHCO3 before measurement, and a metal electrode, e.g., IrO2-coated titanium, as the anode. The construction and suitable materials for these electrochemical cells are generally known.

[0013] The electrodes contain cadmium chalcogenide and / or zinc chalcogenide nanoparticles as catalysts for the reduction of carbon dioxide CO2 to carbon monoxide CO and / or syngas CO / H2. The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably comprise cadmium sulfide CdS, cadmium selenide CdSe, zinc sulfide ZnS, zinc selenide ZnSe, and mixtures of two or more compounds of cadmium sulfide CdS, cadmium selenide CdSe, zinc sulfide ZnS, and zinc selenide ZnSe. The cadmium chalcogenide and / or zinc chalcogenide nanoparticles may contain a mixture of two or more of the compounds cadmium sulfide CdS, cadmium selenide CdSe, zinc sulfide ZnS, and zinc selenide ZnSe in the form of layers or shells of different individual compounds or in the form of an alloy of two or more compounds. In one embodiment, the cadmium and / or zinc chalcogenide nanoparticles contain only cadmium chalcogenide compounds, preferably cadmium sulfide (CdS), cadmium selenide (CdSe), and mixtures of cadmium sulfide (CdS) and cadmium selenide (CdSe), in the form of layers or shells of individual compounds or in the form of an alloy. In this embodiment, the cadmium and / or zinc chalcogenide nanoparticles are cadmium chalcogenide nanoparticles and do not contain zinc chalcogenide compounds.

[0014] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles, preferably the cadmium chalcogenide nanoparticles, preferably contain cadmium selenide CdSe. The cadmium chalcogenide and / or zinc chalcogenide nanoparticles, preferably cadmium chalcogenide nanoparticles, preferably contain cadmium selenide (CdSe) or a mixture of cadmium sulfide (CdS) and cadmium selenide (CdSe), particularly preferably a mixture of cadmium sulfide (CdS) and cadmium selenide (CdSe). The mixture of cadmium sulfide (CdS) and cadmium selenide (CdSe) can be in the form of layers or shells of the individual compounds or in the form of an alloy.

[0015] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably do not contain any further semiconductor materials other than cadmium sulfide CdS, cadmium selenide CdSe, zinc sulfide ZnS, zinc selenide ZnSe, and mixtures of two or more compounds of cadmium sulfide CdS, cadmium selenide CdSe, zinc sulfide ZnS, and zinc selenide ZnSe, preferably other than cadmium sulfide CdS, cadmium selenide CdSe, and mixtures of cadmium sulfide CdS and cadmium selenide CdSe, more preferably other than cadmium selenide CdSe and mixtures of cadmium sulfide CdS and cadmium selenide CdSe, and most preferably other than a mixture of cadmium sulfide CdS and cadmium selenide CdSe.

[0016] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have a selenium (Se) to sulfur (S) molar ratio (Se:S) of 0.001:99.999 to 50.0:50.0, preferably 0.01:99.99 to 25:75, more preferably 0.1:99.9 to 10.0:90.0.

[0017] In addition to a semiconductor material of the cadmium chalcogenide and / or zinc chalcogenide group, the cadmium chalcogenide nanoparticles preferably contain one or more organic ligands on their surface. This organic ligand coating is typically used as an aid to keep the nanoparticles dispersed in a solvent during electrode fabrication. To coat the electrode with a catalyst layer, the organic ligand-coated nanoparticles are typically exposed to high temperatures (e.g., hot-pressing the catalyst layer onto a substrate at 200-300°C), at which point the organic ligands are at least partially or completely pyrolyzed. Therefore, the organic ligands are usually no longer detectable, or only detectable in small amounts, in the finished electrode.

[0018] Suitable organic ligands are, for example, selected from aliphatic carboxylic acids and derivatives thereof, such as saturated and unsaturated fatty acids having 16 to 20 carbon atoms, aliphatic amines and derivatives thereof, such as oleylamine, heterocyclic compounds such as tetrazole, aliphatic mercapto compounds and derivatives thereof, such as octanethiol, alkylphosphoric acid derivatives, such as tri-n-hexyl phosphate, alkylphosphonic acid derivatives, such as hexylphosphonic acid, trioctylphosphine, trioctylphosphine oxide and / or octadecylphosphonic acid, and mixtures thereof.

[0019] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have the shape of spherical particles, coin shapes, or rod shapes, more preferably spherical particles or rod shapes, and most preferably spherical particles.

[0020] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have an average particle size in the direction of smallest extension of 1.5 to 45.0 nm, preferably 3.0 to 30.0 nm, more preferably 4.0 to 25.0 nm. Furthermore, the cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have an average particle size in the direction of maximum extension of 1.5 to 200.0 nm, preferably 5.0 to 125.0 nm, and more preferably 8.0 to 75.0 nm.

[0021] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles in the form of spherical particles preferably have an average particle size of 1.5 to 5.0 nm, preferably 5.0 to 30.0 nm, more preferably 8.0 to 25.0 nm.

[0022] The coin-shaped cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have an average particle size in the direction of smallest extension of 3.0 to 20.0 nm, preferably 5.0 to 17.5 nm, more preferably 7.0 to 15.0 nm. Furthermore, the coin-shaped cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have an average particle size in the direction of maximum extension of 10.0 to 50.0 nm, preferably 15.0 to 40.0 nm, more preferably 20.0 to 30.0 nm.

[0023] The rod-shaped cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have an average particle size in the direction of smallest extension of 2 to 15.0 nm, preferably 3.0 to 10.0 nm, more preferably 4.0 to 7.0 nm. Additionally, the rod-shaped cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have an average particle size in the direction of maximum elongation of 3.0 to 200.0 nm, preferably 5.0 to 125.0 nm, more preferably 8.0 to 75.0 nm.

[0024] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have a particle size of 1.0 to 100.0 m 2 / 100mg, preferably 3.0 to 50.0m 2 / 100mg, more preferably 4.5 to 30.0m 2 / 100 mg. Surface area refers to the total surface area of ​​100 mg of nanoparticles.

[0025] Furthermore, the cadmium chalcogenide and / or zinc chalcogenide nanoparticles are preferably 2 to 50,000 nm 3 , preferably 14 to 15,000 nm 3 , more preferably 50 to 10,000 nm 3The particle volume (volume of a single particle) is

[0026] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably comprise a core and a shell, preferably a cadmium selenide (CdSe) core and a cadmium sulfide (CdS) shell.

[0027] The cadmium chalcogenide and / or zinc chalcogenide nanoparticles preferably have a ratio of average core diameter to average total particle diameter of 1.0:7.0 to 1.0:1.0, preferably 1.0:5.0 to 1.0:2, more preferably 1.0:4.5 to 1.0:3.0.

[0028] Cadmium chalcogenide nanoparticles in the form of spherical particles having a cadmium selenide (CdSe) core and a cadmium sulfide (CdS) shell are particularly preferred. The ratio of the average diameter of the core to the average diameter of the whole particle is preferably in the range of 1.0:7.0 to 1.0:1.0, preferably 1.0:5.0 to 1.0:2, more preferably 1.0:4.5 to 1.0:3. The average particle size is preferably in the range of 1.5 to 40.0 nm, preferably 3.0 to 30.0 nm, and more preferably 5.0 to 25.0 nm. The surface area is preferably 1 to 100 m 2 / 100mg, preferably 3 to 50.0m 2 / 100mg, more preferably 5.0 to 30.0m 2 / 100mg range. The particle volume (volume of a single particle) is preferably 2 to 50,000 nm 3 , preferably 14 to 15,000 nm 3 , more preferably 50 to 10,000 nm 3 is in the range. Fatty acid derivatives, such as saturated and unsaturated fatty acids having 16 to 20 carbon atoms, preferably oleic acid, are preferably used as organic ligands on the surface.

[0029] Information about nanoparticles, such as average particle size, shell composition, shell diameter, surface area, and volume, is typically obtained by imaging methods such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), or X-ray diffraction, or gravimetric methods such as thermogravimetric analysis (TGA).

[0030] In a further aspect, the present invention provides a method for reducing carbon dioxide CO2, comprising: providing an electrochemical cell comprising an electrode as described herein; applying a current to the electrodes; contacting a carbon dioxide-containing gas stream with cadmium chalcogenide and / or zinc chalcogenide nanoparticles within said electrode such that the carbon dioxide is preferably reduced to carbon monoxide CO and / or synthesis gas CO / H; The present invention relates to a method comprising:

[0031] In this case, all aspects and embodiments of the electrodes, cadmium chalcogenide and / or zinc chalcogenide nanoparticles, and electrochemical cells described herein are preferably used in the process according to the invention.

[0032] The current density is preferably 25 to 1000 mA / cm 2 , preferably 35 to 750 mA / cm 2 , more preferably 45 to 500 mA / cm 2 is in the range.

[0033] The carbon dioxide-containing gas stream is preferably an exhaust gas stream, preferably an unpurified exhaust gas stream, more preferably an exhaust gas stream which further contains sulfur-containing compounds.

[0034] The exhaust stream is preferably obtained from an industrial plant, such as a waste incineration plant or a cement plant.

[0035] The species reduced from carbon dioxide, typically carbon monoxide or syngas, is preferably separated from the gas stream. Generally, the species reduced from carbon dioxide may include other species in addition to carbon monoxide or syngas, such as methane (CH4) or formic acid (HCOOH).

[0036] Furthermore, species reduced from carbon dioxide, typically reduced carbon monoxide or synthesis gas, are preferably used to produce carbon derivatives such as methane, olefins, organic acids and their derivatives, and alcohols.

[0037] In the process of the present invention, when using a liquid electrolyte flow cell, 50 mA / cm 2 A faradaic efficiency of carbon monoxide formation in the range of 60 to 90%, preferably 65 to 85%, is preferably achieved.

[0038] Furthermore, in the process of the present invention, when using a liquid electrolyte flow cell, the faradaic efficiency of carbon monoxide formation is 200 mA / cm 2 The range is preferably 1 to 65%, and more preferably 20 to 50%.

[0039] Furthermore, in the process of the present invention, when using a liquid electrolyte flow cell, the faradaic efficiency of hydrogen formation is 50 mA / cm 2 The range is preferably 1 to 30%, and more preferably 5 to 20%.

[0040] Furthermore, in the process of the present invention, when using a liquid electrolyte flow cell, the faradaic efficiency of hydrogen formation is 200 mA / cm 2 The range is preferably 1 to 65%, and more preferably 20 to 50%.

[0041] The overall faradaic efficiency for carbon monoxide and hydrogen formation using the liquid electrolyte flow cell is 50 mA / cm 2 The range is preferably 80 to 99%, and more preferably 90 to 98%.

[0042] The overall faradaic efficiency for carbon monoxide and hydrogen formation using the liquid electrolyte flow cell is 200 mA / cm 2 The range is preferably 85 to 99%, and more preferably 90 to 98%.

[0043] In the process of the present invention, when using a zero-gap electrolytic cell, the faradaic efficiency of carbon monoxide formation is 50 mA / cm 2 The range is preferably 10 to 85%, and more preferably 30 to 80%.

[0044] Additionally, in the process of the present invention, the faradaic efficiency of hydrogen formation is 50 mA / cm when using a zero-gap electrolytic cell. 2 The range is preferably 1 to 60%, more preferably 2 to 20%.

[0045] The overall faradaic efficiency for carbon monoxide and hydrogen formation is 50 mA / cm when using a zero-gap electrolytic cell. 2 The range is preferably 50 to 90%, and more preferably 60 to 85%.

[0046] After poisoning the gas diffusion electrode with catalyst poisons such as Na2S, H2S, SO2, and NO2, the process of the present invention achieves a faradaic efficiency of hydrogen formation of 50 mA / cm when using a liquid electrolyte flow cell. 2 The range is preferably 1 to 30%, more preferably 5 to 25%.

[0047] Furthermore, after poisoning the electrode with catalyst poisons such as Na2S, H2S, SO2, and NO2, 2 Faradaic efficiencies of carbon monoxide formation in the range of 30-85%, preferably 40-80%, are preferably achieved with the process according to the invention when using a liquid electrolyte flow cell.

[0048] The overall faradaic efficiency for carbon monoxide and hydrogen formation using a liquid electrolyte flow cell after poisoning the electrodes with catalyst poisons such as Na2S, H2S, SO2, and NO2 was 50 mA / cm 2The range is preferably 70 to 95%, and more preferably 75 to 90%.

[0049] The electrodes according to the invention have been shown to be only slightly sensitive to catalyst poisons such as NaS, HS, SO, and NO. Therefore, the process according to the invention can also be used to reduce carbon dioxide from untreated exhaust streams, preferably those containing typical catalyst poisons such as sulfur-containing compounds. Thus, high efficiency of electrocatalytic CO conversion has been demonstrated even in the presence of typical catalyst poisons. This allows for the efficient and cost-effective use of the process according to the invention and the electrodes according to the invention in industrial plants for the reduction of carbon dioxide.

[0050] In a further aspect, the present invention relates to the use of cadmium chalcogenide and / or zinc chalcogenide nanoparticles in the electrodes described herein as catalysts for the electrochemical reduction of carbon dioxide CO to reduced species such as carbon monoxide CO and / or syngas CO / H.

[0051] Preferably, all aspects and embodiments of the electrodes, cadmium chalcogenide and / or zinc chalcogenide nanoparticles, electrochemical cells, and methods according to the present invention described herein apply in the use of the present invention. [Example]

[0052] The invention is illustrated below by means of non-limiting examples.

[0053] 1.Measurement method X-ray diffraction Diffractograms of pure nanoparticles were obtained using a Philips X'Pert Pro MPD (Cu-Kα1 / 2 radiation, 45 kV, 40 mA, 30 min).

[0054] Transmission electron microscopy (TEM) To determine the size, shape, and size distribution, TEM images were acquired using a Jeol JEM-1011 or Jeol JEM-2800 (depending on availability) at 100 kV. The nanoparticle solution was diluted to an optical density close to 0.1 and dropped onto a copper grid covered with a carbon film. Quantum-functionalized carbon black was dispersed in water and also dropped onto a copper grid covered with a carbon film.

[0055] Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy SEM images were acquired using a Zeiss Merlin / Gemini II FE-SEM equipped with a thermal Schottky field emission electron source. An Everhardt-Thornley detector was used to detect secondary electrons, and an Oxford Instruments N-Max silicon detector was used for EDX analysis. An acceleration range of 20 kV and a current density of 500 pA were selected for EDX analysis. All samples were sputtered with gold.

[0056] Thermogravimetric analysis (TGA) Analysis was performed by combusting at least 3 mg of dry material from each sample. A rate of 10 degrees per minute was used for measurements from 20 to 650 °C. Measurements were performed using a Netzsch TGA 209 Fl Iris. Residual mass (inorganic mass) was analyzed using Proteus 4.8.4 software.

[0057] 2. Synthesis of Cadmium Chalcogenide Nanoparticles Spherical CdSe quantum dots were prepared according to the protocol of Talapin et al. (Talapin et al., 2001). Spherical CdSe / CdS core / shell and pure CdS quantum dots were prepared according to the protocol of Chen et al. (Chen et al., 2008). Coin-shaped CdSe / CdS quantum dots were synthesized using a modified protocol for CdSe / CdS core / shell quantum dots, but at a higher sulfur flow rate. CdSe / CdS quantum dots in quantum rods were synthesized in a flow facility using the procedure described by Jochum et al. (Jochum et al., 2016). CdS materials were prepared using the above method without the CdSe core. Talapin, DV, Rogach, AL, Kornowski, A., Haase, M. and Weller, H. (2001) 'Highly Luminescent Monodisperse CdSe and CdSe / ZnS Nanocrystals Synthesized in a Hexadecylamine-Trioctylphosphine Oxide-Trioctylphospine Mixture', Nano Letters, Vol. 1, No. 4, pp. 207-211. Chen, Y., Vela, J., Htoon, H., Casson, JL, Werder, DJ, Bussian, DA, Klimov, VI and Hollingsworth, JA (2008) '"Giant" multishell CdSe nanocrystal quantum dots with suppressed blinking', Journal of the American Chemical Society, Vol. 130, No. 15, pp. 5026-5027. Jochum, T., Niehaus, J. and Weller, H. (2016) '27-5L: Late-News Paper: Elongated semiconductor nanorods - Emitter of polarized light in red and green', SID Symposium Digest of Technical Papers, Vol. 47, No. 1, pp. 347-349.

[0058] The following cadmium chalcogenide nanoparticles were obtained: Spherical CdSe particles (CdSe spheres) with a mixture of trioctylphosphine (TOP), trioctylphosphine oxide (TOPO), hexylphosphonic acid (HPA), and octadecylphosphonic acid (ODPA) as organic ligands. Spherical CdS particles (CdS spheres) with oleic acid (OA) as an organic ligand Spherical particles with a CdSe core and a CdS shell containing oleic acid (OA) as an organic ligand (CdSe / CdS spheres) Coin-shaped particles with a CdSe core and a CdS shell (CdSe / CdS coins) containing oleic acid (OA) as an organic ligand Rod-shaped particles with a CdSe core and a CdS shell (CdSe / CdS rods) containing a mixture of trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO), hexylphosphonic acid (HPA), and octadecylphosphonic acid (ODPA) as organic ligands. Rod-shaped CdS particles (CdS rods) with a mixture of trioctylphosphine (TOP), trioctylphosphine oxide (TOPO), hexylphosphonic acid (HPA), and octadecylphosphonic acid (ODPA) as organic ligands. For reference, spherical Ag particles (Ag NPs) with oleic acid (OA) as the organic ligand.

[0059] The properties of the nanoparticles are shown in Table 1.

[0060] [Table 1]

[0061] 3. Electrode preparation and CO electrolysis in a liquid electrolyte flow cell To prepare the catalyst powder mixture, carbon black (ENSACO 250G) was dispersed in n-hexane (Merck, HPLC grade) and the CdSe / CdS particle dispersion was added dropwise under vigorous stirring (25 mg inorganic catalyst mass per gram of CdS). The silver reference electrode (Alfa Aesar, 20–40 nm, 99.9%) was similarly prepared by adding 50 wt% oleic acid (Carl Roth, ≥99%) to the particles and dispersing them at 8000 rpm for 30 seconds using an IKA T18 digital ULTRA-TURRAX. The hexane was allowed to evaporate overnight with stirring. PTFE (3M TF1750, 15% by weight of the total powder mixture) was added and the powder mixture was homogenized in an IKA M20 knife mill for 4 x 15 seconds. Catalyst layer (2 mm thick powder layer, approximately 8 mg cm -2 (resulting in a thermal shock) was applied to a carbon fabric (Fuel Cell Store, W1S1010) at 260°C and 3.6kNcm -2 The electrodes were prepared by hot pressing (Servitec Polystat 300S) at 2.5 mg cm for 10 min. -2 The substrate was drop coated with Sustainion XA-9 and conditioned in 1 M KOH (Carl Roth, 85%) for 72 hours. For the poisoning experiments, the electrodes were stored under SO2, NO2, or 1:1 H2S:N2 atmosphere for 72 hours before Sustainion coating. Electrochemical measurements were performed in a liquid electrolyte flow cell using 1.5 M KHCO3 / 0.1 M K2SO4 dissolved in ultrapure water (Alfa Aesar, 99% and Thermo Scientific, 99+%) as the electrolyte, a Fumatec Fumasep 1120PK cation exchange membrane, a Gaskatel Mini Hydroflex RHE as the reference electrode, and a Pt-coated Ti wire as the counter electrode. For Na2S poisoning experiments, 1.5M KHCO3 / 0.1M Na2S was used as the electrolyte. The CO2 flow was 25 mL / min and a system overpressure of 80 mbar was applied. Product gases were detected by GC-TCD / FID on an Agilent Technologies 7820 GC equipped with HP-PLOT Q and HP-Molsieve 5 Å columns. CO and CO2 were converted in a methanizer for detection by FID.

[0062] 4. Electrode preparation and CO electrolysis in a zero-gap electrolysis cell For application in zero-gap electrolytic cells, 1 mg cm -2 The particle dispersion having a loading of 1000 .mu.m was deposited dropwise onto a carbon cloth substrate. The electrolyte was a Versogen PiperION-A40 membrane, and the anode was an IrO2-coated Ti felt (2-GDL40, Bekaert). Prior to the measurement, the membrane was conditioned in 1 M KOH for 1 h. 0.1 M KHCO3 solution was used as the anode substrate. The electrochemical cell was heated to 60°C and the feed gas (22.5 mL / min CO2 and 2.5 mL / min Ar as internal standard at 40 mbar back pressure) was humidified by passing it through water at 40°C. The electrode is 50mAcm -2 Condition for 20 minutes with CO2 electrolysis at 200 mAcm -2 So I went for two hours. The products were detected using a Shimadzu GC-2010Plus / GCMS-QP2020 equipped with a Supelco Carboxen 1010PLOT column.

[0063] 5. Electrochemical screening in a liquid electrolyte flow cell The gas diffusion electrode was fabricated by mixing CdSe / CdS particles with carbon black as an additional conductive porous support, followed by hot pressing the PTFE mixed powder mixture onto a carbon cloth substrate. Prior to electrochemical measurements, the electrode was coated with Sustainion XA-9 to improve surface wettability and reduce proton availability for the catalyst. 50mAcm -2 and 200mAcm -2 Galvanostatic measurements at 1000 K were performed in a liquid electrolyte flow cell, and the gas phase products were analyzed after 1 and 2 hours. H2 and CO were detected as the main reaction products in varying proportions depending on the type of catalyst used and the current density. Trace amounts of CH4 (FE CH4 <0.5% was also detected. For benchmarking purposes, commercially available electrodes with silver nanoparticles were fabricated and measured. Figure 1 shows the results of the 50 mAcm2 cathode catalysts after 1 and 2 hours using different particle types. -2 (top) and 200 (bottom) mAcm -2 Figure 1 shows the faradaic efficiency (FE) of H2 and CO at 1000 K. 50mAcm -2 In this study, most nanoparticle types exhibit comparable selectivity for CO and hydrogen formation, with the selectivity changing only slightly during electrolysis. Commercially available silver nanoparticles showed 78±1% FE after 1 hour. CO and 22±5%FE H2 After 2 hours, the FE was 76±2% CO and 23±8%FE H2 Shows. The spherical CdSe / CdS particles showed 73±4% FE after 1 hour. CO and 15±1%FE H2 showed comparable selectivity with 70.7±0.1% FE after 2 hours.CO and 14.6±0.3%FE H2 Shows. The spherical CdS particles without a CdSe core had FE of 72±6% after 1 hour and 73±3% after 2 hours, respectively. CO , and an FE of 19±4% after 1 hour and 15±4% after 2 hours H2 shows similar performance. CdSe / CdS coins show similar performance (75±3% FE after 1 hour). CO , 10±2% FE H2 , and 73±4% FE after 2 hours CO , 9±3% FE H2 ). However, the rod-shaped particle type showed a slightly increased FE CO and lower FE H2 Shows. The CdSe / CdS core-shell rods show selectivities for CO of 82.3±0.6% FE after 1 h and 76.7±0.6% FE after 2 h, and selectivities for H of 5±0.2% FE after 1 h and 8±1% FE after 2 h, respectively. The pure CdS rod also showed a FE of 81.1±0.4% after 1 hour. CO , 5.3±0.6% FE H2 , and 80±2% FE after 2 hours CO , 6.0±0.7% FE H2 It shows similar selectivity. 50mAcm -2 In contrast to measurements at 200 mAcm -2 In the , the selectivity of the reaction shifts towards more pronounced hydrogen formation with each measurement, revealing greater differences between particle types. Commercially available Ag NPs showed 70±13% FE after 1 h. CO (39±14%FE H2 ) and achieved 52±22% FE after 2 hours. CO (54±22%FE H2 ) to achieve this. Among CdS-based particles, the highest selectivity for CO continues to be exhibited by electrodes based on spherical CdS particles, with FE CO was 56±5% after 1 hour and 25±11% after 2 hours, and FEH2 was 32±4% after 1 hour and 66±18% after 2 hours. The CdSe / CdS rods still had an FE of 44±6% after 1 hour and 19±10% after 2 hours. CO (FE H2 was 43±7% after 1 hour and 79±7% after 2 hours. Spherical CdSe / CdS particles performed equally well, with an FE of 41±10% after 1 hour. CO and 48±8% FE H2 , and 31±4% FE after 2 hours CO and 57±3% FE H2 It was. The CdS rod still produced CO with selectivity of 33±3% after 1 hour and 7±1% after 2 hours, and the corresponding FE H2 was 56±2% after 1 hour and 90±5% after 2 hours. A significantly lower selectivity for CO2 reduction was again observed for the spherical CdSe particles, with 18 ± 4% FE after 1 h. CO and 16±5% after 2 hours, and 78±7%FE after 1 hour. H2 and 78±6% after 2 hours. However, 50mAcm -2 In contrast to measurements at 200 mAcm, the CdSe / CdSe coins exhibited a higher current density than the other materials. -2 It shows extremely low selectivity for CO2 reduction in FE. CO is only 14±2% after 1 hour and 16±6% after 2 hours, while H2 is produced with FE of 76±2% after 1 hour and 76±7% after 2 hours, respectively.

[0064] 6. Catalyst poisoning Sulfide compounds are postulated to exhibit increased stability against catalyst poisoning. To test this hypothesis, CdS electrodes were exposed to H2S, SO2, and NO2 atmospheres and electrolytes containing Na2S, and the performance of the poisoned electrodes was compared to their untreated counterparts (Figure 2). In particular, the SO2 pretreated electrode showed comparable performance to the untreated electrode (79.2 ± 0.9% FE after 1 h). COand 79.3±0.2% FE after 2 hours. CO , FE of 5.3±0.3% after 1 hour H2 and 4.2±0.1% FE after 2 hours. H2 ). Treatment with H2S also had a negligible effect, with FE of 7.8±0.6% after 1 hour and 7±3% after 2 hours. H2 FE to a stable 74±2% with CO This resulted in a decrease in However, treatment of the electrode with NO2 resulted in a more significant loss of CO2 reduction selectivity, with an FE of 70 ± 1% after 1 h. CO and 11±3% FE H2 (56±1% FE after 2 hours CO and 22±5% FE H2 ) was. S in electrolyte 2- In the presence of CO, the electrode showed significantly reduced selectivity for CO. After 1 h, FE CO was reduced to 54±2%, but FE H2 The conversion reached 32±3%. However, it should be noted that the catalyst is not the only part of the electrode exposed to potential poisoning. It has previously been reported that H2S can also poison Sustainion® membranes, so it is likely that the ionomer coating was also damaged by the sulfide-containing electrolyte [Liu, Z., White, E., Resch, M., and Masel, R. (2021) 'Poison Effects on Alkaline CO2 Electrolyzer Using Sustainion® Membrane', ECS Meeting Abstracts, MA2021-02, No. 26, p. 827].

[0065] 7. CO2 electrolysis in a zero-gap electrolysis cell Particle suspensions of spherical CdS and CdSe / CdS particles, as well as CdS and CdSe / CdS rods, were drop-cast directly onto carbon cloth (GDL) without any ionomer or additional binder. The particle layers obtained using this technique were more homogeneous for spherical particles than for rod-shaped particles. The results of 2 hours of electrolysis are shown in Figure 3.

[0066] Spherical CdSe / CdS particles are 200 mAcm -2 After 20 minutes of electrolysis, the FE was 62±2%. CO and remained stable for 2 hours (58±3%). The spherical CdS particles also initially showed a relatively stable FE of 57±2%. CO This decreased to 45±4% during the electrolysis process. FE achieved with CdSe / CdS rods CO The initial value of 38.4±0.2% fluctuates considerably. -2 It first drops to less than 10% after 60-80 minutes, then rises again to 25±2% after 2 hours. The CdS rods showed a relatively low but stable FE of 19±2% initially and 16±1% after 2 hours. CO results.

Claims

1. Carbon dioxide CO ２ of carbon monoxide CO and / or synthesis gas CO / H ２ Electrodes for the reduction of cadmium and / or zinc chalcogenide nanoparticles to .

2. The electrode of claim 1 , wherein the cadmium chalcogenide and / or zinc chalcogenide nanoparticles are in the shape of spherical particles, coins, or rods.

3. 3. An electrode according to claim 1 or claim 2, wherein the cadmium chalcogenide and / or zinc chalcogenide nanoparticles contain cadmium sulfide CdS, cadmium selenide CdSe, zinc sulfide ZnS, zinc selenide ZnSe, and mixtures of two or more compounds of cadmium sulfide CdS, cadmium selenide CdSe, zinc sulfide ZnS, or zinc selenide ZnSe in the form of layers or shells of different individual compounds or in the form of an alloy, preferably cadmium sulfide CdS, cadmium selenide CdSe, and mixtures of cadmium sulfide CdS with cadmium selenide CdSe in the form of layers or shells of the individual compounds or in the form of an alloy.

4. 4. The electrode of claim 1, wherein the cadmium chalcogenide and / or zinc chalcogenide nanoparticles comprise cadmium selenide (CdSe).

5. 5. The electrode of claim 1, wherein the cadmium chalcogenide and / or zinc chalcogenide nanoparticles contain a core and a shell, preferably a cadmium selenide (CdSe) core and a cadmium sulfide (CdS) shell.

6. 6. The electrode of any one of claims 1 to 5, wherein the cadmium chalcogenide and / or zinc chalcogenide nanoparticles have a selenium (Se) to sulfur (S) molar ratio (Se:S) of 0.001:99.999 to 50.0:50.0, preferably 0.01:99.99 to 25:75, more preferably 0.1:99.9 to 10.0:90.

0.

7. 7. The electrode of claim 1, wherein the cadmium chalcogenide and / or zinc chalcogenide nanoparticles have a ratio of average core diameter to average total particle diameter of 1.0:7.0 to 1.0:1.0, preferably 1.0:5.0 to 1.0:2, more preferably 1.0:4.5 to 1.0:3.

0.

8. 8. The electrode according to any one of claims 1 to 7, wherein the cadmium and / or zinc chalcogenide nanoparticles have an average particle size in the direction of smallest extension of 1.5 to 45.0 nm, preferably 3.0 to 30.0 nm, more preferably 4.0 to 25.0 nm, and / or an average particle size in the direction of largest extension of 1.5 to 200.0 nm, preferably 5.0 to 125.0 nm, more preferably 8.0 to 75.0 nm.

9. The cadmium chalcogenide and / or zinc chalcogenide nanoparticles have a concentration of 1.0 to 100.0 m ２ / 100mg, preferably 3.0 to 50.0m ２ / 100 mg, more preferably 4.5 to 30.0 m ２ 9. The electrode of claim 1, having a surface area of ​​100 mg / 100 mg.

10. The cadmium chalcogenide and / or zinc chalcogenide nanoparticles are 2 to 50,000 nm ３ , preferably 14 to 15,000 nm ３ , more preferably 50 to 10,000 nm ３ 10. The electrode of claim 1, having a particle volume of

11. 11. The electrode according to any one of claims 1 to 10, wherein the electrode is a porous electrode, preferably a gas diffusion electrode.

12. Carbon dioxide CO ２ A method for reducing - providing an electrochemical cell comprising an electrode according to any one of claims 1 to 11; - applying a current to the electrodes; Carbon dioxide is preferably carbon monoxide CO and / or synthesis gas CO / H ２ contacting a carbon dioxide-containing gas stream with the cadmium and / or zinc chalcogenide nanoparticles within the electrode so as to be reduced to A method comprising:

13. 13. The method of claim 12, wherein the carbon dioxide-containing gas stream is an exhaust stream from an industrial plant such as a waste incineration plant or a cement plant, preferably a raw exhaust stream, more preferably an exhaust stream further containing sulfur-containing compounds.

14. 14. The method of claim 12 or claim 13, wherein carbon monoxide or synthesis gas reduced from carbon dioxide is separated from the gas stream and used to produce carbon derivatives such as methane, olefins, organic acids and their derivatives, and alcohols.

15. Carbon dioxide CO ２ of carbon monoxide CO and / or synthesis gas CO / H ２ 12. Use of cadmium chalcogenide and / or zinc chalcogenide nanoparticles in an electrode according to any one of claims 1 to 11 as a catalyst for the electrochemical reduction of cadmium chalcogenide and / or zinc chalcogenide nanoparticles to reduced species such as cadmium chalcogenide and zinc chalcogenide nanoparticles.

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