EP4724634A1

EP4724634A1 - Ccm, preparation method therefor and use thereof

Info

Publication number: EP4724634A1
Application number: EP23940272.0A
Authority: EP
Inventors: Zhiqing ZOU; Yameng Wang; Fengru Zhang
Original assignee: Shanghai H Ray S & T Co Ltd
Current assignee: Shanghai H Ray S & T Co Ltd
Priority date: 2023-06-06
Filing date: 2023-07-20
Publication date: 2026-04-15
Also published as: WO2024250391A1; CN119121275A

Abstract

The invention provides the design and preparation of a catalyst coated membrane (CCM) and its application in proton exchange membrane water electrolysis (PEMWE). The CCM contains a proton exchange membrane (PEM) and a multiscale micro/nano structured catalytic layer with ordered arrays. The ordered multiscale micro/nano structured catalytic layer includes a super-thin metal layer, a conventional catalyst/ionomer layer, and metal nanowires grown on the outermost layer. This ordered multiscale micro/nano structured catalytic layer not only improves the interfacial contact between the gas-liquid diffusion layer and the catalytic layer, building a continuous electron transfer path to reduce the internal resistance, but also exhibits super-hydrophilicity, further improving the mass transfer efficiency of membrane electrode.

Description

CCM, preparation method therefor and use thereof

The present invention claims the priority of the Chinese Patent Application No. CN202310666867X, filed on June 6, 2023, the contents of which are incorporated herein by its entirety.

Field of invention

The present invention relates to the field of hydrogen production by proton exchange membrane water electrolysis (PEMWE) , particularly to a catalyst coated membrane and its preparation method and application.
Prior arts
PEMWE is one of the key technologies to achieve zero-carbon emission hydrogen production. At present, due to the high consumption (2-3 mg cm^-2) of noble metal Ir on the anode side, the cost of PEMWE is greatly increased, which seriously restricts its commercialization process.
The membrane electrode assembly (MEA) is the core component of PEMWE, which should be developed with maximized triple-phase boundaries, rapid mass transport pathways and low ohmic resistance. At present, the structure of the widely used gas-liquid diffusion layer, such as titanium felt and titanium mesh, is randomly distributed, which will lead to uneven interface contact with the catalytic layer, thus resulting in the insufficient utilization of catalyst. At the same time, the hydrophobic of the surface of traditional anode results in poor water-wettability, leading to the high mass transfer resistance. To address the above issues, researchers have developed ultra-thin titanium plates with adjustable pore diameters, titanium layers with gradient pore structures, etc. However, since high porosity is beneficial to mass transfer while low porosity leads to the reduction of the interfacial contact resistance, there is a trade-off between the reduction of the contact resistance and promotion of the mass transfer. Therefore, a design and construction of the catalytic layer to simultaneously reduce ohmic and mass transport resistance is urgently needed.
Content of the present invention
The present invention relates to achieving the above-mentioned purpose, this invention provides a catalyst coated membrane (CCM) with super-hydrophilic multiscale micro/nano structured catalytic layer for PEMWE. The described CCM contains a PEM and a multiscale micro/nano structured catalytic layer with ordered arrays. The ordered multiscale micro/nano structured catalytic layer includes a super-thin metal layer, a conventional catalyst/ionomer layer, and metal nanowires grown on the outermost layer.
The shape of micro/nano structured array is columnar or conical. The thickness of the array ranges from 200 nm to 1.5 μm; The maximum cross-sectional dimension of single array ranges from 50 nm to 1 μm; The distance between two adjacent arrays ranges from 100 nm to 1 μm.
The material of metal layer is one or more kinds of Au, Pt, Ir, Pd, etc.; The material of metal nanowire is one or more kinds of Au, Pt, Ir, Pd, etc.; The material of the metal layer is the same as that of the metal nanowire. The loading of metal layer ranges from 0 to 100 μg cm^-2; The loading of metal nanowire ranges from 0 to 0.2 mg cm^-2. The morphology of metal nanowires-covered catalytic layer includes sea urchin shape, spherical shape, coral shape, dandelion shape and so on.
A preparation method of CCM comprising:
S1. Add the catalyst ink and metal into a hole-patterned template with micro/nano scaled aperture size. The obtain catalyst covered template consists a metal layer and a catalytic layer;
S2. Hot-press the catalytic layer coated-template with the cathodic catalyst-coated PEM to obtain a three-layer CCM with template. The hot-pressing temperature and pressure range from 60 to 180 ℃ and 0.1 to 10 MPa/cm², respectively.
S3. Wash away the template with alkali solution to obtain the three-layer CCM.
S4. Soak the CCM in a mixture solution of metallate and reductant to grow metal nanowires on the ordered catalytic layer.
The catalyst ink comprises the catalyst, ionomer and solvent. The ionomer solution includes 5wt%perfluorosulfonic acid resin solution; The solvent contains H₂O and alcohol. The mass ratio of the catalyst, ionomer, water and alcohol is 1: (1-20) : (1-50) : (1-50) ;
The preparation method of metal layer includes ion sputtering or/and magnetron sputtering, etc.; Preferably, the current of ion sputtering ranges from 0 to 50 mA, and the sputtering time ranges from 0 to 360s; For magnetron sputtering, the sputtering power ranges from 0 to 300 W, and the sputtering time ranges from 0 to 300 s.
The PEM includes Nafion 115, Nafion 117 and Nafion 212. Preferably, the condition of S2 is that the hot-pressing temperature and pressure range from 100 to 150 ℃ and 0.5 to 3 MPa/cm², respectively; The condition of S3 is that the alkali solution contains NaOH/KOH solution, the concentration of NaOH/KOH ranges from 0.05 to 5 M, and the washing time and temperature ranges from 5 to 60 h and 10 to 90 ℃, respectively; The condition of S4 is that the protonation agent contains H₂SO₄, the concentration of H₂SO₄ ranges from 0.1 to 5 M, and the protonation time and temperature ranges from 6 to 60 h and 10 to 80 ℃, respectively;
The reductant of S4 contains one or more kinds of formic acid, sodium borohydride, triethylene glycol, etc.; Preferably, the concentration of the reductant ranges from 0.01 to 5M; The metallate solution includes one or more kinds of chloroplatinic acid, chloroauric acid, chloropalladic acid and chloroiridic acid, and the concentration of the metallate solution ranges from 0.01 to 10 mM; The surfactant includes one or more kinds of cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, and the concentration of surfactant ranges from 0 to 1M; The temperature and time of the reduction reaction ranges from 5 to 100 ℃ and 0 to 48 h, respectively;
This invention provides a CCM, which is prepared according to the above methods; An MEA, wherein the CCM is prepared according to the above methods. This MEA is used in the PEMWE.

Brief description of the drawings

Fig. 1 shows a scanning electron microscopy (SEM) image of a cross-section of the AAO template for the embodiment 1.
Fig. 2 shows the SEM and energy dispersive spectrometer (EDS) images of the product obtained from S3 of the embodiment 1. (a) top view of the multiscale micro/nano structured catalytic layer. (b) C, (c) F, (d) Ir, (e) Pt, and (f) merged images of EDS elemental mapping images.
Fig. 3 shows a schematic diagram of the CCM for embodiment 1
Fig. 4 shows a SEM image of top view of the catalytic layer for the embodiment 2.
Fig. 5 shows the polarization curves of the embodiment 1 and a conventional MEA with the same catalyst loading.
Fig. 6 shows the water contact angle of embodiment 2.
Fig. 7 shows the water contact angle of the comparison embodiment 1.
Illustration of Fig. 3: 1 represents metal nanowires; 2 represents catalytic layer; 3 represents metal layer; 4 represents PEM.
Detailed description of the preferred embodiment
The following examples further illustrate the present invention, but the present invention is not limited thereto.
Below presents preferred embodiments of the present invention based on the drawings in order to illustrate the technical schemes of the present invention in detail.
Embodiment 1
As shown in Fig. 1, the nanopores-patterned AAO template is conical pore structure. The cross-sectional diameter of the taper is 500 nm, the distance between two adjacent taper is 500 nm, and the depth is 700 nm. Before use, the template is dried after ultrasonic treatment with ethanol and deionized water for 3 min, respectively.
The catalyst ink is prepared by sonicated the mixture of 8 mg of IrO₂, 64 mg of 5 wt. %perfluorosulfonic acid solution, 150 mg of water and 100 mg of isopropanol for 1 h. Then, the catalyst ink is taken to spray on the surface of the AAO template. The Ir loading is 0.15 mg cm^- ².
The catalytic layer covered template is placed in an ion sputtering chamber to sputter Pt under 25 mA for 20 s. After sputtering, an ultra-thin Pt layer-coated catalytic layer is obtained.
The CCM is fabricated by hot-pressing the cathodic catalyst-coated membrane and the template containing catalytic layer. The dried template with catalytic layer is clung to the blank side of the Nafion 115 membrane and hot-pressed at 160 ℃ and 1 MPa/cm² for 4 h.
Following the hot-pressing, the composite structure of the catalytic layer, PEM and the template is immersed in 2M NaOH at 25℃ for 10 h. After washing off NaOH, the CCM is soaked in 0.5 M H₂SO₄ for 48 h at 25℃ to transform the Na⁺-formed PEM to acidic form.
As shown in Fig. 2, the sample obtained from S3 displays well-ordered tapered arrays covered with uniform distribution of catalytic layer and metal layer.
The dried CCM is placed on the surface of the mixture solution of 20 ml of water, 200 μL of formic acid and 3 mL of 0.02 mol/L chloroplatinic acid aqueous solution at 25 ℃ for 12 h. The obtained metal nanowires grown-CCM is taken out and cleaned in ultrapure water. Fig. 3 is a schematic diagram of the CCM for embodiment 1, wherein 1 represents metal nanowires, 2 represents catalytic layer, 3 represents metal layer and 4 represents PEM. The loading of metal layer and metal nanowires is 4.2 and 80.7 μg cm^-2, respectively.
Embodiment 2
The catalyst ink is prepared by sonicated the mixture of 8 mg of IrO₂, 50 mg of 5 wt. %perfluorosulfonic acid solution, 200 mg water and 300 mg of tert-butanol for 2 h. Then, the catalyst ink is taken to spray on the surface of the AAO template, which is conical structured. The cross-sectional diameter of the taper is 600 nm, the distance between two adjacent taper is 400 nm, and the depth is 600 nm. Before use, the template is dried after ultrasonic treatment with ethanol and deionized water for 3 min, respectively. The Ir loading is 0.15 mg cm^-2.
The catalytic layer covered template is placed in the chamber of the magnetron sputtering coater to sputter Ir under 120 W for 10 s. After sputtering, an ultra-thin Ir layer-coated catalytic layer is obtained.
The CCM is fabricated by hot-pressing the cathodic catalyst-coated membrane and the template containing catalytic layer. The dried template with catalytic layer is clung to the blank side of the Nafion 117 membrane and hot-pressed at 120 ℃ and 2 MPa/cm² for 2 h.
Following the hot-pressing, the composite structure of the catalytic layer, PEM and the template is immersed in 1M NaOH at 50℃ for 80 h. After washing off NaOH, the CCM is soaked in 1 M H₂SO₄ for 24 h at 50 ℃ to transform the Na⁺-formed PEM to acidic form.
The dried CCM is placed on the surface of the mixture solution of 100 ml of water, 3 mL of triethylene glycol, 12 mg of cetyltrimethylammonium bromide and 2 mL of 0.05 mol/L chloroiridic acid aqueous solution at 200 ℃ for 1 h. The obtained metal nanowires grown-CCM is taken out and cleaned in ultrapure water. The loading of metal layer and metal nanowires is 6.4 and 56.3 μg cm^-2, respectively. Fig. 4 is a SEM image of the catalytic layer of embodiment 2, showing a sea urchin-like structure, and the nanowires are stacked each other.
Comparison embodiment 1
The catalyst ink is prepared by sonicated the mixture of 8 mg of IrO₂, 100 mg perfluorosulfonic acid solution, 300 mg of water and 350 mg of ethanol for 1 h. Then catalyst ink is taken to spray on the surface of the AAO template, which is cylindrical structured. The cross-sectional diameter of the column is 800 nm, the distance between two adjacent column is 300 nm, and the depth is 500 nm. Before use, the template is dried after ultrasonic treatment with ethanol and deionized water for 3 min, respectively. The Ir loading is 0.15 mg cm^-2.
The catalytic layer covered template is placed in an ion sputtering chamber to sputter Pt under 40 mA for 10 s. After sputtering, an ultra-thin Pt layer-coated catalytic layer is obtained.
The CCM is fabricated by hot-pressing the cathodic catalyst-coated membrane and the template containing catalytic layer. The dried template with catalytic layer is clung to the blank side of the Nafion 115 membrane and hot-pressed at 100 ℃ and 3 MPa/cm² for 0.5 h.
Following the hot-pressing, the composite structure of the catalytic layer, PEM and the template is immersed in 3M NaOH at 40 ℃ for 8 h. After washing off NaOH, the CCM is soaked in 1 M H₂SO₄ for 12 h at 50 ℃ to transform the Na⁺-formed PEM to acidic form.
Fig. 5 shows a performance comparison of the MEAs for embodiment 1 with the conventional MEA with Ir loading of 0.15 mg cm^-2 at 60 ℃, which determines that the performance of MEA with ultra-thin metal layer and multiscale micro/nano structure (embodiment 1) is better than that of conventional one.
Fig. 6 and 7 are the water contact angle of the catalytic layer of embodiment 2 and comparison embodiment 1, respectively. As shown, the catalytic layer of embodiment 2 with ultra-thin metal layer and multiscale micro/nano structure has a water contact angle as low as 8.74°, showing a super-hydrophilicity. The catalytic layer of comparison embodiment 1 without metal nanowires presents a water contact angle of 46.77°, which is much larger than that of embodiment 2.

Claims

A CCM, which contains a PEM and a multiscale micro/nano structured catalytic layer with ordered arrays, wherein the ordered multiscale micro/nano structured catalytic layer include a super-thin metal layer, a conventional catalyst/ionomer layer, and metal nanowires grown on the outermost layer.
The CCM according to claim 1, wherein the shape of micro/nano structured array is columnar or conical, wherein the thickness of the array ranges from 200 nm to 1.5 μm, and/or the maximum cross-sectional dimension of single array ranges from 50 nm to 1 μm, and/or the distance between two adjacent arrays ranges from 100 nm to 1 μm.
The CCM according to claim 1 or 2, wherein the material of metal layer is one or more kinds of Au, Pt, Ir, Pd, etc, and/or the material of metal nanowire is one or more kinds of Au, Pt, Ir, Pd, etc, and/or the material of the metal layer is the same as that of the metal nanowire, and/or the loading of metal layer ranges from 0 to 100 μg cm^-2, and/or the loading of metal nanowire ranges from 0 to 0.2 mg cm^-2, and/or the morphology of metal nanowires covered catalytic layer includes sea urchin shape, spherical shape, coral shape, dandelion shape and so on.
A preparation method for CCM comprising:

S1. adding the catalyst ink and metal into a hole-patterned template with micro/nano scaled aperture size, wherein the obtained catalyst-covered template consists a metal layer and a catalytic layer;

S2. hot-pressing the catalytic layer coated-template with the cathodic catalyst-coated PEM to obtain a three-layer CCM with template, wherein the hot-pressing temperature and pressure range from 60 to 180 ℃ and 0.1 to 10 MPa/cm², respectively;

S3. washing away the template with alkali solution to obtain the three-layer CCM;

S4. soaking the CCM into a mixture solution of metallate and reductant to grow metal nanowires on the ordered catalytic layer.
The preparation method for CCM according to claim 4, wherein the template in S1 contains anodic aluminum oxide (AAO) , wherein the catalyst ink comprises the catalyst, ionomer and solvents; preferably, the catalyst includes IrO₂ or Ir, the ionomer solution contains perfluorosulfonic acid resin solution, the solvent contains H₂O and alcohol/isopropanol, wherein the mass ratio of the catalyst, ionomer, water and alcohol is 1: (1-20) : (1-50) : (1-50) ; and/or the preparation method of metal layer includes ion-sputtering or/and magnetron sputtering, etc.; preferably, the current of ion sputtering ranges from 0 to 50 mA, and the sputtering time ranges from 0 to 360 s; for magnetron sputtering, the sputtering power ranges from 0 to 300 W, and the sputtering time ranges from 0 to 300 s.
The preparation method for CCM according to claim 4 or 5, wherein the PEM includes Nafion 115, Nafion 117 and Nafion 212; and /or the optimized condition of S2 is that the hot-pressing temperature and pressure range from 100 to 150 ℃ and 0.5 to 2 MPa/cm², respectively; and /or the condition of S3 is that the alkali solution contains NaOH/KOH solution, the concentration of NaOH/KOH ranges from 0.05 to 5 M, and the washing time and temperature range from 5 to 60 h and 10 to 90 ℃, respectively; the condition of S4 is that the protonation agent contains H₂SO₄, the concentration of H₂SO₄ ranges from 0.1 to 5 M, and the protonation time and temperature ranges from 6 to 60 h and 10 to 80 ℃, respectively;
The preparation method for CCM according to one of claim 4 to 6, wherein the reductant of S4 contains one or more kinds of formic acid, sodium borohydride, triethylene glycol, etc; preferably, the concentration of the reductant ranges from 0.01 to 5M; and /or the metallate solution includes one or more kinds of chloroplatinic acid, chloroauric acid, chloropalladic acid and chloroiridic acid; preferably, the concentration of the metallate solution ranges from 0.01 to 10 mM; and /or the surfactant includes one or more kinds of cetyltrimethylammonium bromide and cetyltrimethylammonium chloride; preferably, the concentration of surfactant ranges from 0 to 1 M; and/or the temperature and time of the reduction reaction ranges from 5 to 100 ℃ and 0 to 48 h, respectively.
A CCM, which is prepared by the preparation method for CCM according to one of claim 4 to 7.
An MEA, which contains the CCM according to one of claim 1-3 and 8.
Use of the MEA according to claim 9 in the PEMWE.