| HE Liangliang,ZHANG Xiangyun,LIU Taikai,XIE Yingchun,CHU Xin.Deposition Mechanism of Porous Coatings and Its Alkaline Water Electrolysis Performance Based on Morphology Control[J],53(24):206-215 |
| Deposition Mechanism of Porous Coatings and Its Alkaline Water Electrolysis Performance Based on Morphology Control |
| Received:December 21, 2023 Revised:May 25, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.24.019 |
| KeyWord:water electrolysis cold spraying pore former NiAl porous electrode electrochemical impedance spectroscopy |
| Author | Institution |
| HE Liangliang |
School of Materials Science and Engineering, Lanzhou University of Science and Technology, Lanzhou , China;National Engineering Laboratory of Surface Engineering Technology for Modern Materials, Institute of New Materials, Guangdong Academy of Sciences, Guangzhou , China |
| ZHANG Xiangyun |
School of Materials Science and Engineering, Lanzhou University of Science and Technology, Lanzhou , China |
| LIU Taikai |
National Engineering Laboratory of Surface Engineering Technology for Modern Materials, Institute of New Materials, Guangdong Academy of Sciences, Guangzhou , China |
| XIE Yingchun |
National Engineering Laboratory of Surface Engineering Technology for Modern Materials, Institute of New Materials, Guangdong Academy of Sciences, Guangzhou , China |
| CHU Xin |
National Engineering Laboratory of Surface Engineering Technology for Modern Materials, Institute of New Materials, Guangdong Academy of Sciences, Guangzhou , China |
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| Abstract: |
| The work aims to explore the effect of pore former morphologies on the deposition mechanism of Ni coatings, structures of porous Ni electrodes and hydrogen evolution performance of alkaline water electrolysis. By applying cold spraying technology, Ni powder and Al powder (the pore former) were deposited on perforated Ni sheets to obtain coatings. The obtained coatings were chemically etched to remove the pore former, then leaving numerous pores in the coatings which were used for further test. By performing SEM/EDS, XPS, XRD, the micro morphology, element state and other properties were characterized and analyzed. Furthermore, LSV, CV, EIS tests were carried out to estimate the HER performance of the obtain porous coatings. Nickel powder and aluminum powder were blended in a volume ratio of 3∶1. Coatings obtained with special Al powder were noted as NsA, and coatings prepared with flake Al powder were marked as NfA. Both NsA and NfA were immersed in a 30wt% KOH solution at room temperature for 24 h to successfully obtain two groups of porous coatings. The morphology of the coating before and after corrosion was analyzed by scanning electron microscopy (SEM). The valence state of elements and phase composition of the coatings were analyzed by EDS, XPS and XRD. The hydrogen evolution performance of the samples was studied through electrochemical tests including linear sweep voltammetry (LSV), cyclic sweep voltammetry, and electrochemical impedance spectroscopy (EIS), etc. The results showed that since the flake Al particles were greatly affected by spray gas, the flight state was extremely unstable, and only a small amount of flake Al powder was deposited as coating. Meanwhile, the spherical Al particle was able to maintain a stable flight state and achieve a high enough velocity to form coating upon the substrate. Consequently, the Al content of the sprayed coatings was high, resulting in more pores and larger specific surface area than that of the flake one. Therefore, the pore forming effect of spherical Al was significantly better than that of flaky Al. At the same time, the hydrogen evolution reaction of both coatings was dominated by the Herovsky step. At current densities of −100 mA/cm2 and −250 mA/cm2, the HER overpotentials of NsA samples were 0.32 V and 0.42 V, respectively, while the overpotentials of NfA samples were 0.4 V and 0.5 V, respectively. The maximum phase angle of sample NsA was 24°, and its corresponding characteristic frequency was 50 Hz. The maximum phase angle of the sample NfA was 30°, and its corresponding characteristic frequency was 1 000 Hz. Therefore, the surface of NfA coatings was rougher and more porous than that of NsA coatings. The difference in electrolysis performance between NsA and NfA samples mainly came from their difference of microstructure. The flake powder resulted in smaller and less pores in the coatings while the spherical powder caused more and larger pores to the coating, assuring sufficient contact between the catalyst and the electrolyte. Therefore, it can be considered that the pore forming effect of spherical Al is significantly better than that of flake Al, and the resulting coating has better electrochemical hydrogen evolution performance. |
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