Abstract
Atomic layer deposition (ALD) is a special type of chemical vapor deposition (CVD) technique that can grow uniformed thin films on a substrate through alternate self-limiting surface reactions. Recently, the application of these thin film materials to catalytic systems has begun to attract much attention, and the capacity to deposit these catalytic films in a highly controlled manner continues to gain importance. In this study, IrO2 and NiO thin films (approximately 25 to 60 nm) were deposited on industrial Ni expanded mesh as an anode for alkaline water electrolysis. Different ALD operating parameters such as the total number of deposition cycles, sublimation and deposition temperatures, and precursors pulse and purge lengths were varied to determine their effects on the structure and the electrochemical performance of the thin film materials. Results from the electrochemical tests (6 M KOH, 80 °C, up to 10 kA/m2) showed the catalytic activity of the samples. Oxygen overpotential values (ηO2) were 20 to 60 mV lower than the bare Ni expanded mesh. In summary, the study has demonstrated the feasibility of using the ALD technique to deposit uniformed and electroactive thin films on industrial metallic substrates as anodes for alkaline water electrolysis.
Highlights
Current research trends focus on developing thin film materials, especially semi-conducting oxides, due to their wide number of technological applications such as in the field of optics, sensors, microelectronics, electrocatalysis, and energy production [1,2,3,4]
The film thickness of nickel oxide (NiO) was measured using X-ray reflectivity (XRR) on the samples deposited on the Si (100) substrate
Iridium and nickel oxide thin films were deposited in an ASM-Microchemistry F-120 flow-type reactor, which was operated under a moderate vacuum of 1 to 3 mbar
Summary
Current research trends focus on developing thin film materials, especially semi-conducting oxides, due to their wide number of technological applications such as in the field of optics, sensors, microelectronics, electrocatalysis, and energy production [1,2,3,4]. Atomic layer deposition (ALD), a special type of chemical vapor deposition (CVD) technique, is considered as one of the most attractive thin film deposition techniques where the conformality, uniformity, and thickness controllability of the films are crucial [6]. This technique relies on the successive, separated, and self-terminating gas–solid reactions of typical two gaseous reactants [7]. Hundreds of materials have been explored and have been developed using this technique, and it has successfully demonstrated its Catalysts 2020, 10, 92; doi:10.3390/catal10010092 www.mdpi.com/journal/catalysts
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